ASCO 2026: Adjuvant Avelumab Reduced Relapse Risk in Stage III Merkel Cell Carcinoma

By: Julia Cipriano, MS, CMPP
Posted: Friday, June 26, 2026

Adjuvant treatment with the anti–PD-L1 antibody avelumab was associated with a lower risk of relapse among patients with Merkel cell carcinoma and lymph node metastases following definitive surgery and/or radiation therapy, based on results from the investigator-initiated, multicenter phase III ADAM trial. At the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting, Shailender Bhatia, MD, of the University of Washington and Fred Hutchinson Cancer Center, Seattle, and colleagues also reported that the high Merkel cell carcinoma–specific survival in both arms may reflect the effectiveness of PD-1/-L1 blockade across adjuvant and metastatic settings.

A total of 100 patients with stage III disease and lymph node metastases who had no radiologic evidence of residual disease after definitive treatment were randomly assigned 1:1 and stratified by primary tumor/lymph node status and radiation therapy status to receive intravenous avelumab (800 mg/dose; n = 48) or placebo (n = 52) for up to 2 years on a de-escalating schedule. Among relapse-free survivors, median follow-up was 4.2 years.

The adjusted stratified hazard ratio (HR) for relapse-free survival failure was 0.54 (P = .069) for avelumab vs placebo. In a nonprespecified relapse analysis, the adjusted stratified HR was 0.47. Relapse rates were lower with avelumab than placebo at 1 year (12.8% vs 40.4%), 2 years (21.3% vs 42.3%), and 3 through 5 years (28.3% vs 44.5%).

Secondary endpoint analyses showed an adjusted stratified HR of 0.89 for distant metastasis–free survival and stratified HRs of 1.81 for disease-specific survival and 2.37 for overall survival; the investigators noted that there were insufficient events to accommodate adjustment for the latter two analyses. Grade 3 or 4 treatment-related adverse events occurred in 15% of patients receiving avelumab and 0% of those receiving placebo. No grade 5 treatment-related adverse events were reported.

The investigators concluded that the findings “will inform future discussions regarding adjuvant therapy in clinical practice.”

Disclosure: For full disclosures of the study authors, visit coi.asco.org.

2026 ASCO Annual Meeting (Abstract LBA9504)