title: Effect of radiotherapy dose and volume on relapse in Merkel cell cancer of the skin.
abstract: OBJECTIVE
  To assess the effect of radiotherapy (RT) dose and volume on relapse patterns in patients with Stage I-III Merkel cell carcinoma (MCC).
  
  
  METHODS
  This was a retrospective analysis of 112 patients diagnosed with MCC between January 2000 and December 2005 and treated with curative-intent RT.
  
  
  RESULTS
  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; in most cases (71%) this was for subclinical disease in the adjuvant or elective setting, whereas 21 patients (19%) were treated with RT to gross nodal disease. With a median follow-up of 3.7 years, the 2-year and 5-year overall survival rates were 72% and 53%, respectively, and the 2-year locoregional control rate was 75%. The in-field relapse rate was 3% for primary disease, and relapse was significantly lower for patients receiving >or=50 Gy (hazard ratio [HR] = 0.22; 95% confidence interval [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; 95% CI, 0.07-0.87). Patients who did not receive elective nodal RT had a much higher rate of nodal relapse compared with those who did (HR = 6.03; 95% CI, 1.34-27.10).
  
  
  CONCLUSIONS
  This study indicates a dose-response for subclinical and gross MCC. Doses of >or=50 Gy for subclinical disease and >or=55 Gy for gross disease should be considered. The draining nodal basin should be treated in all patients.
authors.affiliation: Division of Cancer Services, Princess Alexandra Hospital, University of Queensland, Brisbane, Queensland, Australia. matthew_foote@health.qld.gov.au
authors.forename: Matthew
authors.initials: M
authors.lastname: Foote
authors.forename: Jennifer
authors.initials: J
authors.lastname: Harvey
authors.forename: Sandro
authors.initials: S
authors.lastname: Porceddu
authors.forename: Graeme
authors.initials: G
authors.lastname: Dickie
authors.forename: Susan
authors.initials: S
authors.lastname: Hewitt
authors.forename: Shoni
authors.initials: S
authors.lastname: Colquist
authors.forename: Dannie
authors.initials: D
authors.lastname: Zarate
authors.forename: Michael
authors.initials: M
authors.lastname: Poulsen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015266:Carcinoma, Merkel Cell / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*; D016001:Confidence Intervals; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D015182:Lymphatic Irradiation; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000401:mortality; D012189:Retrospective Studies; D012878:Skin Neoplasms / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*; D015996:Survival Rate