Novel Therapeutic Agent Shows Promise for Treating Triple Negative Breast Cancer

MAY 31, 2009
Christina T. Loguidice
Approximately 15% of breast cancers are triple negative, with a higher incidence of this cancer subtype found in black and Hispanic women and those younger than 40 years. Triple-negative breast cancers (TNBCs) are aggressive and difficult to treat, leading to higher rates of metastases and poorer survival than for other breast cancers. Because TNBCs do not respond to hormone-based or targeted cancer therapies, there are currently no approved treatments for this disease; however, studies have identified an enzyme prominent in these cancers that could be exploited to render them vulnerable to treatment—PARP1 (poly [ADP-ribose] polymerase-1).

Now, a new phase II study provides promising early evidence that PARP inhibitors may be an effective treatment when administered with standard chemotherapy. Researchers at Texas Oncology, Baylor-Charles A. Sammons Cancer Center, Dallas, a US Oncology affiliate, evaluated BSI-201, a potent PARP1 inhibitor, in combination with gemcitabine/carboplatin (G/C) in subjects with metastatic TNBC. The study included patients who had measurable disease and underwent no more than two cytotoxic regimens for metastatic TNBC.

Patients were randomized (1:1) to G/C alone or G/C plus BSI-201. G/C was given on days 1 and 8, and BSI-201 on days 1, 4, 8, and 11 every 21 days. End points were clinical benefit rate, progression-free survival, and overall survival. Approximately 62% of patients receiving BSI-201 along with G/C showed clinical benefit versus 21% of those only receiving G/C. The overall response rate, median survival, and progression-free survival were all greater in those receiving the BSI-201 drug combination than in those receiving G/C alone, with a response of 48% versus 16%, median survival of 9.2 months versus 5.7 months, and progression-free survival of 6.9 months versus 3.3 months, respectively. The incidence of side effects were similar between the groups, and BSI-201 was well-tolerated.

According to Joyce O'Shaughnessy, MD, co-chair of the US Oncology Breast Cancer Research Committee, associate director of clinical research for US Oncology, and co-director of the Breast Cancer Research Program at Texas Oncology-Baylor-Charles A. Sammons Cancer Center and a lead investigator of this study, "The results of this study provide early evidence that BSI-201 is a promising treatment for women with triple-negative breast cancer, an aggressive form of the disease for which we need new, more effective therapies."

All patients who participated in this trial were accrued through 26 sites at community oncology practices affiliated with the US Oncology network.  US Oncology Research represents the largest research network specializing in Phase I-IV oncology clinical trials in the United States, with over 70 open trials being managed at any given time. The research network has accrued more than 38,500 patients since its inception and contributed to the development of 36 of the latest cancer-fighting drugs approved by the FDA.

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