MR spots cancer recurrence following prostatectomy

Endorectal coil MR imaging should join the diagnostic algorithm for patients suspected of local recurrence after prostatectomy, according to a Memorial Sloan-Kettering Cancer Center study. Until now, physicians had to reconcile suspicion of pelvic recurrence with a lack of imaging to demonstrate it. The Sloan-Kettering study may lead to a rethinking of treatment options for these patients, said Dr. Jeffrey C. Weinreb, director of MRI at Yale-New Haven Hospital.

"Now that we can identify it reliably, it may change the way these patients are treated," he said.

Although urologists and oncologists probably know that disease recurrence is common after a radical prostatectomy, many radiologists-who consider the procedure curative-might be surprised to find out how high the rate of recurrence actually is. As a result, MR imaging could eventually become an important influence on patient care, even though its role in postprostatectomy recurrence has yet to be determined, Weinreb said.

Dr. Tamar Sella and colleagues retrospectively assessed 48 patients who had been imaged with a body coil and a pelvic phased-array coil in combination with a balloon-covered expandable endorectal coil for signal reception (Radiology 2004;231:379-385). Seven patients showed no MR or clinical evidence of pelvic local recurrence. Of 41 patients with clinically identified local recurrence, 39 had at least one soft-tissue mass in the postprostatectomy fossa on MR. In these 39 patients, MR revealed 42 sites of local recurrence, for a sensitivity and specificity of 95% and 100%, respectively. All 42 sites of recurrence seen on MR were isointense to muscle on T1-weighted images and slightly hyperintense to muscle on T2-weighted images.

The prostate-specific antigen test and biopsy remain the core screening and diagnostic tests for primary prostate cancer, but ultrasound, MR, CT, PET, and SPECT have also played a role in the diagnosis of primary or metastatic disease and patient follow-up. None of these modalities has been widely used to evaluate local recurrence, according to the study.

CT scans for local recurrence have shown low detection rates, which have been refined only in combination with functional imaging. Transrectal ultrasound has a high detection rate of biopsy-confirmed perianastomotic and retrovesical recurrences. However, 30% of local recurrences in this study occurred at sites often missed by transrectal ultrasound and biopsy.

MR has the potential to direct transrectal biopsy to these sites and may lead to a better diagnostic yield, said Sella, a radiologist at Hadassah University Hospital of Jerusalem collaborating with the MSKCC group. MR imaging with endorectal and pelvic phased-array coils has the ability to check pelvic lymph nodes and bones with a single pass.

The technique might also help radiation oncologists decide when to initiate radiation therapy. MR could feasibly show disease of very small size at minimally elevated PSA levels. These data could in turn help radiation oncologists' decision to initiate salvage radiation therapy at a very early stage of recurrence, Sella said.