Retrospective analysis of pathological response in colorectal cancer liver metastases following treatment with bevacizumab: Updated findings.

Abstract

e14120 Background: Recent reports have shown that pathological response predicts for better outcome (overall survival) following preoperative chemotherapy and surgical resection of colorectal cancer (CRC) liver metastases. The aim of this retrospective analysis was to evaluate the effect of adding bevacizumab (BEV) to standard chemotherapy on pathological response in patients (pts) with CRC liver metastases. Methods: Pts with stage IV CRC with liver metastases who received neoadjuvant chemotherapy (oxaliplatin-or irinotecan-based) at two Spanish centres were analysed retrospectively. Pathological response was evaluated as follows: complete pathological response (cPR), PR1 (<25% of residual viable tumour cells), PR2 (25–50% of residual tumour), PR3 (>50% of residual tumour). cPR or PR1 was considered to be a good response, and PR2 or PR3 a poor response. KRAS status was determined from tumour blocks. Results: 95 pts were evaluated. Of these, 44 received chemotherapy alone and 51 received chemotherapy + BEV. Baseline characteristics were as follows: median age 61.0 years (range 43.0–80.0 years); male/female (68%/32%); tumour location – colon (72%) / rectum (28%); hepatic metastases – synchronous (74%) / metachronous (26%); extrahepatic disease – yes (26%) / no (74%); KRAS status – mutated (37%) / wild type (29%) / not available (34%). The overall response rate (ORR) by RECIST was 51% (1 CR and 47 PRs) and 48% of pts had stable disease. ORR did not appear to vary in pts who did or did not receive BEV. In terms of pathological response, 49% of pts receiving BEV had a good response (cPR + PR1) compared with 27% of those receiving chemotherapy alone (p=0.0302). Good pathological response (cPR + PR1) was slightly lower in pts with mutant (31%) vs wild type (43%) KRAS status (difference not significant). At the end of the analysis, 45% of pts had relapsed and 67% were alive. Conclusions: Adding BEV to standard chemotherapy in the neoadjuvant setting improves pathological response of liver metastases in pts with stage IV CRC. Further studies are required to examine the potential relationship between pathological response and survival outcomes in pts with CRC and liver metastases.