Breast Cancer and Pregnancy

Breast cancer is the most common cancer in women who are pregnant or have just had a baby, occurring in about 1 in 3,000 pregnancies. The average patient is between 32 and 38 years old and, since many women are having children later in life, the numbers of pregnant women with breast cancer will probably increase.

Women who are pregnant or nursing usually have tender, swollen breasts, making small lumps hard to detect and possibly leading to a delay in diagnosing (finding) breast cancer. These delays are common, with an average reported delay of 5 to 15 months between the start of symptoms and the diagnosis. Because of this delay, cancers are usually detected at a later stage than they are in women who are not pregnant.

To detect breast cancer, pregnant and nursing women should examine their breasts and undergo a breast examination as part of the routine prenatal examination by a doctor. If an abnormality is found, ultrasound (a test that uses sound waves to find tumors) and a mammogram (a special x-ray of the breast that may find tumors that are too small to feel) can be performed with little risk to the developing fetus. Twenty-five percent of mammograms in women who are pregnant may be negative even though cancer is present. Therefore, a biopsy (the removal of cells or tissues for examination under a microscope) is important for the diagnosis of any mass that can be felt.

Stage Explanation

Once breast cancer has been found, more tests will be done to find out if the cancer has spread from the breast to other parts of the body. This is called staging. To plan treatment, a doctor needs to know the stage of the disease. The PDQ summary on breast cancer describes the stages used for breast cancer.

The usual procedures that are used to stage breast cancer can be changed slightly to be safer for pregnant women. Blood tests may also be used.

Overall survival of pregnant women with breast cancer may be worse than in nonpregnant women at all stages. However, this may be due to the delayed diagnosis. Ending the pregnancy does not seem to effect the outcome of the breast cancer, and is not usually considered as a treatment option. It may be considered, however, depending on the age of the developing fetus, if the treatment options for the mother, such as chemotherapy and radiation therapy, are severely limited by continuing the pregnancy.

Treatment Option Overview

How breast cancer is treated

There are treatments for all patients with breast cancer. The PDQ summary on breast cancer describes the types of treatments that are used.

Early stage cancer (stages I & II)

Surgery is recommended as the first treatment of breast cancer in pregnant women. Since radiation therapy may be harmful to the fetus, modified radical mastectomy is the treatment of choice. Conservative surgery with radiation therapy after the baby is delivered has been used in order to keep the breast intact. If chemotherapy is needed after surgery, it should not be given during the first 3 months of the pregnancy. Chemotherapy given after this time does not usually lead to birth defects, but may cause early labor and low birth weight. The risk of using hormones after surgery, either alone or with chemotherapy, is not known. Radiation therapy should not be used during pregnancy, due to the risk to the fetus.

Late stage disease (stages III & IV)

Radiation therapy during the first three months of pregnancy should be avoided. Chemotherapy may be given after the first three months as discussed under early stage disease. Because the mother may have a limited time to live (only 10% of women with stage III or IV disease live 5 years), and since there is a risk of damage to the fetus during treatment, continuing the pregnancy should be discussed with the mother and her family. Abortion as a treatment option does not improve survival for the mother.

Breast-feeding

Stopping milk production does not improve survival of the mother. However, if surgery is planned, breast-feeding should be stopped to make the breasts smaller and lessen the blood flow in them. It should also be stopped if chemotherapy is planned, since many drugs, especially cyclophosphamide and methotrexate, may occur in high levels in breast milk, which would effect the nursing baby. In general, women receiving chemotherapy should not breast-feed.

Effects of cancer on the fetus

Breast cancer does not appear to damage the fetus since breast cancer cells do not seem to be transferred to the fetus from the mother

Effect of pregnancy in patients who have previously had breast cancer

Pregnancy does not seem to effect the survival of women who have had breast cancer in the past, and the fetus does not seem to be affected, either. Some doctors recommend that a woman should wait two years before trying to have a baby, so that any early return of the cancer would be detected, which may affect the woman's decision to be a parent. The risks of pregnancy after a woman has received bone marrow transplantation and high-dose chemotherapy with or without total body irradiation are unknown, but may result in early labor and low birth weight.

Source: National Cancer Institute, National Institutes of Health, January 2001