Researchers have identified 12 genetic markers associated with susceptibility for erectile dysfunction following radiotherapy for prostate cancer. This information can be used to better inform men as to which treatment option might be best for their specific cancer and lifestyle.

The two-stage genome-wide association study that yielded this discovery involved men with prostate cancer who were randomly assigned to two groups. Each group of men received brachytherapy, brachytherapy plus external-beam radiation, or external-beam radiation alone, and were followed for a mean of 4 years to determine their level of sexual function posttreatment.

The first group, known as the discovery cohort, included 132 men who developed erectile dysfunction after radiotherapy (cases), and 103 men who underwent similar treatment but did not develop erectile dysfunction (controls). The second group, or the replication cohort, consisted of 128 cases and 102 controls. The discovery cohort was genotyped, and the 940 top-ranking single nucleotide polymorphisms (SNPs) selected from that group were then genotyped in the replication cohort.

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One dozen of the SNPs identified in the discovery cohort and validated in the replication cohort were associated with the development of erectile dysfunction following radiation therapy. The cumulative SNP score model had a sensitivity of 84% and specificity of 75% for prediction of developing erectile dysfunction at the radiation therapy planning stage.

In a finding that Barry S. Rosenstein, PhD, of the radiation oncology department at Mount Sinai Medical School in New York, New York, and fellow investigators described as notable in their report for International Journal of Radiation Oncology.Biology.Physics, the 12 SNPs lie in or near genes involved in erectile function or other normal cellular functions (adhesion and signaling) rather than genes involved in DNA damage repair.