Impact of early tumor shrinkage and depth of response in patients with BRAF V600E-mutant metastatic colorectal cancer.

Abstract

Background: Early tumor shrinkage (ETS) and depth of response (DpR) are early indicators of survival in patients with metastatic colorectal cancer (mCRC) undergoing anti-epidermal growth factor receptor monoclonal antibody treatment. However, their relevance in v-raf murine sarcoma viral oncogene homolog B1 (BRAF) V600E mutant (MT) mCRC remains unclear. In this study, we evaluate the association between ETS/DpR and clinical outcomes in BRAF V600E MT mCRC.

Patients and methods: Patients with mCRC who were diagnosed with BRAF V600E MT and treated with first-line chemotherapy between June 2011 and March 2023 at a single cancer institute were enrolled. The association between ETS/DpR and clinical outcomes in patients with at least one target lesion was assessed. The cutoff value for ETS and DpR was set at 20% and 25%. Multivariate analysis of factors affecting progression-free survival (PFS) and overall survival (OS) was conducted.

Results: In total, 54 patients with BRAF V600E MT mCRC exhibited at least one target lesion. Patients with ETS and DpR were 24 (44.4%) and 27 (50%), respectively. Moreover, median PFS and OS were 7.5 and 17.1 months, respectively. Patients with ETS exhibited longer PFS and tended toward longer OS than those without ETS. Similarly, patients with DpR exhibited longer PFS and OS than those without DpR. Multivariate analysis confirmed a significant association between DpR and longer PFS and OS.

Conclusion: ETS and DpR could serve as early surrogate markers of clinical outcomes in patients with BRAF V600E MT mCRC treated with first-line chemotherapy.