CRD summary

This review concluded that magnetic resonance imaging using diffusion and T2 weighting in combination may be a valuable tool for detecting prostate cancer but further high quality prospective studies were required. The conclusions reflect the evidence presented. The small number of studies and their methodological limitations means the recommendation for further research seems appropriate.

Authors' objectives

To investigate the role of magnetic resonance imaging (MRI) using a combination of diffusion and T2-weighted imaging for the detection of prostate cancer.

Searching

MEDLINE, EMBASE, CancerLit, Science Direct, SpringerLink, Scopus and The Cochrane Library were searched for studies published in English between 2001 and 2011; search terms were reported. Bibliographies of the included studies and reviews were searched.

Study selection

Studies that investigated the diagnostic performance of MRI with combined diffusion and T2-weighted imaging for detecting prostate cancer in at least 10 patients were eligible for inclusion. Studies had to report sufficient data to produce 2x2 tables of test performance.

Most studies used apparent diffusion coefficient maps; native diffusion-weighted imaging was used in some studies. Pelvic phase array coils and MRI magnetic field strength of 1.5 were used in most studies. The strength of diffusion sensitising (b values) ranged from 600 to 2,000 s/mm². Participant ages ranged from 29 to 87 years. The average prostate specific antigen level ranged from 0.7 to 332.1 ng/mL.

Two independent reviewers selected studies for the review.

Assessment of study quality

Study quality was assessed using the 14-point QUADAS criteria; only studies that passed at least nine criteria were included in the review.

The authors did not state how many reviewers assessed study quality.

Data extraction

Two independent reviewers extracted data to produce 2x2 tables of test performance. Sensitivity and specificity were calculated.

Methods of synthesis

Pooled estimates of sensitivity and specificity with 95% confidence intervals were calculated using a random-effects model; positive and negative likelihood ratios (LR+/-) were derived from these estimates. Heterogeneity was assessed using the Χ² and Ι² statistics (Ι²>50% was considered to indicate heterogeneity). Summary receiver operating characteristic curves were presented and the area under the curve (AUC) was calculated. Threshold effect was investigated using Spearman's rank correlation. Meta-regression was used to investigate the impact of study design, blinding, patient recruitment and the technical specifications of the imaging technology, where no threshold effect was observed. Zero cells had 0.5 added to them. Publication bias was investigated using Deeks' funnel plots.

Results of the review

Ten studies were included in the review (627 patients, range 23 to 201): four prospective and six retrospective cohorts. Six studies reported consecutive patient recruitment and seven reported blinding of interpreters of MRI scans. Delay between MRI and radical prostatectomy ranged from one to 90 days.

The pooled sensitivity of MRI using a combination of diffusion and T2-weighting was 76% (95% CI 65 to 84), specificity was 82% (95% CI 77 to 87), LR+ was 4.31 (95% CI 3.12 to 5.92), LR- was 0.29 (95% CI 0.20 to 0.43) and the AUC was 0.84 (95% CI 0.80 to 0.87). Compared to T2-weighting alone, the diffusion and T2-weighting combination (seven studies), combination had a higher pooled sensitivity (72% versus 62%) and specificity (81% versus 77%).

Meta-regression showed patient recruitment and blinding of interpreters of MRI scans were the most important variables contributing to the observed heterogeneity. There was no evidence of a threshold effect of publication bias. Further results from subgroup and sensitivity analyses were reported.

Authors' conclusions

MRI using diffusion and T2 weighting in combination may be a valuable tool for detecting prostate cancer in the overall evaluation of prostate cancer compared to T2 weighting alone.

CRD commentary

The review addressed a clear research question supported by reproducible inclusion criteria. An extensive search was conducted for published studies but the exclusion of studies in languages other than English and lack of searching for unpublished studies means some studies may have been missed. Study selection and data extraction were conducted in duplicate; it was unclear whether similar methods to reduce error and bias were employed during the assessment of study quality. Appropriate criteria were used to assess study quality but the results were poorly reported. The number of criteria met was used to select studies for inclusion but the importance of individual criteria did not seem to be considered. Some studies that failed fewer but more important criteria and were subject to more serious bias may have been included while other studies less prone to the more important biases may have been excluded. The model used for the SROC was unclear. Hierarchical and bivariate models were cited and a summary estimate of sensitivity and specificity were presented on the SROC plot. If one of these models were used, then an appropriate method of synthesis was used. It seemed that covariates were not included in the analysis even though sources of heterogeneity were identified.

The conclusions of the review reflect the evidence presented. The small number of studies found and their methodological limitations mean the recommendation for further research seems appropriate.

Implications of the review for practice and research

Practice: The authors did not state any implications for practice.

Research: The authors stated a need for high quality prospective studies of diffusion and T2 weighting in combination to detect prostate cancer.

Funding

Shanghai Leading Academic Discipline Project; Shanghai Jiaotong University School of Medicine Discipline Project.

Bibliographic details

Wu LM, Xu JR, Ye YQ, Lu Q, Hu JN. The clinical value of diffusion-weighted imaging in combination with T2-weighted imaging in diagnosing prostate carcinoma: a systematic review and meta-analysis. American Journal of Roentgenology 2012; 199(1): 103-110. [PubMed: 22733900]

Original Paper URL

http://www.ajronline.org/content/199/1/103.abstract

Indexing Status

Subject indexing assigned by NLM

MeSH

Diffusion Magnetic Resonance Imaging /methods; Humans; Male; Prospective Studies; Prostate /pathology; Prostatic Neoplasms /diagnosis /pathology; ROC Curve; Sensitivity and Specificity

AccessionNumber

12012036800

Database entry date

10/04/2013

Record Status

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.