October is breast cancer awareness month and patients with triple-negative breast cancer (TNBC) should be aware that data from two clinical trials provide additional evidence that they may derive benefit from checkpoint inhibitor therapy.1-4
About Triple Negative Breast Cancer
Approximately 12% of breast cancers are triple-negative breast cancers, meaning that they are estrogen-receptor negative (ER-), progesterone-receptor negative (PR-), and human epidermal growth factor receptor 2-negative (HER2-). This means that TNBC is not stimulated to grow from exposure to the female hormones estrogen or progesterone, nor through an overactive HER2 pathway.
Unfortunately, many available and effective treatment options for the majority of breast cancers block the growth stimulating effects of ER, PR and/or HER2; therefore, TNBC has limited therapeutic options. Novel treatment options for TNBC have lagged behind that of other types of breast cancers.
About Checkpoint Inhibitors
Checkpoint inhibitors are a novel precision cancer immunotherapy that helps to restore the body’s immune system in fighting cancer. They create their anti-cancer effects by blocking a specific protein used by cancer cells called PD-1 and PD-L1 to escape an attack by the immune system. Once PD-L1 is blocked, cells of the immune system are able to identify cancer cells as a threat, and initiate an attack to destroy the cancer. There are several PD-1 and PD-L1 inhibitors already approved for use to treat multiple cancer types.
Recently at the American Society of Clinical Oncology meetings additional evidence on the role of Keytruda (pembrolizumab), a checkpoint inhibitor was presented. In the KEYNOTE-086 clinical trial patients with previously treated metastatic TNBC had prolonged and durable response rates. Patients with previously untreated PD-L1 positive metastatic TNBC experienced an overall response rate of 23.1%.3
In a second clinical trial (I-SPY2) combining Keytruda with Taxol (paclitaxel) in newly diagnosed, high-risk TNBC patients, a pathologic complete response rate of 60% in the neoadjuvant setting was observed and, compared favorably with the 20% response rate observed with chemotherapy alone.1
Another checkpoint inhibitor Tecentriq (Atezolizumab) has also demonstrated early encouraging results. Among patients with metastatic TNBC; those who responded to Tecentriq lived significantly longer compared with those who did not respond, according to data from a small clinical study presented at the American Association of Cancer Research annual meeting.2
Taken together, these studies suggest that checkpoint inhibitors are active against TNBC. Doctors will continue to evaluate how best to incorporate these novel precision cancer medicines into their overall treatment strategy.
- Schmid P, Cruz C, Braiteh FS, et al: Atezolizumab in metastatic TNBC: Long-term clinical outcomes and biomarker analysis. 2017 AACR Annual Meeting. Abstract 2986. Presented April 3, 2017.
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