Inconsistent Associations Between Risk Factor Profiles and Adjuvant Radiation Therapy (ART) Treatment in Patients with Cutaneous Squamous Cell Carcinoma and Utility of the 40-Gene Expression Profile to Refine ART Guidance

INTRODUCTION

National Comprehensive Cancer Network (NCCN) recommendations for adjuvant radiation therapy (ART) use are similar for High Risk and Very High Risk cutaneous squamous cell carcinoma (cSCC) with negative post-surgical margins. Although studies report reductions in disease progression following ART treatment, ART use is likely inconsistent when guided by available risk factors. This study evaluated the association of ART with clinical risk factors in ART-treated and untreated patients and showed the clinical utility of the 40-gene expression profile (40-GEP) for guiding ART.

METHODS

A multicenter study of 954 patients was conducted with institutional review board (IRB) approval. The 40-GEP test was performed using primary tumor tissue from patients with either a minimum of 3 years of follow-up or a documented regional or distant metastasis. Unsupervised hierarchical cluster analysis identified patterns of clinical risk factors for ART-treated patients, then identified untreated patients with matching risk factor profiles. Results were cross-referenced to 40-GEP test results to determine utility of the test to guide ART.

RESULTS

Analysis demonstrated inconsistent implementation of ART for eligible patients. Cluster analysis identified four patient profiles based on clusters of risk factors and, notably, matching profiles in ART-treated and untreated patients. Further, the analysis identified patients who received but could have deferred ART on the basis of 40-GEP test result and biologically low risk of metastasis, and untreated patients who likely would have benefitted from ART on the basis of their 40-GEP test result.

CONCLUSIONS

ART guidance is not determined by the presence of specific clinicopathologic factors, with treated and untreated patients sharing the same risk factor profiles. cSCC risk determination based on NCCN recommendations for clinical factor assessment results in inconsistent use of ART. Including tumor biology-based prognostic information from the 40-GEP refines risk and identifies patients who are most appropriate and likely to benefit from ART, and those that can consider deferring ART.

Integrating the 40-Gene Expression Profile (40-GEP) Test Improves Metastatic Risk-Stratification Within Clinically Relevant Subgroups of High-Risk Cutaneous Squamous Cell Carcinoma (cSCC) Patients

INTRODUCTION

The validated 40-gene expression profile (40-GEP) test independently stratifies risk of regional or distant metastasis for cutaneous squamous cell carcinoma (cSCC) tumors with high-risk clinicopathologic features. This study evaluated the stratification of risk by the 40-GEP test in a large cohort of tumors with one or more high-risk factors and in clinically relevant subgroups, including tumors within National Comprehensive Cancer Network (NCCN) high- and very-high-risk groups, lower-stage BWH T1 and T2a tumors, and patients > 65 years old.

METHODS

This multicenter (n = 58) performance study of the 40-GEP included 897 patients. Kaplan-Meier analyses were performed to assess risk stratification profiles for 40-GEP Class 1 (low), Class 2A (higher) and Class 2B (highest) risk groups, while nested Cox regression models were used to compare risk prediction of clinicopathologic risk classification systems versus risk classification systems in combination with 40-GEP.

RESULTS

Patients classified as 40-GEP Class 1, Class 2A, or Class 2B had significantly different metastatic risk profiles (p < 0.0001). Integrating 40-GEP results into models with individual clinicopathologic risk factors or risk classification systems (Brigham and Women's Hospital, American Joint Committee on Cancer Staging Manual, 8th Edition) and NCCN demonstrated significant improvement in accuracy for prediction of metastatic events (ANOVA for model deviance, p < 0.0001 for all models).

CONCLUSION

The 40-GEP test demonstrates accurate, independent, clinically actionable stratification of metastatic risk and improves predictive accuracy when integrated into risk classification systems. The improved accuracy of risk assessment when including tumor biology via the 40-GEP test ensures more risk-aligned, personalized patient management decisions.

