Treatment of breast cancer during pregnancy

Breast cancer is diagnosed in about 1 pregnant woman out of 3,000. In general, treatment recommendations depend upon how long the woman has been pregnant.

Radiation therapy during pregnancy is known to increase the risk of birth defects, so it is not recommended for pregnant women with breast cancer. Since breast-conserving surgery (BCS) needs to be followed with radiation, BCS is only an option if radiation can be delayed until after the baby is delivered. But breast biopsy procedures and even mastectomy and lymph node removal are safe for the mother and fetus.

For a long time it was assumed that chemotherapy (chemo) was dangerous to the fetus. But several studies have found that using certain chemo drugs during the second and third trimesters (the fourth to ninth months) does not increase the risk of birth defects. Because of concern about the potential damage to the fetus, the safety of chemo during the first trimester (the first 3 months) of pregnancy has not been studied.

Both hormone therapy and targeted therapy can affect the fetus and should not be started until after the patient has given birth.

Many chemo and hormone therapy drugs can enter breast milk and could be passed on to the baby, so breastfeeding is not usually recommended during chemo,hormone, or targeted therapy.

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