Treatment of breast cancer during pregnancy

Treatment for pregnant women with breast cancer depends on how long the woman has been pregnant.

Radiation treatment during pregnancy is known to increase the risk of birth defects, so it is not recommended for pregnant women with breast cancer. This means that breast-conserving surgery is only an option if treatment (which includes radiation treatment) can wait until after the baby is born. Breast biopsy, and even modified radical mastectomy and lymph node removal, are safe for the mother and the baby.

For a long time it was thought that chemotherapy (chemo) was a danger to the fetus. But some studies have found that using certain chemo drugs during the fourth to ninth months does not increase the risk of birth defects. The safety of chemo during the first 3 months of pregnancy has not been studied.

Targeted therapy drugs, including trastuzumab (Herceptin), may affect the fetus, and cannot be given until after delivery.

Hormone treatment may affect the fetus and should not be started until after the patient has given birth.

Many chemo, hormone therapy, and targeted therapy drugs can enter breast milk and could be passed on to the baby, so breast-feeding is not usually recommended if the woman is having these treatments.

For more information, see our document, Pregnancy and Breast Cancer.