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Breast cancer

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Breast cancer during pregnancy

Although breast cancer is the most common cancer diagnosed during pregnancy, it is rare. About 1 out of every 3000 pregnant women is diagnosed with breast cancer.

When women are pregnant or breast-feeding, their breasts are often tender, swollen and have many small lumps. This makes it harder to find breast cancer early, so breast cancer is often found at a later stage in pregnant women.

Many women who are diagnosed with breast cancer during pregnancy are concerned that they can pass the breast cancer cells to their baby. There is no evidence that a fetus (developing baby) can get cancer from its mother while in the womb. There is also no evidence that a woman can pass cancer cells to her baby through breast-feeding.


It is important for women who are pregnant or breast-feeding to know what is normal for their breasts, and to report any changes to their doctor. The signs and symptoms of breast cancer are the same in pregnant or breast-feeding women as they are in women who are not pregnant or breast-feeding. The most common symptom is a lump in the breast or armpit.

A clinical breast exam should be a regular part of a woman’s physical examination before, during and after pregnancy.

Diagnostic tests may be ordered if the symptoms of breast cancer are present, or if the doctor suspects breast cancer after a physical examination. The tests may include:

  • breast ultrasound
    • Ultrasound does not use radiation, so pregnant women do not require any special precautions.
  • mammography
    • Mammography can be done safely on a pregnant woman by using a special shield to protect the abdomen.
    • Mammography is less reliable in pregnant or breast-feeding women. Changes to and thickening of the breast tissue make it harder for the x-rays to provide a clear picture.
  • biopsy
  • hormone receptor status testing
    • Breast cancer tumours found in pregnant women are less likely to be estrogen and progesterone positive.
  • HER2 status testing
    • The average number of tumours that overexpress HER2 is the same in both pregnant and non-pregnant women. This means that breast cancer in pregnant women has the same likelihood of being HER2 positive as it does in non-pregnant women.

If necessary, further tests will be done:

  • chest x-ray
    • The abdomen is shielded during x-ray to protect the fetus.
  • liver ultrasound
  • bone scan
    • Special procedures may be done to reduce the risk of radiation exposure to the fetus.

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Treatment decisions for breast cancer in pregnancy are based on the:

  • stage of breast cancer
  • age of the fetus

Ending a pregnancy (therapeutic abortion) is not considered a necessary part of treatment because it does not improve a mother’s prognosis or survival.


Surgery is the main treatment for breast cancer during pregnancy. The types of surgery are:

  • modified radical mastectomy – the most common procedure
  • breast-conserving surgery
    • Surgery may be done during pregnancy, but adjuvantadjuvantTreatment given in addition to the first-line therapy (the first or standard treatment) to help reduce the risk of a disease (such as cancer) coming back (recurring). radiation therapy will be delayed until after the baby is born.
  • axillary lymph node dissection
    • Sentinel lymph node biopsySentinel lymph node biopsyThe first lymph node in a chain or cluster of lymph nodes that receive lymph fluid from a tumour. It is the first lymph node that cancer is likely to spread to from the original (primary) site. is not usually done during pregnancy because of concerns about the effects that the dye used during the test will have on the fetus.

Surgery can be safely done at any time during pregnancy. Many doctors wait until the fetus is at least 12 weeks old because there will be less risk of a miscarriage during surgery.


Chemotherapy is not given during the first 3 months (first trimester) of pregnancy because there is a very high risk of hurting the fetus and causing birth defects. Women should not breast-feed during chemotherapy as many of the chemotherapy drugs can be passed on to the baby through breast milk.

Some drugs used to treat breast cancer, such as methotrexate, can cause spontaneous abortion and birth defects. These drugs are not used to treat pregnant women with breast cancer.

Some chemotherapy drugs used to treat breast cancer after the first trimester have been shown to be safest for both the mother and the baby:

  • FAC
    • 5-fluorouracil (Adrucil, 5-FU), doxorubicin (Adriamycin) and cyclophosphamide (Cytoxan, Procytox)

FAC may cause some side effects in the baby, including:

  • slowed growth
  • premature delivery
  • hair loss
  • low white blood cell count (neutropenia)
    • Chemotherapy is often stopped 2 weeks before delivery to reduce the risk of neutropenia in both the baby and the mother.

FAC may cause treatment-induced menopause in the mother, especially if she is over the age of 30.

Two studies have shown that pregnant women who had chemotherapy for breast cancer did not have miscarriages, stillbirths or deaths. Most children did not have any long-term problems. However, there is very little information about children who were exposed to breast cancer chemotherapy during pregnancy.

Researchers are looking for other chemotherapy drugs that may be safe during pregnancy. Other chemotherapy drugs used for breast cancer may be used after the baby is born.

For more detailed information on specific drugs, go to sources of drug information.

Radiation therapy

External beam radiation therapy should not be given during pregnancy. The risk of damage to the fetus is highest during the first trimester, but it remains high throughout pregnancy.

If a woman chooses to have breast-conserving surgery, or if radiation is needed after a mastectomy, it should be done after the baby is born.

Hormonal therapy

Breast cancer is also treated with hormonal therapy. The main hormonal therapy drug used in premenopausal women is tamoxifen (Novaldex, Tamofen). This drug may cause birth defects and miscarriage, so it is not recommended for use during pregnancy. Tamoxifen can also be passed to the baby through breast milk, so women taking this drug should not breast-feed.

Other hormonal therapy drugs are used only with post-menopausal women and would not be used with women who are of child-bearing age.

For more detailed information on specific drugs, go to sources of drug information.

Biological therapy

Biological therapy is another treatment option for breast cancer. Trastuzumab (Herceptin) may be offered for breast cancer tumours that make large amounts of (overexpress) HER2. However, there is not enough evidence that trastuzumab is safe during pregnancy. It may be offered to a woman with breast cancer after the baby is born. Breast-feeding while taking trastuzumab is not recommended because the drug can be passed to the baby through breast milk.

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Pregnant women with breast cancer may have questions about their prognosis and survival. Prognosis and survival depend on many factors. Only a doctor familiar with a woman’s medical history, type of cancer, stage, characteristics of the cancer, treatments chosen and response to treatment can put all of this information together with survival statistics to arrive at a prognosis.

Prognosis for women with breast cancer during pregnancy is hard to determine because there have been very few long-term studies done. One Canadian study that looked at breast cancer in pregnant and non-pregnant women found there was no difference in survival between the 2 groups.

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Pregnancy after breast cancer

Many women are concerned that they will not be able to have children after treatment for breast cancer. Some chemotherapy drugs used for breast cancer, such as cyclophosphamide, can cause fertility problems, especially in women who are over the age of 30 at the time of treatment. Before treatment for breast cancer begins, women should speak with their doctors about options for preserving their fertility.

Women who have had breast cancer during pregnancy are also concerned that another pregnancy will cause their breast cancer to recur. Most studies have shown that women who become pregnant after successful treatment for breast cancer do not have a higher risk of recurrence or a worse prognosis than women who chose not to have more children. However, most doctors will suggest that a woman wait 2 years after treatment has finished. Breast cancer that recurs within 2 years of treatment may be more aggressive, and a new pregnancy may make it more difficult to treat a recurrence.

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