SAN ANTONIO—The combination of capecitabine (Xeloda) and ixabepilone (Ixempra) appears to be robust in patients with the so-called triple-negative breast cancer phenotype, according to an analysis of a predefined subset of the larger 752-patient phase III trial of the combination vs capecitabine alone.
In 187 heavily pretreated metastatic breast cancer patients with the triple-negative subtype, the regimen yielded an overall response rate of 27% and median progression-free survival (PFS) of 4.1 months, Hope Rugo, MD, of the University of California, San Francisco, reported at the 2007 San Antonio Breast Cancer Symposium (abstract 6069).
"This study was an attempt to cull out this very resistant group of patients, which represented 25% of patients in our larger trial. These patients have limited treatment options, and this was quite an effective treatment for them," Dr. Rugo commented.
An aggressive phenotype
Triple-negative breast cancer is characterized by tumors that are estrogen-receptor (ER) negative, progesterone-receptor (PR) negative, and HER2 negative. This is an aggressive phenotype with poor prognosis as a result of its increased mitotic index, central necrosis, proportion of apoptotic cells, and other high-risk pathological features.
Patients with triple-negative tumors develop their disease at an earlier age, are more likely to relapse, and tend to develop visceral and brain metastases as well as bone metastases, compared with other breast cancer subtypes, Dr. Rugo noted.
"Most importantly, such patients have worse survival, compared with other subgroups, and have fewer effective treatment options, since they are not candidates for either hormonal or HER2-targeted therapy," she said.