Targeted Therapy for Early-Stage Breast Cancer

Danielle Shapiro, MD, MPH, Cancer Prevention and Treatment Fund

Breast cancer is the most common type of cancer in women around the world, and the second leading cause of cancer deaths among U.S. women.

Women who are diagnosed with early-stage breast cancer almost always undergo surgery to remove the cancer (either lumpectomy/partial mastectomy or mastectomy). Most will also choose at least one other treatment in addition to surgery.

About 14% of all breast cancers (at all stages) make a protein called HER2. There are several targeted therapies that specifically stop the growth of these cancer cells. These therapies can be used with chemotherapy or hormonal therapy.[1]

How Does Targeted Therapy Work?

Trastuzumab targets breast cancer cells that make HER2, and stops them from growing.[2,3]

How Effective is Targeted Therapy?

Studies show that women with early-stage “HER2-positive” breast cancer may benefit from targeted therapy. The landmark study (called HERA) of this treatment showed that women taking trastuzumab for 1 year in addition to chemotherapy had a 21% chance of cancer returning compared to 28% for women getting chemotherapy alone.[4]

Overall survival refers to how long a woman lives after a diagnosis. For women diagnosed with early-stage HER2-positive breast cancer, 10.7% taking both trastuzumab and chemotherapy died within 4 years compared to 12.3% of women getting chemotherapy alone.  This is obviously a small benefit that would not help most women, but it could save the life of one or two women for every 100 receiving the targeted treatment.

At a 12-year follow up, the researchers found that taking trastuzumab for 2 years was not more beneficial than taking it for one year.[5,6]

What Are the Potential Harms?

Trastuzumab therapy can cause headaches, nausea, swelling, rash, and flu-like illness. In rare cases (less than 1%) trastuzumab can cause serious side effects including heart failure (a weakened heart), sudden difficulty breathing, low blood pressure, and sudden death. All women should have their hearts tested with a sonogram of the heart before deciding whether to take trastuzumab.  If they decide to take it, they should also have their hearts tested during treatment.[7]

In 2018, the American Heart Association recommended women with breast cancer discuss with their doctors their cardiovascular risks (such as family history, or having a diagnosis of diabetes, high blood pressure, or high cholesterol) and the risks of cancer therapies, including trastuzumab as well as many chemotherapy drugs, which can cause or worsen heart conditions. The damage to the heart continues after women have finished the therapies, and can be permanent. This risk to the heart helps explain why a treatment can help prevent breast cancer recurrence but have little benefit in terms of women living longer.[8]

The Bottom Line

For women with HER2-positive, early-stage breast cancer, targeted therapy may be beneficial. Because the therapy can be harmful to the heart, each woman needs to decide whether the benefits outweigh the risks for her. Talk with your doctor about your medical history and family history to decide which treatment options may be right for you.

All articles are reviewed and approved by Dr. Diana Zuckerman and other senior staff.


  1. American Cancer Society. Cancer Treatment and Survivorship: Facts and Figures 2016-2017. Available online:
  2. National Cancer Institute. Breast Cancer Treatment (PDQ). (Nov. 2017). Available online:
  3. Medscape. Adjuvant Therapy for Breast Cancer. (Aug. 2017). Available online:
  4. Gianni L. et al. Treatment with trastuzumab for 1 year after adjuvant chemotherapy in patients with HER2-positive early breast cancer: a 4-year follow-up of a randomised controlled trial. Lancet Oncology. 2011;12(3): 236-44. doi:
  5. Cameron D. et al. 11 years’ follow-up of trastuzumab after adjuvant chemotherapy in HER2-positive early breast cancer: final analysis of the HERceptin Adjuvant (HERA) trial. Lancet. 2017;389(10075): 1195-1205. doi:
  6. Stenger M. ASCO Post: 11-Year Follow-up of Adjuvant Trastuzumab in the HERA Trial. (March 2017). Available online:
  7. Medscape. Drugs and Diseases: Trastuzumab. Available online:
  8. Mehta LS. et al. Cardiovascular Disease and Breast Cancer: Where These Entities Intersect: A Scientific Statement From the American Heart Association. Circulation. 2018; (originally published February 1, 2018).