Prostate Tumor Volume Measurement with Combined T2-weighted Imaging and Diffusion-weighted MR: Correlation with Pathologic Tumor Volume

Abstract

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 ...

MR spectroscopic imaging and diffusion‐weighted imaging of prostate cancer with Gleason scores

“…We found that mean Most of the studies to date that have assessed the utility of DWI in PCa evaluated lesions within the peripheral zone (PZ). Several studies (41)(42)(43)(44) have suggested improvement in tumor detection over T2W, either using DWI alone, or in combination with T2W. Results for comparison between DWI and MRS have been mixed.…”

Diffusion weighted imaging in prostate cancer

“…Miao et al [16] showed that the sensitivity and specificity rates for T2WI was 76% and 70% respectively, compared with 86% and 80% for DWI. Combined T2WI and DWI yield slightly better results, with reported sensitivity and specificity rates of 45-89% and 61-97% respectively, compared with 74-85% and 57-95% respectively for DWI alone and 25-87% and 57-92% respectively for T2WI alone [12,15,[17][18][19][20][21][22][23][24][25][26].…”

“…Several have suggested improvement in tumour detection over T2WI, either using DWI alone, or in combination with T2WI. Mazaheri et al demonstrated high sensitivity (82%) and specificity rates (95%) using an ADC cut-off of 1.6×10 −3 mm 2 /s [15], while improving tumour volume estimation. Miao et al [16] showed that the sensitivity and specificity rates for T2WI was 76% and 70% respectively, compared with 86% and 80% for DWI.…”

The promise of multiparametric imaging in oncology: how do we move forward?

“…recurrence location) using follow-up imaging of various lesions [15][16][17][18]. Another imaging approach is to validate the imaging characteristics with biological properties in the surgical specimen [19][20][21][22]. This data-driven approach is attractive because no complete molecular knowledge is needed: the observations drive the identification of treatment-resistant areas in a pragmatic, agnostic way.…”