The incidence of prostate cancer is relatively low among men diagnosed with skin cancer, according to a study published in the April 15th issue of the American Journal of Epidemiology. The incidence of prostate cancer is relatively low among men diagnosed with skin cancer, according to a study published in the April 15th issue of the American Journal of Epidemiology, suggesting that ultraviolet radiation may protect against prostate cancer.

"Ultraviolet radiation causes skin cancer, but it has been hypothesized to protect against prostate cancer development and possibly progression," Dr. Esther de Vries, of Erasmus Medical Center in Rotterdam, the Netherlands, and colleagues write. "If this hypothesis were true, one would expect skin cancer patients to have a lower prostate cancer incidence than the general population and, more specifically, to have a lower incidence of advanced stage prostate cancer."

To investigate this hypothesis, the researchers followed a population-based cohort of male skin cancer patients diagnosed since 1972 (2620 squamous cell carcinomas, 9501 basal cell carcinomas, and 1420 cutaneous malignant melanomas) for incidence of invasive prostate cancer until January 1, 2005. The team compared the incidence rates of prostate cancer among patients with skin cancer and those in the reference population, resulting in standardized incidence ratios (SIR).

Skin cancer patients had a decreased risk of developing prostate cancer (SIR = 0.89). The lowest standardized incidence ratios occurred shortly after skin cancer diagnosis.

The risk of advanced prostate cancer (stages III and IV) was significantly decreased among skin cancer patients (SIR = 0.73), indicating a possible anti-progression effect of ultraviolet radiation.

"A growing body of evidence, including our findings, support the hypothesis that ultraviolet radiation protects against the development of prostate cancer, possibly through the formation of vitamin D3, although some plasma studies do not clearly suggest a benefit of vitamin D levels on prostate cancer risk," Dr. de Vries and colleagues explain.

If the hypothesis is confirmed, however, "it will be important to modify public health messages regarding ultraviolet radiation exposure," they note. "Levels of ultraviolet radiation that do not result in increased risk of skin cancers should be defined.