Traditionally, human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer treatment has included targeted therapies, such as trastuzumab, pertuzumab, and trastuzumab emtansine, that are regarded as standard-of-care treatments and have demonstrated efficacy in clinical trials.
In the United States, it has not been well-delineated in the real-world setting, what sequencing of treatment and treatment choice are optimal for patients with HER2-positive metastatic breast cancer after first-line therapy.
Jenna Collins of Evidera, Waltham, MA, and colleagues extracted data from an electronic health record–derived database, finding patients who received ≥2 lines of therapy for HER2-positive metastatic breast cancer diagnosed between January 2013 and April 2019. Patterns of treatment from second-line and later were analyzed.
Included in the study were 1390 patients with HER2-positive metastatic breast cancer, who received second-line therapy, and had a mean age of 60.4 years. By the start of second-line therapy, patients had been identified with 1 (37.0%), 2 (28.1%), or ≥3 (33.2%) metastatic sites. Bone (62.7%) was the most common metastatic site, followed by lung (35.5%), liver (34.0%), and brain (16.0%). In the majority of patients, positive hormone receptor status was identified (82.1%).
Stage IV disease at the time of initial breast cancer diagnosis was found in 43.2% of patients, while 20.8% had stage III, and 19.9% had stage II.
Before receiving second-line therapy, approximately half (51.8%) of patients had been treated with a HER2-targeted combination therapy, 15.0% had been given HER2-targeted monotherapy, and 24.2% were administered hormone therapy alone. Among all patients included, 39.6% had ≥4 lines of systemic therapy for metastatic breast cancer, 25.8% had 3, and 34.6% had 2.
Of the patients, 92.8% had used an HER2-targeted agent (monotherapy or in combination) in at least 1 line of therapy, and 79.7% had ≥2 lines of therapy containing an HER2-targeted agent.
The most frequently administered regimens during second-line therapy were trastuzumab monotherapy (13.8%), trastuzumab emtansine monotherapy (15.3%), and pertuzumab plus trastuzumab and taxane (17.7%).
In second-line therapy, nearly 52% of all included patients were treated with HER2-targeted combination therapy, 30.7% were given HER2-targeted monotherapy, 5.9% were treated with chemotherapy, and 8.5% were administered hormone therapy alone.
In 44.7% of patients, hormone therapy was given in combination with chemotherapy or targeted therapy. The median duration of second-line therapy was 6 months. The most common regimens were hormone therapy alone (6.5%), pertuzumab plus trastuzumab and taxane (8.5%), and trastuzumab emtansine (18.7%).
Overall, in the 909 patients who had received third-line therapy, 49.1% patients had HER2-targeted combination therapy, 31.1% had HER2-targeted monotherapy, and 8.6% had chemotherapy, with hormone therapy added to chemotherapy or targeted therapy in 42.7% patients. For third-line therapy, the median duration was 5 months.
In community-based oncology clinics, findings of this real-world study demonstrate that patients receive treatment that is variable in patterns in later-line settings, and there is no clear management strategy being utilized; this is true not only for this patient population but also for patients often being retreated with the same HER2-targeted therapies. With the advent of new targeted therapies that have recently been approved for patients with HER2-positive metastatic breast cancer, improvements in patient outcomes are being seen.
Source: Collins J, Nordstrom B, Kwong J, et al. A real-world evidence study of treatment patterns among patients with HER2-positive metastatic breast cancer. Presented at: 2020 San Antonio Breast Cancer Symposium, December 8-11, 2020. Abstract PS7-82.