The use of oxybutynin led to statistically significant reductions in the number of hot flashes per day compared with placebo for men with prostate cancer receiving androgen-deprivation therapy (ADT), according to findings from the Alliance A222001 trial published in the Journal of Clinical Oncology.
“Oxybutynin demonstrated clear and clinically meaningful improvements in both hot flash frequency and quality of life for men undergoing hormone therapy for prostate cancer,” said lead study investigator Bradley J. Stish, MD, Radiation Oncologist at Mayo Clinic Comprehensive Cancer Center. “These results provide strong support for its use as an effective management option for this challenging and often overlooked side effect of prostate cancer treatment.”
Background and Study Methods
Oxybutynin is frequently used for treating symptoms of an overactive bladder, but has also shown efficacy in reducing the frequency and severity of hot flashes in both men and women.
The randomized, double-blind, placebo-controlled phase II A222001 clinical trial enrolled men with prostate cancer who were receiving stable regimens of ADT and had experienced at least 28 hot flashes per week (n = 88; 81 eligible for final analysis). The patients were randomly assigned to receive either 2.5 mg oxybutynin twice daily, 5 mg twice daily, or matching placebo regimens, each given for 6 weeks.
The primary outcome measure was the change in hot flash score as reported by the patient at 6 weeks.
Key Findings
At baseline, patients had an overall average of 10.1 hot flashes per day and an average daily hot flash score of 18.2. Reductions in the number of hot flashes per day of 2.15 were observed with placebo, 4.77 with 2.5 mg of oxybutynin (P = .02), and 6.89 with 5 mg of oxybutynin (P < .001). The daily hot flash scores reduced by an average of 4.85 points in the placebo arm, by 9.94 in the 2.5-mg oxybutynin arm (P = .07), and by 13.95 points in the 5-mg oxybutynin arm (P = .002).
No treatment-related grade 3 or higher adverse events were reported with oxybutynin. Treatment was considered well tolerated overall, with dry mouth being the most common adverse effect reported.
Total Hot Flash–Related Daily Interference Scale scores improved by 3.1 points in the placebo arm, 14.2 points in the 2.5-mg oxybutynin arm (P = .042), and by 20.7 points in the 5-mg oxybutynin arm (P < .01).
Improvements in symptoms occurred quickly and were generally sustained throughout the trial. Thirty-two percent of patients in the placebo arm, 57% in the 2.5-mg oxybutynin arm, and 79% in the 5-mg oxybutynin arm achieved a reduction in hot flash scores of at least 50%.
“These results are incredibly encouraging,” Dr. Stish added. “Men with hot flashes from hormone therapy now have another therapeutic option available to help reduce their symptom burden. Future research will look to further our understanding of hot flash therapy options in this patient population.”
DISCLOSURE: The study was supported by the National Cancer Institute of the National Institutes of Health. For full disclosures of the study authors, visit ascopubs.org.
