The Effect of Radiotherapy Dose and Volume on Relapse in Merkel Cell Cancer of the Skin

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Purpose/Objective(s)To assess the effect of radiotherapy (RT) dose and volume on relapse patterns in patients with Stage I–III Merkel cell carcinoma (MCC).Materials/MethodsRetrospective analysis of 112 patients diagnosed with MCC between January 2000 and December 2005 and given radiotherapy with curative intent. The effect of dose on relapse rate was analysed with adjustments for stage and surgical margins.ResultsOf the 112 evaluable patients 88% had RT to the site of primary disease for gross (11%) or subclinical (78%) disease. Eighty-nine percent of patients had RT to the regional lymph nodes; gross disease accounting for 19% and subclinical disease (adjuvant or elective) in 71%. The 2 year and 5 year overall survival (OS) was 72% and 53%, respectively, and the 2 year loco-regional control (LRC) rate was 75%. The in-field relapse rate was 3% for primary disease and relapse was significantly lower for patients receiving ≥ 50 Gy (HR = 0.22, CI: 0.06–0.86). Surgical margins did not affect the local relapse rate. The in-field relapse rate was 11% for RT to the nodes with dose being significant for nodal gross disease (HR = 0.24, CI: 0.07–0.87) and subclinical disease (HR = 0.44, CI: 0.14–1.42). Patients not receiving elective nodal RT had a much higher rate of nodal relapse compared to those who did (HR = 6.03, CI: 1.34–27.10).ConclusionsThis study indicates a dose response for subclinical and gross MCC. Doses of 50 Gy for subclinical disease and 55–60 Gy for gross disease are recommended. The draining nodal basin should be treated in all patients. Purpose/Objective(s)To assess the effect of radiotherapy (RT) dose and volume on relapse patterns in patients with Stage I–III Merkel cell carcinoma (MCC). To assess the effect of radiotherapy (RT) dose and volume on relapse patterns in patients with Stage I–III Merkel cell carcinoma (MCC). Materials/MethodsRetrospective analysis of 112 patients diagnosed with MCC between January 2000 and December 2005 and given radiotherapy with curative intent. The effect of dose on relapse rate was analysed with adjustments for stage and surgical margins. Retrospective analysis of 112 patients diagnosed with MCC between January 2000 and December 2005 and given radiotherapy with curative intent. The effect of dose on relapse rate was analysed with adjustments for stage and surgical margins. ResultsOf the 112 evaluable patients 88% had RT to the site of primary disease for gross (11%) or subclinical (78%) disease. Eighty-nine percent of patients had RT to the regional lymph nodes; gross disease accounting for 19% and subclinical disease (adjuvant or elective) in 71%. The 2 year and 5 year overall survival (OS) was 72% and 53%, respectively, and the 2 year loco-regional control (LRC) rate was 75%. The in-field relapse rate was 3% for primary disease and relapse was significantly lower for patients receiving ≥ 50 Gy (HR = 0.22, CI: 0.06–0.86). Surgical margins did not affect the local relapse rate. The in-field relapse rate was 11% for RT to the nodes with dose being significant for nodal gross disease (HR = 0.24, CI: 0.07–0.87) and subclinical disease (HR = 0.44, CI: 0.14–1.42). Patients not receiving elective nodal RT had a much higher rate of nodal relapse compared to those who did (HR = 6.03, CI: 1.34–27.10). Of the 112 evaluable patients 88% had RT to the site of primary disease for gross (11%) or subclinical (78%) disease. Eighty-nine percent of patients had RT to the regional lymph nodes; gross disease accounting for 19% and subclinical disease (adjuvant or elective) in 71%. The 2 year and 5 year overall survival (OS) was 72% and 53%, respectively, and the 2 year loco-regional control (LRC) rate was 75%. The in-field relapse rate was 3% for primary disease and relapse was significantly lower for patients receiving ≥ 50 Gy (HR = 0.22, CI: 0.06–0.86). Surgical margins did not affect the local relapse rate. The in-field relapse rate was 11% for RT to the nodes with dose being significant for nodal gross disease (HR = 0.24, CI: 0.07–0.87) and subclinical disease (HR = 0.44, CI: 0.14–1.42). Patients not receiving elective nodal RT had a much higher rate of nodal relapse compared to those who did (HR = 6.03, CI: 1.34–27.10). ConclusionsThis study indicates a dose response for subclinical and gross MCC. Doses of 50 Gy for subclinical disease and 55–60 Gy for gross disease are recommended. The draining nodal basin should be treated in all patients. This study indicates a dose response for subclinical and gross MCC. Doses of 50 Gy for subclinical disease and 55–60 Gy for gross disease are recommended. The draining nodal basin should be treated in all patients.