Elderly Patients With HER2+ Advanced Breast Cancer Experience Poorer Outcomes, Increased Toxicity

Despite having similar disease characteristics and treatment patterns, elderly patients with HER2-positive advanced breast cancer aged ≥ 70 years experienced shorter chemotherapy durations than patients under the age of 70, as well as, poorer overall survival (OS), and increased rates of adverse events (AEs) in a real-world study.

Although HER2-targeted therapies have significantly improved the outcomes of patients with HER2-positive advanced breast cancer, the elderly population is often excluded from clinical studies. The real-world study of an Australian population aimed to evaluate the treatment patterns and outcomes for these patients who are 70 years or older. Data were collected from the Treatment of Advanced Breast Cancer in the HER2-positive Australian Patient (TABITHA) multicenter clinical registry, and patients were stratified by age, for a total of 252 patients in the < 70 years age group and 67 in the ≥ 70 group.

Baseline characteristics showed the ECOG performance status in the younger and older groups was 0 in 68% and 55%, respectively, 1 in 27% and 37%, and 2 or greater in 3% and 16% (P <.001), and the Charlson Comorbidity Index was 0-1 in 50% and 72%, 2 in 2% and 19%, and 3 or greater in 1% and 9% (P <.001). The majority of patients in the younger and older groups, respectively, had estrogen receptor (ER)-positive disease (56%, 70%), did not have de novo metastatic disease (57%, each), and had visceral disease (68%, 66%).

In terms of frontline treatment characteristics, 93% of patients in the younger arm and 85% in the older group had a prior anti-HER2 therapy (P =.054). Among these patients, the median duration of therapy was 22 months for those aged < 70 years and 16 months for those 70 and older (P =.702). For 82% of the younger group and 74% of the older group, patients received frontline chemotherapy (P =.139), and the duration of chemotherapy was 3.5 months and 2.7 months, respectively (P =.018).

Although differences in the proportion of patients who received frontline chemotherapy was not observed, the elderly population had shorter median chemotherapy durations. The median duration was 2.7 months in the older patients versus 3.5 months in those under the age of 70 (P =.02). The overall survival (OS) was significantly longer in the younger group (HR, 0.51; 95% CI, 0.29-0.87; P <.001).

Rates of adverse events (AEs) were higher in the frontline setting for the older population, in which the AE rate was 34% compared with 20% in the younger population (P =.04). The cardiotoxicity rate was also higher in the older group (7%) than the younger group (0.9%; P =.02. On-treatment deaths occurred in 5% of the older group compared with 0% in the younger population (P =.01).

More patients in the age group of 70 or older experienced hospitalization or prolongation of hospital stay (28%) compared with the younger group (18%).

Overall, prospective clinical trials are needed to further explore the outcomes and treatment patterns observed in the elderly population.

_Reference

_{Evans N, Anton A, Wong R, et al. Real-world outcomes in elderly patients with HER2-positive advanced breast cancer. Presented at: 2020 ESMO Asia 2020 Virtual Meeting; November 20-22, 2020; Virtual. Abstract #51P.}