OBJECTIVES: In this international, single-arm, open-label, multicenter, phase 2 trial (NCT02155647), treatment-naive patients with metastatic Merkel cell carcinoma (MCC) received avelumab 10 mg/kg treatment every 2 weeks with a follow-up of ≥15 months. In this preplanned sub-analysis, a patient-relevant endpoint of health-related quality of life (HRQOL) deterioration-free survival (QFS) was evaluated in relation to the typically used clinical endpoint, progression-free survival (PFS).

METHODS: HRQOL outcomes were assessed using the disease-specific Functional Assessment of Cancer Therapy - Melanoma (FACT-M) and the generic EQ-5D questionnaires. QFS was defined as a definite deterioration in terms of HRQOL, with “deterioration” defined as a patient reaching or exceeding a predefined minimal important difference threshold of deterioration at least once during the study and no further improvement thereafter. QFS was reported as (1) median QFS time in months and (2) QFS rates (ie, percentage of patients who had deteriorated at 6 and 12 months). Median QFS and QFS rates were qualitatively compared with median PFS and PFS rates, respectively.

RESULTS: In 116 patients enrolled in this study, the HRQOL questionnaire compliance rate was over 75% across the study period. Median QFS was longer across all HRQOL scores (range of medians, 4.5-20.9 months) when compared with median PFS (4.1 months; 95% CI: 1.4-6.1 months). Furthermore, QFS rates were consistently higher/better (6-month data: range, 49%-72%; 12-month data: range, 40%-58%) compared with PFS rates of 41% and 31% at 6 and 12 months, respectively.

CONCLUSIONS: These findings show unique, long-term HRQOL data for a rare condition, metastatic MCC. The substantially longer median QFS and substantially higher QFS rates compared with PFS estimates suggest patient-relevant, positive outcomes in the context of an aggressive cancer like MCC, with several patients reporting stable or improved HRQOL with avelumab treatment across time points.