Paper Information

To describe characteristics of patients with hormone receptor positive, HER2 negative, metastatic breast cancer (HR + MBC) who have long-term disease control with single-agent, first-line endocrine therapy (ET).

One in 8 patients with HR + MBC has long-term disease control with first-line, single-agent ET. These are younger patients with good performance status, non-visceral metastases, and tumors that express PR. Further research is needed to identify tumor characteristics that predict long-term disease control with ET alone.

Patients with HR + MBC starting first-line ET between January 1, 2011 and October 13, 2021 were selected from a US-based electronic health record-derived de-identified database. The group was divided by duration of disease control: long-term, ≥3 years without progression, and short-term, < 3 years to progression. Characteristics were compared between groups. Demographic and clinical variables were included in the multivariable analysis.

Of the 2374 included patients, 296 (12.5%) were progression-free at 3 years and 136 (5.7%) were progression-free at 5-years. In multivariable analysis, higher number of comorbidities (1 vs none [OR = 1.64, p < .001] or 2 + comorbidities vs none [OR = 1.71, p < .01]) and Medicare insurance coverage (Medicare alone versus commercial OR = 2.89, p < .001) and Medicare/other coverage versus commercial (OR = 2.67, p < .001)] were associated with long-term disease control. Factors inversely associated with disease control included older age (OR = 0.95, p < .001), being in the category of ``All other'' race (not Black or Hispanic) (OR = 0.66, p < .01), worse performance (PS 2 vs 0, p < .001), the presence of visceral metastases compared to with bone-only metastases (OR = 0.60, p < .001), and having ER+/PR- status compared to those with ER/PR + status (OR = 0.55, p < .001).