Castle Biosciences, Inc. (CSTL) Earnings Call Transcript & Summary

Good afternoon, and welcome to Castle Biosciences Fourth Quarter and Full Year 2023 Conference Call. As a reminder, today's call is being recorded. We will begin today's call with opening remarks and introductions, followed by a question-and-answer session. I would now like to turn the call over to Camilla Zuckero, Vice President, Investor Relations and Corporate Affairs. Please go ahead.

Thank you, operator. Good afternoon, everyone. Welcome to Castle Biosciences' Fourth Quarter and Full Year 2023 Financial Results Conference Call. Joining me today is Castle's Founder, President and Chief Executive Officer, Derek Maetzold; and Chief Financial Officer, Frank Stokes. Information recorded on this call speaks only as of today, February 28, 2024. Therefore, if you are listening to the replay or reading the transcript of this call, any time-sensitive information may no longer be accurate. A recording of today's call will be available on the Investor Relations page of the company's website for approximately 3 weeks following the conclusion of the call. Before we begin, I would like to remind you that some of the statements made today will contain forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. These forward-looking statements include, but are not limited to, statements about our financial outlook, TAM and similar items referenced in our earnings release issued today and statements containing projections regarding future events or our future financial or operational performance, including our anticipated 2024 total revenue and our 2025 outlook, our expectations regarding reimbursement for our products and the impact of our investments in growth initiatives and expanded commercial team. Forward-looking statements are based upon current expectations and involve inherent risks and uncertainties. There can be no assurances that the results contemplated in these statements will be realized. A number of factors and risks could cause actual results to differ materially from those contained in these forward-looking statements. These factors and other risks and uncertainties are described in detail in the company's annual report on Form 10-K for the year ended December 31, 2023 under the heading Risk Factors and in the company's other documents and reports filed or to be filed with the Securities and Exchange Commission. These forward-looking statements speak only as of today, and we assume no obligation to update or revise these forward-looking statements as circumstances change. In addition, some of the information discussed today includes non-GAAP financial measures such as adjusted revenue, adjusted gross margin and adjusted EBITDA, that have not been calculated in accordance with generally accepted accounting principles in the United States or GAAP. These non-GAAP items should be used in addition to and not as a substitute for any GAAP results. We believe these metrics provide useful supplemental information in assessing our revenue and operating performance. Reconciliations of these non-GAAP financial measures to the most directly comparable GAAP financial measures are presented in the tables at the end of our earnings release issued earlier today, which has been posted on the Investor Relations page of the company's website. I will now turn the call over to Derek.

