Dr Vaz Batista on Treating Patients With HER2+ Breast Cancer and Leptomeningeal Carcinomatosis

Marta Vaz Batista, MD, medical oncologist, Hospital Fernando Fonseca, discusses the efficacy of fam-trastuzumab deruxtecan-nxki (Enhertu; T-DXd) in patients with HER2-positive or HER2-low advanced breast cancer and pathologically confirmed leptomeningeal carcinomatosis, as evaluated in cohort 5 of the phase 2 DEBBRAH study (NCT04420598).

Results from this patient subgroup analysis were presented at the 2023 San Antonio Breast Cancer Symposium. Forty-one patients across Spain and Portugal were enrolled into the single-arm, open-label, 5-cohort study, 7 of whom were enrolled into cohort 5, where treatment with T-DXd resulted in clinical responses. At the meeting, investigators shared that the median overall survival (OS) with T-DXd in cohort 5 was 13.3 months (95% CI, 2.5-not reached; P <.001). Notably, the 16-week OS rate was 86% (95% CI, 33%-98%), and the 24-week OS rate was 71% (95% CI, 26%-92%).

The primary aim of evaluating patients with HER2-positive breast cancer and leptomeningeal carcinomatosis in cohort 5 of DEBBRAH was to assess OS with T-DXd due to the recognized poor prognosis of this patient population, Vaz Batista begins. Quantifying additional treatment options for this patient subgroup, where the current standards of care are associated with limited efficacy, has proven challenging, she notes.

Although leptomeningeal carcinomatosis is a terminal event in patients with breast cancer, in this cohort of 7 patients, 2 patients were still undergoing treatment at the data cutoff, indicating notable progress in progression-free survival for this population, she continues. Patients with leptomeningeal carcinomatosis have unmet needs, as treatment strategies remain uncertain upon the development of this metastasis, Vaz Batista emphasizes. Although retrospective analyses with various drugs have been explored, this trial represents the first prospective phase 2 study demonstrating the efficacy of T-DXd in patients with leptomeningeal carcinomatosis, she states.

This trial, despite its phase 2 nature, stands as a significant contribution to clinical practice, showcasing promising outcomes with T-DXd in this difficult-to-treat patient population, Vaz Batista says. Conducting phase 3 trials in this patient population in the foreseeable future may be impractical due to the infrequency of leptomeningeal carcinomatosis cases, Vaz Batista concludes.

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