ORLANDO, Fla.—Having a sibling with a genitourinary cancer significantly increases a person’s risks of developing the same cancer, researchers reported at the 2015 Genitourinary Cancers Symposium.

“The results from our study may be useful clinically in counseling patients at risk for genitourinary cancer, as well as informing cancer prevention efforts,” lead researcher Lorelei Mucci, ScD, MPH, of Harvard University’s School of Public Health in Boston, told Renal & Urology News.

To determine whether familial risks exist with these cancers, Dr. Mucci and her colleagues analyzed data from more than 200,000 siblings from the Nordic Twin Study, which included both identical and same-sex fraternal twins. During a period of 32 years, 5,041 cases of genitourinary cancer were diagnosed. The cumulative incidences of prostate, bladder, kidney, and testes cancer were 10.5%, 2.2%, 0.8%, and 0.5%, respectively.

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Dr. Mucci’s group found the strongest familial effects for testicular cancer: a 6% estimated familial risk for fraternal twins and a 14% risk for identical siblings, which translates to a 12-fold and 28-fold higher risk of testicular cancer, respectively, when a co-twin had the malignancy.

Familial risks were also elevated for prostate, bladder, and kidney cancers. Compared with fraternal twins, identical twins had greater risks of these cancers.

The proportion of risk attributed to shared genetics was 57% for prostate cancer and 38% for kidney cancer. Environment played a role in testicular cancer. Shared genetic and environmental factors contributed to testicular cancer by 37% and 24%, respectively, the investigators found.