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

Abstract

The role of postoperative radiation therapy (PORT) in early stage Merkel cell carcinoma (MCC) is controversial. We analyzed the roleof PORT in preventinglocal recurrences (LR)among patients withlow-risk,pathologicstage IMCCbased on the location of the primary tumors: head/neck (HN) versus non-HN sites. One hundred forty-seven patients with MCC were identified that had "low risk" disease (pathologic T1primary tumor, negative microscopic margins, negative pathologic node status,no immunosuppressionorprior systemic therapy).LR was defined as tumor recurrence within 2 cm of the primary surgical bed, andits frequency wasestimated with thecumulative incidencemethod. Seventy-ninepatients receivedPORT (30HN,49non-HN) with a median dose of 50 Gy (range, 8-64 Gy) and68patients were treated with surgery alone (30HN,38non-HN). Overall, PORT was associated with a decreased risk of LR (5-year rate: 0% vs 9.5%; P=.004) with6LRs observed in the surgery alone group. Although the addition of PORT significantly reduced LR rates among patients with HN MCC (0% vs. 21%; P=.034), no LRs were observed in patients with non-HN MCC managed with surgery alone. There was no significant difference inMCC-specific survival comparing HN versus non-HN groups, with or without PORT. Forlow-risk,pathologic stage IMCCoftheextremitiesand 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.