UroToday - Imaging accuracy for local recurrence of prostate cancer (CaP) and the use of endorectal magnetic resonance (eMR) has not been significantly assessed. In the online version of European Radiology, Dr. Stefano Cirillo and colleagues from Italy evaluated the diagnostic performance of eMR for diagnosing local CaP recurrence following radical prostatectomy (RP) in the face of an increasing serum PSA level. They also evaluated the benefit of contrast media compared to unenhanced imaging alone.

A total of 72 patients met the inclusion criteria; history of perineal RP, undetectable PSA after surgery and then rising to >0.1ng/ml, negative metastatic evaluation and more than one year's follow-up. Mean patient age was 67 years, mean PSA 1.23ng/ml, and the interval between surgery and eMR imaging was a mean of 1.23 years. Eight patients had an abnormal digital rectal exam, suggesting local recurrence. eMR was performed using a 1.5-T MR system and pelvic phased-array coil.

The prostate bed was imaged using transverse, coronal, and sagital T2-weighted fast spin-echo images. Four 3D fast spoiled gradient echo sequences were obtained, 3 of these after administration of 0.1ml/kg body-weight of paramagnetic contrast medium. All eMR images were interpreted on 2 occasions, by 2 experienced radiologists, blinded to the data. On the first reading, only unenhanced images were reviewed. Four months later the contrast enhanced-MR images were reviewed.

Positive correlative criteria included a positive prostatic fossa biopsy, positive 11C-choline PET in the prostatic fossa, or decrease in PSA after fossa radiotherapy. Negative criteria for a fossa recurrence included one of the following; decrease in PSA without treatment, or with radiotherapy with a subsequent positive Ch-PET scan for distant metastasis.

In relation to the reference criteria standards, 44 patients were positive for a local recurrence and 28 were negative. In the first interpreting session, 44.4% of patients were suspected of having local recurrence, and the positive predictive value (PPV) was 84.3%. Five patients had a false positive result (15.6%). The diameter of the local recurrences ranged from 0.8 to 4.2cm. Unenhanced eMR was negative in 40 of the 72 men (55.5%) for true negative findings in 23 of 40 men (negative PV of 57.5%) and false negative finding in 42.5%. In the second reading session by the radiologists with contrast images, 55.6% were suspected of having a local recurrence on CE-eMR (PPV=92.5%) and 3 men were false positive (7.5%). CE-eMR imaging was negative in relation to the reference criteria in 44.4%.

Overall, using the described criteria, eMR was accurate in identification of local CaP recurrences, and contrast enhancement was better than T2-weighted imaging alone.

Cirillo S, Petracchini M, Scotti L, Gallo T, Macera A, Bona MC, Ortega C, Gabriele P, Regge D.
Eur Radiol. 2008 Sep 30. Epub ahead of print.

UroToday Contributing Editor Christopher P. Evans, MD, FACS

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