Thank you, Camilla, and good afternoon, everyone. I'm happy to report that we closed an outstanding fourth quarter, achieving very strong results for 2023. With fourth quarter revenue of $66.1 million, we grew revenue 60% year-over-year for the full year to $219.8 million, nearly [ $45 million ] above the midpoint of our expectations at the beginning of 2023. We've now grown revenue at a 43% CAGR rate over the last 5 years, continuing our track record of consistent execution. We also achieved impressive test volume results by delivering a total of 70,429 total test reports in 2023, representing 59% growth compared to 2022. Furthermore, the fourth quarter marked the second consecutive quarter in which we achieved positive cash flow from operations and positive adjusted EBITDA. In 2023, we achieved numerous accomplishments, and I would like to take this opportunity to highlight some of them. We opened our new state-of-art laboratory in Pittsburgh, Pennsylvania, received Advanced Diagnostic Laboratory Test, or ADLT, status for our DecisionDx SCC test, bringing our total to 5 tests that have been designated as ADLTs; extended our significant body of evidence across our entire test portfolio, made progress across our pipeline initiatives and won multiple awards for being a top workplace. None of our accomplishments will be possible without the hard work and strong execution of the entire Castle team, and I can't thank them enough. As I just mentioned, we expanded our significant body of evidence across our entire test portfolio in 2023. I want to touch base on data specifically on DecisionDx-Melanoma. We have demonstrated clinical validity, utility and patient impact in 50 peer-reviewed publications and studied the test in more than 10,000 patients, including two 2023 publications, demonstrating an association with the clinical use of our test and improved patient outcomes. The first publication is from our collaboration with the National Cancer Institute's SEER program in an unselected prospectively tested real-world patient population, which shows that testing with DecisionDx-Melanoma was associated with lower melanoma-specific and overall mortality relative to untested patients, that is patients who received DecisionDx-Melanoma as part of their clinical care live longer. Specifically, DecisionDx-Melanoma testing was associated with a 29% lower melanoma-specific mortality and a 17% lower overall mortality relative to patients who did not receive DecisionDx-Melanoma as part of their clinical care. The second publication is from an independent multicenter study of sentinel lymph node-negative patients, showing that patients who receive routine imaging after high-risk DecisionDx-Melanoma test scores, had an earlier recurrence diagnosis, with lower tumor burden leading to better clinical outcomes, including improved overall survival. We believe these studies demonstrate the clear positive impact testing with DecisionDx-Melanoma has on patient outcomes. And further, the DecisionDx-Melanoma is the only melanoma prognostic test shown to be associated with improved patient survival. Now let me take you through execution strategy highlights from the fourth quarter and the fiscal year, and then Frank will provide additional financial highlights before we turn to your questions. Let's start with our core dermatology business, which continues to perform extremely well. For DecisionDx-Melanoma and DecisionDx-SCC combined, test volume was 44,772 in 2023, a 33% increase over 2022. We are very pleased with our volume performance and believe these 2 core dermatology offerings continue to represent a significant growth opportunity. We continue to see overlap between clinicians who order our DecisionDx-Melanoma test and those who adopt DecisionDx-SCC. In fact, during the year ended December 31, 2023, approximately [ 78% ] of all clinicians ordering the DecisionDx-SCC had also ordered our DecisionDx-Melanoma test during the same period. We believe this is evidence of a high unmet clinical need that our tests are designed to address, coupled with the fact that clinicians who diagnose and manage early-stage cutaneous melanoma skin cancer also diagnose other skin cancers like cutaneous squamous cell carcinoma. For DecisionDx-Melanoma, we delivered 33,330 test reports in 2023, a 20% year-over-year increase. Consistent with prior years, our third and fourth quarter test volume reflected normal seasonality. We believe the documented clinical impact our test has in improving outcomes in patients diagnosed with cutaneous