Increased Mortality in Women with Breast Cancer Detected during Pregnancy and Different Periods Postpartum

Background: Because of a continued trend toward postponed childbearing, the incidence of pregnancy-associated breast cancer (PABC) is likely to increase. This study investigated the mortality in women with PABC in relation to when the tumor was detected (during pregnancy, different postpartum periods) and by time since diagnosis, compared with women with non-PABC. Methods: A population-based cohort study of 15,721 Swedish women diagnosed with breast cancer between ages 15 to 44 years, of whom 1,110 (7%) had a PABC (diagnosed during or within two years after pregnancy). Information on outcome and potential confounders was obtained from population-based health registers. Mortality rates and HRs with 95% CIs were estimated. Results: Women with PABC had higher mortality compared with women with non-PABC diagnosed at the same age and calendar period. Among women with PABC, 46% died within 15 years after diagnosis, whereas 34% died among non-PABC patients. The mortality in both groups peaked at around two years after diagnosis, with the highest peak occurring in women diagnosed 4 to 6 months after delivery (HR = 3.8, 95% CI: 2.4-5.9). An increased mortality among women with PABC remained until 10 years after diagnosis. Conclusions: Women with PABC had a poorer prognosis compared with women with breast cancer and no recent birth. The mortality increase was most pronounced in the subgroup of women diagnosed shortly after delivery. Impact: An increased awareness among clinicians may help reduce the mortality in women with PABC, for example, by avoiding undue delays in diagnosis and treatment. Cancer Epidemiol Biomarkers Prev; 20(9); 1865-72. (C)2011 AACR.