Monitoring Metastatic Breast Cancer Treatment Response: 5 Things to Know

Victoria Stern


November 23, 2020

4. Some patients with MBC are survival outliers.

Certain patients defy all odds and live for decades with MBC. Mark Burkard, MD, PhD, a medical oncologist at the University of Wisconsin-Madison Carbone Cancer Center, has been studying these extreme survivors. Burkard is currently enrolling patients in the Extreme Long-Term Survivors with Metastatic Cancer study "to identify habits, medical care, and genes that help people live with cancer for a longer-than-expected time," but elucidating these factors a remains a challenge.

So far, preliminary data show that among 647 participants with MBC, the majority (about 70%) have HR-positive, HER2-negative disease and the fewest (3.8%) have triple-negative disease. But in a survey of 476 people with MBC, Burkard and colleagues reported that long and short-term survivors with MBC seemed to share many disease and behavioral features, making it challenging to pinpoint the factors driving long-term survival.

In fact, some preliminary data on apparent distinguishing characteristics of long-term survivors may conflict. Brufsky, who compared 122 long-term survivors with 191 short-term survivors, found that more long-term survivors had HER2-positive (not HER2-negative) or ER-positive primary tumors. Long-term survivors also tended to have lower Charlson Comorbidity Index scores, higher household incomes, and to be diagnosed with de novo MBC.

"We want everyone to be an exceptional responder, but we're not there yet," Carey said. "Understanding this small population of outliers may be critical to getting us closer to that holy grail."

Shapiro said that he has treated about a dozen exceptional responders with MBC over his 30-year career. "If you've been in practice long enough, you've seen these patients — people whose pathology paints a dire picture but who ultimately defy the odds," Shapiro said. "Even with these patients, we can't get rid of the cancer but are able to control it for long periods of time, and at the same time, hopefully, give them a decent quality of life."

5. Monitoring treatment response and disease progression requires a host of screening tools.

Simply identifying key genetic mutations and other biomarkers that can help match a patient's tumor biology to an existing drug does not tell a complete story of that person's disease.

"Would we like to have a molecular test that takes care of all facets of monitoring patients' treatment response and disease progression?" Brufsky said. "Absolutely. But no one tool, no matter the hype, is going to answer every question I have or track all facets of a patient's status. Oncologists need to put a range of screening tools together to evaluate MBC."

According to Brufsky, these tools include imaging modalities — CT scans, MRI, ultrasound — to monitor tumor progression as well as patient visits to check on symptoms, which can signal aspects of a patient's disease status that a molecular test will not pick up. But how often an oncologist should check a patient's symptoms or perform a scan or molecular test is unclear and a topic of debate, especially for patients with MBC whose disease progression has been stable for several years, Brufsky noted.

"Still, that's a good debate to be having," Brufsky said. "I don't want to be overly optimistic, but this debate signals that we're moving into an era where some patients are living long enough with stable disease to even ask that question."

Disclosures: Dr Brufsky has disclosed relevant financial relationships with Puma Biotechnology, Roche, Pfizer, Lilly, Novartis, AstraZeneca, and Daiichi. Drs Carey and Shapiro have disclosed no relevant financial relationships.

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