melanoma, including improved survival, coupled with our prior commercial expansion investments, have been and continue to be significant drivers of growth. Moving on to our DecisionDx-SCC test. We continue to see a very strong test report volume momentum, with 11,442 test reports delivered in 2023, an increase of 92% compared to 2022. As with our growth in DecisionDx-Melanoma, we believe that our strong growth for DecisionDx-SCC is due in large part to the combination of a high clinical need in the high-risk patient population, coupled with the value that our test provides. We continue to expand on [ embodied ] evidence surrounding the test. For instance, the study published just last month in the Journal of Clinical and Aesthetic Dermatology, found that using DecisionDx-SCC to guide decisions surrounding adjuvant radiation therapy, or ART, could result in significant Medicare health care savings of up to approximately $972 million annually. Data shows that integrating the objective DecisionDx-SCC test into the management of patients diagnosed with high-risk SCC who are ART eligible, can identify those who may safely avoid ART, leading to an improvement not only in health outcomes, but also a reduction in the cost in the Medicare population. I would now like to turn to our TissueCypher tests. I'll remind you that as part of our strategic growth plans, we acquired Cernostics in the TissueCypher test in December of 2021. The adoption of TissueCypher Barretts's Esophagus test has exceeded our expectations to date. As you may recall, this test expanded our estimated in-market commercial U.S. time by $1 billion, and we believe that it contributes to long-term value creation and also positions us to make a meaningful impact on patient care in other areas with unmet clinical needs. We delivered 9,100 TissueCypher test reports in 2023 compared to 2,128 test reports in 2022, which is more than 300% growth. We continue to be extremely pleased with the reception of TissueCypher by the gastroenterology clinician community. And based on current volume growth trends, we plan to expand this commercial team modestly in the second quarter of 2024. As you may recall, we had multiple data announcements during 2023, bringing our total to 14 peer-reviewed publications, demonstrating the ability and performance of our TissueCypher test in risk-stratifying patients with Barrett's Esophagus disease to guide risk-appropriate treatment plan decisions. Turning to our mental health business. We delivered 10,921 IDgenetix test reports in 2023 compared to 3,249 test reports in 2022, which is more than 200% growth. We believe a significant driver of growth is our differentiated test for the treatment of mental health conditions, including identifying drug-drug, drug gene and lifestyle factors to improve medication response and remission rates in a large underpenetrated mental health market. In fact, real-world evidence confirmed the consistent impact of [ Hydrogenics ] medication response and remission rates in patients with major depressive disorder or MDD. Specifically, the study found that real-world patient outcomes were strongly aligned to the results of a previously published randomized controlled trial, which show that patients whose medication management was guided by [ IDgenetix ] were 2.65x more likely to achieve remission of depressive symptoms compared to patients whose medication was not guided by our test. Moving on to our inflammatory disease pipeline initiative to develop a genomic test or a series of tests aimed at predicting response to systemic therapy in patients with moderate to severe atopic dermatitis, psoriasis and related conditions. Last quarter, we shared some early, yet promising, discovery data. The data demonstrated that in patients with moderate to severe atopic dermatitis, we're able to show that using our noninvasive method of tissue sampling, coupled with gene expression [ profile ], can separate out responders and nonresponders. Furthermore, our inflammatory skin disease pipeline test could help distinguish atopic dermatitis, psoriasis and mycosis fungoides skin lesions to help ensure proper therapy selection based upon an individual patient's molecular profile. We expect to provide you with additional development updates in the second half of 2024, with the test targeted for launch for the end of 2025, assuming a positive outcome of our discovery, development and validation efforts. I will now turn the call over to Frank, who will provide details relating to our financial results and outlook.

