Assessing Tumor Perfusion and Treatment Response in Rectal Cancer with Multisection CT: Initial Observations

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Abstract
To use first-pass perfusion computed tomography (CT) to prospectively investigate tumor vascularity in rectal cancer and to determine whether any of the perfusion parameters would predict tumor response to chemotherapy and radiation therapy. The institutional review board approved this study, and informed prior consent was obtained from participants. Perfusion CT of rectal cancer was performed with four-section multi-detector row CT in 15 patients (13 men, two women; mean age, 62.1 years; age range, 46-84 years). Five patients with prostate cancer served as controls. All patients with rectal cancer underwent 6-8 weeks of chemotherapy and radiation therapy followed by surgery. In nine patients, perfusion CT was repeated after completion of chemotherapy and radiation therapy. Contrast medium-enhanced dynamic CT was performed with a static table position for 45 seconds, and the data were analyzed by using commercial software to calculate tissue blood flow (BF), blood volume, mean transit time (MTT), and vascular permeability-surface area product. Perfusion parameters of normal rectum and tumor were compared. Perfusion parameters before and after chemotherapy and radiation therapy were compared. A tumor was considered to have responded if its stage at pathologic analysis indicated regression compared with the preoperative stage. Baseline perfusion values were compared between responders and nonresponders. Statistical analysis was performed with the Student t test. Rectal cancer showed higher BF and shorter MTT compared with those of normal rectum (P < or =.05). After chemotherapy and radiation therapy, tumors showed significant reduction in BF and increase in MTT (P < or =.05). There was a significant difference in baseline BF and MTT values between responders and nonresponders (P < or =.05). Tumors in three patients with high initial BF and short MTT showed poor response. Perfusion CT of rectal cancer can enable assessment of tumor vascularity and perfusion changes that result from chemotherapy and radiation therapy. In this small patient sample, tumors with initial high BF and short MTT values tended to respond poorly to chemotherapy and radiation therapy.