A study exploring practice patterns in HER2-positive breast cancer in the United States found that the most common second-line treatment following first-line pertuzumab plus trastuzumab were trastuzumab emtansine (T-DM1)-based regimens.

This study was presented at the virtual 2021 ASCO Annual Meeting.

“Limited real-world data exists on the treatment of HER2-positive metastatic breast cancer following pertuzumab plus trastuzumab-based regimens in first-line setting,” explained Sandhya Mehta, PhD, Health Economics and Outcomes Research, AstraZeneca US, Gaithersburg, MD, and colleagues.

“Real-world treatment effectiveness data following first-line P+T [pertuzumab plus trastuzumab] could complement clinical trial data to help inform understanding of unmet needs of HER2-positive metastatic breast cancer patients requiring second-line treatment,” they added.

The IQVIA Oncology EMR database was used to identify adult patients in the US with confirmed HER2-positive metastatic breast cancer who were treated with a first-line pertuzumab plus trastuzumab-based regimen between January 2015 and September 2019.

A total of 710 patients were identified with a median follow-up of 20.3 months. The median first-line treatment duration was 15.3 months.

Overall, 302 (43%) patients discontinued first-line treatment during the study. Of these patients, 222 patients moved on to second-line therapy with a median follow-up of 9.6 months after second-line therapy initiation.

Of the 222 patients who received second-line therapy, 214 (96%) received anti-HER2-based regimens (hormonal therapy and/or chemotherapy). The most common anti-HER2-based regimens were T-DM1-based regimens (n = 159; 72%), followed by trastuzumab-based regimens (n = 29; 13%), lapatinib-based regimens (n = 13; 6%) and neratinib (n = 13; 6%).

The median duration of second-line treatment overall was 5.9 months. The median time to treatment failure, defined as initiation to a new line of therapy or death, was 8.6 months. Median overall survival (OS) was 25.4 months.

Among patients receiving T-DM1-based regimens in the second-line setting, the median treatment duration was 5.7 months, median time to treatment failure was 7.9 months, and median OS was 24.4 months.

“There remains an unmet need of a more effective treatment for HER2-positive metastatic breast cancer after first-line treatment,” Dr Mehta and colleagues concluded.—Janelle Bradley

Mehta S, Pavilack M, Xie J, et al. Treatment patterns following first-line pertuzumab + trastuzumab in patients with HER2+ metastatic breast cancer in the United States. Presented at: the 2021 ASCO Annual Meeting; June 4-8, 2021; virtual. Abstract e18746.