Physical activity and mortality in melanoma patients within the Norwegian Women and Cancer study (NOWAC)

Pre‐ and post‐diagnosis physical activity (PA) have been associated with decreased mortality and recurrence in cancer patients, but its effect is under‐studied in patients with cutaneous melanoma. We investigated the association between pre‐diagnosis PA (most recent level and long‐term trajectories) and melanoma‐specific, other‐cause, and overall mortality. Additionally, PA levels before and after a melanoma diagnosis were compared. We used information at recruitment and follow‐ups in the prospective population‐based Norwegian Women and Cancer cohort linked to the Cancer Registry of Norway. In total 1829 women were diagnosed with a first primary melanoma in 1991─2020, aged 34–93 years. We used Cox regression adjusted for age at diagnosis, education, smoking status, region of residence, melanoma thickness, and summary stage. Most recent pre‐diagnosis PA was non‐significantly associated with lower risk of melanoma‐specific mortality (hazard ratio (HR) = 0.69, 95% confidence interval (CI) = 0.44─1.07, high vs. low) and significantly associated with other‐cause (HR = 0.50, 95% CI = 0.28─0.89) and overall mortality (HR = 0.59, 95% CI = 0.42─0.82). Four pre‐diagnosis PA trajectory classes were identified using a latent class mixed model (low, decreasing, moderate, and high). The PA trajectory classes were not significantly associated with melanoma‐specific mortality. However, significantly decreased risks of other‐cause (HR = 0.51, 95% CI = 0.30─0.87) and overall mortality (HR = 0.59, 95% CI = 0.42─0.84) were found in the moderate versus low class. Only 275 patients reported both pre‐ and post‐diagnosis PA, and among those, 69% had a similar PA level before and after melanoma diagnosis. Our results suggest that pre‐diagnosis PA reduces mortality in middle‐aged Norwegian women with melanoma.