DIANA WEST, BA, IBCLC, updated by Ann Calandro, MSN, RN, IBCLC

Originally published December 2011, updated November 2015, updated February 2022 and republished with the permission of the author, Diana West.

The technical information in this paper has been compiled in consultation with physicians having professional knowledge and clinical experience with cancer and breastfeeding. See the list of references at the end of the article for sources to share and explore with your healthcare providers.

When seeking answers regarding the safety of continued breastfeeding when a nursing parent needs a radiopharmaceutical, the parent and attending radiologist will need to engage in shared decision making. Patients can ask that medications be chosen that are most compatible with breastfeeding. Although most common imaging and nuclear medicine procedures performed during breastfeeding do not require interruption of breastfeeding or weaning, there are some exceptions.

Parents may wish to refer their treating physician to the 2019 Academy of Breastfeeding Medicine Protocol #31 Radiology and Nuclear Medicine Studies in Lactating Women. Dr. Thomas Hale’s Medications and Mother’s Milk 2019 is another helpful resource for physicians. Additional information about medication is available on Lactmed, as well as E-lactancia, a free resource in English and Spanish.

The Academy of Breastfeeding Medicine has published guidelines for mothers who have been diagnosed with cancer during pregnancy or postpartum. These guidelines offer more detailed information on breastfeeding and cancer for parents and providers (ABM Protocol #34 Breast Cancer and Breastfeeding).

Answers to some of the most common questions asked when facing the possibility or reality of cancer while breastfeeding:

Cancer in the Lactating Breast

Breastfeeding from a breast with cancer – There is no research to indicate that baby can “catch” cancer from nursing on an affected breast. “There is no evidence that breastfeeding increases the risk of breast cancer recurring or of a second breast cancer developing, nor that it carries any health risk for the child.” (Helewa et al., 2002)

There is no scientific evidence that infants refuse to feed from a cancerous breast, although this has been reported anecdotally by some breastfeeding patients.

Microcalcifications are tiny calcium deposits in breast tissue that that can be benign (non-cancerous) or suspicious for atypical cells or cancer. They occur more frequently in women who have breastfed, particularly for extended periods. It is not possible to feel these microcalcifications, so they are identified on screening or diagnostic mammograms. Even distributions are normal and usually not an indication of cancer. However, it is important to have all breast concerns checked out by a medical professional and biopsies performed, if recommended.

“The majority of persistent breast masses warrant diagnostic imaging. Although several breast masses may occur in the setting of lactation and are benign, imaging generally
is required to distinguish these from non-lactation-specific breast masses. Both benign and malignant masses unrelated to lactation also may present during the postpartum period.” (ABM Clinical Protocol #30 Breast Masses, Breast Complaints, and Diagnostic Breast imaging in the Lactating Woman.)

Imaging techniques used for diagnosis of breast pathology may include ultrasound, mammogram, magnetic resonance imaging (MRI), positron emission tomography (PET) scan, 2-Methoxy Isobutyl Isonitrile (MIBI) scan, electrical impedance tomography (EIT) scan, computer axial tomography (CAT) scan, thermography, or diaphanography. These techniques are non-invasive and usually do not affect milk production or safety. The Academy of Breastfeeding Medicine mentions that ultrasound is often the first diagnostic test used to determine the nature of a mass in a lactating breast. It may be more difficult to interpret breast tissue results due to the increased density from lactation, but it is not impossible. Feeding or pumping before the imaging is recommended, to improve the quality and sensitivity of the scan. It is usually not necessary to interrupt or suspend breastfeeding for these procedures with the exception of the PET scan, which requires separation of the breastfeeding dyad for 12 hours, though the milk itself is safe. As always, it is important for the prescribing physician and radiologist to consult reliable updated sources before the imaging.

Needle aspiration to remove the contents of fluid-filled cavities and galactoceles does not affect milk production or safety. Continued feeding or pumping is recommended to reduce the occurrence of a milk fistula.

Patients may have undergone a breast biopsy prior to pregnancy and breastfeeding to remove tissue for diagnostic analysis. Biopsies can damage lactation ducts or nerves depending on the technique, amount of tissue removed, and location of the incision. There are three ways to obtain a sample of breast tissue – fine needle aspiration cytology, core biopsy and open surgical biopsy. The most commonly performed is a core biopsy, either freehand, under ultrasound or mammography guidance. Local anesthetic is injected into the biopsy site prior to making an incision to insert the biopsy needle. It is safe to feed or pump milk with local anesthetic in the breast.

While lactating, incisions in the upper, inner quadrants of the breast usually impact milk-making tissue the least, while circular incisions around the areola can damage nerve response affecting milk ejection. Incisions pointing toward the nipple sever fewer milk ducts and do less damage. Scars or infections from a biopsy also may harm the milk-making tissue. Some surgeons may be reluctant to perform biopsies on a lactating breast because it can be more difficult to see the affected tissue, but it can be done, and the milk will not delay wound healing.

