A new Australian study presented at the seventh European Breast Cancer Conference (EBCC7) in Spain has reported that women who are diagnosed within 12 months of giving birth have a 48% higher risk of death from breast cancer than similar women without associated pregnancy. Women diagnosed with gestational breast cancer (defined as diagnosed while pregnant or within 12 months of giving birth) have been reported to have poor survival when compared to other young women with breast cancer. However, the influence of pregnancy on the survival of young women who develop breast cancer has not been well studied. The study included the cohort of 2,752 women under age 45 diagnosed with breast cancer in Western Australia between 1982 and 2003. The study took into account age at diagnosis, histological tumor grade, disease stage, lymph node status, pregnancy status (no pregnancy, pregnant or postpartum), length of survival and mortality. Overall survival was defined as the time from diagnosis to the date of death or year-end 2007, whichever came first.

A total of 182 women were diagnosed with gestational breast cancer (55 pregnant at diagnosis and 127 within a year of giving birth). Not unexpectedly, higher tumor grade, more advanced disease stage, and positive lymph node status each were associated with poor survival for all women in the study. However, postpartum breast cancer cases were found to have a 48% increased risk of death compared to breast cancer cases without a related pregnancy. On the other hand, women who were pregnant at diagnosis had only a 3% increased risk of death compared to non-gestational breast cancer cases. The authors conclude that women who were diagnosed with breast cancer within 12 months of giving birth were more likely to die than other young women diagnosed with breast cancer whereas women who were pregnant at diagnosis had only slightly increased risk. The results suggest that the combined cumulative effect of pregnancy plus breast feeding plays a role in breast cancer prognosis and needs further investigation.

Pregnancy and breast cancer

Generally speaking, pregnancy and breastfeeding have been found to decrease the long-term risk of breast cancer. Both reduce the lifetime number of menstrual cycles and the associated hormonal fluctuations and cumulative exposure to progesterone. This may explain findings in previous studies of reduced risks of breast cancer in women who had ever given birth or who had given birth and nursed their babies.

However, there appears to be a temporary period of elevated breast cancer risk associated with pregnancy and breastfeeding. The present study indicates that this period of higher risk is also associated with increased breast cancer-related mortality. It is not clear whether that this is because pregnancy and nursing introduce temporary changes in the breast or hormone levels that are more favorable for the development of breast cancer or that such cancer tends to be more advanced when it is diagnosed because changes in the breast mask breast cancer. In any case, it is important for women who become pregnant not to assume that all breast symptoms or abnormalities are benign, particularly if the symptoms persist.