Avelumab treatment for patients with metastatic Merkel cell carcinoma can be safely stopped after 1 year and a PET/CT–confirmed complete response

Abstract

AbstractBackgroundImmune checkpoint inhibitor treatment of patients with metastatic Merkel cell carcinoma (mMCC) has shown high response rates, ranging from 33% to 73%. The ideal duration of treatment, however, is currently unknown. The aim of this study was to evaluate if avelumab treatment for mMCC can be safely stopped after 1 year of treatment and a complete response (CR) confirmed by fluorodeoxyglucose positron emission tomography/computed tomography (FDG‐PET/CT) imaging.MethodsPatients who received more than one dose of avelumab treatment for mMCC between November 2017 and February 2022 were included in this study. Treatment was discontinued in case of a FDG‐PET/CT confirmed CR after 1 year (26 cycles) of avelumab or a CR and unacceptable toxicity earlier. The primary end point was recurrence‐free survival (RFS).ResultsSixty‐five patients were included: 25 (38%) had a FDG‐PET/CT–confirmed CR at discontinuation of avelumab. In those 25 patients, reasons for discontinuation of treatment were completion of 1 year of treatment in 13 (52%), toxicity in five (20%), and patient preference in seven (28%). Median duration of treatment in this group was 11 months (interquartile range, 6.1–11.7). Median follow‐up was 27 months (interquartile range, 15.8–33.8). The 12‐month RFS was 88% (95% CI, 0.74–1) and median RFS was not reached. Two patients (8%) had a recurrence at 4 and 7 months after discontinuation of treatment.ConclusionsPatients with mMCC who acquire a CR on PET/CT imaging appear to have durable responses after discontinuation of treatment after 1 year.