Are you pregnant and considering breastfeeding? Do you also have a family history of breast cancer? If you are preparing for childbirth you may have many questions surrounding breast cancer and also concerns about breastfeeding.
Did you know that women can develop breast cancer during pregnancy? Pregnancy-associated breast cancer is breast cancer that is diagnosed during pregnancy, in the first year following birth, or any time during breastfeeding.1
Breast cancer is the most common cancer in the United States except for skin cancers, and it accounts for 1 in 3 new cancers impacting women each year.2 It is rare, but some women develop cancer, including breast cancer, during pregnancy. Breast cancer is the most common type of cancer seen in pregnancy and after birth, occurring in about 1 in 3000 pregnant women and usually between ages 32 years and 38 years.3
In women under age 30, about 20 percent of breast cancers are associated with pregnancy.1
If you develop breast cancer while you’re pregnant, there are special considerations for treatment and challenges that may affect the safety of both you and your fetus. In this article, we will cover how breast cancer can affect pregnancy and breastfeeding.
How is Breast Cancer in Pregnancy Diagnosed?
Some of the typical symptoms seen in breast cancer, such as breast tenderness and enlargement, are symptoms also seen in pregnancy. Physicians may mistake the symptoms of undiagnosed cancer as symptoms of pregnancy, leading to delays in diagnosis.3,4 Breast cancer in pregnancy is typically not diagnosed until 5 to 15 months after symptoms start.3
If you are suspected of having breast cancer while pregnant, your doctor may be hesitant to perform certain diagnostic procedures due to risks to your fetus. Even if they choose to do further testing, your pregnancy can lead to misdiagnosis or false-negative results.
Some of the tests and procedures to diagnose breast cancer during pregnancy include:
- Breast exam (self-exams and clinical exams)
- Ultrasound or MRI
- Mammogram
- Biopsy and hormone receptor test
If you detect something abnormal during your self-examination, you should see your doctor to have a clinical breast exam. It’s recommended that your doctor perform a detailed clinical breast exam at your first prenatal visit and diligently consider that breast cancer may be present.5
Ultrasounds and MRIs are imaging procedures that do not require the fetus to be exposed to radiation. Ultrasounds are also inexpensive and effective at detecting solid masses in 97% of people.5 Ultrasounds are preferred in pregnancy over other methods like CT scans.4 An MRI may not cause radiation risks to the fetus, but can potentially cause harm because of heating.
Serum tumor markers are typically useful in cancer diagnosis, but they are not useful in pregnancy due to changes in serum levels.
Surgical procedures such as biopsies (which may require the use of anesthetic drugs) are considered safe during pregnancy and are recommended if necessary.4 Mammograms may not be effective during pregnancy. About 25% of mammograms performed during pregnancy may give a false-negative result because of increased breast density.3,5 Biopsies are recommended over mammograms in pregnancy.3
Treatment of Breast Cancer During Pregnancy
The focus of breast cancer treatment during pregnancy is to remove the cancer while also protecting the fetus. There are both surgical and medical options for treating cancer in this special population.
Surgery
Surgical treatment is the preferred way to treat pregnancy-associated breast cancer.4,5 Surgery is not associated with known birth defects; however, there are risks associated with surgery.
It does increase your chance of having a miscarriage. There is also an increased chance that you may go into labor prematurely and your baby would have a low birth weight.4 There are no anesthetic drugs used in surgery that have been shown to be fatal to the fetus.
Mastectomy (complete breast removal) is recommended in the first trimester. If you are in your second or third trimester, lumpectomy (removal of only the cancerous lump in the breast) followed by radiation after delivery is recommended.5
Although surgical treatment is recommended during pregnancy to treat cancer, reconstructive surgical procedures should be delayed until after giving birth.
If you have a lumpectomy during pregnancy, it may decrease your milk supply and make breastfeeding difficult.