Thank you, Derek, and good afternoon, everyone. Reiterating Derek's sentiment, we're excited with the strong year we had in 2023 and the momentum we are carrying forward. In the fourth quarter of 2023, we delivered total revenue of $66.1 million, a 72% increase over the fourth quarter of 2022. And we delivered $219.8 million for the full year 2023, a 60% increase over 2022. The increase was driven by higher ASPs and test volume growth. Adjusted revenue, which excludes the effects of revenue adjustments in the current period related to tests delivered in prior periods, was $70.2 million for the quarter and $224.3 million for the full year 2023. For 2024, we anticipate generating total revenue of $235 million to $240 million, driven by further consistent execution on our growth plans. Our gross margin here in the fourth quarter was 77.8% compared to 69.4% in the fourth quarter of 2022, and our gross margin for the full year was 75.4% compared to 70.6% in 2022. Our adjusted gross margin, which excludes the effects of intangible asset amortization related to our acquisitions and excludes the effects of revenue adjustments in the current period associated with test reports delivered in prior periods, was 82.3% for the quarter and 79.9% for the year, compared to 74.6% and 77% for the same periods in 2022. Turning to expenses. Our total operating expenses, including cost of sales for the quarter ended December 31, 2023, were $71.8 million compared to $61.2 million for the prior year and were $287.8 million for the full year compared to $209.9 million for 2022. Sales and marketing expense increased by $27.1 million or 31.2% for the year ended December 31, 2023, compared to the year ended December 31, 2022, primarily attributable to higher personnel costs. General and administrative expenses increased by $10.1 million or 17.9% for the year ended December 31, 2023, compared to the year ended December 31, 2022, primarily attributable to higher personnel costs and higher information technology and software related costs. R&D expense increased by $1.7 million in the fourth quarter and by $8.7 million for the full year 2023 compared to 2022, primarily consisting of higher personnel costs and higher clinical studies expense, partially offset by lower expense from advisory boards and consulting services. Total noncash stock-based compensation expense, which is allocated among cost of sales, R&D expense and SG&A expense, totaled $51.2 million for the year ended December 31, 2023, compared to $36.3 million for the year ended December 31, 2022. We expect material increases in stock-based compensation expense in future periods, attributable to both existing awards outstanding and anticipated additional grants to our current and future employees. We expect to complete an annual grant of equity awards to our employees in March of 2024. Interest income was $10.6 million for the full year 2023 compared to $4 million in 2022, primarily a result of higher interest rates and our purchases of marketable investment securities beginning in the third quarter of 2022. Our net loss for the fourth quarter of 2023 was $2.6 million compared to a net loss of $20.6 million for the fourth quarter of 2022. And our net loss for the full year 2023 was $57.5 million compared to a net loss of $67.1 million for 2022. Diluted loss per share for the fourth quarter was $0.10 compared to diluted loss per share of $0.78 in the fourth quarter of 2022. Diluted loss per share for the full year 2023 was $2.14 compared to diluted loss per share of $2.58 for 2022. Adjusted EBITDA for the fourth quarter was $9.4 million compared to negative $10.4 million for the comparable period in 2022, an improvement of $19.8 million. For the full year 2023, adjusted EBITDA was negative $4.4 million compared to negative $42.6 million in 2022, an improvement of $38.2 million. Net cash provided by operating activities was $18.6 million for the fourth quarter, and net cash used in operating activities was $5.6 million for the year ended December 31, 2023. We expect the first quarter of 2024 to be a net operating cash use quarter due to annual cash bonus payments and certain health care benefit payments that are not expected to recur during the remaining 3 quarters of 2024. Net cash used in investing activities was $16.2 million for the 12 months ended December 31, 2023 and consisted primarily of purchases of marketable investment securities of $189.1 million and purchases of property and equipment of $13.6 million, partially offset by the maturity of marketable investable securities of $186.5 million. We've increased our cash position by more than [ $13 million ] in the fourth quarter of 2023 compared to the third quarter of 2023, ending the year with cash, cash equivalents and marketable securities of $243.1 million. In the current high interest rate environment, we believe our strong financial position allows us to continue to invest in our business, execute on our strategic growth plans and maintain our competitive lead. In 2024, we expect our capital allocation priorities to remain consistent. These include the continued assessment and evolution of our commercial team, focused R&D efforts to build evidentiary support and develop tests and as a lesser priority, exploring strategic opportunities in our current therapeutic areas. In conclusion, our 2023 financial and operational results were outstanding. We delivered strong growth in both revenue and test report volume as we continue to execute on our growth initiatives. I'll now turn the call back over to Derek.

