Delaying the use of cytotoxic chemotherapy is a primary goal of treating patients with metastatic breast cancer (MBC). This is accomplished with the use of “an unprecedented number of endocrine-based treatment options that can improve long-term outcomes, while preserving or optimizing quality of life,” Adam M. Brufsky, MD, PhD, co-director of the Comprehensive Breast Cancer Center at the University of Pittsburgh in Pennsylvania, wrote in Cancer Treatment Reviews.1

The article examined the role for sequential and combination endocrine-based therapies for patients with hormone receptor (HR)-positive, HER2-negative metastatic breast cancer, noting that sequential therapy can often extend progression-free and overall survival “without [oncologists] resorting to chemotherapy.”

Cancer Therapy Advisor asked Dr Brufsky to comment on the evolving role of endocrine-based therapy for this patient population, including combinations of targeted and immunotherapy agents based on molecular and genetic profiling.

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Cancer Therapy Advisor (CTA): You note that of the estimated 250,000 new cases of breast cancer diagnosed in the US annually, about 6% present initially with metastatic disease and, among those diagnosed with primary breast cancer, 20% to 50% will develop metastatic disease. Is it possible to estimate how many patients are being treated at any one time with metastatic disease?

Dr Brufsky: Based on the number of deaths from metastatic breast cancer annually, 40,000, I’d estimate up to 250,000 women with metastatic breast cancer are receiving treatment.

CTA: What percentage of patients have HR-positive, HER2-negative MBC, the focus of your review?

Dr Brufsky: Half of those, or 125,000 patients.

CTA: Approximately how long would you predict patients with metastatic disease may be treated with endocrine therapy, including following resistance, in years?

Dr Brufsky: Most women with HR-positive disease live about 5 years and have hormone therapy for 3 to 4 years, so two-thirds of that time.

CTA: How often would you recommend that patients have their metastatic tumors biopsied for genomic sequencing or ctDNA, especially given the speed at which new targeted and immunotherapeutic agents are being developed?

Dr Brufsky: We are still trying to figure out what to do with the results of these tests. The true clinical utility of this testing remains unclear, and it is still a research tool.

In the next year or 2, however, ctDNA will likely be of clinical utility. For a patient who has passed through multiple different chemotherapeutic agents and there are no options left, this may represent a setting for testing. But there is no proven efficacy for the use of testing at this point.