Preliminary research suggests that criteria based on computed tomography imaging of changes in tumors from colorectal liver metastases after chemotherapy with bevacizumab may have the potential to predict overall survival, according to a study in the December 2 issue of the Journal of the American Medical Association.
The addition of bevacizumab to cytotoxic chemotherapy is known to be associated with increased survival in patients with Stage IV colorectal cancer and higher pathologic response rates in patients undergoing resection of colorectal liver metastases.
“Recently, pathologic response to preoperative chemotherapy has been shown to correlate with improved survival and has been proposed as a new outcome endpoint after resection of colorectal liver metastases,” explained the authors, led by Yun Shin Chun, MD, of the University of Texas M. D. Anderson Cancer Center. “To date, a noninvasive method of predicting pathologic response to chemotherapy in colorectal liver metastases, particularly biologic agents, is lacking.”
After bevacizumab-containing therapy, colorectal liver metastases tend not only to decrease in size but also to undergo unique morphologic changes on CT.
Dr. Chun and her colleagues attempted to validate tumor response criteria based on morphologic changes observed on CT in patients with colorectal liver metastases treated with bevacizumab-containing chemotherapy regimens. The team analyzed 234 colorectal liver metastases from 50 patients who underwent hepatic resection after preoperative chemotherapy that included bevacizumab, from 2004 to 2007; the date of last follow-up was March 2008.
All patients underwent routine contrast-enhanced CT at the start and end of preoperative therapy. Radiologists evaluated images for morphologic response, based on metastases changing from heterogeneous masses with ill-defined margins into homogeneous lesions with sharp borders. These criteria were validated with a separate group of 82 patients with unresectable colorectal liver metastases treated with bevacizumab-containing chemotherapy.
The results showed that morphologic criteria correlated strongly with the percentage of residual tumor cells and also with pathologic response stratified as complete, major, or minor using 50% residual tumor cells as the cutoff value between major and minor pathologic response.
Optimal morphologic response to preoperative therapy translated into a survival benefit after hepatic resection. In a separate validation cohort of patients with unresectable colorectal liver metastases, response by morphologic criteria was also associated with increased overall survival.
The researchers said that although the sample size in the surgical group was small, the results highlight the importance of response rather than baseline clinical factors in determining patient outcome after liver resection.
“Our results indicate that morphologic response may be a useful, noninvasive surrogate marker of pathologic response and improved survival in patients with colorectal liver metastases receiving a bevacizumab-containing regimen. It provides complementary information to traditional size-based criteria in assessing CT response to bevacizumab in colorectal liver metastases.”