Thank you, Frank. We believe our success in 2023 has allowed us to enter 2024 with momentum and the potential to further position the company as an industry leader. I would like to conclude today by thanking our Castle team. Our excellent progress in 2023 is due to their accomplishments and dedication to the patients that we serve. This concludes our remarks. I thank you again for your continued interest in Castle Biosciences. Operator, we are now ready for Q&A.

[Operator Instructions] First person we have online is Kyle Mikson of Canaccord.

Congrats on the quarter. Wanted to start with the '24 guidance and the underlying growth in the dermatologic test business. If you back out SEC revenue in '23, you might have had like $160 million to $170 million in core revenue. If you annualize the sequential growth in the fourth quarter, you got about maybe 17%, 19% annual growth. Do you apply that to the core revenue base there to get you maybe like $200 million in revenue next year? But -- then the guide would imply that the new test like TissueCypher, IDgenetix like don't grow next year or I guess this current year or so. Maybe just talk about what the core growth of the derm tests X SCC looks like this year and if there's anything to be happening in 2024 that causes growth like decelerate a bit to lever levels?

Yes, sure, Kyle. I might need to get with him and write down. I wouldn't [ track ] in your [ math ] there. Yes, you should recall that the 2023 actual results have a full year of SCC revenue included. The 2024 expectation only has this quarter for SCC. We're taking out our SCC test for -- out of that guidance for the rest of the year, Q2, Q3 and Q4. So to apples -- if you want to apples-to-apples the growth, you need to sort of either back out SCC from 2023 or kind of think about what it would look like for '24 just in order to avoid having to reduce or change guidance negatively if SCC is no longer reimbursed, we just -- we take it out for the rest of the year. And that would be -- as we talked about in the past, Kyle, that would be just a terrible outcome for patients. I mean we've already got significant evidence that we've published, showing that ART is widely used. It's really bad for patients. And if you properly use ART only where it's appropriate, our test can save the system of about $900 million a year. So that would be a poor outcome for health care costs and for patients, but we are assuming we don't have that coverage for the rest of the year. The second part, we don't think that TissueCypher or the other tests are not growing. We expect those tests to continue to grow.

Yes. I think that you kind of clarified the -- what's going on -- like the dynamics in the guide, so that was great. Just a follow-up, a simple one, on gross margins. I guess going forward, if we are kind of like taking out SCC for a little while, should we model like a lower gross margin than what we've seen in the past? Because you still have the volume, but like you've had such great, low [ 80s ], gross margins. What's the right way to think about that, going forward? And maybe just related to cash, I mean, could you guys -- did you kind of say you could generate cash this year based on what you've done in the past couple of quarters?

Let me take the first part. As you know better than we do, Kyle, when you're not paid appropriately for a service you provide, it has a negative impact on gross margins. So if we were to not have coverage for one or any of our test, then that would impact that gross margin. With appropriate coverage in place, we think those margins are stable. If you recall, our long-range guidance was gross -- adjusted gross margins, let me -- I should correct that, adjusted gross margins in the 80% range. So those should be stable. This quarter will be a cash-use quarter from operations, I would expect. And then the rest of the year, it will depend on what the reimbursement picture looks like.

We now have Subha Nambi of Guggenheim.

Do you hear me okay?

Yes, we got you.

You guys hear me okay? Awesome. This is [indiscernible]. Can I ask a quick two-parter on TissueCypher? All right. A quick two-parter parter on TissueCypher. Can you hear me?

Yes, we can hear you.

Okay. Got it. Sorry about that. Just a quick two-parter on TissueCypher. You mentioned in your last call that some of the key performance drivers were that newly diagnosed or rescoped patient population of about 400,000 patients. And then secondly, the need for -- the patients in the non-dysplastic group making up about 95% of the overall patient population. I just wanted to clarify, what impact did that have in the fourth quarter? And what are your expectations for both of those drivers, going into 2024?

Yes. So we -- as I think we shared, we think the market there may be a little bit bigger than we had anticipated when we first were looking at TissueCypher. The right population for us to think about there is the surveillance endoscopy, so patients that are having a surveillance endoscopy or an upper GI endoscopy for Barrett's Esophagus. And we've got really good data now that says there are about 417,000 or so of those a year, which is a higher number than we thought. Now the second piece of that -- so that's the total pool. But we're not appropriate -- well, it would not be useful to physicians to test on patients who have that procedure and then come back from pathology with high-grade dysplasia. And that's about 5% or 6% of those cases that are high-grade dysplasia. And the reason is just that at that point, that's going to be concerning enough that the physician is going to want to go ahead to ablate that patient. So you can kind of take -- if you want to use round numbers, take 90% of the [ 417,000 ], and that's the group we think we are appropriate for each year. Now that's more of a -- you would want to think of that as [ more ] of an incidence-type measure because there are certainly more patients than that, that have Barrett's. But if they're not having that surveillance endoscopy, then they're not candidates or we wouldn't be able to test. That's the tissue we test, is the pitch biopsy tissue from the surveillance endoscopy.

