Shigeru Kobayashi MD, Presenter: Nothing to Disclose

Hideharu Sugimoto MD, Abstract Co-Author: Nothing to Disclose

To assess whether diffusion-weighted magnetic resonance imaging (DW MR imaging) could predict the responders to radiotherapy (RT) or chemoradiotherapy (CRT) in patients with locally advanced lower rectal cancer.

Between February 2007 and August 2009, thirty one patients (23 men and 8 women, mean age of 59.6 years) who were clinically diagnosed as locally advanced lower rectal adenocarcinomas (cT3 or cT4/Nx/M0), received preoperative RT/CRT and subsequent surgery were enrolled in the study. All patients underwent 1.5-T rectal MR imaging including DW MR imaging before and after RT/CRT. When down stage was confirmed histologically from cT3-cT4 to ypT0-ypT2, the patient was defined as responder. When the invasion into the perirectal far or moreover (ypT3-ypT4) was confirmed histologically, the patient was defined as nonresponder. For qualitative analysis, pretreatment apparent diffusion coefficient (ADC) map image at the central slice of tumor was selected and three circular regions of interest in viable area were drawn, ADC values were obtained and averaged. The difference of mean ADC value at the central slice of tumor between the responder and non-responder groups were statistically analyzed.

Pretreatment mean ADC ([0.763 ± 0.130] x 10-3 mm2/s) (standard deviation) of the responder group (n = 9) at the central slice of tumor was significantly lower than that [(0.965 ± 0.170) x 10-3 mm2/s] of the non-responder group (n = 22) (P < .01). The differential diagnostic values of ADC at the central slice of tumor with a threshold of less than 0.8 x 10-3 mm2/s was sensitivity of 77.8%, specificity of 86.4%, positive predictive value of 70% and negative predictive value of 90.5%, respectively.

Pretreatment mean ADC value at the central slice of tumor could predict the responder to RT/CRT in patients with locally advanced lower rectal cancer.

The results of this study will give important information to select optimal therapy for locally advanced lower rectal cancer.

Kobayashi, S, Sugimoto, H, Could Diffusion-weighted Magnetic Resonance Imaging Predict the Responders to Preoperative Radiotherapy or Chemoradiotherapy in Patients with Locally Advanced Lower Rectal Cancer?.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9013200.html