LAUSR

INTRODUCTION Pregnancy rarely coincides with breast cancer, but when it does, uncertainties remain about how survival is affected. In a nation-wide study, we investigated survival in women diagnosed with breast cancer during pregnancy. MATERIALS AND METHODS Through health registries, we identified women with breast cancer at ages 15-44 years from 1973-2016 in Denmark and included 156 who were pregnant at diagnosis and 11,110 who were not. We compared overall mortality in pregnant and non-pregnant women using multivariate Cox regression stratified by time since cancer: <2 and ≥2 years. RESULTS During the first 2 years after diagnosis, the hazard ratio of overall death was 2.28 (95% CI: 1.48-3.52) for pregnant versus non-pregnant breast cancer patients after adjustment for age and calendar period and 1.62 (95% CI: 1.05-2.50) after further adjustment for extent of disease. Adjusting for additional tumor characteristics, the hazard ratio was still significantly increased. Beyond the first 2 years, there was no excess mortality. CONCLUSION Our study identifies the early period after breast cancer as a period of particular interest in future studies on survival after breast cancer in pregnancy. We found no evidence that survival is affected by pregnancy when 2 or more years have passed since diagnosis.