title: Transrectal ultrasound and magnetic resonance imaging measurement of extramural tumor spread in rectal cancer.
abstract: OBJECTIVE
  To evaluate the agreement between transrectal ultrasound (TRUS) and magnetic resonance imaging (MRI) in classification of ≥ T3 rectal tumors.
  
  
  METHODS
  From January 2010 to January 2012, 86 consecutive patients with ≥ T3 tumors were included in this study. The mean age of the patients was 66.4 years (range: 26-91 years). The tumors were all ≥ T3 on TRUS. The sub-classification was defined by the penetration of the rectal wall: a: 0 to 1 mm; b: 1-5 mm; c: 6-15; d: > 15 mm. Early tumors as ab (≤ 5 mm) and advanced tumors as cd (> 5 mm). All patients underwent TRUS using a 6.5 MHz transrectal transducer. The MRI was performed with a 1.5 T Philips unit. The TRUS findings were blinded to the radiologist performing the interpretation of the MRI images and measuring the depth of extramural tumor spread.
  
  
  RESULTS
  TRUS found 51 patients to have an early ≥ T3 tumors and 35 to have an advanced tumor, whereas MRI categorized 48 as early ≥ T3 tumors and 38 as advanced tumors. No patients with tumors classified as advanced by TRUS were found to be early on MRI. The kappa value in classifying early versus advanced T3 rectal tumors was 0.93 (95% CI: 0.85-1.00). We found a kappa value of 0.74 (95% CI: 0.63-0.86) for the total sub-classification between the two methods. The mean maximal tumor outgrowth measured by TRUS, 5.5 mm ± 5.63 mm and on MRI, 6.3 mm ± 6.18 mm, P = 0.004. In 19 of the 86 patients the following CT scan or surgery revealed distant metastases; of the 51 patients in the ultrasound ab group three (5.9%) had metastases, whereas 16 (45.7%) of 35 in the cd group harbored distant metastases, P = 0.00002. The odds ratio of having distant metastases in the ultrasound cd group compared to the ab group was 13.5 (95% CI: 3.5-51.6), P = 0.00002. The mean maximal ultrasound measured outgrowth was 4.3 mm (95% CI: 3.2-5.5 mm) in patients without distant metastases, while the mean maximal outgrowth was 9.5 mm (95% CI: 6.2-12.8 mm) in the patients with metastases, P = 0.00004. Using the MRI classification three (6.3%) of 48 in the MRI ab group had distant metastases, while 16 (42.1%) of the 38 in the MRI cd group, P = 0.00004. The MRI odds ratio was 10.9 (95% CI: 2.9-41.4), P = 0.00008. The mean maximal MRI measured outgrowth was 4.9 mm (95% CI: 3.7-6.1 mm) in patients without distant metastases, while the mean maximal outgrowth was 11.5 mm (95% CI: 7.8-15.2 mm) in the patients with metastases, P = 0.000006.
  
  
  CONCLUSIONS
  There is good agreement between TRUS and MRI in the pretreatment sub-classification of ≥ T3 tumors. Distant metastases are more frequent in the advanced group.
authors.affiliation: Department of Radiology, DCCG South, Institute of Regional Health Services Research, University of Southern Denmark, Vejle Hospital, Kabbeltoft 25, 7100 Vejle, Denmark. soeren.rafael.rafaelsen@slb.regionsyddanmark.dk
authors.forename: Søren R
authors.initials: SR
authors.lastname: Rafaelsen
authors.forename: Chris
authors.initials: C
authors.lastname: Vagn-Hansen
authors.forename: Torben
authors.initials: T
authors.lastname: Sørensen
authors.forename: John
authors.initials: J
authors.lastname: Pløen
authors.forename: Anders
authors.initials: A
authors.lastname: Jakobsen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009367:Neoplasm Staging; D012004:Rectal Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology*; D012007:Rectum / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed; D014463:Ultrasonography