Integrating 40-GEP Testing to Improve Clinical Recommendations for Adjuvant Radiation for Cutaneous Squamous Cell Carcinoma: Multidisciplinary Consensus Guidelines

Early identification and intervention in patients with cutaneous squamous cell carcinoma (cSCC) who are at high risk for metastasis is important for optimal outcomes. Prognostic tools (e.g., American Joint Committee on Cancer, 8th edition [AJCC-8]) and management guidelines (National Comprehensive Cancer Network® [NCCN]) are useful in helping to identify high-risk patients with cSCC who might benefit from adjuvant therapies, such as radiation and/or immunotherapies; however, traditional staging and management guidelines rely on clinicopathologic risk factors to predict risk, which limits their prognostic accuracy. Gene expression profiling (GEP) is a clinically available, objective metric that can be used in conjunction with traditional clinicopathological staging to help clinicians stratify risk in patients with cSCC. The validated 40-GEP test can accurately classify patients with at least one high-risk feature as being at low (Class 1), higher (Class 2A), or highest (Class 2B) biological risk of nodal or distant metastasis within three years of diagnosis. A multidisciplinary panel comprising radiation oncologists and dermatologists/Mohs micrographic surgeons with expertise in cSCC management convened in June 2023 to discuss the utility of 40-GEP testing in cSCC clinical decision-making in regard to adjuvant radiation therapy (ART). The panel identified gaps in clinical practice in which 40-GEP testing has particular utility: in escalation of care for lower-stage patients with high-risk tumors; in de-escalation of care for patients for whom the risks of ART may outweigh the benefits; and in decision-making regarding elective radiation to the nodal basin. The expert panel developed a risk-based clinical workflow for ART in patients with cSCC, utilizing 40-GEP testing within NCCN management guidelines and AJCC-8 staging.

Using Gene Expression Profiling to Personalize Skin Cancer Management

Risk-stratification of cancer, traditionally performed through staging, directs optimal disease management decisions with the result of improved patient outcomes. Many forms of cutaneous cancer have overall excellent survival rates, but conventional staging methods are imperfect in identifying high-risk patients. Gene expression profiling (GEP) is a clinically available, objective metric that can be used in conjunction with traditional clinicopathological staging to help clinicians stratify risk in patients with skin cancer, even in those who lack traditional risk markers. For patients with melanoma, the 31-GEP test provides personalized prognostic information that can guide risk-appropriate clinical management and surveillance decisions. The i31-GEP integrates 31-GEP results with clinicopathological features to provide a risk of recurrence (i31-GEP for ROR) and likelihood of having a positive sentinel lymph node biopsy (SLNB) (i31-GEP for SLNB) for patients with melanoma. For patients with cutaneous squamous cell carcinoma who have at least one risk factor, the 40-GEP test allows for better risk stratification by identifying the high-risk patients who are most likely to develop metastasis. These tests can be easily integrated into clinical practice to help guide treatment choices.

Clinical Utility of the 40-Gene Expression Profile (40-GEP) Test for Improved Patient Management Decisions and Disease-Related Outcomes when Combined with Current Clinicopathological Risk Factors for Cutaneous Squamous Cell Carcinoma (cSCC): Case Series

Introduction

While improvements have been made to risk assessment of cutaneous squamous cell carcinoma (cSCC) patients, there is a critical need for a uniform and more precise stratification system of their care. To address this unmet clinical need, a prognostic 40-gene expression profile (40-GEP) test has recently been developed and independently validated to show improved stratification of metastatic risk in high-risk cSCC patients compared with current staging systems.

Methods

Two cSCC cases, both male with similar patient profiles and the same staging status across two different staging systems, yet with opposing outcomes, were chosen for retrospective review of their primary biopsy using the 40-GEP test.

Results

Case 1 declined further treatment, even when presented with evidence of a small focus of cSCC found in the last layer of nonmarginal tissue obtained from Mohs micrographic surgery (MMS). Case 1 remained recurrence free, and retrospective analysis of the initial biopsy with the 40-GEP test provided a Class 1 result (low likelihood of metastasis). Case 2, even with subsequent clearing of the primary cSCC with MMS, noted another metastatic cSCC 3 months later. Case 2, after multimodal adjuvant treatments, died due to disease progression. Retrospective analysis of the initial biopsy with the 40-GEP test provided a Class 2B result (high likelihood of metastasis).

Conclusions

The cases discussed highlight the utility in 40-GEP to provide additional information to guide treatment decisions and improve outcomes. Integrating novel molecular prognostication with traditional clinicopathological risk factors can improve stratification of high-risk cSCC patients and may inform selection of risk-appropriate treatment and surveillance strategies.