Perfusions-index values evaluated by dynamic magnetic resonance imaging inadvanced rectal carcinoma: A new predictor of response to preoperative chemoradiation?

Purpose: The aim of our study was to evaluate in vivo the influence of tumo r microcirculation data on therapy outcome. Patients and Methods: Tumor perfusion data of primary rectal carcinoma (n = 14, cT3) who underwent preoperative chemoradiation have been analyzed (Tab le 1). The perfusion data were acquired at the beginning and at the end of therapy by use of an ultrafast T1-mapping sequence on a whole-body magnetic resonance imager. The gadolinium-DTPA concentration-time-curves were evalu ated for arterial blood and tumor before, during and after intravenous cons tant rate infusion and from that the perfusion index (PI) was calculated. S ubsequent resection of the tumors allowed for a correlation of perfusion in dex values with the pathological classification. Results: Nine patients showed a T downstaging (ypT0-2, group 1), 5 patients did not (ypT3, group 2). The initial mean perfusion index value of group 1 (n = 9) was 8.2 ml/min/100 g (+/- 2) and for group 2 (n = 5) 10.4 ml/min/1 00 g (+/- 0.4). The difference in perfusion index values before chemoradiat ion between group 1 and group 2 was significant different (p = 0.012, Mann- Whitney test). The perfusion index value at the end of therapy of group 1 ( n = 6) was 9.6 ml/min/100 g (+/- 2.8) and for group 2 (n = 4) 10.7 ml/min/1 00 g (+/- 1.6). The difference in perfusion index values after chemoradiati on between group 1 and group 2 was not significant different (Table 2). Conclusion: Our used perfusion index value combines 2 parameters: tumor per fusion and extraction fraction. Therefore a significant negative influence on therapy outcome of high perfusion index values could be explained possib ly by areas with a high portion of high perfusion (e.g. av-shunts) and a lo w extraction fraction (= low exchange of nutrients). However. we could show a significant negative influence of high perfusion index values on therapy outcome (p = 0.012). Because the tumor stage has a significant influence o n tumor-free survival, there is a possibility for using initial perfusion i ndex values as a new prognostic factor in rectal carcinoma without sphincte r infiltration undergoing a preoperative chemoradiation. To examine this hy potheses a prospective trial is in preparation.