CT perfusion for the monitoring of neoadjuvant chemotherapy and radiation therapy in rectal carcinoma: Initial experience

Purpose: To prospectively monitor changes in rectal cancer perfusion after combined neoadjuvant chemotherapy and radiation therapy with perfusion computed tomography (CT) and to evaluate whether perfusion CT findings correlate with response to therapy. Materials and Methods: The study was approved by the institutional ethics committee of the European Institute of Oncology; written informed consent was obtained from all participants before the study. Twenty-five patients with rectal adenocarcinoma (18 men, seven women; age range, 42 - 72 years; mean age, 61.3 years) underwent perfusion CT; all of them underwent neoadjuvant chemotherapy and radiation therapy, followed by surgery. In 19 patients, perfusion CT was repeated after chemotherapy and radiation therapy. Dynamic perfusion CT was performed for 50 seconds after intravenous injection of contrast medium (40 mL, 370 mg iodine per milliliter, 4 mL/ sec). Blood flow (BF), blood volume (BV), mean transit time, and permeability-surface area product (PS) were computed in the tumor and in normal rectal wall by two independent blinded radiologists. Microvessel density was evaluated in pretreatment biopsy specimens in nine patients and in surgical specimens in seven patients. Wilcoxon signed- rank and rank sum tests were used for paired and independent comparisons, respectively. Results: BF, BV, and PS were significantly higher in rectal cancer than in normal rectal wall (P <.001). BF, BV, and PS significantly decreased after combined chemotherapy and radiation therapy (P <.009). No correlation was found between perfusion parameters and microvessel density, neither in baseline values nor in posttherapy changes. Baseline BF and BV in the seven patients who failed to respond to treatment were significantly lower than in the 17 responders ( P <.02 for BF and <.001 for BV). Conclusion: Perfusion CT has potential for monitoring the effects of combined neoadjuvant chemotherapy and radiation therapy and predicting the response of rectal cancer to such therapy.