Detection of the index tumour and tumour volume in prostate cancer using T2-weighted and diffusion-weighted magnetic resonance imaging (MRI) alone.

OBJECTIVE: To examine the performance of T2-weighted (T2W) and diffusion-weighted (DW) magnetic resonance imaging (MRI) for detecting the index tumour in patients with prostate cancer and to examine the agreement between MRI and histology when assessing tumour volume (TV) and overall tumour burden. PATIENTS AND METHODS: The study included 199 consecutive patients with biopsy confirmed prostate cancer randomised to MRI before radical prostatectomy from December 2009 to July 2012. MRI-detected tumours (MRTs) were ranked from 1 to 3 according to decreasing volume and were compared with histologically detected tumours (HTs) ranked from 1 to 3, with HT 1 = index tumour. Whole-mount section histology was used as a reference standard. The TVs of true-positive MRTs (MRTVs 1-3) were compared with the TVs found by histology (HTVs 1-3). All tumours were registered on a 30-sector map and by classifying each sector as positive/negative, the rate of true-positive and -negative sectors was calculated. RESULTS: The detection rate for the HT 1 (index tumour) was 92%; HT 2, 45%; and HT 3, 37%. The MRTV 1-3 vs the HTV 1-3 were 2.8 mL vs 4.0 mL (index tumour, P < 0.001), 1.0 mL vs 0.9 mL (tumour 2, P = 0.413), and 0.6 mL vs 0.5 mL (tumour 3, P = 0.492). The rate of true-positive and -negative sectors was 50% and 88%, κ = 0.39. CONCLUSION: A combination of T2W and DW MRI detects the index tumour in 92% of cases, although MRI underestimates both TV and tumour burden compared with histology.

Does preoperative magnetic resonance imaging reduce the rate of positive surgical margins at radical prostatectomy in a randomised clinical trial?

BACKGROUND: Magnetic resonance imaging (MRI) has the potential to help the surgeon tailor radical prostatectomy (RP) more accurately according to the location and extent of the tumour and thereby reduce the rate of positive surgical margins (PSMs). OBJECTIVE: To evaluate the benefit of performing MRI prior to RP. DESIGN, SETTING, AND PARTICIPANTS: This single-institution randomised trial included 438 patients between December 2009 and June 2012 who were scheduled for robot-assisted laparoscopic prostatectomy. The study was registered (ClinicalTrials.gov identifier NCT01347320). INTERVENTION: Patients were preoperatively randomly assigned to non-MRI or MRI groups. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: The primary end point was the difference in the PSM rates between the two groups. Secondary end points were the rates of PSMs in clinical subgroups. Summary statistics were extracted from descriptive analyses, chi-square, or Fisher exact test, and logistic regression was used to analyse the data according to the intention-to-treat principle. RESULTS AND LIMITATIONS: A total of 216 patients were randomised to non-MRI; 222 were randomised to MRI. There were 49 cases (23%) of PSMs in the non-MRI group and 43 cases (19%) in the MRI group (p=0.4). The relative and absolute risk reduction was 15% and 4%, respectively. Patients with cT1 constituted 55% of the cohort, in which the rate of PSMs was 27% in the non-MRI group and 16% in the MRI group (p=0.035). The relative and absolute risk reduction was 41% and 11%, respectively. A limitation was suboptimal communication between the radiologist and urologist. CONCLUSIONS: MRI prior to RP did not reduce the overall risk for PSMs in this patient cohort. However, at subgroup analysis we observed a possible benefit of MRI in patients with cT1. PATIENT SUMMARY: This study could not demonstrate a definite benefit of performing magnetic resonance imaging before surgery for all patients. However, there was a possible improved result in patients in which physical examination could not detect the cancer.