Next question comes from Sung Ji Nam of Scotiabank.

Congrats on the year. Maybe starting out with SCC, just kind of -- DecisionDx-SCC. You talked about the overlap with the DecisionDx-Melanoma in terms of -- I think, over 70% of the orders are coming in for both, if there's overlap. Just kind of curious, given that you've had SCC commercially available now over a year, just curious, kind of what you're seeing from the same-store sales, if you will, standpoint, just based on -- with the physicians and their experiences with SCC? Kind of if you're seeing any trends in terms of reordering patterns and things like that?

Sung Ji, Derek here. We hadn't disclosed that in filing today or the press release, as far as I recall. We do expect and did expect early on that clinicians who diagnose a skin cancer of cutaneous melanoma will also be the same medically-oriented dermatologists who will diagnose the skin cancer squamous cell carcinoma. So we assume there'll be significant kind of overlap from a perspective of will this dermatology customer be seeing these kinds of patients. And two, it was also our belief that if these clinicians who adopted or we're using our DecisionDx-Melanoma test appropriately for medical necessary purposes that they would be more open to, I guess, seeing how the use of our test for squamous cell carcinoma would go ahead and fill what we see as a significant unmet need. So the -- what I think we're seeing is the actual experience of our expectation, which is good, by the way. But I think the other aspect here is to say, Why? And the why part to me is that in patients with high-risk squamous cell carcinoma, there's this pinch point here. And as Frank mentioned earlier, 99% of patients that we test today are eligible under our guidelines for adjuvant radiation therapy, or ART. And adjuvant radiation therapy has been recognized as an effective treatment for high-risk patients for, I think, at least 2 or 3 decades. We've published data recently, presented last summer to the Medicare contractors, demonstrating that not only can our tests identify patients who are in this high-risk category, who will have a low risk of progression or a high risk of progression compared to the population-based estimate, but also able to go ahead and demonstrate that we can find people who are eligible for ART, who actually have a very, very [ little luck ] of getting any kind of response. And the benefit to that, of course, is avoidance of radiation complications, the therapy itself. And at least based upon a publication back in January of this year, the use of our test in these ART-eligible patients to help rule out unnecessary intervention probably saved the Medicare Trust Fund north of $900 million, which is a great way to improve health care outcomes by reducing complications with no benefit and, of course, cost extraction.

Got it. And then just on -- just a follow-up on the TissueCypher, obviously, great to see that product outperforming your expectations. Just kind of curious, looking back, what do you think are the key drivers of the outperformance other than that market being actually bigger than you had initially estimated?

You took away one of the drivers, but okay. I think that what we saw during diligence prior to the acquisition was a fairly rapid sort of head nodding, as I would call it, from the gastroenterologists that we contacted during diligence about market interest is what's the clinical unmet need really like. And I think to a [ tea ] there was good recognition saying, "Hey, we have this FDA-approved device, radiofrequency ablation tool or tools that we use in people with high-risk Barrett's disease on pathology, high risk on pathology, and this tool has shown to be very, very effective at really stopping progression to esophageal cancer in it's tracks." The problem is that we also recognize that because we don't intervene with people with non-dysplastic Barrett's Esophagus disease, which then ends up being the larger population of people who actually progress to cancer because we're just surveying them. And so the ability of our test to say, "Hey, you can take a non-dysplastic Barrett's disease, which has a lower chance as a population of progressing compared to a high risk on pathology Barrett's patient," and we can demonstrate with our test that the risk of progression is actually higher or the same as -- depending on what study one looks at as a high-risk pathology patient that. Therefore, the use of intervention like RFA ablation, would be a fantastic way to basically help those patients like they're progressing. And so that was a fairly easy concept to present to gastroenterologists during diligence. And I think besides sort of undersizing the market opportunity during diligence a couple of years ago, and that obviously has an impact in terms of volume, the other area is that the assumptions we made in terms of physician interest in really getting to a better treatment plan for their patients is being realized.

