Endorectal ultrasonography versus phased-array magnetic resonance imaging for preoperative staging of rectal cancer

Abstract

Aim: To compare the diagnostic accuracy of pelvic phased-array magnetic resonance imaging (MRI) and endorectal ultrasonography (ERUS) in the preoperative staging of rectal carcinoma.

Methods: Thirty-four patients (15 males, 19 females) with ages ranging between 29 and 75 who have biopsy proven rectal tumor underwent both MRI and ERUS examinations before surgery. All patients were evaluated to determine the diagnostic accuracy of depth of transmural tumor invasion and lymph node metastases. Imaging results were correlated with histopathological findings regarded as the gold standard and both modalities were compared in terms of predicting preoperative local staging of rectal carcinoma.

Results: The pathological T stage of the tumors was: pT1 in 1 patient, pT2 in 9 patients, pT3 in 21 patients and pT4 in 3 patients. The pathological N stage of the tumors was: pN0 in 19 patients, pN1 in 9 patients and pN2 in 6 patients. The accuracy of T staging for MRI was 89.70% (27 out of 34). The sensitivity was 79.41% and the specificity was 93.14%. The accuracy of T staging for ERUS was 85.29% (24 out of 34). The sensitivity was 70.59% and the specificity was 90.20%. Detection of lymph node metastases using phased-array MRI gave an accuracy of 74.50% (21 out of 34). The sensitivity and specificity was found to be 61.76% and 80.88%, respectively. By using ERUS in the detection of lymph node metastases, an accuracy of 76.47% (18 out of 34) was obtained. The sensitivity and specificity were found to be 52.94% and 84.31%, respectively.

Conclusion: ERUS and phased-array MRI are complementary methods in the accurate preoperative staging of rectal cancer. In conclusion, we can state that phased-array MRI was observed to be slightly superior in determining the depth of transmural invasion (T stage) and has same value in detecting lymph node metastases (N stage) as compared to ERUS.

Figure 1

A: MRI demonstrates a large tumor passing through the muscularis propria and invading the mesorectal fatty tissue within very close proximity to the mesorectal fascia; lymph nodes are also present; The MRI prediction was a T4 tumor; B: This was predicted as a T3 tumor by ERUS examination; C: Macroscopic specimen shows that the tumor has already filled all the mesorectal fatty tissue but the mesorectal fascia is still intact; D: Pathological examination reveals that this is a T3 stage tumor.

Figure 2

A: ERUS shows the tumor invading the muscularis propria which can be regarded as a T2 tumor. A lymph node is also seen; B: MRI clearly demonstrates that the tumor is confined to the muscularis propria and does not invade the mesorectal fatty tissue. Lymph nodes are also seen; C: Macroscopic specimen reveals the tumor does not extend to the mesorectal fat; D: Pathology confirms that this is a T2 stage tumor.

Figure 3

A: ERUS examination shows the tumor extend to the mesorectal fat by passing beyond the muscularis propria. A lymph node is also seen; B: MRI defines the tumor as violating the muscularis propria and extending to the mesorectal fatty tissue. Lymph nodes are seen; C: Operation specimen confirms mesorectal invasion; D: Pathology specimen demonstrates tumor cells invading the mesorectum which is indicative of a T3 tumor.

Figure 4

A: ERUS shows perirectal fat invasion of the tumor and predicts it as T3; B: MRI demonstrates that the tumor is not invading the mesorectal fatty tissue and is confined to the rectum which is considered as a T2 tumor. The lymph nodes are also present in the mesorectal fatty tissue; C: Operation specimen reveals that the tumor does not extend beyond the muscularis propria; D: Pathology confirms that this is a T2 stage tumor.