Maintenance Durvalumab Shows Activity in Certain Breast Cancer Subgroups

Although durvalumab monotherapy in the maintenance setting did not improve outcomes in patients with metastatic breast cancer when compared with chemotherapy, exploratory analyses revealed subgroups of patients that may benefit. The results were from the phase 2 randomized SAFIR02-IMMUNO trial, which were presented at the 2019 San Antonio Breast Cancer Symposium (SABCS) in San Antonio, Texas.

The SAFIR02-IMMUNO trial, which is a substudy of the SAFIR02_Breast trial (ClinicalTrials.gov Identifier: NCT02299999), included 191 patients with metastatic breast cancer, of whom 190 were women. Patients were randomly assigned to receive either durvalumab or chemotherapy in the maintenance setting. 

The rate of adverse events leading to treatment discontinuation was similar between the durvalumab and chemotherapy arms (6.2% vs 9.5%). The durvalumab arm had a higher rate of serious adverse events compared with the chemotherapy arm (18.6% vs 1.6%). No adverse events that lead to death were reported for either arm of the study. 

Maintenance durvalumab did not improve median progression-free survival (PFS) compared with chemotherapy (2.7 vs 4.6 months; hazard ratio [HR], 1.40; 1.00-1.96; P=.047) or overall survival (OS; 21.7 vs 17.9 months; HR, 0.84; 0.54-1.29; P=.42).

“This study suggests that durvalumab as monotherapy is not effective in the whole population of patients with [estrogen receptor]-positive metastatic breast cancer,” said study presenter Florence Dalenc, MD, of the Institut Claudius Regaud in France.

However, according to a subgroup analysis, patients with triple-negative breast cancer had an improved OS with maintenance durvalumab compared with chemotherapy (21 vs 14 months; HR, 0.54; 0.30-0.97; P=.0377). Patients with PDL1-positive tumors also had an improved OS with maintenance durvalumab compared with chemotherapy (26 vs 12 months; HR, 0.42; P =.0552)

“Subgroup analyses should be considered exploratory,” cautioned Dr Dalenc. “This study generates the hypothesis that durvalumab as single agent could improve outcome in metastatic triple-negative breast cancer.”

Disclosure: Some authors of this study disclosed financial relationships with the pharmaceutical industry. For a full list of disclosures, please refer to the original abstract.

Reference

1. Dalenc F, Garberis I, Filleron T, et al. Durvalumab compared to maintenance chemotherapy in patients with metastatic breast cancer: Results from phase II randomized trial SAFIR02-IMMUNO. Oral presentation at: 2019 San Antonio Breast Cancer Symposium; December 10-14, 2019; San Antonio, TX. Abstract GS3-02.

This article originally appeared on Cancer Therapy Advisor