Apparent diffusion coefficient for evaluating tumour response to neoadjuvant chemoradiation therapy for locally advanced rectal cancer.
OBJECTIVE
To determine whether change in the apparent diffusion coefficient (ADC) before and after neoadjuvant chemoradiation therapy (CRT) for locally advanced rectal cancer (LARC) would more accurately predict pathological complete response (pCR) than analysing the pre- or post-CRT ADC individually.


METHODS
76 patients with LARC (≥ T3 or lymph node-positive) underwent pre- and post-CRT, 1.5-T diffusion-weighted imaging. A blinded radiologist measured the tumour ADCs. The three measures were compared with regard to CR and non-CR. To calculate accuracy for determining pCR, receiver-operating characteristic curve (ROC) analysis was applied to the three measures.


RESULTS
The post-CRT ADC (1.43 ± 0.10) (× 10(-3) mm(2)/s) and the percentage change (70.0 ± 23.5%) in the CR (n = 11) were significantly higher than those in the non-CR (n = 65) (1.14 ± 0.18, 30.2 ± 21.7%, respectively)(both, P < 0.0001). The pre-CRT ADC (0.85 ± 0.10) of the pCR did not differ significantly from that of the non-pCR (0.88 ± 0.14)(P = 0.4094). The post-CRT ADC showed comparable relative accuracy for determining pCR to that of the percentage change (P = 0.788). However, overall accuracy of the former (87%) was higher than that of the latter (75%) (P = 0.049).


CONCLUSIONS
Analyzing post-CRT ADC alone can reliably differentiate pCR from non-pCR in LARC.
Department of Radiology, Seoul National University College of Medicine, Yongon-dong 28, Chongno-gu, Seoul 110-744, South Korea.
Seung Ho
SH
Kim
Jae Young
JY
Lee
Jeong Min
JM
Lee
Joon Koo
JK
Han
Byung Ihn
BI
Choi
D000328:Adult; D000368:Aged; D004058:Diffusion; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D005260:Female; D006801:Humans; D008198:Lymph Nodes / Q000473:pathology; D008297:Male; D008495:Medical Oncology / Q000379:methods; D008875:Middle Aged; D020360:Neoadjuvant Therapy / Q000379:methods*; D012372:ROC Curve; D012004:Rectal Neoplasms / Q000188:drug therapy* / Q000532:radiotherapy*; D015203:Reproducibility of Results; D016896:Treatment Outcome