German Breast Group (GBG) Studies Demonstrate Subanalyses Of Tumor DNA Repair Mutations Can Help Guide Treatment Selection And Predict Response In Preoperative Breast Cancer

CHICAGO & NEU-ISENBURG, Germany--(BUSINESS WIRE)--The German Breast Group (GBG) presented two analyses that can serve as predictors of response to treatment by further subdividing preoperative (neoadjuvant) patients with HER 2 positive breast cancer and those with triple negative breast cancer based on tumor DNA repair capabilities and related factors.

“Although these retrospective and exploratory results have to be confirmed by other independent studies, they might help identify patients where the benefits of treatment can be improved by giving carboplatin in addition to the traditional use of anthracycline-taxane-based chemotherapy.”

Prof. Dr. Gunter von Minckwitz, president of the GBG Research Institute, noted, “Taken together these studies demonstrate that a deeper understanding of the variations among breast cancer types that go beyond hormone response and BRCA gene mutations can inform treatment options with increased precision.”

One study (Abstract No: 1004) from lead author Dr. von Minckwitz found cancer-related BRCA mutations in the tumor are more common (30.3%) than inherited BRCA mutations (19.8%) in patients with triple-negative breast cancer. The homologous recombination (HR) assay measures DNA repair capacity beyond those related to BRCA mutation. HR deficiency defined as having either a BRCA mutation of the tumor or a high HR score was found in 70.5% of the patients. These findings can affect treatment options. Patients with a tumor BRCA mutation and/or a high HR score showed a high complete response to preoperative (neoadjuvant) chemotherapy. Our findings suggest those patients are also benefiting more from the additional use of carboplatin than tumors without HR deficiency.

Dr. von Minckwitz also noted that, “Although these retrospective and exploratory results have to be confirmed by other independent studies, they might help identify patients where the benefits of treatment can be improved by giving carboplatin in addition to the traditional use of anthracycline-taxane-based chemotherapy.”

A second study (Abstract No: 51) presented a meta-analysis from prospectively conducted clinical trials (Gepar STUDIES, Neo-ALTTO, CHERLOB) evaluating the effect of a double blockade with trastuzumab and lapatinib of HER2 positive breast cancer patients looking at the predictive values of mutations in the PIK3CA gene. PIK3CA occurs in about 30% of invasive breast tumors.

“This is a large data set that included more than 900 patients, investigating the role of PIK3CA mutation,” said Prof. Dr. Sibylle Loibl, lead study author and Chairperson of the GBG. “While we have shown that PIK3CA mutation carriers (tumors) have a lower response to a double blockade, we have demonstrated here that the response to a double blockade treatment is especially low in patients with both a hormone receptor positive HER2+ breast cancer and a PIK3CA mutation (pCR rate of 5.5%). In these patients alternative treatments should be investigated.”

The findings were presented at the 2015 annual meeting of the American Society of Clinical Oncology (ASCO).

ABOUT THE GERMAN BREAST GROUP

GBG is a large independent academic network of over 500 study centers in Germany with the world-wide largest experience in conducting neoadjuvant breast cancer trials. Since 1998, with joined forces from AGO-B, over 12,000 patients participated in the neoadjuvant “Gepardo” trial series. GBG has recruited at totality of over 35,000 patients to participate in trials for breast cancer of all indications. Reports on these trials were previously published in the New England Journal of Medicine, The Lancet Oncology, the Journal of Clinical Oncology and the Journal of the National Cancer Institute (for more information go to www.germanbreastgroup.de or www.gbg.de).