Castle's DecisionDx-SCC Provides Clarity in Assessing Risk SCC Spread in Challenging Staging Situations


DecisionDx-SCC can significantly stratify the risk of metastasis in high-risk cSCC patients with an ambiguous tumor differentiation status.

Castle Biosciences, Inc.’s DecisionDx-SCC test provides objective, independent and significant risk-stratification for cutaneous squamous cell carcinoma (cSCC) tumors with uncertainty in differentiation status. 

The data were shared in an oral presentation given at the American Society of Dermatopathology (ASDP) 59th Annual Meeting by Sarah Estrada, M.D., dermatopathologist with Affiliated Dermatology in Scottsdale, Arizona.

Overall, these data demonstrate how DecisionDx-SCC can significantly stratify the risk of metastasis in high-risk cSCC patients with an ambiguous tumor differentiation status. Additionally, the study suggests that incorporating the test’s results into clinical cSCC risk assessments could improve risk-stratification and enhance current patient management decisions to improve patient outcomes.

Subjective pathology variability in the histologic grading of cSCC tumors is an important clinical issue, particularly when comparing moderately differentiated tumors. Poor differentiation has been shown to be an independent risk factor associated with poor patient outcomes. However, there is a lack of consistency in differentiation assessment which can adversely impact the value of differentiation as a prognostic factor. 

In fact, the two most widely used cSCC staging systems, American Joint Committee on Cancer Staging Manual Eighth Edition (AJCC8) and Brigham and Women’s Hospital (BWH), vary on their inclusion of poor differentiation as a risk factor for staging; BWH includes it, while AJCC8 does not.

“A single clinicopathologic risk factor, including a cSCC tumor’s differentiation status, can affect staging and thereby escalate or deescalate patient treatment plans,” commented Estrada. “Objective risk-stratification that is independent of clinicopathologic factors and staging, as provided by DecisionDx-SCC test results, can identify high-risk cSCC lesions and provide clarity in challenging staging situations.”

The presentation, titled “Incorporating the 40-GEP test for poorly differentiated cutaneous squamous cell carcinoma (cSCC) tumors mitigates risk assessment uncertainty from histologic grading,” describes the results of a study involving a cohort of 420 high-risk cSCC patients divided into either moderately or poorly differentiated statuses, based on their pathology report and review by an independent dermatopathologist.

A sub-cohort of 171 tumors with differentiation uncertainty was then staged using BWH criteria. The differentiation status of the tumors in this “differentiation uncertainty cohort” was then manually changed so that poorly differentiated was changed to moderately differentiated and vice versa, and changes to BWH staging were analyzed.

The study data showed that:

  • For 40% of patients in the sub-cohort, the BWH stage changed based upon the alteration of differentiation status, which could impact treatment decisions.
  • DecisionDx-SCC independently and significantly stratified the sub-cohort according to metastatic risk; patients with a low-risk (Class 1) result had a statistically significant higher three-year metastasis free survival than both moderate-risk (Class 2A) and high-risk (Class 2B) patients (90.1% vs. 78.6% and 62.5%, respectively; p=0.02).

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