Occurrence and significance of morphologic changes in patients with metastatic triple negative breast cancer treated with Cabozantinib.

OBJECTIVE: To compare performance of RECIST1.1 and Choi criteria in assessment of patients with metastatic triple-negative breast cancer treated with cabozantinib.

METHODS: Thirty patients with metastatic triple-negative breast cancer enrolled in phase 2 clinical trial received cabozantinib. Clinical benefit rates assessed by prospectively determined RECIST1.1 and retrospectively assessed Choi criteria were compared.

RESULTS: Decreased tumor density (≥15%) at first follow-up was seen in 22/30(73%) patients. CBR was 40% (95%CI:23-59%) by RECIST1.1, and 73% (95%CI:54-88%) by Choi (NPV=100%, 95%CI:63-100%; PPV=55%, 95%CI:32-76%).

CONCLUSIONS: Morphologic changes are seen in the majority of patients treated with cabozantinib, making Choi criteria valuable in response assessment.