Herceptin (chemical name: trastuzumab) is a targeted therapy used to treat HER2-positive breast cancer. Heart problems, including heart muscle damage and heart failure, are possible serious side effects of Herceptin.
Because of this, women diagnosed with HER2-positive breast cancer being treated with Herceptin should be regularly monitored for possible heart problems as soon as they start Herceptin.
A study has found that most older women being treated with Herceptin don’t receive heart monitoring that follows current guidelines.
The study was published online on May 11, 2015 by the Journal of Clinical Oncology. Read the abstract of “Cardiac Monitoring During Adjuvant Trastuzumab-Based Chemotherapy Among Older Patients With Breast Cancer.”
HER2-positive breast cancers make too much of the HER2 protein. The HER2 protein sits on the surface of cancer cells and receives signals that tell the cancer to grow and spread. About one out of every four breast cancers is HER2-positive. HER2-positive breast cancers tend to be more aggressive and harder to treat than HER2-negative breast cancers.
Herceptin works by attaching to the HER2 protein and blocking it from receiving growth signals. Herceptin, which is given intravenously, is approved by the U.S. Food and Drug Administration (FDA) to:
- treat advanced-stage, HER2-positive breast cancers
- lower the risk of recurrence (the cancer coming back) of early-stage, HER2-positive breast cancers with a high risk of recurrence
A newer form of Herceptin, Herceptin Hylecta (chemical name: trastuzumab and hyaluronidase-oysk), can be given as an injection.
In the study, the researchers looked at the records of 2,203 women age 66 or older with full Medicare insurance coverage who were diagnosed with stage I to stage III (early-stage), HER2-positive breast cancer between 2005 and 2009 and were treated with a combination of Herceptin and chemotherapy.
Current guidelines call for women being treated with Herceptin to have a baseline heart function assessment in the 4 months before starting Herceptin and follow-up heart function evaluations every 3 months while being treated with Herceptin.
In the study, the researchers said acceptable heart monitoring meant the women had a baseline heart function assessment in the 4 months before starting Herceptin and follow-up heart function evaluations every 4 months while being treated with Herceptin. The researchers said they added 30 days to the standard every-3-month follow-up time to allow for flexibility in scheduling and to allow for differences in practices and resources.
The researchers found that:
- 78.8% of the women had a baseline heart function assessment
- 68.2% had a follow-up heart function evaluation during the first 4 months they were being treated with Herceptin
But the heart function evaluations dropped off after that. Only 42.6% of the women had a follow-up heart function assessment at least every 4 months while they were being treated with Herceptin. Overall, only 36% of the women had heart function monitoring that met current guidelines.
Older women were less likely to receive adequate heart monitoring.
The researchers found that certain factors were linked to a woman being more likely to receive adequate heart monitoring while being treated with Herceptin, including:
- being diagnosed more recently
- being treated with an anthracycline chemotherapy along with Herceptin (anthracylines also may cause heart problems)
- having a female doctor
- having a doctor that graduated from medical school after 1990
Women who had existing heart problems were no more likely to have adequate heart monitoring while being treated with Herceptin than women who didn’t have existing heart problems.
"We suspected that the rates of cardiac monitoring were going to be low, but we were surprised at how low, particularly in this high-risk group of patients," said Mariana Chavez-MacGregor, M.D., a medical oncologist at the MD Anderson Cancer Center in Houston and lead author of the study, in an interview. "Of particular concern was that even among patients with cardiac comorbidities the rates of cardiac monitoring were not higher."
Because heart problems linked to Herceptin usually go away when women stop taking Herceptin, the researchers said that it’s important to increase the number of women who receive adequate heart monitoring, especially older women who may be more likely to have existing heart problems. The researchers called on hospitals, training programs, and medical societies to distribute the current heart monitoring guidelines to raise awareness of them.
If you’re 66 or older and have been diagnosed with HER2-positive, early-stage breast cancer, you may want to ask your doctor about this study if Herceptin and/or anthracycline chemotherapy will be part of your treatment plan. It’s a good idea to ask your doctor about your personal risk of treatment-related heart damage and whether or not visiting a cardiologist before treatment starts is a good idea for you. The cardiologist can evaluate your heart function and decide if you’re at high risk for developing heart disease or heart failure from breast cancer treatment. It’s also important to ask your oncologist how your heart function will be monitored during treatment.
Together, you can decide on the best treatment and heart monitoring plan for your unique situation.
Editor’s Note: This article was updated with information about Herceptin Hylecta, which the FDA approved on Feb. 28, 2019.