Breast Cancer During Pregnancy

  • Diagnosis of a breast cancer during pregnancy:
    • Requires a complex treatment plan with multiple multidisciplinary providers, from both oncology and obstetrics:
      • Coordinating the timing of cancer treatment and the delivery of a high-risk pregnancy
  • Gestational or pregnancy-associated breast cancer:
    • Refers to any breast cancer diagnosed during pregnancy or within the first year after childbirth
    • This is a rare diagnosis, yet remains the most common cancer in pregnant women:
      • Affecting approximately 15 to 35 per 100,000 deliveries:
        • Approximately 0.05%
    • The majority of pregnancy-associated breast cancers:
      • Are ductal in origin;
        • More likely to be poorly-differentiated ER negative or PR negative and HER2-positive compared to non-pregnant women, and present at advanced stages
  • Evaluation of a dominant breast mass should include:
    • Ultrasound and mammogram with fetal shielding, and core biopsy
  • Interpretation of mammography can be difficult in the highly dense tissue of pregnant women:
    • Use of MRI during pregnancy is both contraindicated and unhelpful:
      • Gadolinium contrast may cause fetal harm during the first trimester and is typically avoided
    • Although the majority (approximately 80%) of breast biopsies in pregnant women will be benign:
      • It is critical that malignancy be ruled out
      • Fine needle aspiration during pregnancy:
        • Is associated with a higher rate of false positive and false negative results, without receipt of tumor markers, therefore core biopsy is recommended
  • Staging should be performed in women with advanced disease, and in those with symptoms concerning for metastases:
    • This should include chest radiograph with fetal shielding, liver ultrasound or MRI without contrast, and “low-dose” radionuclide bone scans
  • When possible, treatment of pregnancy-associated breast cancers should follow similar guidelines to non-pregnant patients:
    • And if at all possible, the pregnancy should be carried to term
  • Systemic treatment of breast cancer during pregnancy involves special consideration of both the mother and baby
  • Surgery is safe at all stages
  • Chemotherapy can be delivered:
    • From 14 weeks of gestation following completion of organogenesis through 35 weeks:
      • When it should be stopped to avoid leukopenia in preparation for delivery
  • Data from a single-institution prospective study indicates that FAC chemotherapy (5-FU, doxorubicin, and cyclophosphamide):
    • Is safe during the second and third trimesters:
      • With fetal malformations approximating 1%
  • Experience with taxanes remained limited:
    • But National Comprehensive Cancer Network (NCCN) guidelines recommend weekly paclitaxel if warranted
  • Methotrexates:
    • Are contraindicated due to teratogenic side effects
  • Although 20% of pregnancy-associated breast cancers are HER2-positive:
    • Anti-HER2 therapy including trastuzumab has not been proven safe during pregnancy and is best delivered in the adjuvant setting
  • MotHER, a prospective U.S. registry, is evaluating women exposed to trastuzumab +/- pertuzumab during pregnancy or within 6 months of conception and following pregnancy outcomes and infants for the first month of life:
    • Current recommendations suggest that targeted anti-HER2 therapy be delayed until after delivery
  • Breast conservation is not recommended if radiation would be timed during pregnancy because this is contraindicated:
    • However, it can be performed if radiation falls after delivery
  • Axillary lymph node dissection was previously recommended:
    • But sentinel lymph node biopsy is feasible and should be offered
  • Hormone therapy should be postponed until after childbirth
  • Chemotherapy during pregnancy can cause concerns for the fetus which depend on the timing of drug administration:
    • Congenital malformations can occur in the first trimester, and in the second and third trimesters prematurity, low birth weight and myelosuppression are the greatest concerns:
      • Among approved chemotherapy agents, long-term outcomes of children with in-utero exposure demonstrate normal development, cognition, and school performance when prematurity is controlled for


1. Macdonald HR Pregnancy associated breast cancer. Breast J. 2020 Jan 14. doi: 10.1111/tbj.13714. [Epub ahead of print]

2. Goidescu I, Nemeti G, Caracostea G, Eniu DT, Chiorean A, Pintican R, Cruciat G, Muresan D. The role of imaging techniques in the diagnosis, staging and choice of therapeutic conduct in pregnancy associated breast cancer. Med Ultrason. 2019 Aug 31;21(3):336-343. doi: 10.11152/mu-1958. Review.

3. Alfasi A, et al. Breast Cancer During Pregnancy- Current Paradigms, Paths to Explore. Cancers. 2019; 11: 1669

4. National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines). Breast Cancer. Available with login at:

5. Gooch JC1,2, Chun J1, Kaplowitz E1, Guth A1, Axelrod D1, Shapiro R1, Roses D1, Schnabel F1. Pregnancy-associated breast cancer in a contemporary cohort of newly diagnosed women Breast J.2019 Aug 25. doi: 10.1111/tbj.13510. [Epub ahead of print]

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