Abstract
BACKGROUND: Patients' diets can influence the outcome of several common cancers, but the effect on melanoma prognosis is unknown. OBJECTIVE: To assess the association between quality of melanoma patients' prediagnosis diets and primary tumour thickness, the main prognostic indicator for melanoma. METHODS: We used baseline data from patients newly diagnosed with tumour stage Ib to IV cutaneous melanoma, with completed questionnaires about food intake in the past year and other factors. Diet quality was measured by the Healthy Eating Index (HEI) and melanoma thickness was extracted from histopathology reports. We estimated prevalence ratios (PR(adj) ) and 95% confidence intervals (CIs) adjusted for confounding factors using Poisson regression models to assess associations between HEI scores and melanoma thickness. RESULTS: Of 634 study patients, 238 (38%) had melanomas >2 mm thick at diagnosis. Patients with the highest HEI scores were significantly less likely to be diagnosed with thick melanoma than patients with lowest HEI scores (PR(adj) 0.93, 95% CI 0.86-0.99) (P(trend) = 0.03). There was no evidence of effect modification by age, sex, previous melanoma or comorbidities. CONCLUSIONS: Melanoma thickness at diagnosis is significantly associated with quality of patients' diets before diagnosis.