Accuracy of thin section magnetic resonance using phased-array pelvic coil in predicting the T-staging of rectal cancer

Magnetic resonance (MR) imaging may contribute to staging rectal cancer and inform the decision regarding administration of pre-operative radiotherapy. The accuracy of MR has been debated. The aim of the present study was to determine the accuracy of thin section T2-weighted MR images in rectal cancer patients. MR results were compared with histological assessment of resection specimens. Over a 2-year period, 42 patients were studied. Histological staging was pT2 n=13, pT3 n=25 and pT4 n=4. MR diagnostic accuracy was 74%. MR sensitivity and specificity was 62% and 79% for pT2 lesions, 84% and 59% for pT3 lesions and 50% and 76% for pT4 lesions. Estimation of tumour penetration by thin section MR imaging of rectal cancers using pelvic phased-array coil has moderate diagnostic accuracy. The limitations of MR should be acknowledged when selecting rectal cancer patients for pre-operative radiotherapy.