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

October 3, 2023



Publication Date

October 3, 2023


Zijlker, L. P., Levy, S., Wolters, W., van Thienen, J. V., van Akkooi, A. C. J., & Tesselaar, M. E. T.

Merkelcell.org Summary

The ideal duration for continuing immunotherapy is still being studied. This study assessed 25 patients who stopped avelumab (a type of immunotherapy) after 1 year of treatment (26 infusions) and a PET/CT scan that confirmed a complete response to the treatment. The study found that 88% of these patients remained MCC-free 12 months after stopping treatment, indicating that patients who show a PET/CT-confirmed response to immunotherapy one year after starting may be able to stop treatment quite safely.


Background: Immune 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.

Methods: Patients 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).

Results: Sixty-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.

Conclusions: Patients with mMCC who acquire a CR on PET/CT imaging appear to have durable responses after discontinuation of treatment after 1 year.

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