Herceptin (trastuzumab) is a monoclonal antibody used to treat HER2 overexpressing (HER2+) breast cancer. HER2 has a role in the signaling pathways leading to cell growth and differentiation, which accounts for the reputation of aggressiveness of this type of breast cancer. Herceptin binds selectively to the HER2 protein, thereby reducing cancer cell growth and proliferation.
Herceptin normally is administered intravenously alone or in combination with a chemotherapy regimen. There are a few foods and spices that have been shown to amplify the effects of Herceptin, thereby increasing its effectiveness.
Herceptin and other similar monoclonal antibodies can result in side effects such as flu-like symptoms (fever, nausea, vomiting, diarrhea, increased cough, headache), low white blood cell count, anemia, increased infections, and muscle pain. Herceptin is also suspected of causing heart damage, although it is not clear whether Herceptin amplifies the heart damage that may be caused by anthracycline- and taxane-based chemotherapy. Statins (lipid-lowering drugs that block cholesterol synthesis) have been shown to protect against Herceptin-induced heart damage. There are some foods that support heart health while also being associated with lower risk of breast cancer or its recurrence. Other foods may have the opposite effect.

Foods that increase the anti-cancer effects of Herceptin

The following foods are good sources of compounds that have been found to amplify the effects of Herceptin against HER2-overexpressing breast cancer:

Foods that counteract Herceptin's toxic side effects

The foods below have been found to support heart health while also protecting against breast cancer:
Breast cancer patients receiving chemotherapy at the same time as Herceptin should also incorporate appropriate food choices for the drugs used (e.g., Taxol or Adriamycin).

Foods to limit or avoid during Herceptin treatment

The following foods are significant sources of compounds that have been shown to reduce the effectiveness of Herceptin, promote HER2+ breast cancer growth, or increase HER2+ expression:

Supplements for patients being treated with Herceptin

There is no supplement or combination of supplements that has been proven to reliably reduce the risk of HER2+ breast cancer recurrence in women. Attempting to increase the treatment effects of micronutrients and other dietary components by using supplements carries the risk of adverse and paradoxical effects, including promoting breast cancer growth and metastasis.
What is known is that when a beneficial micronutrient is administered at low doses by consuming food, it is likely to have subtle chemopreventive effects, whereas when the same micronutrient is administered at high doses, it is more likely to have pharmacological effects, with mostly unknown results. It is best to obtain beneficial compounds by consuming food, if possible. Supplements should be used if medically necessary or to make up for deficiencies that are difficult to correct through diet.
The following supplements generally have been found to be safe and beneficial for HER2+ patients and survivors on Herceptin:
CoQ10 (if needed for heart health)100 to 400 mg/day
Fish oil (from wild-caught fish)1000 to 2000 mg/day
Vitamin D1000 to 2000 IU/day
Avoid taking supplements during the two days before, the day of, and the day after any Herceptin and/or chemotherapy treatment. Please consult your oncology team for advice concerning your situation and dosages. It might make sense to be tested for deficiency in vitamin D and plan for follow up to determine if your reading has reached a desirable level.

Supplements to limit or avoid during Herceptin treatment

Although study findings are inconsistent, the t10,c12-CLA normally found in CLA supplements has been found to promote mammary tumor development in animal models of HER2+ breast cancer.
There is some evidence that taking anti-oxidant vitamin supplements could potentially enable early stage HER2+ tumor cells to survive when they otherwise would die.
The Chinese medicine Si-Wu-Tang has been shown to interfere with the effectiveness of Herceptin.
For additional supplements that are relevant to HER2+ breast cancer (and for which study results may not be available for Herceptin), see diet for HER2+ breast cancer.

Anti-anemia drugs may interact with Herceptin treatment

Anti-anemia drugs based on erythropoietin have been shown to reduce the effectiveness of Herceptin. Erythropoietin controls the body's red blood cell production and is the basis for drugs such as epoetin alfa (Procrit), epoetin beta (Mircera), and darbepoetin alfa (Aranesp). These drugs should not be avoided if they are necessary to treat chemotherapy-related anemia, thereby eliminating the need for a blood transfusion. However, based on the available evidence, they should be used as sparingly as possible during Herceptin treatment.

Foods detrimental to heart health

The following foods have been found to be potentially detrimental to heart health as well as being associated with increased risk of breast cancer and should be limited or avoided:

Additional comments

Breast cancer patients and survivors with HER2/neu-overexpressing breast cancer should eat a wide variety of the foods on our recommended list and limit or avoid those on our avoid list, in addition to emphasizing the foods and spices on the lists above. Please also see our article on how to optimize your breast cancer diet for information on what to eat during all stages of treatment and recovery.
Below are links to recent studies on Herceptin. For a more complete list of studies, please click on the tag Herceptin.