title: Diffusion-weighted magnetic resonance imaging in monitoring rectal cancer response to neoadjuvant chemoradiotherapy.
abstract: OBJECTIVE
  To prospectively monitor the response in patients with locally advanced nonmucinous rectal cancer after chemoradiotherapy (CRT) using diffusion-weighted magnetic resonance imaging. The histopathologic finding was the reference standard.
  
  
  METHODS
  The institutional review board approved the present study. A total of 62 patients (43 men and 19 women; mean age, 64 years; range, 28-83) provided informed consent. T(2)- and diffusion-weighted magnetic resonance imaging scans (b value, 0 and 1,000 mm(2)/s) were acquired before, during (mean 12 days), and 6-8 weeks after CRT. We compared the median apparent diffusion coefficients (ADCs) between responders and nonresponders and examined the associations with the Mandard tumor regression grade (TRG). The postoperative nodal status (ypN) was evaluated. The Mann-Whitney/Wilcoxon two-sample test was used to evaluate the relationships among the pretherapy ADCs, extramural vascular invasion, early percentage of increases in ADCs, and preoperative ADCs.
  
  
  RESULTS
  Low pretreatment ADCs (<1.0 × 10(-3)mm(2)/s) were correlated with TRG 4 scores (p = .0011) and associated to extramural vascular invasion with ypN+ (85.7% positive predictive value for ypN+). During treatment, the mean percentage of increase in tumor ADC was significantly greater in the responders than in the nonresponders (p < .0001) and a >23% ADC increase had a 96.3% negative predictive value for TRG 4. In 9 of 16 complete responders, CRT-related tumor downsizing prevented ADC evaluations. The preoperative ADCs were significantly different (p = .0012) between the patients with and without downstaging (preoperative ADC ≥1.4 × 10(-3)mm(2)/s showed a positive and negative predictive value of 78.9% and 61.8%, respectively, for response assessment). The TRG 1 and TRG 2-4 groups were not significantly different.
  
  
  CONCLUSIONS
  Diffusion-weighted magnetic resonance imaging seems to be a promising tool for monitoring the response to CRT.
authors.affiliation: Department of Bioimaging and Radiological Sciences, Catholic University School of Medicine, Rome, Italy. bbarbaro@rm.unicatt.it
authors.forename: Brunella
authors.initials: B
authors.lastname: Barbaro
authors.forename: Renata
authors.initials: R
authors.lastname: Vitale
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Valentini
authors.forename: Sonia
authors.initials: S
authors.lastname: Illuminati
authors.forename: Fabio M
authors.initials: FM
authors.lastname: Vecchio
authors.forename: Gianluca
authors.initials: G
authors.lastname: Rizzo
authors.forename: Maria Antonietta
authors.initials: MA
authors.lastname: Gambacorta
authors.forename: Claudio
authors.initials: C
authors.lastname: Coco
authors.forename: Antonio
authors.initials: A
authors.lastname: Crucitti
authors.forename: Roberto
authors.initials: R
authors.lastname: Persiani
authors.forename: Luigi
authors.initials: L
authors.lastname: Sofo
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Bonomo
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D059186:Chemoradiotherapy, Adjuvant / Q000379:methods*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D008198:Lymph Nodes / Q000473:pathology; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy / Q000379:methods*; D009367:Neoplasm Staging; D011446:Prospective Studies; D012004:Rectal Neoplasms / Q000473:pathology / Q000628:therapy*; D018709:Statistics, Nonparametric; D016896:Treatment Outcome