Breastfeeding With Breast Cancer

Though it isn’t a common occurrence to be diagnosed with breast cancer during or soon after a pregnancy, it is something that happens. We want to help you understand the benefits and risks associated with breastfeeding with breast cancer. Much of your decision rests on what type of treatment you are receiving. Certain cancer therapies/medications can be present in breast milk and make breastfeeding an unsafe activity.

Can you breastfeed with cancer? Frequently asked questions

If I’ve been in treatment during pregnancy, how long do I need to let that get out of my system before breastfeeding?

This depends on the type of treatment.

If I want to breastfeed, does that mean I have to postpone treatment?

Though breastfeeding is being shown to be more and more important, that doesn’t mean that it is worth jeopardizing your life and wellbeing. Look into “safe” therapies, formulas, and even into donated breast milk.

If I have a unilateral lumpectomy or mastectomy, is breastfeeding with only one breast healthy/okay?

Typically, yes! It is safe and okay. There are some tips to help make it more comfortable. Usually, lumpectomies require radiation therapy afterward, and so if the plan is to breastfeed, a mastectomy may be suggested if you are not interested in breast-preserving surgery.

Which cancer treatments can show up in my breastmilk and are not safe for my baby?

Quite a few can be present in breastmilk, which presents a concern for what your baby is ingesting. The information below should not be taken as medical advice but is meant to help guide your conversations with your doctor.

Here is a partial list of targeted therapy drugs that are not safe to take while breastfeeding (brand names in parentheses):

  • Everolimus (Afinitor, Afinitor Disperz, Zortress) – avoid breastfeeding for 2 weeks after the last dose; use birth control for 8 weeks after the last dose if TTC (from their website)
  • Trastuzumab (Herceptin) – avoid bf & TTC for 7 mos after d/t & website
  • Palbociclib (Ibrance) – avoid TTC for 3wks after the last dose; avoid bf at same time d/t website
  • Pertuzumab (Perjeta) – use bc for 7 mos after the last dose before TTC; avoid bf at same time d/t website
  • Ribociclib (Kisqali) – avoid bf & TTC for 3 wks after d/t & website
  • Ado-trastuzumab emtansine (Kadcyla) – avoid TTC for 7 mos after the last dose; avoid bf at same time d/t website
  • Lapatinib (Tykerb) – should not TTC, be preg, or bf while on it d/t site
  • Toremifene (Fareston) – only used in postmenopausal women
  • Raloxifene (Evista) – only used in postmenopausal women

Here is a partial list of hormone therapy drugs that are not safe to take while breastfeeding (brand names in parentheses):

  • Tamoxifen (Nolvadex, Soltamox, Genox, Tamoxifen) – very useful to decrease milk production; not to be used during preg or TTC or bf
  • Anastrozole [Aromatase inhibitor] (Arimidex) – do not take during preg or TTC; only for postmenopausal women
  • Letrozole [Aromatase inhibitor] (Femara) – do not take during preg or TTC or bf; only for postmenopausal women
  • Exemestane (Aromasin) – do not take during pregnancy, wait for 1 month after the last dose to TTC or to bf

Will cancer treatments reduce the amount of milk I produce?

This is very possible. Again, it depends on quite a number of factors.

Are there “safe” treatments during the breastfeeding period?

Other than possible surgery (mastectomy or biopsy), there are no other suggested treatments that will allow you to continue breastfeeding. Some doctors will suggest to stop breastfeeding before surgery to prevent infection and decrease blood flow to and swelling of the breast(s).

If I haven’t had a mass removed yet, is it safe to offer breast milk from that breast?

This very much depends on your doctor’s orders. He or she will take into account what part of the breast has been affected by cancer if it even can or will produce milk, and how soon it will need to be removed.


Compiled using information from the following sources:

1. American Cancer Society:  Breast Cancer Treatment (if women about to start treatment, should stop/not begin breastfeeding; most treatments enter breast milk such as chemo, hormone, targeted therapy treatments; also is good to stop before surgery b/c reduces blood flow & less infection risk/milk spill during surgery; names of therapy drugs)

2. The Susan G. Komen Breast Cancer Foundation, Inc.: Breastfeeding (breastfeeding at all, 1 yr, 2 yrs, 3 + years total breastfeeding time reduces risk of BR-CA more with add’l time; also especially good at reducing risk of triple-negative and/or estrogen receptor-negative BR-CA)

3. The Susan G. Komen Breast Cancer Foundation, Inc.:  Breast Cancer Treatment During Pregnancy (avoid breastfeeding also during radiation therapy & ones above in #1; surgery/radiation can make breastfeeding difficult from the treated breast)

4. HealthLine: What You Should Know About Breast Cancer While Breastfeeding (only 5% of BR-CA diagnoses are to women before age 40 – so it’s unlikely; controversial to tell a woman to stop breastfeeding for diagnostic tests – go both ways; need to ask about meds before and after surgery to see if it’s safe for breastfeeding b/c might have to pump and dump; NO for chemo; says might be possible with radiation if being from non-treated breast; side effects from treatment may make it difficult to keep up strength and nutrition)

5. (information on Trastuzumab, Ribociclib, & Tamoxifen)

6. Living Beyond Breast Cancer (LBBC): Breastfeeding After Treatment for Early-Stage Breast Cancer (more info about breastfeeding after radiation, lumpectomy, mastectomy, etc. and about breastfeeding from one breast – READ MORE)