Impact of the interruption of tamoxifen for pregnancy on the recurrence and survival outcomes among young women with breast cancer

Abstract

Background: Young survivors of breast cancer often consider pregnancy after completing or interrupting endocrine therapy. However, concerns remain regarding the safety of tamoxifen interruption for pregnancy and its impact on survival outcomes. We aimed to evaluate the impact of interrupting and resuming tamoxifen for pregnancy on recurrence and mortality in patients with breast cancer, using real-world data. Methods: We conducted a retrospective cohort study using data from the Korean National Health Insurance Service National Health Information Database. Among 32,378 women aged 18–45 years diagnosed with invasive breast cancer and who underwent surgery between 2009 and 2014, patients were categorized into groups based on tamoxifen interruption and pregnancy: Group 1 (interruption and resumption, n = 126), Group 2 (interruption without resumption, n = 261), Group 3 (initiation of tamoxifen after childbirth, n = 41), and Control (no interruption nor pregnancy, n =428). The control group was age-matched to the interruption groups in a 1:1 ratio. Clinical outcomes, including recurrence and mortality, were compared among groups. Results: Over a median follow-up of 8.5 years, Groups 1 and 2 showed significantly lower risks of recurrence than the control group did (hazard ratio [HR] 0.41, 95 % confidence interval [CI]: 0.22–0.76, P = 0.005; HR 0.30, 95 % CI: 0.18–0.50, P < 0.001). In multivariate analysis, Group 2 also showed better survival outcomes (HR 0.18, 95% CI: 0.08–0.41, P < 0.001). Pregnancy outcomes differed across groups: Groups 1 and 2 had higher rates of full-term pregnancies, whereas Group 3 had a significantly higher abortion rate (23.8 %, 23.4 % vs. 56.1 %, respectively). Conclusion: These findings suggest that temporary tamoxifen interruption for pregnancy may be a viable option for young survivors of breast cancer. Further studies are warranted to clarify the long-term impact of tamoxifen interruption on prognosis.