Early Tumor Size Reduction of at least 10% at the First Follow-Up Computed Tomography Can Predict Survival in the Setting of Advanced Melanoma and Immunotherapy.

ABSTRACT

RATIONALE AND OBJECTIVES: Early tumor size reduction (TSR) has been explored as a prognostic factor for survival in patients with advanced melanoma in clinical trials. The purpose of this analysis is to validate, in a routine clinical milieu, the predictive capacity of TSR by 10% for overall survival (OS) and progression-free survival (PFS) and to compare its predictive performance with the RECIST 1.1 criteria. MATERIALS AND METHODS: This retrospective study was approved by the local ethics committee. A total of 152 patients with both CT before immunotherapy initiation and at first response evaluation after immunotherapy initiation were included. Prior to statistical analysis, treatment response was trichotomized as follows Complete response and/or partial response, stable disease and progressive disease. Furthermore, response was dichotomized regarding TSR (TSR ≥ 10% and TSR < 10%). Kaplan-Meier survival estimates, Cox regression and Harrel's concordance index (C-index) were computed for prediction of overall survival and progression-free survival. RESULTS: Tumor size reduction by at least 10% significantly differentiated between patients with increased survival from the ones with decreased survival (median OS TSR ≥ 10% 2137 days vs. TSR < 10% 263 days) (p < 0.001) (median PFS TSR ≥ 10% 590 days vs. TSR < 10% 11 days) (p < 0.001). RECIST 1.1. criteria had a slightly higher C-index for overall survival reflecting a slight superior predictive capacity (RECIST 0.69 vs TSR 0.64) but a similar predictive capacity regarding progression-free survival (both 0. 63). CONCLUSION: Early tumor size reduction serves as a simple-to-use metric which can be implemented on the first follow-up CT. Tumor size reduction by at least 10% can be considered an additional biomarker predictive of overall survival and progression-free survival in routine clinical care and not only in the context of clinical trials in patients with advanced melanoma undergoing immunotherapy. Nevertheless, RECIST-based criteria should remain the main tool of treatment response assessment until results of prospective studies validating the TSR method are available.