Introduction: The accuracy of pretherapeutic staging of lymph nodes (LN) in rectal cancer by MR imaging (MRI) is still limited. The aim of the study was to determine the sensitivity and specificity of different morphological criteria in nodal staging.
Material and methods: LN were analyzed by MRI in 60 patients with rectal cancer and primary surgery. Signs of LN metastasis (cN+) were spiculated/indistinct border contour, inhomogeneous signal intensity, or LN size. The accuracy of these signs for clinical LN staging was analyzed with conclusive postoperative histological lymph node examination.
Results: 68.3% of patients with nodal metastasis (pN+) were correctly identified by size with a cutoff value of 7.2 mm. This, however, was not inferior to the 76.7% identified using the inhomogeneous morphological signal intensity and spiculated/indistinct border contour criteria (p = 0.096). 3.3 versus 5% were overstaged, and 28.3 versus 18.3% understaged by these criteria. Sensitivities/specificities for (a) size, (b) spiculated/indistinct border contour, and (c) inhomogeneous signal intensity and spiculated/indistinct border contour were (a) 32%/94%, (b) 56%/86%, and (c) 56%/91%, respectively.
Conclusions: The accuracy of LN staging in rectal cancer was not improved by morphological criteria. These limitations suggest being reticent when recommending neoadjuvant chemoradiation merely based on preoperative positive LN staging.
Keywords: Chemoradiation; Lymph nodes; MRI; Rectal cancer; Staging.