In recent decades, the incidence rates of breast cancer have been increasing rapidly in Asian countries. Previous studies have shown that pregnancy has dual effects on breast cancer. However, with increasing incidence of breast cancer in young women and delayed childbearing, the incidence of pregnancy‐related breast cancer may have been increasing in East Asia.
Dr. Shu‐Chun Chuang and team from the Institute of Population Health Sciences conducted a retrospective cohort study to examine the associations between breast cancer diagnosed during pregnancy and up to 5 years postpartum and total mortality. Breast cancer patients were identified from the Taiwan Cancer Registry (2002–2014). All pregnancies up to 5 years before breast cancer diagnosis were abstracted from the National Health Insurance database and data were then linked to the Taiwan National Death Certificate Database. Follow‐up was calculated from the date of breast cancer diagnosis to the date of death or 31 December, 2014, whichever came first. The hazard ratios (HRs) and the 95% confidence intervals (CI) of the association between pregnancy and total mortality were estimated using Cox proportional hazard models.
The results found that among the 30,230 breast cancer patients, 90 were diagnosed during pregnancy, 347 within a year postpartum, and 1993 during 1–5 years postpartum. By the end of 2014, 2,920 patients were dead. The major cause of death was breast cancer (89%). Compared to patients without pregnancy records, the HRs were 1.42 (95% CI = 0.83–2.45) for patients diagnosed during pregnancy, 1.29 (0.96–1.74) for those diagnosed within a year postpartum, 1.27 (0.95–1.70) for those diagnosed within 1 to 2 years postpartum, and 1.06 (0.88–1.27) for those diagnosed ≥2 to 5 years postpartum, after adjustment for tumor characteristics and treatment. Subgroup analyses revealed an increased risk of mortality for patients diagnosed within a year postpartum in ER+ cancers (HR = 2.11, 95% CI = 1.28–3.47).
Dr. Chung’s findings suggested a recent pregnancy may be associated with higher mortality among ER+ patients. In addition, the higher crude mortality in patients diagnosed during pregnancy could be due to delayed diagnosis and management. Both patients and physicians should be aware of the risk of breast cancer for pregnant or recent postpartum women. Patients diagnosed during pregnancy should receive chemotherapy as early as possible.
Citation: Chuang, SC;Lin, CH;Lu, YS;Hsiung, CA. Association of pregnancy and mortality in women diagnosed with breast cancer: A nationwide population based study in Taiwan. International Journal of Cancer. 2018 Aug 2; Article in Press.