HER2-Positive Breast Cancer Research: Some Women Can Bypass Radiation

A new study led by physician researchers at Lynn Cancer Institute and Miami Cancer Institute, part of Baptist Health, is showing that more women with breast cancer may be able to avoid the toxicities of radiation therapy after mastectomy. The research, published in the journal Radiotherapy & Oncology, indicates that for a specific subset of women with HER2-positive breast cancer, radiation following surgery may be unnecessary since outcomes are already excellent.

The findings are especially important when considering the risk/benefit ratio of treatment for such patients. Radiation therapy can cause side effects such as damage to the heart, lungs and other healthy tissues, skin irritation and lymphedema, said Youssef Zeidan, M.D., Ph.D., a radiation oncologist with Lynn Cancer Institute and the study’s principal investigator.

“In the last few decades, treatment for breast cancer has evolved tremendously,” he said. “Because of the growing understanding of tumor biology, targeted drugs have been developed that are very effective in the treatment of HER2-positive breast cancer.”

Dr. Zeidan led the study group that included Joseph Panoff, M.D., a radiation oncologist with Miami Cancer Institute, and physicians from Belgium, Lebanon and Mayo Clinic Jacksonville. Over a period of two years, they analyzed data from two international clinical trials that used modern targeted therapy.

Some 20 percent of breast cancers test positive for human epidermal growth factor receptor 2 (HER2), according to the American Cancer Society. Tumors with high levels of HER2 tend to grow faster than those that are HER2-negative, but they also usually respond well to treatment with targeted drugs. Medications such as Trastuzumab and Pertuzumab are among those commonly given to HER2-positive patients before surgery to shrink tumors and eliminate as much of the cancer as possible.

Dr. Zeidan and his team evaluated HER2-positive patients who had biopsy-proven cancer in the lymph nodes. They compared patients whose cancer had been eliminated before surgery (confirmed through pathology from tissue and lymph nodes removed during mastectomy surgery) with those who still had some cancer remaining at the time of surgery. Those who had no residual lymph node involvement had excellent outcomes whether or not they underwent post-mastectomy radiation. Those with residual disease in the lymph nodes, however, had a better local disease control when they had radiation.

He cautioned that while the study is promising, it needs to be corroborated. He is looking forward to the results from another ongoing large clinical trial that Miami Cancer Institute and Lynn Cancer Institute participated in, but data isn’t expected for another year or two because patients must be followed for several years after treatment to obtain accurate outcomes information.

“The data needs to be further validated, but it’s really an exciting time because we have reached a day and age where we have been able to tailor treatment to the individual,” Dr. Zeidan said. “We have been basing our recommendations on an era when these targeted drugs weren’t available. The standard of care was to send all of these patients for post-mastectomy radiation therapy. Moving forward, we believe we will be able to safely say which patients can skip radiation.” In addition to avoiding the physical complications that can occur with radiation therapy, patients also have the stress of scheduling and undergoing many more treatments, not to mention the extra costs.

While waiting for future prospective studies to report, Dr. Zeidan is excited that he has been named to the Post-Mastectomy Radiation Therapy Guideline Committee of the American Society for Radiation Oncology, which will be working on updated guidelines this year.