May 07, 2019

Castle Biosciences’ Cutaneous Squamous Cell Carcinoma Prognostic Test Development Update Presented at the American College of Mohs Surgery Annual Meeting

Also presented were results from a meta-analysis of DecisionDx-Melanoma in 1,479 patients which provides the highest level of evidence (1A) as an independent, significant predictor of risk in cutaneous melanoma

Friendswood, TX – May 7, 2019 – Castle Biosciences, Inc., a skin cancer diagnostics company providing personalized genomic information to improve cancer management decisions, today announced two presentations at the 2019 American College of Mohs Surgery (ACMS) Annual Meeting held in Baltimore from May 2-5.

Progress in the development of a prognostic gene expression profile test in cutaneous squamous cell carcinoma (cSCC) was highlighted in an oral presentation. The total number of deaths from cSCC, one of the most common cancers in the U.S., is approaching or surpassing that from melanoma. Many patients with cSCC will have a favorable prognosis, but 25-40% of high-risk subsets will experience metastasis or develop recurrences. Current cSCC staging systems are evolving but more accurate methods of risk prediction are needed to appropriately direct workup and treatment. The goal of this development program is to identify and validate a clinical test that improves upon existing clinicopathologic staging systems to identify patients who have a high risk for regional/distant metastasis and enable more informed clinical management decisions.

In an ongoing development study, primary cSCC specimens with associated clinical outcome data were accrued from 18 centers. The discovery phase of the program included determining genes identified for their expression in recurrent and non-recurrent tumors. Researchers successfully identified genes that exhibited significant differential expression in cSCC samples from patients who experienced a recurrence, including several specific to regional/distant metastasis. In an archival training cohort of 122 patients, gene expression data from 140 candidate genes were used to identify a preliminary gene set and predictive algorithm.

To assess the predictive value of this assay, Kaplan-Meier survival analysis was performed in an independent validation cohort of 107 patients. Results from the analysis support the predictive value of the test to identify two groups of patients with significantly different risk for regional/distant metastasis (p<0.0001). The positive predictive value of the test in this preliminary validation study was 60%, which compares favorably to the performance of current staging systems in this cohort.

Based on these preliminary validation results, an expanded validation program for the cSCC prognostic test is now underway, including additional archival studies and a prospective validation study.

“The continued progress toward validation of this prognostic test for cSCC demonstrates that improvements in risk identification based on tumor biology are feasible,” said Sarah T. Arron, M.D., Ph.D., University of California San Francisco and the San Francisco VA Health System, an investigator in the study. “Clinical use of a validated prognostic test such as this could help inform clinical decisions on staging and adjuvant therapy, and improve upon currently used staging systems.”

Second study presented at ACMS

A second study presented as a poster at ACMS highlighted results from a meta-analysis evaluating the performance of the DecisionDx®-Melanoma gene expression profile test in four unique, independent patient cohorts.

Results from this meta-analysis with 1,479 patients from four independent cohorts confirm that the DecisionDx-Melanoma test is a significant, independent predictor of recurrence and metastasis in patients with Stage I-III melanoma. Patients identified as highest risk (Class 2B) by the DecisionDx-Melanoma test were 2.9 times more likely to experience recurrence than those identified as lowest risk (Class 1A, p<0.0001), independent of other clinicopathologic features. The meta-analysis, a statistical method considered to be among the highest level of evidence (Level 1A) for prognostic tests, supports the use of the DecisionDx-Melanoma gene expression profile test to inform patient management decisions.

About Cutaneous Squamous Cell Carcinoma

Cutaneous squamous cell carcinoma (cSCC), a non-melanoma skin cancer, is one of the most common cancers. Approximately 200,000 patients per year are diagnosed with cSCC with high-risk features. Most patients have a favorable prognosis, but a subset of patients will develop metastasis and up to 15,000 patients each year die from their disease. As current staging parameters have a low positive predictive value, many more patients are considered high risk than actually develop metastatic disease. Conversely, many patients who develop metastatic disease are misidentified as low risk. This may lead to over and undertreatment of a substantial number of cSCC patients. To address this clinical need, Castle Biosciences is developing a gene expression profile test designed to improve upon current staging systems and identify patients with cSCC at high risk for metastasis or recurrence, in order to enable more informed clinical decisions regarding adjuvant therapy and other management options.

About DecisionDx-Melanoma

DecisionDx-Melanoma is a gene expression profile test that uses an individual patient’s tumor biology to predict individual risk of cutaneous melanoma metastasis or recurrence, as well as sentinel lymph node positivity, independent of traditional staging factors, and has been studied in more than 2,900 patients. Using tissue from the primary melanoma, the test measures the expression of 31 genes. The test has been validated in three multicenter studies that have included 690 patients and have demonstrated consistent results. Performance has also been confirmed in five prospective studies including more than 780 patients. The consistent high performance and accuracy demonstrated in these studies provides confidence in disease management plans that incorporate DecisionDx-Melanoma test results.

Prediction of the likelihood of sentinel lymph node positivity has also been validated in two prospective multicenter study cohorts that included over 1,400 patients. Impact on patient management plans for one of every two patients tested has been demonstrated in multicenter and single-center studies. More information about the test and disease can be found at

About Castle Biosciences
Castle Biosciences is a skin cancer diagnostics company dedicated to helping patients and their physicians make more informed decisions about treatment and follow-up care based on the individual molecular signature of the patient’s tumor. The Company currently offers tests for patients with cutaneous melanoma (DecisionDx®-Melanoma, DecisionDx®-CMSeq; and uveal melanoma (DecisionDx®-UM, DecisionDx®-PRAME and DecisionDx®-UMSeq;, with programs in development for other underserved cancers, the most advanced of which is focused on patients with cutaneous squamous cell carcinoma. Castle Biosciences is based in Friendswood, Texas (Houston), and has laboratory operations in Phoenix, Arizona. More information can be found at

DecisionDx-Melanoma, DecisionDx-CMSeq, DecisionDx-UM, DecisionDx-PRAME and DecisionDx-UMSeq are the trademarks of Castle Biosciences, Inc. Any other trademarks are the property of their respective owners.



Derek Maetzold, President and CEO