PROSTATE CANCER AND MELANOMA RISK

Men with prostate cancer have a significantly increased risk for melanoma, according to an analysis of 2 large cohort studies of health professionals that date from the 1980s.

A team of researchers from the National Cancer Institute and a number of universities has found that a personal history of prostate cancer is associated with a roughly 2-fold increased risk for melanoma.

The team also looked at other cancers to see if men with prostate cancer were at increased risk for them. They were not, report Jiali Han, PhD, from Harvard University in Boston and Tianjin Medical University Cancer Institute in China, and colleagues.

However, they speculate that "high androgen levels might contribute to the association between prostate cancer and the risk of melanoma."

The study was published online November 4 in the Journal of Clinical Oncology.

Severe acne, which is a "surrogate for androgen activity," has been positively associated with melanoma in 2 studies, and prostate cancer is a "well-recognized androgen-related cancer." Furthermore, melanoma has "long been hypothesized to be androgen dependent," they note, citing multiple studies.

Therefore, the research team guessed that prostate cancer might be associated with an increased risk for melanoma.

They identified 539 cases of melanoma in the Health Professionals Follow-up Study (HPFS), a long-term cohort that began in 1986 and involves more than 42,000 people. Participants report melanoma and other cancers biennially.

A personal history of prostate cancer was associated with an increased risk for melanoma (multivariate-adjusted hazard ratio [HR], 1.83; 95% confidence interval [CI], 1.32 - 2.54). There was no similarly significant association with nonmelanoma skin cancer.

In addition, men with prostate cancer did not have an increased risk for other cancers.

The authors looked at a second long-term cohort, the Physician's Health Study (PHS), which began in 1982 and involves more than 18,000 participants.

They performed a "lag analysis" in which prostate cancer diagnosis occurring at least 2 years before melanoma diagnosis served as the exposure. With this, they confirmed the association between a history of prostate cancer and risk for melanoma (HR, 2.17; 95% CI, 1.12 - 4.21).

This is not the first time an increased risk for melanoma has been found in men with prostate cancer. Two other studies made the same finding, but in both, cancer registries were used as the data source.

Dr. Han and colleagues explain that, unlike their study, those registry studies did not have a cancer-free group as a reference, and did not adjust for covariates beyond age and calendar time. In short, the cancer registry studies are less authoritative.

In their multivariate analyses of the HPFS, Dr. Han's team made adjustments for a wide range of factors, including age, body mass index, smoking status, alcohol intake, physical activity, use of erectile dysfunction drugs, childhood history of sunburn, hair color, family history of melanoma, and years of exposure to the sun during adolescence.

The confirmatory analyses of the PHS data were adjusted for age, smoking status, alcohol intake, and physical activity.

The authors assert that their study "holds public health significance" and could help clinicians working with patients who have a history of prostate cancer.

Did Treatment for Prostate Cancer Cause Risk Increase?

Interestingly, there was no increased risk for prostate cancer associated with melanoma. In other words, it is not a 2-way street or, in the parlance of the researchers, it is not a "bidirectional relationship."

This "raises a possible concern about the impact of prostate cancer treatment in elevating melanoma risk," they acknowledge.

But the authors are not certain that therapy was pivotal because they did not "extensively" examine the prostate cancer treatment data.

If there is a "potential role for androgens in the etiology of melanoma" — and the authors believe there is — "it will be interesting to examine the effects of continuous androgen deprivation for prostate cancer" on the risk for melanoma, they note.

The study was supported by the Intramural Research Program of the National Institutes of Health. The authors have disclosed no relevant financial relationships.

J Clin Oncol. Published online November 4, 2013. Abstract