We now have the next question from Mason Carrico Stephens, Inc.

This is Jacob on for Mason. Just one on SCC real quick. So on the potential of updated NCCN guidelines, including DecisionDx-SCC, do you perhaps have any insight into what level of inclusion or what the language would have to look like in NCCN guidelines to meet the threshold of the Novitas draft LCD, based on how it's currently written? Or maybe what are the different ways that SCC could be included in the updated guideline, but for whatever reason, still not be covered?

So we don't have any insight in terms of how that might be considered or discussed. I can tell you what we think is probably appropriate maybe. So within the current squamous cell carcinoma NCCN guidelines, there is a table that sort of defines patients in the categories of risk. Having one or more of these clinical pathologic factors puts you in kind of the high-risk patient population, and having a subset or multiple factors puts you in what they call the very high-risk patient population. Both of those populations are eligible for adjuvant radiation therapy. We would think it's probably appropriate, given how it's structured in the NCCN guidelines, to basically add our DecisionDx-SCC test result as a molecular factor in that sort of clinical pathologic and now molecular factor table, putting people in the categories of high-risk or very high-risk disease. That, to me, makes the most logical sense, under the current structure. So that might be an expectation we would kind of have because it seems to be the easiest way to have a clinician contemplate the value of our tests. The second question is, if the Novitas LCD finalizes as is, what does that mean, I guess, was your question, if I got it right, Jacob. I would think that, one, nobody has any experience with this Novitas LCD to see how different inclusions are approached with different tests. But I assume if it was included somewhere like I just described, then that should be considered a covered test, at least based upon -- I don't want to say just natural common logic there, but that seems to make the most sense.

Yes, that makes sense, and that's helpful. And then one follow-up here on your pipeline atopic dermatitis test. You mentioned it on the call that you plan on launching it by the end of 2025 and maybe some additional data this year. But just in terms of reimbursement for that test, is there a foundational LCD in place that you could obtain Medicare coverage for? Or would it have to go through the whole submission draft to final LCD process?

That's an excellent question. So there is no foundational LCD or even test-specific LCD covering these kinds of tests that could help guide which systemic therapy one should use for psoriasis or atopic dermatitis patients. So that doesn't exist at all to date. However, it's also important to understand that we think that the inflammatory skin disease test is likely to be a younger population anyway. So you're looking at different reimbursement opportunities besides sort of Medicare playing an important role relative to, say, melanoma or skin cancer.

We now have Catherine Schulte of Baird.

This is Tom Peterson on for Catherine. And congrats on a solid quarter and solid 2023. I guess maybe one for Frank to start. How should we be thinking about OpEx growth in 2024? And I heard your comments on sort of the cash flow from operations cadence here in '24. But given the reimbursement outlook, I guess, how confident are you in achieving the positive cash from operations target in 2025 that you had previously set?

Thanks for the question. As we said before, we still -- we haven't changed or amended that long-range target guidance that we gave, I guess, year and half ago, maybe at this point. So we're still on track for that. I think you'll see OpEx growth will be lower than revenue growth. But like other companies, we continue to see pressure on costs, and inflation is real. So it impacts every aspect of your business at this point. So there's growth to grow the business. There's growth as a result of inflation in the economy. And then there's also -- we're working hard to be financially disciplined to make sure we manage to that. So still maintaining the guidance we gave and feel good about getting there.

We now have Thomas Flaten of Lake Street.

Congrats on the quarter. Just to clarify, Frank, just it was implied in an answer you gave earlier, but if Novitas finalizes as it is, you will continue accepting SCC claims, even though you're not going to get paid on them, is that a fair assumption?

