ATLANTA—The number of comorbidities a man has prior to prostate cancer (PCa) radiotherapy influences his risk of erectile dysfunction (ED) after treatment, according to study findings reported at the American Society for Radiation Oncology’s 55th annual meeting.

The study looked at the association between development of post-radiotherapy ED and the presence of hypertension, diabetes, and hyperlipidemia prior to treatment.

“Erectile dysfunction is very high in the population we studied, but we need to better understand which men have a higher risk of development of post-treatment ED,” said co-investigator Yuefeng Wang, PhD, a research scientist at Emory University in Atlanta. “We found that if a man had no vascular comorbidities, then his increased risk for ED post radiation therapy was 40%, but if he had all three comorbidities then the risk for ED went up [by] approximately 75%.”

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“This is the first study of its type,” said co-investigator Ashesh Jani, MD, Professor of Radiation Oncology at Emory in Atlanta. “Our study shows vascular morbidity has a direct consequence on the ability to preserve erections after radiation therapy.”

Vascular comorbidities are known ED risk factors, but no data were previously available on the effects of vascular comorbidities on ED incidence after PCa radiotherapy, he said.  

The study cohort included 267 Caucasian and 465 African-American men who received external beam radiotherapy, brachytherapy, or both, with or without hormone therapy, from 1999 to 2010. The Caucasian and African-American groups had mean ages of 68.6 and 63.4 years, respectively.

Researchers ascertained patients’ number of pre-radiation vascular comorbidities by medical history and medication list. They defined ED by use of erectile aids or by documentation of moderate or high sexual dysfunction on patient history. ED rates were analyzed pre-radiation therapy as well as one, two, and four years post-radiation therapy.

For the overall cohort, ED incidence progressively increased from 22% prior to radiotherapy to 58% at four years post-radiation therapy. Pre-radiation therapy incidence rates were slightly among African Americans than Caucasians (23% vs. 20%) due to a higher incidence of vascular comorbidities in the African Americans.

Among Caucasians, the presence of zero, one, two, or three comorbidities was associated with a 40%, 55%, 60%, and 71% incidence of ED, respectively. Among African Americans, the incidences were 46%, 57%, 64%, and 76%, respectively. None of the differences between the groups were statistically significant.

“Clinicians can use the results of the study to provide estimates of post-radiotherapy erectile dysfunction as a function of vascular comorbidities when counseling patients on treatment options for prostate cancer,” Dr. Jani told Renal & Urology News. The study also provides preliminary data for prospective trials aimed at aimed at decreasing the likelihood of this complication, he added.