Background
Phase III trial (STAMP) investigating pembrolizumab in stage I–III Merkel cell carcinoma (MCC); accrual completed, results pending at time of review.
Interventions and follow up
Arm A: Pembrolizumab (dosing per protocol)
Arm B: Standard adjuvant therapy (comparator per trial design)
Primary endpoint: Disease-free survival or recurrence-free survival in stage I–III MCC
mFollow up: Study ongoing; results pending
Arm B: Standard adjuvant therapy (comparator per trial design)
Primary endpoint: Disease-free survival or recurrence-free survival in stage I–III MCC
mFollow up: Study ongoing; results pending
Results
Preliminary context: CheckMate 358 reported 54.5% response rate (n=33 evaluable) with nivolumab first-line MCC. ADAM phase III (adjuvant avelumab) and other trials show benefit in node-positive post-surgery/radiation disease with manageable toxicity profile (nausea, fatigue, pruritus).
Adverse events
Main adverse events: Expected immune-related adverse events consistent with ICI class (fatigue, rash, elevated transaminases); exact rates pending STAMP results publication.
Conclusions
STAMP represents significant advancement in adjuvant/early-line MCC therapy; pending results expected to inform standard-of-care in stage I–III disease.
Key Limitations
Key Limitations: Results not yet published at time of database entry; comparator and exact endpoints require publication review; MCC rarity limits trial size.
Clinical Context
ICIs (nivolumab, pembrolizumab, avelumab) now established in MCC across first-line and adjuvant settings; 40–60% response rates reported historically. STAMP completion expected to refine staging-dependent treatment approach for stage I–III resectable and node-positive disease.
References
References: Tai et al, Cancers 2025 (review)