Castle Biosciences DecisionDx-SCC can help identify cutaneous squamous cell carcinoma (SCC) patients who will benefit from adjuvant radiation therapy (ART), a new study in Future Oncology confirms.
This is the second study to demonstrate the ability of the test to identify patients who are more or less likely to benefit from ART, confirmed in an independent cohort of high-risk cutaneous SCC patients.
DecisionDx-SCC is a 40-gene expression profile test that uses an individual patient’s tumor biology to stratify risk of metastasis in patients with cutaneous squamous cell carcinoma who have one or more NCCN high-risk factors. The test result, in which patients are stratified into a Class 1 (low), Class 2A (higher) or Class 2B (highest) risk category, predicts individual metastatic risk to inform risk-appropriate management and guide decision-making regarding the use of adjuvant radiation therapy.
In the study, a novel, independent cohort of patients with high-risk SCC tumors (399 patients; 423 tumors) from two academic centers were tested using DecisionDx-SCC and analyzed for five-year metastasis-free survival and projected time to metastasis. Samples were controlled for bias by clinicopathologically matching ART-treated and untreated patients.
A comparison of the new study and a report by Arron et al.1 demonstrated similar results:
Both studies showed that patients with DecisionDx-SCC Class 2B (highest metastatic risk) test results who were treated with ART had a 50% decrease in metastatic disease progression, on average, and a significant deceleration of disease progression compared to patients who did not receive ART.
Both studies reported no difference in disease progression rates when comparing ART-treated and untreated patients with DecisionDx-SCC Class 1 (lowest metastatic risk) test results, suggesting these patients may consider deferring treatment due to low metastatic risk and a low likelihood of benefitting from treatment. The majority of patients had Class 1 results, confirming the significance of clinical utility in ruling out ART in these patients.
Additionally, both studies observed a lack of ART-related benefit for patients with Class 2A (higher metastatic risk) test results, despite having an intermediate-level risk of metastasis compared to patients with Class 1 and Class 2B test results. This suggests that a specific pattern of gene expression captured uniquely by a DecisionDx-SCC Class 2B result may be driving the identification of the benefit from ART.
“Some patients with high-risk SCC are eligible for adjuvant radiation therapy once their primary tumor has been removed; however, determining which patients should seek treatment is complicated and involves weighing numerous pros and cons against the risk of the patient’s cancer returning,” says study author Emily S. Ruiz, MD, a dermatologist and Mohs micrographic surgeon at Brigham and Women’s Hospital and an Associate Professor of Dermatology at Harvard Medical School in Boston, MA, in a news release “In this study, we were successful in validating, in an independent SCC patient cohort, that DecisionDx-SCC can objectively inform these challenging decisions by identifying patients for whom ART would be beneficial, as well as those who may be best served by avoiding it.”
“This marks the sixth study since the start of 2024 demonstrating the value of DecisionDx-SCC test results in improving risk-aligned patient care through precise, tumor-biology-based risk stratification,” adds Derek Maetzold, president and chief executive officer of Castle Biosciences. “The more than 20 peer-reviewed papers published since the launch of our test four years ago speaks to the breadth of evidence supporting the test’s validity, as well as its ability to improve upon clinicopathologic-based staging systems to drive optimized decision-making regarding appropriate treatment pathways for patients with high-risk SCC.”
References:
- Arron ST, Cañueto J, Siegel J, et al. Association of a 40-gene expression profile with risk of metastatic disease progression of cutaneous squamous cell carcinoma (cSCC) and specification of benefit of adjuvant radiation therapy. IJROBP. 2024. doi: https://doi.org/10.1016/j.ijrobp.2024.05.022
