Incidence
Breast cancer is the most common cancer in pregnant and postpartum women and occurs in about 1 in 3,000 pregnant women. The average patient is between the ages of 32 years and 38 years. Because many women are choosing to delay childbearing, it is likely that the incidence of breast cancer during pregnancy will increase.
Anatomy
Anatomy of the female breast. The nipple and areola are shown on the outside of the breast. The lymph nodes, lobes, lobules, ducts, and other parts of the inside of the breast are also shown.
Diagnostic Evaluation
The natural tenderness and engorgement of the breasts of pregnant and lactating women may hinder detection of discrete masses and early diagnosis of breast cancer. Delays in diagnosis are common, with an average reported delay of 5 to 15 months from the onset of symptoms.[
The following tests and procedures may be used to diagnose breast cancer during pregnancy:
To detect breast cancer, pregnant and lactating women should consider practicing self-examination and undergo a clinical breast examination as part of the routine prenatal examination by a doctor. If an abnormality is found, diagnostic approaches such as ultrasound and mammography may be used. With proper shielding, mammography poses little risk of radiation exposure to the fetus.[
Because at least 25% of mammograms in pregnancy may be negative in the presence of cancer, a biopsy is essential for the diagnosis of any palpable mass. Diagnosis may be safely accomplished with a fine-needle aspiration, core biopsy, or excisional biopsy under local anesthesia. To avoid a false-positive diagnosis as a result of misinterpretation of pregnancy-related changes, the pathologist should be advised that the patient is pregnant.[
Breast cancer pathology is similar in age-matched pregnant and nonpregnant women. Hormone receptor assays using a competitive binding assay are usually negative in pregnant patients with breast cancer, but this may be the result of receptor binding by high serum estrogen levels associated with the pregnancy. Enzyme immunocytochemical receptor assays are more sensitive than competitive binding assays. A study that used both assay methods indicated similar receptor positivity between pregnant and nonpregnant women with breast cancer.[
For more information, see the Diagnosis section in Breast Cancer Treatment.
Prognosis
The overall survival of pregnant women with breast cancer may be worse than that of nonpregnant women at all stages.[
References:
Staging Evaluation
The following procedures are used to determine the extent of the cancer:
Procedures used for determining the stage of breast cancer are modified for pregnant women to avoid radiation exposure to the fetus. Nuclear scans cause fetal radiation exposure.[
Chest x-rays with abdominal shielding are considered safe, but as with all radiological procedures, they are used only when essential for making treatment decisions.[
For the diagnosis of bone metastases, a bone scan is preferable to a skeletal series because the bone scan delivers a smaller amount of radiation and is more sensitive. A bone scan delivers 0.001 Gy.[
Evaluation of the liver can be performed with ultrasound, and brain metastases can be diagnosed with an MRI scan. Data on MRI during pregnancy are not available, but gadolinium crosses the placenta and is associated with fetal abnormalities in rats.[
American Joint Committee on Cancer (AJCC) Stage Groupings and Definitions of TNM
For more information, see the Stage Information for Breast Cancer section in Breast Cancer Treatment.
References:
Generally, pregnant women with stage I or stage II breast cancer are treated in the same way as nonpregnant patients, with some modifications to protect the fetus.
Treatment options for early/localized/operable breast cancer in pregnant women include the following:
The use of trastuzumab during pregnancy is contraindicated.
Surgery
Surgery is recommended as the primary treatment of breast cancer in pregnant women.
The data regarding safety of sentinel lymph node biopsy in pregnant patients are limited to several retrospective case series. One study examined sentinel lymph node biopsy in eight patients in the first trimester, nine patients in the second trimester, and eight patients in the third trimester. Technetium Tc 99m alone was used in 16 patients, methylene blue dye alone was used in seven patients, and two patients had unknown mapping methods. All 25 patients had live-born infants, of whom 24 were healthy, and one had a cleft palate (in the setting of other maternal risk factors).[
Because radiation in therapeutic doses may expose the fetus to potentially harmful scatter radiation,[
Chemotherapy
Data suggest that it is safe to administer certain chemotherapeutic drugs after the first trimester, with most pregnancies resulting in live births with low rates of morbidity in the newborns.
