EGFR is a growth stimulus that has been found in other cancers to produce a more aggressive disease, but this study is the first to firmly link expression of that protein to poor outcome in breast cancer, say the researchers, who presented their findings at the San Antonio Breast Cancer Symposium.
"This is potentially important news in that new drugs have been developed that block the EGFR pathway. These data provide a rationale for studying these agents in selected patients with breast cancer," says Thomas Buchholz, M.D., associate professor of radiation oncology, who conducted the study. One such trial of the EGFR inhibitor drug, Iressa, combined with the endocrine therapy, Arimidex, will begin shortly at 15 centers nationwide, led by M. D. Anderson.
In Buchholz's study, researchers evaluated expression of EGFR in preserved tissue samples from 82 locally-advanced breast cancer patients treated between 1989-1996 in clinical trials that tested use of chemotherapy before surgery. EGFR expression was positive in 14 cases (16 percent) and negative in 68 cases (84 percent).
They then examined whether EGFR expression correlated with outcome, and found that patients with EGFR-positive disease had both a worse disease-free survival and overall survival than patients with EGFR-negative cancer. For example, EGFR-positive patient had an overall survival at nine years after treatment of 43 percent compared to 60 percent in EGFR-negative patients.
"This is a small study, but we can clearly see that EGFR expression correlated with survival," says Buchholz. "This is relatively surprising, because EGFR has not been widely studied in breast cancer and these data suggest that it may have prognostic significance."