Perfusion CT: Noninvasive Surrogate Marker for Stratification of Pancreatic Cancer Response to Concurrent Chemo- and Radiation Therapy

Purpose: To prospectively determine whether perfusion computed tomography (CT) parameters, such as volume transfer constant (Ktrans) between blood plasma and extracellular extravascular space (EES) and blood volume calculated from dynamic CT data, can be used to predict response of pancreatic cancer to concurrent chemotherapy and radiation therapy (CCRT). Materials and Methods: This prospective study was institutional review board approved, and written informed consent was obtained. Thirty patients with pancreatic cancer underwent perfusion CT with 64-detector row CT before gemcitabinebased CCRT. Two perfusion parameters (Ktrans and blood volume) measured before treatment were compared between patients who responded to treatment and those who did not, as determined with World Health Organization criteria from first and second posttherapeutic follow-up CT examinations, which were performed at 3- and 6-month followup. Statistical analysis was performed with the two-sample t test. A receiver operating characteristic curve was used to determine the best cutoff value of perfusion parameters for differentiation of responders from nonresponders. Results: Twenty of 30 patients examined at 3- month follow-up responded to therapy. Their pretreatment Ktrans value was significantly higher than that of nonresponders (50.8 mL/100mL/min +/- 30.5 [standard deviation] vs 19.0 mL/100 mL/min +/- 10.8, P=.001). The best cutoff value for differentiating between responders and nonresponders was 31.8 mL/100 mL/min, which yielded 75.0% sensitivity and 90.0% specificity. Ten of 18 patients examined at 6-month follow-up responded to therapy. Their pretreatment Ktrans value was significantly higher than that of nonresponders (58.6 mL/100mL/min +/- 43.2 vs 19.8 mL/100 mL/min +/- 0.9, P=.002). Responders also had higher blood volume values, but this difference was not significant. Conclusion: Tumors with a high pretreatment Ktrans value tended to respond better to CCRT than did tumors with a low pretreatment Ktrans value. Perfusion CT may be used to predict tumor response to CCRT in patients with pancreatic cancer. This might aid in development of a tailored approach to therapy in these patients. (C) RSNA, 2008