A novel single-fraction radiation approach for metastatic Merkel cell carcinoma is well tolerated and demonstrates strong efficacy linked to intact cellular immunity

Publication Type:

Journal Article


Journal of Investigative Dermatology, Volume 134, p.S100-S100 (2014)


2014, Clinical Research Division, Clinical Research Division Public Health Sciences Division May 2014 2014Q2 CCSG, May 2014, Public Health Sciences Division


Over 30% of Merkel cell carcinoma (MCC) patients eventually develop distant metastatic disease that is typically treated with chemotherapy despite toxicity and short duration of response. Because cellular immunity is important for MCC-specific survival and mouse model data suggest that single-fraction radiotherapy (SFRT) promotes tumor immunity, we began treating patients with an 8 Gray SFRT approach in 2010. 93 tumors were targeted in 26 patients (median age: 68 years). Median follow up among living patients was 252 days (range: 76-699 days) and median tumor size was 4 cm (range: 1 – 19 cm). The average number of tumors treated per patient in this study was 3.5 (range: 1 – 28). Patients were categorized as high-risk (HR) or low-risk (LR) based on their presumed immune function. There were 60 tumors among 13 HR patients who had known immune suppression and/or preceding chemotherapy (3.5 month median interval from chemotherapy to SFRT). There were 33 tumors among 13 LR patients (no known immune suppression or preceding chemotherapy). 81% percent of tumors in LR patients had a complete response compared to 52% in HR patients (p=0.008). Regardless of risk category, no tumor that had a complete response ever recurred. Only 9% (3/32) of LR patient tumors recurred compared with 30% (17/57) for HR (p=0.02). Importantly, only 2 of 26 patients had even transient side effects (flare pain that resolved within 72 hours). SFRT was highly effective, durable, and convenient for patients with metastatic disease as compared to the multiple visits required for chemotherapy or fractionated radiation. SFRT could be combined with emerging systemic immune stimulants to improve outcomes for this aggressive disease by lowering tumor burden and exposing viral/tumor antigens.


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