Oxybutynin shows promise for managing hot flashes among breast cancer survivors

SAN ANTONIO — Oxybutynin significantly reduced the frequency and severity of hot flashes among breast cancer survivors, according to results of the randomized controlled ACCRU SC-1603 study presented at San Antonio Breast Cancer Symposium.

“Hot flashes are a significant problem across the general population, but even more so among breast cancer survivors,” Roberto A. Leon-Ferre, MD, assistant professor of oncology at the Mayo Clinic in Rochester, Minnesota, said during a press conference. “Hot flashes may affect up to 75% of midlife women and can persist for more than 15 years. It is no surprise that hot flashes can negatively impact patients’ quality of life, interfering with work, sleep and relationships.”

Various factors contribute to the increased severity of hot flashes among breast cancer survivors, including treatment with chemotherapy, antiestrogen medications and hormone replacement therapy.

Hormone replacement therapy is the most effective treatment to manage hot flashes, but that is not a viable option for breast cancer survivors. Thus, there is a need for nonhormonal therapeutic interventions to treat hot flashes among this population.

Oxybutynin — an FDA-approved agent for overactive bladder — has been shown to reduce hot flash symptoms among menopausal women.

Leon-Ferre and colleagues conducted the double-blind SC-1603 study to compare oxybutynin with placebo for treatment of hot flashes. Investigators also assessed subsequent improvement in quality of life.

The analysis included 113 breast cancer survivors who reported experiencing at least 28 hot flashes per week for longer than 30 days. More than half (62%) were treated with tamoxifen or an aromatase inhibitor during the study period.

Investigators randomly assigned women to one of three treatment: Oxybutynin dosed at 2.5 mg twice daily (n=40), oxybutynin dosed at 2.5 mg twice daily for 1 week with a subsequent increase to 5 mg twice-daily (n=35), or placebo (n=38).

Treatment duration was 6 weeks.

Intrapatient change in weekly hot flash score and frequency served as the primary endpoint. Secondary endpoints included change in the hot flash-related daily interference scale and change in self-reported symptoms.

Women assigned oxybutynin at the consistent 2.5mg dose demonstrated a greater mean change in hot flash score compared with those assigned placebo (–10.6 vs. –5.7). These oxybutynin-treated women also experienced an average of 4.8 fewer hot flashes per day, compared with an average of 2.6 fewer hot flashes per day in the placebo group.

Women assigned to the higher-dose oxybutynin regimen derived even greater benefit, with a mean change in hot flash score of –16.9 and an average of 7.5 fewer hot flashes per day.

Women in both oxybutynin treatment groups reported improvements in work, social activities, leisure activities, sleep, relations, life enjoyment and overall quality of life.

Adverse events associated with oxybutynin included diarrhea, constipation, dry mouth, dry eyes, episodes of confusion and difficulty urinating.

“The use of oxybutynin is associated with positive impact in several quality-of-life metrics,” Leon-Ferre said. “[Although] the two oxybutynin doses were not formally compared, the 5-mg twice-daily dose appeared to be more effective.

“One limitation of this study is that it was short term,” he added. “There have been some concerns that taking these agents for a longer period of time can lead to cognition issues. With this caveat, I would say that we could prescribe this to patients today, but ideally I would suggest to use the agent for a short period of time.” – by Jennifer Southall

Reference:

Leon-Ferre R.A., et al. Abstract GS6-02. Presented at: San Antonio Breast Cancer Symposium; Dec. 4-8, 2018; San Antonio.

Disclosures: Breast Cancer Research Foundation funded this study. Leon-Ferre reports no relevant financial disclosures. Please see the abstract for all other authors’ relevant financial disclosures.