More Data Needed on Tissue-Agnostic Therapy Use in Breast Cancer

A new report suggests that much remains to be seen about tissue-agnostic therapies’ effectiveness for treating breast cancer, as “a paucity of data” exists regarding this relatively new treatment’s impact on the disease, and that additional studies are needed to evaluate how well these therapies work on treating metastatic breast cancer (mBC).

The investigators reviewed existing medical literature on tissue-agnostic therapies’ efficacy for patients with breast cancer, and their findings appeared in a recent issue of NPJ Breast Cancer.

The FDA has approved 3 tissue-agnostic therapies since 2017—pembrolizumab, larotrectinib, and entrectinib—but only a handful of patients with mBC were included in the trials leading up to those approvals, according to the report. These therapies, which attack tumors regardless of their site of origin, target genomic alterations that are not often triggered by breast cancer, complicating the process of studying this patient group, the report said.

These approved therapies work on patients with high–microsatellite instability (MSI-H) tumors, high tumor mutational burden (TMB-H,) and NTRK fusions.

“Additional data assessing the degree of benefit and optimal treatment sequence in patients with mBC harboring these genomic alterations are needed,” the researchers wrote.

To avoid the difficulties of finding patients with breast cancer with these genomic alterations for a study, future investigators could call for real-world experiences from clinicians who happen to be treating these patients, the researchers suggested. “An international registry capturing experience from physicians around the world would be of value in this situation,” they wrote.

The researchers recommend that oncologists perform regular tests on their patients with breast cancer to see if they have these genomic alterations, with the first test occurring after the patient receives their diagnosis.

“Following the diagnosis of metastatic breast cancer, formalin-fixed, paraffin-embedded (FFPE) tissue blocks from archival tissue or from a new tumor biopsy should be used to evaluate the status of 1 of the 3 discussed biomarkers: MSI, TMB-H, or NTRK fusions,” the researchers wrote.

After that, “we recommend routinely performing tests to evaluate the status of these 3 biomarkers among patients with mBC, if feasible,” the researchers wrote.

Continuing to collect data on tissue-agnostic therapies’ impact on breast cancer is important because these treatments stand at “the apex of precision oncology,” and breast cancer is still common and deadly, they concluded.

Reference

Weis LN, Tolaney SM, Carrios CH, Barroso-Sousa R. Tissue-agnostic drug approvals: how does this apply to patients with breast cancer? NPJ Breast Cancer. Published online September 13, 2021. doi:10.1038/s41523-021-00328-3