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

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.