Oxybutynin for vasomotor symptoms across cancer-related and menopause-associated settings: A systematic review and meta-analysis of randomised control trials and observational studies.

Abstract

10627 Background: Vasomotor symptoms, including hot flashes, are a frequent and debilitating adverse effect among postmenopausal women and patients receiving cancer-directed hormonal therapies, particularly endocrine therapy in breast cancer and androgen deprivation therapy in prostate cancer. Hormone-based therapies are often contraindicated in cancer populations, underscoring the need for effective non-hormonal treatment strategies. Oxybutynin, an anticholinergic agent approved for overactive bladder, has emerged as a potential non-hormonal therapy for vasomotor symptoms; however, the magnitude of benefit and tolerability across randomized studies in diverse clinical populations has not been comprehensively quantified. Methods: A systematic search of PubMed, Embase, Cochrane CENTRAL, and clinical trial registries was performed to identify randomized controlled trials evaluating oxybutynin for vasomotor symptoms in postmenopausal women and cancer populations, including patients receiving endocrine therapy and androgen deprivation therapy. Outcomes included change in hot flash composite score (frequency × severity), change in hot flash frequency, and discontinuation due to adverse effects. Results: 5 studies were identified, including four randomized controlled trials and one observational cohort (409 randomized participants). Oxybutynin was associated with a significant improvement in hot flash composite score compared with control (mean difference 8.81, 95% confidence interval 6.51–11.10; p < 0.00001; I² = 54%). Subgroup analyses demonstrated greater improvement with higher doses (5 mg twice daily) compared with lower doses (2.5 mg twice daily), although both dose ranges were superior to control. Hot flash frequency was significantly reduced with oxybutynin (mean difference 3.88 episodes per day, 95% confidence interval 2.96–4.80; p < 0.00001; I² = 42%), with larger reductions observed with higher-dose regimens. Treatment discontinuation due to adverse effects was more frequent with oxybutynin (odds ratio 2.90, 95% confidence interval 1.19–7.10; p = 0.02; I² = 0%), consistent with a dose-related increase in anticholinergic adverse effects, most commonly dry mouth. Conclusions: Across studies in women and men with cancer-related and menopause-associated vasomotor symptoms, oxybutynin was associated with clinically meaningful reductions in symptom frequency and severity, with evidence of a dose-response relationship and a trade-off with increased anticholinergic adverse effects. These findings inform the role of oxybutynin as a non-hormonal therapeutic option in populations in whom hormonal therapies are limited or contraindicated.