Postoperative Radiation Therapy Is Indicated for “Low-Risk” Pathologic Stage I Merkel Cell Carcinoma of the Head and Neck Region but Not for Other Locations
Marika Bierma, Peter H. Goff, Daniel S. Hippe, Kristina Lachance, Stephanie K. Schaub, Kent E. Wallner, Yolanda D. Tseng, Jay J. Liao, Smith Apisarnthanarax, Paul Nghiem, Upendra Parvathaneni
Abstract
IntroductionThe role of post-operative radiation therapy (PORT) in early-stage Merkel cell carcinoma (MCC) is controversial. We analyzed the role of PORT in preventing local recurrences (LR) among patients with low-risk, pathological stage I MCC based on the location of the primary tumors: head/neck (HN) vs. non-head and neck (non-HN) sites.Materials/MethodsOne hundred forty-seven patients with MCC were identified that had “low risk” disease (pathological T1 primary tumor, negative microscopic margins, negative pathologic node status, no immunosuppression or prior systemic therapy). LR was defined as tumor recurrence within 2 cm of the primary surgical bed, and its frequency was estimated with the cumulative incidence method.ResultsSeventy-nine patients received PORT (30 HN, 49 non-HN) with a median dose of 50 Gy (range: 8-64 Gy) while 68 patients were treated with surgery alone (30 HN, 38 non-HN). Overall, PORT was associated with a decreased risk of LR (5-year rate: 9.5% vs. 0%, p=0.004) with 6 LRs observed in the surgery alone group. While the addition of PORT significantly reduced LR rates among HN patients (21% vs. 0%, p=0.034), no LRs were observed in non-HN patients managed with surgery alone. There was no significant difference in MCC-specific survival comparing HN versus non-HN groups, with or without PORT.ConclusionsFor low-risk, pathological stage I MCC of the extremities and trunk, excellent local control rates were achieved with surgery, and PORT is not indicated. However, PORT was associated with a significant reduction in LRs among low-risk MCC of the HN.