Quantitative evaluation of liver metastases density on computed tomography: A new tool to evaluate early response to bevacizumab-containing chemotherapy

Background Response Evaluation Criteria in Solid Tumors (RECIST) are used to assess tumour shrinkage after cytotoxic chemotherapy, but may be inadequate for efficacy evaluation of anti-angiogenic therapies. Aims This study aimed to identify novel radiologic tumour response criteria based on early changes in tumour size and density, observed on computed tomography (CT), in patients with colorectal liver metastases (CRLM) treated with bevacizumab-containing chemotherapy. Methods CT of 71 and 68 CRLM patients treated with bevacizumab and non-bevacizumab-based regimens, respectively, were retrospectively reviewed. Tumour size, tumour density, and tumour-to-liver density (TTLD) ratio were determined at baseline and at first restaging. We tested their correlation with progression-free (PFS) and overall survival (OS) using the log-rank test. Results In the bevacizumab group, neither RECIST response nor tumour density variation was correlated with PFS or OS. In contrast, PFS and OS were significantly longer in patients with tumour size reduction ≥15% (RECIST−15%) and/or decrease in TTLD ratio not exceeding −10% (TTLD−10%) than in patients who did not reach any of those criteria, in univariate and multivariate analysis. Only size-response criteria predicted clinical outcome in the non-bevacizumab group. Conclusions This study highlights new quantitative CT criteria that may early predict the efficacy of bevacizumab in CRLM patients.