SAN FRANCISCO – A GP2 peptide vaccine to prevent breast cancer recurrence appears most effective in women whose tumors had the highest HER2 overexpression. In a video interview, Dr. Erika J. Schneble of the San Antonio (Tex.) Military Medical Center describes the phase II adjuvant vaccine study she presented at a breast cancer symposium sponsored by the American Society of Clinical Oncology.
Results of an intent-to-treat analysis of all patients showed that 88% of 89 vaccinated women and 81% of 91 patients in the control group remained disease free after a median follow-up of 34 months (P = .43). Among patients who completed treatment, disease-free survival rates were 94% among 83 patients in the vaccine group and 85% among 87 patients in the control group, the investigators reported (P = .17).
In prespecified subgroup analyses based on the level of expression of human epidermal growth factor receptor 2 (HER2), the greatest potential effect was seen in those with the highest HER2 overexpression. In this subgroup, disease-free survival rates were 94% in 51 patients in the vaccine group and 89% in 50 patients in the control group, in an intent-to-treat analysis (P = .86). Excluding two of these patients who developed early recurrences during the primary vaccine series and one patient who developed a non-breast malignancy, however, no recurrences were seen in the vaccine group. Disease-free survival rates were 100% in 48 women in the vaccine group and 89% in 50 women in the control group (P = .08).
Dr. Schneble conducted the 180-patient trial with primary investigator Dr. Elizabeth A. Mittendorf, a surgical oncologist at the University of Texas MD Anderson Cancer Center, Houston, and her associates.
Also in the video, Dr. Hope S. Rugo, director of the Breast Oncology Clinical Trials Program at the University of California, San Francisco, gives her perspective on the study findings. She was not involved with the trial.
Dr. Schneble reporting having no financial disclosures. Dr. Mittendorf’s institution receives per-patient support to enroll patients in vaccine trials sponsored by Galena Biopharma, Antigen Express, and Norwell. One of their coinvestigators has partial inventor rights to GP2. Dr. Rugo disclosed financial associations with Genomic Health, Plexxikon, Merck, and Novartis. She is on the scientific advisory board of Galena Biopharma.
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