Monitoring Metastatic Breast Cancer Treatment Response: 5 Things to Know

Victoria Stern


November 23, 2020

2. Molecular testing is shifting MBC care closer to personalized medicine.

Over the past few years, the FDA has approved a number of drugs alongside companion diagnostic tests. By identifying salient genetic mutations, receptors, or proteins — estrogen and progesterone receptors, HER2, PD-L1, BRCA1, BRCA2, and PIK3CAmolecular tests can help guide treatment choice.

When the FDA gave alpelisib the green light, the agency also approved the companion diagnostic test, therascreen PIK3CA RGQ PCR KIT, which detects the PIK3CA mutation in tissue or liquid biopsy samples.

Although personalizing treatment to a patient's actionable biomarkers can predict better outcomes and fewer deaths, questions remain about how best to use the information gleaned from these tests. First, Carey said, how do oncologists choose the optimal therapy when a patient with MBC has several actionable abnormalities? One example Carey gave is of a patient with metastatic HR-positive, HER2-negative disease whose next-generation sequencing reveals high tumor mutational burden (an indication for immunotherapy) and a PIK3CA E545K hotspot mutation (an indication for adding alpelisib to endocrine therapy). Second, according to Carey, should an oncologist change patients' treatment regimens if their abnormalities change over time?

"We are still learning how cancers evolve under selective pressures of time and drugs," Carey said. "Multiple studies have shown shifts in the tumor phenotypes between primary breast cancer and metastases, but these changes might not 'stick' and the cancer could revert to the initial phenotype. Plus, how those changes should affect treatment decisions and how often we need to monitor molecular signatures are less clear."

3. Knowing when it's time to switch to palliative care.

Providing palliative care early in patients with MBC can improve quality of life and symptoms, as well as avoid unnecessary care and reduce medical costs. Despite these benefits, palliative care services are often underused.

Although analyses on the use of palliative care in MBC tend to be limited to single-institution experiences, these studies suggest delays or poor uptake of these services. A 2018 study, for instance, found that just under 45% of patients with MBC (105/234) at a safety net hospital in Texas received referrals to palliative care. Another analysis, which retrospectively reviewed the use of palliative and hospice care in hospitalized patients with MBC at a tertiary care center in Boston, found that only 17% (16/94) went to an outpatient palliative care appointment, even though 57% received an evaluation from an inpatient palliative care team. A third study, out of the University of California, San Francisco, found that breast cancer oncologists referred about 20% of patients with MBC to palliative care, and just over half (11.5%) saw a palliative care doctor.

"Our biggest mistake as oncologists is making palliative care referrals too late," said Charles Shapiro, MD, director of translational breast cancer research at Tisch Cancer Institute at Mount Sinai, in New York City. "Sometimes it's hard to tell patients there's nothing else we can do therapeutically, but eventually you run out of treatment options that make sense, and it's important to acknowledge when therapeutics will no longer help patients."

Shapiro explained that the time to consider palliative care in MBC varies from patient to patient, but oncologists should not fear this option. In fact, in 2017, the American Society of Clinical Oncology (ASCO) recommended that all patients with metastatic cancer should simultaneously receive palliative care alongside their cancer regimen within 8 weeks of receiving a diagnosis, not just at the end of life.

"Transitioning to palliative care is not giving up; it is choosing options like symptom relief that we know we can effect in a positive way, rather than giving another chemotherapy with a very marginal benefit and all the side effects," Shapiro said.


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