Epidemiology of Pregnancy-Associated Breast Cancer

Abstract

Breast cancer diagnosed during pregnancy or lactation up to 1 year post-partum is often referred to as pregnancy-associated breast cancer (PABC) , although the definition varies with length of post-partum period. The incidence rate has been reported to range from 17.5 to 39.9 per 100,000 births, but the rate is substantially lower during pregnancy (ranging from 3.0 to 7.7) than during the post-partum period (ranging from 13.8 to 32.2). The PABC incidence rate is increasing in many populations, and higher maternal age at birth is a likely explanation. Linkable population-based data on pregnancies and cancer are required to obtain reliable estimates of PABC incidence. In studies comparing outcomes in women with PABC to other young breast cancer patients, it is crucial to adjust for age, since the age distribution of PABC depends both on age at pregnancy and age at breast cancer. Large studies have shown similar prognosis for women with PABC compared to other young women with breast cancer, when accounting for differences in age, stage and other tumour characteristics.

Keywords: Age confounding; Exposure; Incidence; Pregnancy risk window; Prognosis.