Background: The clinical significance of discordant radiological and pathological response to preoperative chemotherapy of colorectal liver metastases (CLM) is unknown.
Methods: From 2011 to 2016, all eligible patients undergoing resection for CLM after preoperative chemotherapy were included at two centres. Patients were categorized according to radiologic response using RECIST as Rad-responders (complete/partial response) or Rad-non responders (stable disease) and according to Blazer et al. pathologic response grade as Path-responders (complete/major response) or Path-non responders (minor response). Survival outcome was analysed according to radiologic and pathologic response.
Results: Among 413 patients undergoing resection of CLM, 119 fulfilled the inclusion criteria. Among these, 52 (44%) had discordant radiologic and pathologic response including 27 Rad-non responders/path responders and 25 Rad-responders/Path-non responders. Rad-non responders/path responders and Rad-responders/Path-non responders had similar characteristics except for the proportion receiving more than 6 cycles of preoperative chemotherapy (7/27 vs 16/25; P = 0.017). Median disease-free survival was not different in patients with or without discordant radiologic and pathologic responses (P = 0.195) but the type of discordance had an impact on oncologic outcome as median disease-free survival was 13.9 months (95% CI 5.7-22.2 months) in Rad-non responders/Path responders and 8.6 (6.2 - 10.9 months) in Rad-responders/Path-non responders (P = 0.034). Univariate and multivariate analysis showed that major pathologic response was associated with improved disease-free survival (OR 0.583, 95% CI 0.36-0.95, P = 0.031).
Conclusion: A discordant radiologic and pathologic response is common after preoperative chemotherapy for CLM. In these patients, pathologic response drives oncologic outcome.