Castle Biosciences Presents New Data on the Validity and Accuracy of DecisionDx-Melanoma in Patients With T1 Cutaneous Melanoma Tumors at the 19th Annual South Beach Symposium

Castle Biosciences, Inc. (Nasdaq: CSTL), a skin cancer diagnostics company providing personalized genomic information to improve cancer treatment decisions, today announced virtual posters on its three skin cancer gene expression profile tests at the 19th Annual South Beach Symposium, taking place from Feb. 4 – 7, 2021.

DecisionDx®-Melanoma:

DecisionDx-Melanoma is Castle’s 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 (SLN) positivity, independent of traditional staging factors.

Castle Biosciences is highlighting data on DecisionDx-Melanoma with two posters. The first highlights new data and is entitled, “31-Gene expression profiling improves risk stratification in patients with T1 cutaneous melanoma.”

Study methods and findings:

• Nearly 70% of melanomas are diagnosed with tumor thickness that is less than or equal to 1.0 mm (T1 tumors), and recurrence-free survival (RFS) is generally good among these patients. However, up to 15% of patients with T1 tumors may experience a recurrence. Moreover, due to the large number of patients with T1 tumors, 27-30% of melanoma-related deaths occur in patients originally diagnosed with a T1 tumor, suggesting better identification of T1 patients at high risk of recurrence or metastasis is needed.
• DecisionDx-Melanoma is designed to classify a patient’s recurrence risk as low (Class 1: Class 1A lowest) or high (Class 2: Class 2B highest) and has been validated in multiple prospective and retrospective studies.
• Univariate analysis of the study data shows DecisionDx-Melanoma to be a stronger predictor of RFS than SLN status.
• Multivariable analysis shows DecisionDx-Melanoma to be a strong, independent predictor of RFS.
• With Class 2B RFS status similar to SLN positive status, Class 2B patients warrant follow-up strategies similar to SLN positive patients.

The second DecisionDx-Melanoma poster is entitled, “The clinical and financial impact of the 31-gene expression profile testing on sentinel lymph node biopsy patients selection in patients with T1b cutaneous melanoma.”

Study methods and findings:

• DecisionDx-Melanoma identifies patients with T1 tumors who have less than a 5% risk of SLN positivity and who have good survival outcomes. These outcomes suggest that such patients could forego the sentinel lymph node biopsy (SLNB) surgical procedure.
• The authors analyzed all clinical DecisionDx-Melanoma tests that were reported from Jan. 3, 2019 through Sept. 4, 2020. The data showed that 75% of eligible patients with T1b tumors had a Class 1A result and could potentially forego SLNB. The authors estimate that foregoing SLNB in these patients could reduce healthcare expenditures by up to $120 million in SLNB-related costs.

DecisionDx® DiffDx™-Melanoma:

DecisionDx DiffDx-Melanoma is designed to aid dermatopathologists in characterizing difficult-to-diagnose melanocytic lesions.

The virtual poster is entitled, “Development, Validation, and Clinical Utility of the 35-Gene Expression Profile Test for Use as an Adjunctive Melanoma Diagnostic Tool.”

Study methods and findings:

• DecisionDx DiffDx-Melanoma has demonstrated accuracy metrics of: 99.1% sensitivity, 94.3% specificity, 93.6% positive predictive value and 99.2% negative predictive value; the test also provides a modest intermediate-risk zone of 3.6% and a technical success rate of 96.6%.
• Dermatopathologists who used DecisionDx DiffDx-Melanoma to refine their diagnoses in lesions reported increased diagnostic confidence by 51%. Dermatologists used the test result to gauge prognosis, case difficulty, office visit frequency and re-excisions, which were influenced by DecisionDx DiffDx-Melanoma’s result in the appropriate manner in most responses.
• The diagnosis of challenging melanocytic lesions and subsequent clinical management decisions were determined to be influenced by the test in agreement with its result, potentially alleviating uncertainty in difficult-to-diagnose lesions. Therefore, DecisionDx DiffDx-Melanoma could lead to a potential increase in accurate diagnoses and focused reduction of burdensome and unnecessary procedures for cases that receive a benign DecisionDx DiffDx-Melanoma result.

DecisionDx®-SCC:

DecisionDx-SCC is Castle’s prognostic gene expression profile test for patients diagnosed with high-risk cutaneous squamous cell carcinoma (SCC) designed to use a patient’s tumor biology to predict individual risk of metastasis for patients with SCC and one or more risk factors.

The virtual poster is entitled, “Clinical utility of the 40-gene expression profile (40-GEP) for improved patient management decisions and disease related outcomes when combined with current clinicopathological risk factors for cutaneous squamous cell carcinoma (cSCC): Case Series.”

“National guidelines for high-risk SCC patients leave room for subjectivity in assessing which patients warrant additional management,” said study author and assistant professor of clinical dermatology at the Indiana University School of Medicine, Ally-Khan Somani, M.D., Ph.D. “Meanwhile, the incidence of SCC is rising with time, which increases the need for physicians to assess metastatic risk objectively for these patients, so that we can provide care accordingly. We have found that DecisionDx-SCC, by predicting tumor aggressiveness based on its gene expression, may stratify risk when integrated with commonly used staging factors to better inform SCC management decisions.”

Study methods and findings:

• Two SCC cases were presented that highlight DecisionDx-SCC’s utility in stratifying risk in SCC.
  • The cases were very similar at diagnosis, both presenting with a history of immunosuppression along with identical staging (T2a per Brigham and Women’s Hospital staging; T1 per American Joint Committee on Cancer staging), but had divergent outcomes:
    • Case 1 did not recur, despite incomplete resection.
    • Case 2 developed local recurrence and regional metastasis, and died from SCC, despite clear surgical margins, radiation and chemotherapy treatments.
  • Subsequent DecisionDx-SCC test results yielded risk level assignments that correlated with the two patients’ outcomes:
    • Case 1 had a retrospective low-risk (Class 1) DecisionDx-SCC result.
    • Case 2 had a highest-risk (Class 2B) DecisionDx-SCC result.
  • The authors concluded that incorporating DecisionDx-SCC as a prognostic factor with traditional clinicopathological risk factors can improve stratification of high-risk SCC patients with at least one risk factor, thereby informing risk-appropriate management strategies.

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 5,700 patient samples. Using tissue from the primary melanoma, the test measures the expression of 31 genes. The test has been validated in four archival risk of recurrence studies of 901 patients and six prospective risk of recurrence studies including more than 1,600 patients. Prediction of the likelihood of sentinel lymph node positivity has also been validated in two prospective multicenter studies that included more than 3,000 patients. Impact on patient manageme