Pucar D et al. (2005) Prostate cancer: correlation of MR imaging and MR spectroscopy with pathologic findings after radiation therapy—initial experience. Radiology, 236: 545–553

Salvage radical prostatectomy is indicated in a proportion of patients who fail external-beam radiation therapy for prostate cancer, but the detection of local recurrence remains a challenge. A new report by Pucar et al. suggests that a combination of MRI and magnetic resonance spectroscopy (MRS) might be useful in this setting.

This retrospective evaluation included nine patients with a mean interval of 55 months between external-beam radiation therapy and MRI/MRS. Sextant biopsy, digital rectal examination, MRI and MRS were used to detect local recurrence, and all patients subsequently underwent salvage radical prostatectomy.

The investigators used step-section pathologic findings as the reference standard to calculate the sensitivity of MRI (68%), MRS (77%), biopsy (48%), and digital rectal examination (16%) for the detection of local recurrence. The estimated specificity of MRS (78%) was lower than that of the other three techniques (>90%).

These results suggest that the use of MRI and MRS might improve the sensitivity of sextant localization of prostate cancer recurrence. The authors suggest that these techniques might be incorporated into the routine assessment of patients exhibiting a rise in prostate-specific antigen after radiation therapy.