SAN ANTONIOIn first-line hormonal therapy for advanced breast cancer, elevated levels of HER-2/neu predict lower response rates and shorter time to disease progression, compared with normal HER-2 levels, according to a large international study.
Allan Lipton, MD, professor of medicine and oncology, Pennsylvania State University, Hershey, presented the findings at the 24th Annual San Antonio Breast Cancer Symposium (abstract 6).
The study was part of a phase III study comparing the aromatase inhibitor letrozole(Drug information on letrozole) (Femara) with tamoxifen(Drug information on tamoxifen) (Nolvadex) as first-line therapy in 907 postmenopausal women with advanced breast cancer. That study found a significant benefit for letrozole.
The companion study reported by Dr. Lipton used the Bayer Immuno 1 automated assay to determine HER-2 levels in pretreatment serum samples from 566 of the 907 participants.
The objective response rate according to HER-2 status, irrespective of treatment, was significantly higher in HER-2-negative than in HER-2-positive patients. Overall response rate was 31% vs 15%; clinical benefit rate (complete and partial responses plus stable disease for 24 weeks) was 50% vs 29%; and time to progression was 9.4 vs 5.6 months for HER-2-negative vs positive patients, respectively. These differences were all significant (P < .0001), Dr. Lipton said.
Multivariate analysis revealed elevated serum HER-2 as a negative predictor of overall response rate, clinical benefit rate, time to progression, and time to treatment failure, he said.
When HER-2-positive patients were analyzed according to treatment arm, patients receiving letrozole had numerically higher responses, although the differences were not significant. For letrozole vs tamoxifen, respectively, the objective response rate was 17% vs 13%; clinical benefit rate 32% vs 26%; and median time to progression 6.1 months vs 3.3 months.