Merkel cell carcinoma of the head and neck: Is adjuvant radiotherapy necessary?

Background. Controversy exists regarding the optimal management of patients with Merkel cell carcinoma. The primary aim of this study was to determine whether combined treatment with surgery and radiotherapy improves outcome in a multi-institutional cohort of patients with Merkel cell carcinoma of the head and neck. The secondary aims were to determine by stage, which patients derive benefit from combined therapy and to identify predictors for survival on multivariable analysis. Methods. A retrospective analysis of 110 patients with Merkel cell carcinoma of the head and neck was performed. Data were collected from 3 tertiary care institutions (Westmead Hospital, Sydney, Australia; Princess Margaret Hospital, Toronto, Canada; Royal Prince Alfred Hospital, Sydney). There were 78 males and 32 females, median age was 70 years, and mean follow-up of survivors was 2.3 years. Sixty-six patients underwent combined treatment, and 44 patients had either surgery or radiotherapy alone. Analysis by stage was performed using 2 staging systems. Results. Local and regional control at 5 years was 84% and 69%, respectively. Combined treatment improved both local (p = .009) and regional control (p = .006). Overall and disease-specific survival at 5 years was 49% and 62%, respectively. Combined treatment was associated with significantly better disease-free survival on univariable analysis (p = .013) When analyzed by stage, patients with stage IIb (primary >1 cm, node negative) disease who underwent combined treatment had improved disease-free (p = .005) and disease-specific survival (p = .035). Predictors of survival on multivariable analysis were age >70 years (HR 6.19, p < .001), primary tumor size >1 cm (HR 7.55, p < .001), number of nodal métastases divided into none, ≤ 2 and >2 (HR 3.71 per stratum, p < .001). When analyzed with age and disease stage, treatment modality trended toward significance as a predictor of disease-specific (p = .081) and overall survival (p = .076). Disease stage was the most powerful independent predictor on Cox regression (HR 5.43 per stratum, p < .001). Conclusions. Merkel cell carcinoma is an aggressive cutaneous malignancy. Age and disease stage are the most important predictors of survival. Combined surgery and radiotherapy improves both locoregional control and disease-free survival. Patients with stage II disease appear to derive the greatest benefit from adjuvant radiotherapy, including improved disease specific survival.