MONDAY, June 2, 2014 (HealthDay News) -- Breast cancer patients with small-sized "HER2-positive" tumors have a low risk of cancer recurrence, even without chemotherapy and an especially potent drug called trastuzumab, a new study finds.
HER2-positive breast cancer, which accounts for 15 percent to 20 percent of all breast cancer cases in the United States, has been shown to respond well to the antibody medication trastuzumab. However, the drug can cause heart failure in some patients, particularly those who are older and have other diseases, the authors of the new study noted.
"Our results suggest that trastuzumab therapy may not be needed for patients with HER2-positive tumors that are 0.5 centimeters in size or smaller," lead author Dr. Lou Fehrenbacher, medical director of Kaiser Permanente Oncology Clinical Trials and oncologist with Kaiser Permanente Vallejo Medical Center, said in a Kaiser news release.
In the study, Fehrenbacher's team reviewed nearly 17,000 cases of breast cancer diagnosed between 2000 and 2006. They found that 5-year survival without a "distant" recurrence of the tumor was 99 percent for patients with the smallest (0.5 centimeters or less) HER2-positive tumors who did not receive treatment with trastuzumab or get traditional chemotherapy.
Distant recurrence -- cancer that spreads outside the breast to other organs -- is considered to be more life threatening than cancer that recurs in the breast.
The 5-year survival rate without distant recurrence was 97 percent among patients with HER2-positive tumors that were 0.6 to 1 centimeter, according to the study, published June 2 in the Journal of Clinical Oncology.
Fehrenbacher stressed that the size of the tumor seems to be key. Trastuzumab treatment "should be considered for patients with larger tumors, with stronger consideration as the tumor size nears 1 centimeter," he said.
Two experts were cautiously optimistic about the study results.
"One challenge of treatment is to decide who should be treated and what will be the individual's benefit-and-risk ratio," said Dr. Marleen Meyers, assistant professor in the department of medicine at the Perlmutter Cancer Center at NYU Langone Medical Center in New York City.
"While this study is very compelling, the decision to treat a person with HER2-positive breast cancer still needs to be made on an individual basis," she said.
Dr. Amy Tiersten is associate professor of medical oncology at the Icahn School of Medicine in New York City. She said that in early stage HER2-positive breast cancer, the combination of trastuzumab and standard chemotherapy "has been shown to dramatically reduce the risk of the cancer returning."
Tiersten also noted that the new trial is retrospective in nature, and not the "gold-standard" prospective, controlled trial.
However, the new data "reassures us that in these very small [HER2-positive] cancers we may be able to hold off on treatments that have definite side-effects because the chance of a distant recurrence or 'spread' of these cancers is so low without any treatment."
There's more on treating HER2-positive breast cancers at the U.S. National Cancer Institute.