Radiotherapy
Radiation is not recommended as a treatment for pregnancy-associated breast cancer because of the potential risk to the fetus.4,5 It can create fatal risks to the fetus and also increase the likelihood of childhood cancers and blood disorders.5 If radiation is needed, it should be delayed until after childbirth.4,5,6
Radiation of breast tissue during pregnancy can affect your milk ducts and decrease your breast milk supply, making breastfeeding challenging.
Chemotherapy
Standard treatment for breast tumors larger than 1 cm is 4-6 months of chemotherapy.5 The problem in pregnancy is that all chemotherapy medications used to treat breast cancer cause serious malformations in the fetus.4,5 (Pregnancy Category D)
Some research suggests that it may be safe to take some types of chemotherapy after the first trimester.3,6
Endocrine Therapy
Endocrine therapy should be avoided until after childbirth.3 These medications work by blocking estrogen and progesterone in the body. These hormones are needed for a healthy pregnancy and development of the fetus. Tamoxifen is the most commonly used type of endocrine therapy used in breast cancer for non-pregnant women. Tamoxifen has been shown to cause harm to the fetus and should not be used in pregnancy.4,5
Special Considerations for Pregnancy and Breast Cancer
There is no research that shows that breast cancer cells transfer to the fetus. As long as the cancer stays within the breast tissue, breast cancer itself does not cause damage to the fetus.
If you’ve been previously diagnosed with breast cancer, doctors recommend that you wait at least 2 years after diagnosis before becoming pregnant. The delay will give additional time if the cancer returns.3
Breast Cancer Effects on Breastfeeding
If you were considering breastfeeding before you were diagnosed with breast cancer, you may be wondering if your diagnosis will affect your ability to breastfeed once you deliver the baby.
Breast cancer treatments can decrease your milk supply and make breastfeeding difficult.
Radiation of the breast tissue can lead to changes in the nipple and milk ducts that will make breastfeeding challenging.5 If you only had breast cancer and radiation in one breast, it may be possible to breastfeed from the non-treated breast.6
Endocrine therapies, such as tamoxifen, can lead to abnormalities in the fetus and should be avoided until after delivery. If your doctor suggests endocrine therapy for you, they may suggest that you start these medications after you give birth. These treatments can pass into breast milk and increase in the breast milk over time, so it is not recommended that you breastfeed if you are prescribed an endocrine therapy after childbirth.7,8
Chemotherapy medications can pass into the breastmilk and it is not recommended that you breastfeed while you are receiving chemotherapy or shortly after your treatments end.6,9
References
- Up To Date. (2024). Gestational Breast Cancer: Epidemiology and Diagnosis. https://www.uptodate.com/contents/gestational-breast-cancer-epidemiology-and-diagnosis Accessed September 16, 2024
- American Cancer Society. (2024). Key Statistics for Breast Cancer https://www.cancer.org/cancer/types/breast-cancer/about/how-common-is-breast-cancer.html
- National Cancer Institute. (2024). Breast Cancer Treatment During Pregnancy. https://www.cancer.gov/types/breast/hp/pregnancy-breast-treatment-pdq Accessed September 16, 2024
- Hepner Adriana et al. (2019). Cancer During Pregnancy: The Oncologist Overview https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6396773/ Accessed September 17, 2024
- Woo Junda C. MD et al. (2003). Breast Cancer in Pregnancy: A Literature Review https://doi.org/10.1001/archsurg.138.1.91
- Breast Cancer Now. (2024). Breastfeeding and breast cancer treatment. https://breastcancernow.org/about-breast-cancer/primary-breast-cancer/breast-cancer-in-younger-women/breastfeeding-and-breast-cancer-treatment/ Accessed September 22, 2024
- National Breast Cancer Foundation Inc. (2024). Breast Cancer During Pregnancy. https://www.nationalbreastcancer.org/breast-cancer-and-pregnancy/
- Drugs and Lactation Database. (2024). Tamoxifen. https://www.ncbi.nlm.nih.gov/books/NBK501106/ Accessed September 22, 2024
- Drugs and Lactation Database. (2024) Methotrexate. https://www.ncbi.nlm.nih.gov/books/NBK501341/ Accessed September 22, 2024
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