A comparison between the reference values of MRI and EUS and their usefulness to surgeons in rectal cancer

For these patients with colorectal cancers, improving their quality of life is just as important as clearing them of their tumor burden.

To assess the reference value to surgeons of magnetic resonance imaging (MRI) and endorectal ultrasound (EUS) in local staging of rectal cancer.

According to the criteria we set, 69 patients received MRI and 60 patients received EUS, all by senior doctors. We compared two groups in staging accuracy of depth of penetration (T), lymph nodes positive (N) and combined T and N (TN) result. Strategy one (Str1.) was chosen based on MRI or EUS staging. Strategy two (Str2.) took into account clinical parameters, such as computed tomography (CT) and colonoscopy. Strategy three (Str3.) was the best treatment strategy; this was, in part, based on analysis of patients' specimen pathological results. Compared to Str.1 and Str.2, the use of Str.3 as the reference standard separately reflected the reference values of MRI and EUS for surgeons and actual treatment accuracy.

EUS had higher sensitivity in T1 (p = 0.044 < 0.05) and specificity in T2 (p = 0.039 < 0.05) than MRI. MRI had higher sensitivity in N staging (p = 0.046 < 0.05) and was more accurate in pT1~4N1~2 (p < 0.05) than EUS. Reference values for surgery (comparing appropriate rates of Str.1 with Str.3) of MRI and EUS were 79.7% vs. 76. 7%, respectively (p > 0.05). The actual treatment accuracy (comparing appropriate rates of Str.2 with Str.3) was increased up to 94.2% vs. 91.7%, respectively (p > 0.05).

EUS is good for early-stage patients but MRI for local advanced ones. Strategies both could be improved by combining clinical factors that lead to similar reference values for surgery.