In this study, we evaluated the incidence and outcomes of pregnancy after the diagnosis of breast cancer. Additionally, we evaluated the prognosis of patients who became pregnant after breast cancer, according to the treatment.
This was a retrospective cohort study of women aged 20–45 years who were surgically treated for breast cancer between 2004 and 2014 using the Korean National Health Insurance database. Patients were classified according to the treatment: (1) patients who did not receive any treatment, (2) patients who received endocrine therapy-only, (3) chemotherapy-only, (4) endocrine therapy and chemotherapy, (5) chemotherapy and targeted therapy, and (6) endocrine therapy, chemotherapy, and targeted therapy.
Of the 49,348 patients aged 20 to 45 years and who had been newly diagnosed with breast cancer, 2,045 (4.1%) became pregnant after a breast cancer diagnosis. In survival analysis, the pregnant group had a better prognosis and reduced risk of death than the non-pregnant group (HR, 0.41; 95% CI, 0.33 to 0.51, p < 0.001). Among the pregnant group, the HR of the risk of death was 0.17 (95% CI, 0.07 to 0.41, p < 0.001) for patients who became pregnant ≥ 49 months after the diagnosis. In the endocrine therapy-only and the chemotherapy-only groups, pregnant group had a significantly lower risk of death than those in the non-pregnant group (HR, 0.34; 95% CI, 0.12 to 0.98, p = 0.045; HR, 0.29; 95% CI, 0.21 to 0.4, p < 0.001). In patients who received endocrine therapy and chemotherapy, the pregnant group had a better prognosis than the non-pregnant group (HR, 0.57; 95% CI, 0.41 to 0.79, p < 0.001). There was no significant difference between the pregnant group and the non-pregnant group in patients who received chemotherapy and targeted therapy with or without endocrine therapy.
The risk of death was low in women who became pregnant ≥ 49 months after the diagnosis of breast cancer. The prognosis of the pregnant group was better than that of the non-pregnant group, regardless of endocrine therapy. The prognosis of pregnant women was non-inferior to that of non-pregnant women, even in women who received targeted therapy. These findings provide reassurance to patients with HER2-positive cancer who are considering future pregnancy.
Clinical trial identification
Legal entity responsible for the study
Korean Breast Cancer Society.
All authors have declared no conflicts of interest.