ESR1 mutations are known to confer resistance to endocrine therapy in the metastatic breast cancer setting. These mutations herald a poor prognosis, so their clearance early in the treatment course may greatly reduce the risk of recurrence, according to the early results of the prospective phase III PADA-1 trial, reported during the ASCO20 Virtual Scientific Program.

When paired with palbociclib in the first-line treatment of metastatic breast cancer, fulvestrant and letrozole performed comparably, with no statistical superiority in progression-free or overall survival shown for either endocrine agent, in the phase II PARSIFAL study presented by Antonio Llombart-Cussac, MD, PhD, during the ASCO20 Virtual Scientific Program.

Patients who have breast cancers with double PIK3CA mutations seem to have a more robust response to PI3Kα inhibitors than those with a single PIK3CA mutation, based on an analysis of the phase III SANDPIPER trial, which tested taselisib plus fulvestrant, according to a presentation during the 2020 American Association for Cancer Research Virtual Annual Meeting II.

An exploratory subgroup analysis of the KAMILLA trial represents the largest reported cohort of patients with HER2-positive breast cancer and brain metastases treated with the anti-HER2 antibody-drug conjugate ado-trastuzumab emtansine, or T-DM1, in a prospective setting. Researchers observed clinically meaningful antitumor activity, regardless of whether patients had or had not undergone prior radiotherapy. The findings by Montemurro et al were published in Annals of Oncology.

In a study reported in JCO Oncology Practice, Stephanie L. Graff, MD, and colleagues found that patients with breast cancer seen by a physician with training in using an established pathway for genetic counseling and testing referral were more frequently referred for such services vs patients seen by non–pathway-trained physicians or those seen before pathway implementation.