Seung Ho Kim MD, Presenter: Nothing to Disclose

Jae Young Lee MD, Abstract Co-Author: Nothing to Disclose

Jeong-Min Lee MD, Abstract Co-Author: Nothing to Disclose

Joon Koo Han MD, Abstract Co-Author: Nothing to Disclose

Byung I. Choi MD, PhD, Abstract Co-Author: Research collaboration, Taewoong Medical Co, Ltd

To prospectively determine whether analyzing a change in the apparent diffusion coefficient (ADC) values between pre- and post-chemoradiotherapy (CRT) diffusion-weighted imaging (DWI) would more accurately predict favorable responders than analyzing the absolute ADC values on pre-and post-CRT DWI for locally advanced rectal cancer.

Fifty-six patients (38 men, 18 women; mean age, 60 years; range, 32–82 years) with locally advanced rectal cancer (≥T3 or lymph node positive) who underwent CRT and subsequent surgery, were included in this study. All patients underwent pre- and post-CRT, 1.5-T rectal MRI with DWI (b value of 0, 1000 s/mm2). A blinded radiologist who measured three times the pre-and post-CRT ADC values of the rectal cancer. The mean ADC values of the pre-and post-CRT DWI were compared between the favorable responders (complete response + near complete response) and the poor responders. To identify the optimal cut-off value for discriminating favorable responders from poor responders, receiver operating characteristic curve (ROC) analysis was applied to the pre-and post-CRT mean ADC values as well as to the percentage of the ADC difference. Pathology reports served as the reference standard. 

The post-CRT mean ADC (1.42 ± 0.12 ×10-3 mm2/s) of the favorable responder group (n=21) was significantly higher than that (1.12 ± 0.17 ×10-3 mm2/s) of the poor responder group (n=35) (P<0.0001). The pre-CRT mean ADC (0.94 ± 0.09 ×10-3 mm2/s) of the favorable responders did not differ significantly from that (0.95 ± 0.12 ×10-3 mm2/s) of the poor responders (P=0.8783). The post-CRT mean ADC showed a comparable diagnostic accuracy (Az, 0.943; 95% CI, 0.846-0.987) to that of the percentage of the ADC difference (Az, 0.876; 0.761-0.949) (P=0.141). The optimal cut-off value (1.21 ×10-3 mm2/s) of the post-CRT ADC also showed a comparable diagnostic accuracy to that of the specific cut-off value (an increase of 30%) of the percentage of the difference (89.3%, 82.1%; P=0.2188).

A post-CRT ADC as well as a percentage of the difference between pre- and post-CRT ADC can reliably differentiate favorable responders from poor responders to CRT for locally advanced rectal cancer.

A post-CRT ADC as well as a percentage of the difference between pre- and post-CRT ADC can reliably differentiate favorable responders from poor responders to CRT for locally advanced rectal cancer.

Kim, S, Lee, J, Lee, J, Han, J, Choi, B, Apparent Diffusion Coefficient for Predicting Tumor Response to Neoadjuvant Chemoradiotherapy for Locally Advanced Rectal Cancer.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8007768.html