MR spectroscopic imaging measurement of prostate tumor (Cho + Cr)/Cit and tumor volume correlate with pathologic Gleason score. There is overlap between MR spectroscopic imaging parameters at various Gleason score levels, which may reflect methodologic and physiologic variations. MR spectroscopic imaging has potential in noninvasive assessment of prostate cancer aggressiveness.

The combination of ADC and MET performs significantly better than MET for differentiating between benign and malignant ROIs in the PZ.

Purpose:To retrospectively determine the accuracy of diffusionweighted (DW) magnetic resonance (MR) imaging for identifying cancer in the prostate peripheral zone (PZ) and to assess the accuracy of tumor volume measurements made with T2-weighted imaging and combined T2-weighted and DW MR imaging by using surgical pathologic examination as the reference standard. Materials and Methods:The institutional review board issued a waiver of informed consent for this HIPAA-compliant study. Forty-two patients underwent endorectal MR at 1.5 T before undergoing radical prostatectomy for prostate cancer and had at least one PZ tumor larger than 0.1 cm 3 at surgical pathologic examination. On T2-weighted images, an experienced radiologist outlined suspected PZ tumors. Two apparent diffusion coefficient (ADC) cutoff values were identified by using the Youden index and published literature. Image cluster analysis was performed on voxels within the suspected tumor regions. Associations between volume measurements from imaging and from pathologic examination were assessed by using concordance correlation coefficients (CCCs). The sensitivity and specificity of ADCs for identifying malignant PZ voxels were calculated. Results:In identifying malignant voxels, respective ADC cutoff values of 0.0014 and 0.0016 mm 2 /sec yielded sensitivity of 82% and 95% and specificity of 85% and 65%, respectively. Sixty PZ cancer lesions larger than 0.1 cm 3 were found at pathologic examination; 43 were detected by the radiologist. CCCs between imaging and pathologic tumor volume measurements were 0.36 for T2-weighted imaging, and 0.46 and 0.60 for combined T2-weighted and DW MR imaging with ADC cutoffs of 0.0014 and 0.0016 mm 2 / sec, respectively; the CCC of combined T2-weighted and DW MR imaging (ADC cutoff, 0.0016 mm 2 /sec) was significantly higher (P ϭ .006) than that of T2-weighted imaging alone. Conclusion:Adding DW MR to T2-weighted imaging can significantly improve the accuracy of prostate PZ tumor volume measurement. RSNA, 2009 Supplemental Note: This copy is for your personal, non-commercial use only. To order presentation-ready copies for distribution to your colleagues or clients, use the Radiology Reprints form at the end of this article.A ccurate noninvasive measurement of prostate cancer tumor volume could substantially improve the determination of tumor prognosis and assist in the selection of appropriate treatment. Studies (1-4) have shown that pathologic tumor volume correlates with pathologic stage, pathologic Gleason grade, margin status, and disease progression after radical prostatectomy. Tumors smaller than about 0.5 cm 3 and with no Gleason pattern 4 or 5 cancer are considered to be clinically insignificant and potentially appropriate for deferred therapy (5). McNeal et al (6) found that capsule penetration, seminal vesicle invasion, and positive surgical margins all correlated strongly with cancer volume. The latter study also showed that metastasis is highly likely when tumor volume is larger than 12 cm 3 , whereas ...

from surgical pathology as organ-confined cancer of ≤ 0.5 cm 3 with no poorly differentiated elements. The accuracy of predicting insignificant prostate cancer was assessed using areas under receiver operating characteristic curves (AUCs), for previously reported clinical models and for newly generated MR models combining clinical variables, and biopsy data with MRI data (MRI model) and MRI/MRSI data (MRI/MRSI model). RESULTSAt pathology, 41% of patients had insignificant cancer; both MRI (AUC 0.803) and MRI/MRSI (AUC 0.854) models incorporating clinical, biopsy and MR data performed significantly better than the basic (AUC 0.574) and more comprehensive medium (AUC 0.726) clinical models. The P values for the differences between the models were: base vs medium model, < 0.001; base vs MRI model, < 0.001; base vs MRI/MRSI model, < 0.001; medium vs MRI model, < 0.018; medium vs MRI/MRSI model, < 0.001. CONCLUSIONSThe new MRI and MRI/MRSI models performed better than the clinical models for predicting the probability of insignificant prostate cancer. After appropriate validation, the new MRI and MRI/MRSI models might help in counselling patients who are considering choosing deferred therapy.