Prostate Cancer: Correlation of MR Imaging and MR Spectroscopy with Pathologic Findings after Radiation Therapy–Initial Experience

Abstract

PURPOSE:To prospectively evaluate magnetic resonance (MR) imaging and MR spectroscopy for depiction of local prostate cancer recurrence after external-beam radiation therapy, with stepsection pathologic findings as the standard of reference. MATERIALS AND METHODS:Study received institutional approval, and written informed consent was obtained. Study was compliant with Health Insurance Portability and Accountability Act. Sextant biopsy, digital rectal examination, MR imaging, MR spectroscopy, and salvage radical prostatectomy with step-section pathologic examination were performed in nine patients with increasing prostate-specific antigen levels after external-beam radiation therapy. MR imaging criterion for tumor was a focal nodular region of reduced signal intensity at T2-weighted imaging. MR spectroscopic criteria for tumor were voxels with choline (Cho) plus creatine (Cr) to citrate (Cit) ratio ([Cho + Cr]/Cit) of at least 0.5 or voxels with detectable Cho and no Cit in the peripheral zone. Sensitivity and specificity of sextant biopsy, digital rectal examination, MR imaging, and MR spectroscopy were determined by using a prostate sextant as the unit of analysis. For feature analysis, MR imaging and MR spectroscopic findings were correlated with step-section pathologic findings. RESULTS:MR imaging and MR spectroscopy showed estimated sensitivities of 68% and 77%, respectively, while sensitivities of biopsy and digital rectal examination were 48% and 16%, respectively. MR spectroscopy appears to be less specific (78%) than the other three tests, each of which had a specificity higher than 90%. MR spectroscopic feature analysis showed that a metabolically altered benign gland could be falsely identified as tumor by using MR spectroscopic criteria; further analysis of MR spectroscopic features did not lead to improved MR spectroscopic criteria for recurrent tumor. CONCLUSION:In summary, MR imaging and MR spectroscopy may be more sensitive than sextant biopsy and digital rectal examination for sextant localization of cancer recurrence after external-beam radiation therapy.

Long-Term Post-Treatment MR and PET/CT Imaging in Prostate Cancer Patients in Complete Remission after Curative Radiotherapy with or without Androgen Deprivation: The Image of Cure

“…After RT, however, the ratio Cho+Cr/Ci is of limited use due to citrate and choline signals that are often undetectable. MRI studies before salvage prostatectomy have shown sensitivity and specificity rates of 36-76% and 65-81%, respectively [14,16]; thus in good agreement with our findings (i.e., equivocal or false positive images in 75% of cases).…”

“…The value of MRS in recurrent prostate cancer after RT is controversial [14,15]. Spectroscopy usually detects prostate cancer based on the ratio between a high choline + creatinine signal (tumor) and a reduced citrate signal (normal tissue).…”

A computer-aided system for the detection of prostate cancer based on magnetic resonance image analysis

“…The potential of the proposed system has to be explored further with respect to different features that can be extracted from both of the aforementioned imaging modalities. Equally important, information from other MRI techniques, such as T2 ADC mapping methods [26] and magnetic resonance spectroscopy [27] might increase the separation ability between malignant and benign tissue even more. Moreover, the performance of other pattern recognition schemes such as the Support Vector Machines [28] has to be evaluated so as to determine a good combination of features and classifier for the problem at hand.…”

The role of dynamic contrast enhanced MRI in the detection of recurrent prostate carcinoma after external beam radiotherapy-correlation with transrectal ultrasound and pathological findings

“…Because an irradiated prostate gland usually appears small and diffusely hypointense in T2-weighted images, MRS, which detects abnormal metabolism rather than abnormal anatomy, has been shown to be a better technique for the detection of local tumor recurrence and complete metabolic atrophy (1). In addition, MRS allows tumors to be distinguished from normal glandular tissue on the basis of an increased choline plus creatine to citrate ratio (19). In studies analyzing the correlation between whole-mount histopathology and MRS, the sensitivity and specificity of MRS range between 29-89% and 62-95%, respectively (20); however, the sensitivity of MRS depends on the Gleason score.…”