Factors associated with worsening sexual function during adjuvant endocrine therapy in a prospective clinic-based cohort of women with early-stage breast cancer

Purpose Sexual function problems are common but under-reported among women receiving adjuvant endocrine therapy for breast cancer. Worsening scores on patient-reported outcomes (PROs) may identify those at risk for sexual function problems during treatment. We performed a secondary analysis of prospectively collected PROs in women receiving adjuvant endocrine therapy to identify factors associated with worsening sexual function. Methods Women with stage 0–III breast cancer initiating adjuvant endocrine therapy participating in a prospective cohort completed PROs at baseline, 3, 6, 12, 24, 36, 48, and 60 months. Sexual function was evaluated by the MOS-SP measure. Other measures included PROMIS pain interference, fatigue, depression, anxiety, physical function, and sleep disturbance and the Endocrine Symptom Subscale of the FACT-ES. We evaluated associations between score worsening of at least the minimal important difference (MID) in PROMIS T-scores (4 points) and FACT-ES scores (5 points) with score worsening of at least the MID in MOS-SP scores (8 points) using logistic regression. Results Among 300 participants, 45.7% experienced ≥ 8-point worsening of MOS-SP score at any time point compared to baseline. Worsening endocrine symptoms (OR 1.34, 95% CI 1.22–1.49, p < 0.001), worsening physical function (OR 1.09, 95% CI 1.00–1.18, p = 0.06), and prior mastectomy (OR 1.45, 95% CI 0.94–2.23, p = 0.09) were associated with MOS-SP score worsening by at least the MID. Conclusion Worsening endocrine symptoms and physical function identified on PROs are associated with worsening sexual function during adjuvant endocrine therapy. Routine assessment of these domains with PROs may identify women at risk for sexual function problems. Trial registration number NCT01937052; Date of Registration: 09/09/2013.