|ECR 2015 / C-1504|
|Computed Tomography vs Magnetic Resonance Imaging in the evaluation of intra- and extra-peritoneal rectal cancer|
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38 patients were included: 24 (63%) men and 14 (37%) women with a mean age of 68.8±9.4 years (range: 55-83 years). Mean height and weight of male patients were 172.2±9.8 cm and 73.6±8.8 kg, respectively, and mean BMI was 23.8±3.3. Mean height and weight of female patients were 164.3±9.2 cm and 64.1±9.7 kg, respectively, and mean BMI was 24.0±2.9. 2 patients had a stage I (T1/2, N0, M0) rectal cancer, 7 patients had a stage II (T3 or T4, N0, M0) rectal cancer, and 29 patients presented a stage III (T1/2, T3, T4, N1 or N2, M0) tumor. The prevalence of extra-peritoneal cancers was 35/38 (92%), while that of intra-peritoneal cancers was 3/38 (8%).
Image analysis and diagnostic performance
The APR was appreciable in all (100%) MRI examinations and in 36/38 (94.7%) patients on CT images: reviewing MR images, the quality of individuation of the APR was defined excellent by the two readers in 14/38 (36.8%) MRI examinations, good in 22/38 (57.9%) and poor in 2/38 (5.3%) cases; reviewing CT images, the quality of individuation of the APR was defined excellent by the two readers in 6/38 (15.8%) examinations, good in 19/38 (50%) cases, poor in 11/38 (28.9%) cases and, as previously reported, not visible in 2/38 (5.3%) cases (Table 1).
On MR images the mean distance from the APR to the anal verge was 100.8±20.5 mm (range 73-133) for males and 95.9±15.7 mm (range 70-121) for females (p=0.4426, t-test for independent samples); on CT examinations the mean distance from the APR to the anal verge was 102.2±13.1 mm (range 81-124) for males and 97.5±12.5 mm (range 78-115) for females (p=0.4579, t-test for independent samples). Mean distances from the APR to the anal verge for all patients were 98.97±18.8 mm at MR and 100.6±12.9 mm at CT (p=0.6653, t-test for independent samples) (Table 2).
MR, as previously described , was characterized by an excellent diagnostic performance: sensitivity 100% (95% CI: 89.62% to 100.00%), specificity 75% (95% CI: 20.34% to 95.88%), positive predictive value 97.14% (95% CI: 85.03% to 99.52%), negative predictive value 100% (95% CI: 30.48% to 100.00%). Diagnostic performance of CT, excluding 2 patients without visualization of APR, resulted as follows: sensitivity 100% (95% CI: 89.32% to 100.00%), specificity 60% (95% CI: 15.40% to 93.51%), positive predictive value 94.29% (95% CI: 80.81% to 99.13%), negative predictive value 100% (95% CI: 30.48% to 100.00%) (Table 3).
The mean distance from the inferior edge of tumors to the anal verge was 62.3±21.2 mm at MR and 62.5±20.1 mm at CT (p=0.8181 Mann-Whitney test for independent samples) (Table 2). The two measurements were strongly correlated (Spearman's coefficient of rank correlation (rho): 0.995; p<0.0001).
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