Breast Cancer

Breast Cancer

When considering breast cancer and breastfeeding, the discussion must be categorized into history of breast cancer versus breast cancer diagnosed during lactation. The open access ‘Academy of Breastfeeding Medicine Protocol #34, Breastfeeding and Breast Cancer’ provides a comprehensive review of these patients and is available at (PDF).

History of Breast Cancer

Modern breast cancer treatment involves a multidisciplinary approach to care, including chemotherapy, surgery, radiation, and endocrine therapy.   Young survivors may have undergone some or all of these therapies prior to pregnancy and lactation.

Previous chemotherapy does not preclude future breastfeeding.  However, chemotherapy intended to concentrate in breast tissue to treat breast cancer may result in long-lasting effects on lactational ability1. Patients should be referred for support and guidance during pregnancy and in the postpartum period.

A history of a total mastectomy, skin sparing total mastectomy, or nipple sparing total mastectomy precludes breastfeeding on the affected side.  It should be noted that a mastectomy removes 95% or greater of breast parenchyma2. However, due to variation in mastectomy technique, some patients may have more residual functional breast tissue than others.  This may hypertrophy during pregnancy and give the appearance of functionality.  However, no normal lactation should be expected from this breast.

A history of partial mastectomy (“lumpectomy” or “segmental mastectomy”) does not preclude breastfeeding in itself.  However, a patient with a history of partial mastectomy for cancer very likely would have undergo post-operative adjuvant radiation therapy.  Radiation therapy affects the functional ability of the breast, the elasticity of the skin, and its effects can continue for years after treatment3. Limited lactational ability has been reported from a treated breast4, but the more efficacious approach to lactation may be to augment the unaffected breast capacity.

Endocrine may be recommended adjuvantly.  Breastfeeding is contraindicated with use of aromatase inhibitors (AI’s), as they transfer readily into breastmilk and may suppress estrogen in the infant5. As above, SERM’s are also contraindicated with breastfeeding.  The Pregnancy Outcome and Safety of Interrupting Therapy for women with endocrine responsIVE breast cancer (POSITIVE) trial, which is evaluating the interruption of up to two years of endocrine therapy, will help inform discussions regarding potential for safe periods of interruption for breastfeeding6.

Breast Cancer Diagnosed During Lactation

As in patients with a history of breast cancer, those women who present with a new diagnosis of breast cancer while lactating in the postpartum period will be managed by a multidisciplinary team.  Because many cancers that present in the postpartum period are biologically aggressive and locally advanced at presentation7, many patients will undergo chemotherapy prior to surgery.

Due to long half lives and high transfer of cytotoxic agents into breastmilk, breastfeeding is contraindicated with chemotherapy for breast cancer8. Some patients may seek to express and discard milk. However, due to the general 4-6 month duration of breast cancer regimens, we recommend weaning prior to chemotherapy to reduce the risk of mastitis and other complications during treatment9. Patients should also consider the fact their infant may not want to resume breastfeeding after many months of not breastfeeding, or breastfeeding very intermittently at certain time points during chemotherapy. Breastmilk volume also will be decreased by chemotherapy.

A patient may undergo upfront surgery and wish to continue breastfeeding from the affected breast. This is not possible in the setting of total mastectomy, skin sparing total mastectomy, or nipple sparing total mastectomy. It is possible in the setting of partial mastectomy; wound complication rates in lactating patients has been reported consistent with those of non-lactating patients10. However, as described above, a patient who undergoes partial mastectomy very likely will require post-operative adjuvant radiation therapy. As above, we recommend weaning the affected breast and augmenting supply on the contralateral side.

Regarding adjuvant endocrine therapy, see above.


  1. Moore GH, Schiller JE, Moore GK. Radiation-induced histopathologic changes of the breast: the effects of time. Am J Surg Patho. 2004;28(1):47-53.
  2. Kato M and Simmons RM in Kuerer (ed.) Kuerer’s Breast surgical oncology, 1st edition. 2010, chapter 67.
  3. Leal SC, Stuart SR, Carvalho HeA. Breast irradiation and lactation: a review. Expert Rev Anticancer Ther. 2013;13(2):159-164.
  4. Leal SC, Stuart SR, Carvalho HeA. Breast irradiation and lactation: a review. Expert Rev Anticancer Ther. 2013;13(2):159-164.
  5. Infant Risk
  6. Pagani O, Ruggeri M, Manunta S, et al. Pregnancy after breast cancer: Are young patients willing to participate in clinical studies? Breast. 2015;24(3):201-207.
  7. Callihan EB, Gao D, Jindal S, et al. Postpartum diagnosis demonstrates a high risk for metastasis and merits an expanded definition of pregnancy-associated breast cancer. Breast Cancer Res Treat. 2013;138(2):549-559.
  8. Pistilli B, Bellettini G, Giovannetti E, et al. Chemotherapy, targeted agents, antiemetics and growth-factors in human milk: how should we counsel cancer patients about breastfeeding? Cancer Treat Rev. 2013;39(3):207-211.
  9. Griffin SJ, Milla M, Baker TE, Liu T, Wang H, Hale TW. Transfer of carboplatin and paclitaxel into breast milk. J Hum Lact. 2012;28(4):457-459.
  10. Dominici LS, Kuerer HM, Babiera G, et al. Wound complications from surgery in pregnancy-associated breast cancer (PABC). Breast Dis. 2010;31(1):1-5.