A new study has shown that a combination of the targeted therapies, which play different roles in breast cancer, can offer a personalized therapy approach to treat women with advanced stages of the disease.
Adding Afinitor to Herceptin, the main treatment for HER2-positive metastatic breast cancer, helps some women with disease that has been resistant to previous Herceptin-based therapies, it was found.
"Herceptin (trastuzumab) works well for many patients, but about 30 percent of those with advanced disease do not respond to the drug, even combined with chemotherapy," said PK Morrow, M.D., assistant professor in the Department of Breast Medical Oncology and lead co-author of the study.
"Even if metastatic HER2-positive breast cancer initially responds to Herceptin, the disease usually eventually progresses on standard Herceptin-based therapy."
Resistance to Herceptin has been linked to activation of the PI3K/mTOR cancer pathway. PTEN, a protein that acts as a tumor suppressor, can counteract P13K. However in the absence of PTEN, the mTOR cancer pathway may be activated.
Afinitor (everolimus) overcomes resistance by inhibiting the mTOR pathway.
"Combining these two agents offers patients with metastatic HER2-positive breast cancer a chemotherapy-free option," Morrow said.
"Despite the fact that most of these women had received multiple chemotherapy regimens, this regimen offered additional clinical benefit and less toxicity for many of patients," he added.
The study has been published in the Journal of Clinical Oncology.