CT-based morphologic criteria accurately predicted OS in bevacizumab-treated colorectal liver metastases

Morphologic criteria based on CT predicted pathologic response and OS in patients with colorectal liver metastases treated with bevacizumab-containing chemotherapy.

Researchers from the University of Texas M.D. Anderson Cancer Center developed new CT criteria based on treatment induced morphologic changes to predict response to bevacizumab (Avastin, Genentech), a biologic agent not accurately assessed with RECIST criteria alone.

In their retrospective study, they identified 234 colorectal liver metastases from 50 patients who received first-line chemotherapy that included bevacizumab before having hepatic resection between March 2004 and March 2007. They also identified 82 patients with unresectable disease treated with bevacizumab-containing chemotherapy.

Contrast enhanced CT was conducted at the start and end of therapy. Three blinded radiologists evaluated the metastases for changes in morphology unrelated to size.

Researchers found that optimal morphologic criteria — a cystic-like appearance of the tumors in association with well defined borders — correlated with pathologic response and survival.

The median values of (pathologic response) percentage of residual tumor cells for morphologic response were 70% for no response, 50% for incomplete response and 20% for optimal response. For RECIST, the values were 70% for progressive disease, 50% for stable disease and 30% for partial response. The RECIST criteria showed less specificity than morphologic criteria in predicting pathologic response.

In patients who underwent resection median OS was not reached in responders and was 25 months (95% CI, 20.2-29.8) for nonresponders when morphologic criteria were used.

For patients with unresected tumors, median OS was 31 months (95% CI, 26.8-35.2) for those with optimal response and 19 months (95% CI, 14.6-23.4) for those with incomplete or no response by morphologic criteria.

For patients with both resected and unresected tumors, RECIST was not associated with survival.

Chun YS. JAMA. 2009;302:2338-2344.