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Prostate Cancer survival is dependent on season of diagnosis

Newswise — A report in the September 2007 issue of The Prostate by Dr. Lagunova and associates from Norway and Oregon suggests that men diagnosed with prostate cancer (CaP) in the summer and autumn seasons have better survival.

The work was based upon the knowledge that racial and environmental factors affect CaP rates and prognosis. Vitamin D deficiency is linked to higher CaP mortality. The authors hypothesized that calcidiol levels are higher during summer and autumn and thus may impact CaP incidence and outcome.

They cite Giovannucci who reported that a high calcidiol level reduced the overall death rate by 29% and the incidence rates by 17%. The researchers divided Norway into three regions based upon annual solar exposures and documented vitamin D consumption. Clinic and demographic data was available from Norwegian national databases.

Seasons were defined as winter (December-February), spring (March-May), summer (June-August), and fall (September-November).

Relative risks of death during the 36 months after diagnosis of CaP were estimated for winter normalized to 1. It is noted that while CaP risk increases with age the photosynthesis of vitamin D3 decreases with age. As such, men diagnosed with CaP were divided into 2 age groups; age <65 years and age >65 years.

The dietary intake of vitamin D is 7% and 13% higher in the middle and northern regions of Norway, compared to the south. This is primarily due to the intake of fat fish. The relative risk of death assessed 36 months after diagnosis followed seasonal variation similar to that of serum calcidiol. The best prognosis was for summer and autumn compared with winter and spring. Summer and autumn were the seasons with the highest serum calcidiol concentrations in both studied age groups. This seasonal survival benefit persisted after stratification by region and age. The authors also evaluated that there was no difference between the 3 regions with regard to the frequency of holiday vacations to southern regions.