We haven't -- that's a bigger question, Thomas. You stop making a test available if it's not being appropriately reimbursed. I don't know if we've made that decision. I think that -- there's a lot that goes into that. It's a valuable test. It's important for patients. We're seeing every day with literally thousands of doctors how it's changing the way they're treating their patients. And you and I have talked about it. My dad is 85. And if he had a small squamous cancer on his head, and just because it was a little bit over a centimeter, and the doctor wants to do head, above the shoulders, radiation therapy, that's awfully tough. I mean that's that would be tough to put a patient through. So we haven't made any decisions about keeping or dropping availability of the test, but we would have to wrestle with that at some point if it got there, I guess.

Got it. And you mentioned expanding the TissueCypher sales force. And I think last time you mentioned specific numbers, 24 reps. Is that going up to 30? Can you give us some quantify -- can you quantify that? And then as a follow-on to that, any changes you're making to the IDgenetix sales team?

[ I don't think ] we've discussed the numbers we're targeting growth. The plan we're working towards is an early second quarter expansion plan. But I don't think we've disclosed numbers that we can...

And then on IDgenetix, Thomas, we're keeping an eye on that one. As you saw from the report we're getting, we're very pleased with the traction we're getting there. Again, it's just -- it's such a -- that test makes such a difference to the physicians who are ordering in their patients. And we really would like to increase the size of the [ megaphone ] for that. It's a great test, and it's it gets good traction. But we're also -- reiterating an earlier answer, we're also being very careful on operating expenses and trying to balance that. So we're likely not seeing the volume growth that we could possibly see there, but we're making sure that we also don't have a big increase in cash usage.

We now have Mark Massaro of BTIG.

This is Vivian in for Mark. I'll maybe just keep it to one. So on the recent publication in [ DDM ], also recognizing that you did publish a study on SCC fairly recently earlier this year, what additional evidence of readouts should we be expecting on the SCC front?

So we had discussed, I guess, back in the summertime that we had presented data that have been published in abstract form to both Medicare contractors that were reviewing our SCC test. One piece of data was a sort of request, I guess, you would say, from the MolDX program to really have a more clearer understanding of the independent value that our SCC test adds on top of NCCN or [ BDOH ] staging systems. And so a publication that focuses on that has been accepted, and it shall come out shortly. So that's one significant piece of data that we think answers a significant portion, if not all, we're [ thinking ] the all is too aggressive there, of the Palmetto-MolDX questions, I guess, you could call those, in the draft LCD. The other article, which has also been accepted, and we presented this data last summer or last fall, certainly, to both Medicare and also clinicians; focuses on the newer data of our test to take patients who are eligible for adjuvant radiation therapy, identify the proportion of patients who get a really strong benefit from that intervention and more importantly, perhaps from a health care system and patient care perspective, identify the majority of patients who appear to get no benefit from adjuvant radiation therapy. And as such, that allows a clinician and a patient in a shared decision-making process to say, "Hey, you are eligible for ART based upon the DecisionDx-SCC test result; however," say it was a low-risk Class 1 test result, "you have a low likelihood of progressing. So it's not zero, but it's a lower likelihood than I thought. You would be at risk for relative to your clinical and pathological factors. And by the way, a Class 1 test result in this test from Castle also demonstrates that you have a very low likelihood of actually receiving any benefit from adjuvant radiation therapy." So that study has also been accepted and again, should be out shortly. So I think those are some noteworthy near-term publication milestones that are not only important for the clinical use of our test with clinicians thinking through "where do I use this test, how do we -- how to get value out of it," but also, hopefully, for both of the Medicare contractors.

We have no further questions, so I would like to hand back to CEO, Derek, for any final remarks.

This concludes our fourth quarter and full year 2023 earnings call. We thank you again for joining us today and for your continued interest in Castle Biosciences.

Thank you. This concludes our fourth quarter, full-year earnings call. You may now disconnect your lines. And please, enjoy the rest of your day.