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Independent Data Presented at Society for Surgical Oncology Conference Demonstrates DecisionDx®-Melanoma Outperforms T-Stage in Identifying Patients at Low Risk for Sentinel Node Positivity

FRIENDSWOOD, Texas–(BUSINESS WIRE)–Castle Biosciences, Inc. (Nasdaq: CSTL), a company that improves health through innovative tests that guide patient care, today announced new data further demonstrating the performance of DecisionDx®-Melanoma and i31-SLNB to provide a better prediction of the risk of sentinel lymph node (SLN) positivity, compared to the use of T stage factors alone, in patients with cutaneous melanoma. The data will be shared in a poster presentation at the Society of Surgical Oncology (SSO) 2022 International Conference on Surgical Cancer Care, to be held in Dallas and virtually, March 9-12, 2022.

“While the sentinel lymph node biopsy (SLNB) surgical procedure is a common technique for determining possible tumor metastasis, our current biopsy criteria may overestimate a person’s risk of having a positive lymph node. This means that we can do more sentinel node biopsies than necessary; and while we certainly don’t want to miss lymph node metastases, we also don’t want to perform procedures unnecessarily,” said study author Joseph Bennett. , MD, Chief of Surgical Oncology and Director of the Multidisciplinary Melanoma and Sarcoma Clinic at ChristianaCare Helen F. Graham Cancer Center & Research Institute, Newark, Delaware.”The study data shows that DecisionDx-Melanoma has the ability to more accurately stratify risk for patients with melanoma, which can help guide risk-focused discussions about ant patients who should be offered the GLS procedure and who may opt out, based on their personal biorisk of positive GLS. We expect that by using DecisionDx-Melanoma and i31-SLNB in ​​addition to standard criteria, we can avoid doing SLNB procedures in many low-risk patients without missing melanoma metastases.

The poster, titled “Integrating the 31-Gene Expression Profile Test with Clinical and Pathologic Features Can Provide Personalized Accuracy Estimates for Sentinel Lymph Node Positivity”, evaluated the performance of the proprietary algorithm i31-SLNB from DecisionDx-Melanoma to predict the risk of SLNB positivity in 156 melanoma patients with known SLN outcomes at ChristianaCare Helen F. Graham Cancer Center & Research Institute.

In the study, the DecisionDx-Melanoma test outperformed T-stage in identifying patients with low-risk tumors who might forgo SLNB, with an area under the curve (AUC) of 0.89 versus 0.78 for T-stage in patients with T1-T2 tumors, indicating that DecisionDx-Melanoma provides improved predictions over those of the T-stage system. Additionally, the test accurately identified all patients with T1-T2 tumors who were at low risk (

“The study results demonstrate that DecisionDx-Melanoma, with its proprietary i31-SLNB algorithm, can enable more accurate and personalized management of melanoma patients and improve patient selection for SLNB surgery, potentially enabling a reduction in unnecessary health care costs. said Derek Maetzold, President and CEO of Castle Biosciences.

About DecisionDx-Melanoma

DecisionDx®-Melanoma is a gene expression profile test that uses an individual patient’s tumor biology to predict the individual risk of metastasis or recurrence of cutaneous melanoma, as well as the risk of sentinel lymph node positivity, independent of traditional staging factors, and has been studied in over 6,000 patient samples. Using tissue from primary melanoma, the test measures the expression of 31 genes. The test has been validated in four archived recurrence risk studies involving 901 patients and six prospective recurrence risk studies involving more than 1,600 patients. The impact on patient management plans for one in two patients tested has been demonstrated in four multicenter and single-center studies including more than 560 patients. The consistent performance and accuracy demonstrated in these studies provides confidence in disease management plans that incorporate DecisionDx-Melanoma test results. To predict the risk of recurrence and the likelihood of sentinel node positivity, the Company uses its proprietary algorithms, i31-ROR and i31-SLNB, to produce an integrated test result. Through December 31, 2021, DecisionDx-Melanoma has been ordered 90,154 times for use in patients with cutaneous melanoma.

More information about the test and the disease can be found at www.CastleTestInfo.com.

About Castle Biosciences

Castle Biosciences (Nasdaq: CSTL) is a leading diagnostics company that improves health through innovative tests that guide patient care. The Company aims to transform disease management by putting people first: patients, clinicians, employees and investors.

Castle’s current portfolio includes tests for skin cancers, uveal melanoma and Barrett’s esophagus. Additionally, the Company has active research and development programs for testing in other diseases of high clinical need, including its test in development to predict systemic therapeutic response in patients with moderate to severe psoriasis, atopic dermatitis and related conditions. To learn more, visit www.CastleBiosciences.com and connect with us on LinkedIn, Facebook, Twitter and Instagram.

DecisionDx-Melanoma, DecisionDx-CMSeq, DecisionDx-SCC, myPath Melanoma, DecisionDx DiffDx-Melanoma, DecisionDx-UM, DecisionDx-PRAME, DecisionDx-UMSeq and TissueCypher are registered trademarks of Castle Biosciences, Inc.

Forward-looking statements

This press release contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended, which are subject to the “sphere of security” created by these sections. These forward-looking statements include, but are not limited to, statements regarding DecisionDx-Melanoma’s ability to more accurately stratify risk for patients with melanoma and to guide risk-aligned discussions with patients regarding the SLNB procedure; the overall ability of DecisionDx-Melanoma to enable more accurate and personalized management of patients with melanoma and improve patient selection for SLNB surgery; and the potential for reduced healthcare costs resulting from the DecisionDx-Melanoma test result. The words “anticipate”, “believe”, “estimate”, “expect”, “intend”, “may”, “plan”, “project”, “will”, “would” and Similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain such identifying words. We may not actually achieve the plans, intentions or expectations disclosed in our forward-looking statements, and you should not place undue reliance on our forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in the forward-looking statements we make. These forward-looking statements involve risks and uncertainties that could cause our actual results to differ materially from those in the forward-looking statements, including, without limitation, the effects of the COVID-19 pandemic on our business and efforts. to cope with its impact. about our company, the results and conclusions of subsequent studies may contradict the results and conclusions of prior studies, including with respect to the discussion of DecisionDx-Melanoma in this press release, the actual application of our tests to patients may not provide the above benefits observed in the retrospective study, and the risks set forth under “Risk Factors” in our Annual Report on Form 10-K for the twelve months ended December 31, 2021, and in our other documents filed with the SEC. Forward-looking statements speak only as of the date they are made, and we assume no obligation to update forward-looking statements except as required by law.