Correlation between MRS and serum PSA in the diagnosis of local recurrence after radical prostatectomy

Background: Multifocality, multicentricity and extension beyond the prostate capsule are all characteristics of prostatic adenocarcinoma that may escape diagnosis by conventional CT scanning or MRI. This study was designed to assess the diagnostic value of magnetic resonance spectroscopy (MRS) in prostatic carcinoma and its compatibility with prostatic specific antigen (PSA) as the conventional method.Methods: In this cross-sectional study, we recruited 139 patients with previous radical prostatectomy referring to Radiology department of Hazrate-e-Rasul Hospital during the first half of 2011 for the evaluation of local recurrence. Traditionally, local recurrence is defined as serum PSA concentration >0.2 ng/dl. We used 1.5-tesla Siemens Avanto MRI unit with endorectal coil and measured creatine, choline and citrate levels before calculating choline-creatine/citrate ratio. Correlation between MRS findings with PSA concentration was evaluated in regards to the multiple levels of the previously mentioned ratio.Results: Local recurrence was found in 107 (77%) patients based on PSA levels. The mean values for serum PSA levels and creatine-choline/citrate ratio were significantly different in patients with and without local recurrence. Creatine-choline/citrate ratios greater than 50, 100 and 150 (as different cut-off points of recurrence) were respectively seen in 104, 102 and 97 patients and agreement ratio between MRS and PSA in these levels were 94.1%, 94.4% and 85.1%, respectively. Correlation coefficient between these two methods was 0.481.Conclusion: MRS is a valuable tool for evaluating recurrence inpatients with prostate cancer treated by radical prostatectomy and it is in good agreement with serum PSA levels