Patients’ characteristics
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 [4],
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).