Detecting metastases in normal-sized pelvic lymph nodes in patients with bladder cancer: comparison of computed tomography and magnetic resonance imaging

Abstract

Objective To estimate the diagnostic performance of computer tomography (CT) and magnetic resonance imaging (MRI) for detecting metastasis in pelvic lymph nodes with normal size in patients with bladder cancer. Methods Imaging of CT and MRI and clinical data of 118 patients who underwent radical cystectomy and pelvic lymphadenectomy were reviewed. The diagnostic efficacy of CT and MRI were analyzed when taking lymph nodes short axis diameter ≥0.3 cm and ≥1.0 cm respectively as diagnostic criterion of metastasis with correlation of pathological results. Results 22.7% (27/118) of patients were confirmed lymph nodes malignancies among 118 patients based on pathology. Totally 1 705 lymph nodes were detected in surgery and 119 of them were observed malignancy according to pathological presentation. The malignant nodes were mainly distributed in the perivesical (35.4%, 41/119), internal iliac (12.6%, 15/119), external iliac (30.3%, 36/119), obturator region (21.0%, 25/119) and presarcal region (1.7%, 2/119). Imaging of CT and MRI showed that when taking nodes with ≥0.3 cm in maximum short-axis diameter (MSAD) as positive, the sensitivity (Se), specificity (Sp), and positive predictive values (PPV) were 16.0%, 99.2%, 54.2% and 56.5%, 99.2%, 86.7% respectively. While taking MSAD≥1.0 cm as malignant, the Se, Sp and PPV of CT and MRI were 6.2%, 99.9%, 83.3% and 13%, 100%, 100% respectively. When taking MSAD ≥0.3 cm as positive, the Se and PPV between CT and MR were statistically different(P<0.001 and P=0.036, respectively). When taking MSAD ≥1.0 cm as positive, there was no statistically difference (P=0.275 and 1.000, respectively). Conclusions The incidence of normal-sized lymph node metastasis was higher in patients with bladder cancer. At this phase the MRI evaluation was superior to that of CT. When the MSAD ≥1.0 cm, there was no significant difference between CT and MRI. Key words: Bladder cancer; Lymph node metastasis; Computed tomography(CT); Magnetic resonance imaging(MRI); Diagnosis