Adjuvant immunotherapy after surgery may help prevent the metastasis of Merkel cell carcinoma (MCC), but it did not significantly reduce the overall risk of recurrence, according to a new cancer clinical trial by the ECOG-ACRIN Cancer Research Group (ECOG-ACRIN).
The randomized Phase 3 STAMP trial (EA6174), the largest clinical study to date evaluating pembrolizumab (Keytruda, Merck & Co., Inc.), as adjuvant therapy for MCC following surgical removal of the tumor, was presented at the European Society for Medical Oncology (ESMO) 2025 Congress in Berlin, Germany.
After two years, 73% of patients receiving pembrolizumab showed no cancer recurrence, compared with 66% among those who did not receive the drug. Although this difference did not reach statistical significance, patients receiving pembrolizumab had a 42% lower risk of developing distant metastases, which was a secondary objective of the study.
“The STAMP trial provides the first evidence that immunotherapy with pembrolizumab after surgery may help people with Merkel cell carcinoma by preventing their cancer from returning in organs considered distant from the site of the original disease,” says lead investigator Janice M. Mehnert, MD, co-chair of the ECOG-ACRIN Melanoma Committee and Director of Melanoma and Cutaneous Medical Oncology at NYU Langone Health’s Perlmutter Cancer Center in New York City, in a news release. “This is much-needed good news for people who are living with the highly aggressive cancer that is Merkel cell carcinoma.”
The Phase 3 multicenter study was conducted from 2018 to 2023 and involved 293 patients whose tumors had been surgically removed. Of these, 147 were randomly assigned to receive pembrolizumab infusions after surgery, while 146 were observed without additional drug therapy. Some participants also received radiation, as advised by their physicians. Supported by the National Cancer Institute (NCI), part of the National Institutes of Health (NIH), ECOG-ACRIN opened the study at over 500 hospitals and cancer centers nationwide, through the NCI’s National Clinical Trials Network.
Pembrolizumab is approved by the US Food and Drug Administration (FDA) for treating recurrent locally advanced or metastatic MCC. Overall survival, the other co-primary endpoint of the trial, continues to be followed and will be reported at a later date. Stay tuned.
PHOTO CAPTION: Janice M. Mehnert, MD, is co-chair of the ECOG-ACRIN Cancer Research Group’s Melanoma Committee and Director of Melanoma and Cutaneous Medical Oncology at NYU Langone Health’s Perlmutter Cancer Center.
PHOTO CREDIT: NYU Langone