Anthracycline-based chemotherapy (doxorubicin plus cyclophosphamide or fluorouracil, doxorubicin, and cyclophosphamide [FAC]) appears to be safe to administer during the second and/or third trimester on the basis of limited prospective data.[
Evidence (use of chemotherapy during the second and/or third trimester of pregnancy):
Fluorouracil dosing
The DPYD gene encodes an enzyme that catabolizes pyrimidines and fluoropyrimidines, like capecitabine and fluorouracil. An estimated 1% to 2% of the population has germline pathogenic variants in DPYD, which lead to reduced DPD protein function and an accumulation of pyrimidines and fluoropyrimidines in the body.[
Endocrine Therapy
Endocrine therapy is generally avoided until after delivery. Case reports and a literature review of tamoxifen during pregnancy show that tamoxifen administration during pregnancy is associated with vaginal bleeding, miscarriage, congenital abnormalities such as Goldenhar syndrome, and fetal death.[
Targeted Therapy
The use of trastuzumab during pregnancy is contraindicated based on results of a systematic review of 17 studies (18 pregnancies, 19 newborns).[
References:
There is no standard treatment for patients with advanced (stage III or stage IV) breast cancer during pregnancy. Most studies show a 5-year survival rate of 10% in pregnant patients with stage III or IV disease.
First-trimester radiation therapy should be avoided. Chemotherapy may be given after the first trimester as discussed in the section on Treatment of Early/Localized/Operable Breast Cancer During Pregnancy.
Because the mother's life span may be limited, and there is a risk of fetal damage with treatment during the first trimester,[
References:
Lactation
Suppression of lactation does not improve prognosis. If surgery is planned, however, lactation is suppressed to decrease the size and vascularity of the breasts. If chemotherapy is to be given, lactation is also suppressed because many antineoplastic agents (i.e., cyclophosphamide and methotrexate), when given systemically, may occur in high levels in breast milk and would affect the nursing baby. Women receiving chemotherapy should not breastfeed.[
Fetal Consequences of Maternal Breast Cancer
No damaging effects on the fetus from maternal breast cancer have been demonstrated,[
Pregnancy in Patients With a History of Breast Cancer
Based on limited retrospective data, pregnancy does not appear to compromise the survival of women with a previous history of breast cancer, and no deleterious effects have been demonstrated in the fetus.[
Little is known about pregnancy after bone marrow transplant and high-dose chemotherapy with or without total-body irradiation. In one report of pregnancies after bone marrow transplant for hematologic disorders, a 25% incidence of preterm labor and low birth weight for gestational-age infants was noted.[
References:
The PDQ cancer information summaries are reviewed regularly and updated as new information becomes available. This section describes the latest changes made to this summary as of the date above.
Treatment of Early/Localized/Operable Breast Cancer During Pregnancy
Added Fluorouracil dosing as a new subsection.
This summary is written and maintained by the
Purpose of This Summary
This PDQ cancer information summary for health professionals provides comprehensive, peer-reviewed, evidence-based information about the treatment of breast cancer during pregnancy. It is intended as a resource to inform and assist clinicians in the care of their patients. It does not provide formal guidelines or recommendations for making health care decisions.
Reviewers and Updates
This summary is reviewed regularly and updated as necessary by the
Board members review recently published articles each month to determine whether an article should:
Changes to the summaries are made through a consensus process in which Board members evaluate the strength of the evidence in the published articles and determine how the article should be included in the summary.
The lead reviewers for Breast Cancer Treatment During Pregnancy are:
Any comments or questions about the summary content should be submitted to Cancer.gov through the NCI website's
Levels of Evidence
Some of the reference citations in this summary are accompanied by a level-of-evidence designation. These designations are intended to help readers assess the strength of the evidence supporting the use of specific interventions or approaches. The PDQ Adult Treatment Editorial Board uses a formal evidence ranking system in developing its level-of-evidence designations.
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The preferred citation for this PDQ summary is:
PDQ® Adult Treatment Editorial Board. PDQ Breast Cancer Treatment During Pregnancy. Bethesda, MD: National Cancer Institute. Updated <MM/DD/YYYY>. Available at:
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Last Revised: 2024-07-11
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