Tumor microcirculation and diffusion predict therapy outcome for primary rectal carcinoma

The aim of our study was to correlate perfusion indices and apparent diffusion coefficients with therapy outcome after chemoradiation.

In 34 patients with primary rectal carcinoma (cT3) undergoing preoperative chemoradiation, pretherapeutic perfusion indices and apparent diffusion coefficients were obtained by dynamic or diffusion-weighted magnetic resonance imaging. Therapy response was defined if the pathologic observation revealed no invasion into the perirectal fat after chemoradiation.

In 18 patients, a response and in 16, no response was observed. Statistically significant differences were found for the mean perfusion index (p < 0.001; 7.5 +/- 1.5 mL/min/100 g vs. 10.7 +/- 2.7 mL/min/100 g) and for the intratumoral cumulative fraction of pixels with perfusion-indices > 12 mL/min/100 g (p < 0.001, 3.7 +/- 4.0% vs. 24.7 +/- 17.9%). A three-way ANOVA resulted in significant effects for therapy responder/nonresponder (p < 0.001) and for apparent diffusion coefficient and the individual patients.

Perfusion indices and apparent diffusion coefficients inside the tumor region seem to be of predictive value for therapy outcome of preoperative therapy in patients with primary rectal carcinoma. Higher parameter levels in the nonresponding group could be explained by increased shunt flow or increased angiogenic activity in aggressive tumor cell clusters resulting in reduced nutrients supply and higher fraction of intratumoral necrosis respectively.