Surgeons often quote concerns of milk fistula as a reason to delay biopsy or surgery until after weaning. With continued lactation support to feed or pump in the biopsied breast, the chance of milk fistula is low. (Johnson and Mitchell, 2019)

Breastfeeding may continue normally after the procedure. There is a risk that a milk-filled cyst (galactocele) could develop, but it can be left untreated, or treated with needle drainage (aspiration). If infection occurs, it can be treated with antibiotics that are safe during breastfeeding.

Radiation from diagnostic procedures using x-rays, mammograms, MRI, and CT(also called CAT) scans are all safe during lactation. Most radiopaque and radiocontrast agents typically used in CT/CAT, MRI, MIBI scan, or PET scan diagnostic tests are extremely inert and virtually unabsorbed when taken orally. Some are given through IVs and may pass into the milk. However, infant absorption is not a concern. The Academy of Breastfeeding Medicine states that ultrasound is the initial imaging modality used for diagnosing breast imaging of areas of concern. It is not necessary to interrupt breastfeeding when they are used. However, because there are many different contrast agents, it is always important that current reliable sources be checked before undergoing the diagnostic procedure and to verify that no interruption is needed.

Radioactive isotopes: According to ABM Clinical Protocol #31, when physicians advise a breastfeeding patient, consideration must be given to the fact that the child may be exposed to radiation through two routes – the ingested milk and externally through proximity to the mother. Lactating mothers should expect their physicians to share evidence-based information on the safety of the recommended radioisotope.

Radiation therapy is destructive to milk-making tissue, and mothers should not expect the radiated breast to be able to produce milk after this therapy. Although some milk may be produced from the affected breast during therapy, individual advice should be taken whether to breastfeed from that breast. This is because the nipple and areola tissue may have reduced sensitivity and be more prone to trauma, bleeding, and therefore infection. The same is true for the use of a Supplemental Nursing System on the irradiated side, and the negative pressure of an infant suckling can be quite strong.

Milk production in the breast that did not receive radiation will not be affected and it is safe to breastfeed from the non-affected breast during and after therapy.

Breastfeeding during chemotherapy is usually absolutely contraindicated because the medications used to eradicate cancer are highly toxic and transfer into milk. However, some mothers receiving lower dose chemotherapy, or chemotherapeutics with relatively shorter half lives (ABM protocol #34, Table 1) may be able to temporarily wean, or express milk and return to breastfeeding between doses after seeking guidance from medical professionals. Breastfeeding may be possible after chemotherapy has been completed, either by relactation or as a result of another pregnancy, depending upon the drugs that were used (Pistilli, 2013)

Nursing mothers who are scheduled for chemotherapy should discuss the duration of breastfeeding and timing of weaning with their oncologist. Some may decide to pump and plan to return to breastfeeding after completion of their course of treatment. They may find, however, that their babies may lose interest in breastfeeding after not being offered the breast over a period of time.

The risk of breast cancer recurrence is not increased by breastfeeding. (Helewa et al., 2002)

Cancer in Other Parts of the Body and the Effects on Lactation

Thyroid imaging and treatment– I-131 is a treatment modality for destruction of the thyroid for thyroid cancer and for Graves Disease. It is not for imaging. It necessitates complete weaning four weeks before treatment begins to reduce radiation dose to the breast. I-123 is used for a thyroid update and diagnostic scan. It is rarely necessary to use I-123 during lactation. However, if it is required, it may require cessation of breastfeeding for several days. (ABM Clinical Protocol #31.)

When lactation needs to be temporarily ceased due to radioisotopes for diagnostic purposes, it is possible to pump after treatment until it is safe to resume breastfeeding. The expressed milk can be stored in a freezer away from others, allowing the radiation count to diminish over time. The radiologist can share further information. The milk can be checked by a local hospital nuclear medicine department to determine when the radiation has disappeared so that it can be used for feeding. (Mitchell, 2019.)

Local anesthesia, such as numbing injections done for dental procedures or small areas of skin, does not transfer into milk in detectable levels, so it is not necessary to interrupt breastfeeding in any way when it is used. (Reece-Stremtan, 2017.)
General anesthesia does not require weaning or the interruption of breastfeeding. As soon as the patient awakens fully from general anesthesia, it is safe to nurse or pump because general anesthetic medications are rapidly metabolized. There is no need to “pump and dump” milk. (Reece-Stremtan,2017.)

Weaning for diagnostic or tissue-removal surgery: The healthcare team caring for the lactating mother needs to include lactation care in the plan of care for the patient. The patient will need to nurse or pump immediately prior to the diagnostic or tissue-removal surgery to drain the breasts and promote comfort. If it is a long surgery, milk expression needs to be planned during surgery. Milk expression should be arranged in the post-operative unit, as well. Weaning is rarely necessary. (ABM Clinical Protocol #35: Supporting Breastfeeding During Maternal or Child Hospitalization)

Experience has shown that weaning will not help a mother “conserve her strength.” Breastfeeding is considerably more convenient, relaxing, and timesaving than bottle-feeding. It provides an emotional connection and intimacy that is nurturing to both mother and baby when they need it most.


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Revised February 2022