Edith Perez, M.D., an internationally known breast cancer researcher, and deputy director at large of the Mayo Clinic Cancer Center, is fond of finding simplicity in treatment where possible. Her recent study has done just that. Published in the Journal of Clinical Oncology, a national team of researchers, including investigators at Mayo Clinic in Florida and Minnesota, found it is not necessary to test for presence of tumor suppressor PTEN protein in the HER2-positive subset of breast tumors.
“Many people hypothesized that this marker would be very important for treatment decisions — that it could predict resistance to trastuzumab, which is standard therapy. It almost became something people took as a fact,” Dr. Perez says. “Several small studies gave conflicting results, but people still paid more attention to the positive results.”
The study was the first to thoroughly test for this protein marker in the setting of long-term follow up of 1,802 patients with early stage HER2-positive breast cancer. The results conclusively showed that there was no difference in disease-free survival between PTEN-positive and PTEN-negative tumors, Dr. Perez says. Clinically, then, patients with HER2-positive early breast cancer with or without PTEN benefit from treatment with trastuzumab.
“This will help many investigators now and in the future because we can focus our attention on evaluating other markers that predict effectiveness of trastuzumab treatment in the adjuvant setting, instead of continuing to test for PTEN protein,” she says.