The association of ultraviolet radiation-B (305 nm), season of diagnosis, and latitude on the survival outcome of prostate cancer in the high UV environment of Australia

Background: Positive associations between sun exposure and cancer survival have been observed in regions of high latitudes, where ambient solar ultraviolet (SUV) radiation is generally low. Purpose: We examined the effects of ambient ultraviolet-B radiation (UVB) at time of diagnosis, season of diagnosis and latitude of residence on survival outcome from prostate cancer. Method: Regression models for relative survival were used to estimate relative excess risks (RER) of death after diagnosis of prostate cancer from cancer registries in Eastern Australia (Queensland, New South Wales, Victoria and Tasmania). Results: Relative excess risks was increased with diagnosis in summer (RER = 1.20; 95 % CI 1.14-1.26) relative to winter, high ambient UVB at the time of diagnosis (>60 mW/m²; RER = 1.10; 95 % CI 1.05-1.15) relative to low SUV (<30 mW/m²), and with residence in high latitudes (35 S-43 S; RER = 1.20; 95 % CI 1.14-1.26) relative to low latitudes (9 S-29.9 S). RER was highest for summer diagnosis in all three latitude bands, after adjusting for age, follow-up period, and socioeconomic status. Conclusion: The contradictory outcome from season and latitude suggests that their use as surrogates for UV warrants validation. Our data suggest that high ambient solar ultraviolet radiation at the time of diagnosis of prostate cancer increases the risk of dying from this cancer.