The Lynx Group

Preventive Therapy Preserves Sexual Function after Radiotherapy for Patients with Prostate Cancer

February 2013, Vol 4, No 2

Boston, MA—Patients with prostate cancer reported significantly better sexual function for up to 2 years after radiation therapy when they took sildenafil (Viagra) on a daily basis during and after treatment, according to results of a placebo-controlled clinical trial.

Scores on the erectile function domain of the International Index of Erectile Function (IIEF) remained significantly better with sildenafil compared with placebo throughout the follow-up.

The findings are consistent with those reported for patients who underwent surgery for localized pros­­tate cancer, Michael J. Zelefsky, MD, Vice Chair for Clinical Research in Radiation Oncology at Memorial Sloan-Kettering Cancer Center in New York, reported at the 2012 American Society for Radiation Oncology meeting.

“This is the first randomized, controlled trial demonstrating a benefit for pharmacologic intervention in a preventive mode—penile rehabilitation—in the treatment of patients who receive radiation for prostate cancer,” said Dr Zelefsky.

Previous studies showed that sildenafil (and other members of the phosphodiesterase type-5 inhibitor class) leads to restoration of potency after definitive radiation therapy for prostate cancer in 60% to 70% of men. The success rate reflects the use of the drug as needed after treatment.

The concept of preventive therapy had not been evaluated in men treated with radiation therapy. To test the concept, investigators enrolled 290 men with localized prostate cancer who were treated with external-beam radiation therapy, brachytherapy, or a combination of the 2 treatments. Patients were randomized in a 2:1 ratio to sildenafil 50 mg daily or to placebo, beginning 3 days before treatment and continuing through 6 months after the treatment. Patients then switched to as-needed dosing. Eligible patients had an IIEF score of ≥7, representing good sexual function at baseline.

The trial investigators randomized 295 patients, who were followed at 3-month intervals for a year and thereafter at 6 and 24 months. The patients completed the IIEF at each follow-up visit. The study population included 31 men who received short-course androgen deprivation therapy. None of the men benefited from preventive treatment with sildenafil, so they were excluded from analysis.

The final analysis comprised 142 men who completed the pretreatment IIEF survey and at least 1 posttreatment survey. The primary end point was total IIEF score and scores on the individual domains of the scale.

The IIEF total score was significantly higher in the patients receiving sildenafil versus those receiving placebo at 6 months after definitive radiation therapy (58.6 vs 49.4, respectively; P = .006), as well as at 12 months and 24 months.

The group receiving sildenafil also had a significant improvement in total International Prostate Symptom Scale score versus the group receiving a placebo (P <.001).

These findings make preventive treatment with phosphodiesterase type 5 a new standard of care “for the time being,” said invited discussant Thomas M. Pisansky, MD, Professor of Radiation Oncology at the Mayo Clinic in Rochester, MN. Although more study is needed to confirm the results, the workup and follow-up of patients with prostate cancer who are treated with radiation therapy should include a validated assessment of sexual function, such as the IIEF, he added.

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