Background
Exposure to ultraviolet (UV) radiation is a well-established modifiable risk factor for the initial development of cutaneous melanoma. However, its role in melanoma progression after diagnosis is less clear. Melanoma recurrence, defined as local, regional, or distant return of the original cancer, is distinct from the development of a new primary melanoma or separate lesion. Identifying factors associated with patients at high-risk recurrence may help guide surveillance or management strategies, ultimately improving survival.
Methods
Patients with newly diagnosed, histologically confirmed T1b to T4b melanoma in Queensland, Australia, were recruited between 2010 and 2014. Participants were followed for a minimum of 7 years, with all recurrences recorded. Occupational sun exposure since leaving school was self-reported as mainly indoors, both indoors and outdoors, or mainly outdoors. Adjusted Cox proportional hazards models assessed associations with recurrence and Fine-Gray competing risk models examined melanoma-specific mortality.
Results
Participants with mainly outdoor occupations (n=124) had a significantly higher risk of recurrence than those with mainly indoor occupations (n=252) (adjusted hazard ratio [aHR] 1.81, 95% confidence interval [CI] 1.09–3.02; P=0.02). Participants reporting mixed indoor and outdoor occupations (n=323) also had elevated recurrence risk, although this did not reach statistical significance (aHR 1.39, 95% CI 0.95–2.03).
Among participants with recurrence (n=190), the mean time from diagnosis to recurrence was 32.7 months (SD 26.8), with no significant difference between exposure groups. Compared with mainly indoor occupations, mainly outdoor occupations were also associated with increased melanoma-specific mortality (subdistribution hazard ratio [sHR] 2.64, 95% CI 1.28–5.43). Mixed exposure showed a similar direction of effect but was not statistically significant.
Conclusions
Greater occupational UV exposure was associated with increased risks of melanoma recurrence and melanoma-specific mortality in our cohort. Looking beyond traditional prognostic factors such as Breslow thickness, ulceration, and mitotic rate, could facilitate our understanding of why two patients with comparable disease at diagnosis may have different recurrence risks or survival trajectories.