Post Chemotherapy CT Image Changes May Predict Survival
In a preliminary research study published in the December 2 issue of JAMA it appears that changes in computed tomography (CT) imaging after chemotherapy for stage IV colorectal cancer may help predict overall survival.
Yun Shin Chun, M.D., of the University of Texas M. D. Anderson Cancer Center, Houston, and colleagues conducted a study to validate tumor response criteria that are based on morphologic changes observed on CT in patients with colorectal liver metastases treated with bevacizumab-containing chemotherapy regimens.
For the study, the researchers analyzed a total of 234 colorectal liver metastases from 50 patients who underwent hepatic resection (removal of tumors involving the liver) 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 beginning and end of preoperative therapy.
Radiologists evaluated images for morphologic response criteria, 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 (unable to be removed by surgery) colorectal liver metastases treated with bevacizumab-containing chemotherapy.
The researchers found that the morphologic CT criteria correlated strongly with the percentage of residual tumor cells and also with pathologic response stratified as complete, major, or minor. A 50% residual tumor cells level was used as the cutoff value between major and minor pathologic response.
Optimal morphologic response to preoperative therapy translated into an improved overall survival benefit after hepatic resection. This held true in the patients with unresectable colorectal liver metastases.
The addition of bevacizumab to cytotoxic (toxic to cells) chemotherapy is associated with improved survival in patients with stage IV colorectal cancer and higher pathologic response rates in patients undergoing resection (surgical removal) 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 end point after resection of colorectal liver metastases. To date, a noninvasive method of predicting pathologic response to chemotherapy in colorectal liver metastases, particularly biologic agents, is lacking,” the authors write. They add that it has been observed that after bevacizumab-containing therapy, colorectal liver metastases tend not only to decrease in size but also to undergo unique morphologic (form and structure) changes on CT.
The sample size in the surgical group was small, however, the authors believe “these results highlight the importance of response rather than baseline clinical factors in determining patient outcome after liver resection.”