CT vs MRI in diagnosis of recurrent rectosigmoid carcinoma.

OBJECTIVE

Our goal was to compare the relative values of MRI vs. CT in diagnosing recurrent rectosigmoid cancer.

MATERIALS AND

METHODS

We conducted a retrospective review of 18 patients who had surgical resection of primary rectosigmoid carcinoma and suspected recurrence. They were studied with CT and MR and followed for up to 4 years.

RESULTS

At the time of the initial imaging, 10 patients had recurrent tumor and 4 of the remaining 8 patients later demonstrated local recurrence. Magnetic resonance demonstrated 91% sensitivity, 100% specificity, a positive predictive value (PPV) of 100%, and a negative predictive value (NPV) of 89% with a 95% accuracy. Computed tomography demonstrated a sensitivity of 82% and a specificity of 50% with a PPV of 69% and an NPV of 67% with an accuracy of 68%. In three cases interpreted on CT as presacral masses, all were shown on MR to represent displaced but normal pelvic structures. In four cases MR revealed tumor involving the sacrum and sacral nerves not apparent on CT.

CONCLUSION

Magnetic resonance showed superior sensitivity, specificity, and accuracy to CT and better definition of the extent of tumor.