Prospective Study of Diagnostic Accuracy Comparing Prostate Cancer Detection by Transrectal Ultrasound–Guided Biopsy Versus Magnetic Resonance (MR) Imaging with Subsequent MR-guided Biopsy in Men Without Previous Prostate Biopsies

Abstract

Background

The current diagnosis of prostate cancer (PCa) uses transrectal ultrasound–guided biopsy (TRUSGB). TRUSGB leads to sampling errors causing delayed diagnosis, overdetection of indolent PCa, and misclassification. Advances in multiparametric magnetic resonance imaging (mpMRI) suggest that imaging and selective magnetic resonance (MR)–guided biopsy (MRGB) may be superior to TRUSGB.

Objective

To compare the diagnostic efficacy of the magnetic resonance imaging (MRI) pathway with TRUSGB.

Design, setting, and participants

A total of 223 consecutive biopsy-naive men referred to a urologist with elevated prostate-specific antigen participated in a single-institution, prospective, investigator-blinded, diagnostic study from July 2012 through January 2013.

Intervention

All participants had mpMRI and TRUSGB. Men with equivocal or suspicious lesions on mpMRI also underwent MRGB.

Outcome measurements and statistical analysis

The primary outcome was PCa detection. Secondary outcomes were histopathologic details of biopsy and radical prostatectomy specimens, adverse events, and MRI reader performance. Sensitivity, specificity, negative predictive values (NPVs), and positive predictive values were estimated and basic statistics presented by number (percentage) or median (interquartile range).

Results and limitations

Of 223 men, 142 (63.7%) had PCa. TRUSGB detected 126 cases of PCa in 223 men (56.5%) including 47 (37.3%) classed as low risk. MRGB detected 99 cases of PCa in 142 men (69.7%) with equivocal or suspicious mpMRI, of which 6 (6.1%) were low risk. The MRGB pathway reduced the need for biopsy by 51%, decreased the diagnosis of low-risk PCa by 89.4%, and increased the detection of intermediate/high-risk PCa by 17.7%. The estimated NPVs of TRUSGB and MRGB for intermediate/high-risk disease were 71.9% and 96.9%, respectively. The main limitation is the lack of long follow-up.

Conclusions

We found that mpMRI/MRGB reduces the detection of low-risk PCa and reduces the number of men requiring biopsy while improving the overall rate of detection of intermediate/high-risk PCa.

Patient summary

We compared the results of standard prostate biopsies with a magnetic resonance (MR) image–based targeted biopsy diagnostic pathway in men with elevated prostate-specific antigen. Our results suggest patient benefits of the MR pathway. Follow-up of negative investigations is required.

Introduction

PCa is the most common male malignancy and the second most common cause of male cancer-related death [1]. Randomised trials have shown that early detection, through prostate-specific antigen (PSA) screening, can alter the natural history of the disease and reduce mortality [2]. However, this benefit is associated with the diagnosis of many indolent tumours, for which radical treatment leads to an adverse impact on quality of life without altering survival [3], [4], [5], [6], [7]. Population-based reports suggest little disconnect between diagnosis and treatment [8], [9], [10]. The overdiagnosis and overtreatment of PCa has caused various professional organisations to review their PSA screening guidelines [11], potentially reversing recent declines in disease-specific mortality [12].

Another approach to minimise overtreatment would be to reduce the overdiagnosis of low-risk PCa. Urologists use PSA followed by systematic transrectal ultrasound–guided biopsy (TRUSGB) rather than imaged-based diagnosis due to poor discrimination of PCa with transrectal ultrasound (TRUS). Due to the high prevalence of low-risk PCa, the TRUSGB diagnostic pathway finds many indolent tumours. TRUSGB also causes difficulties in managing patients with high PSA values but benign biopsies, and it also misclassifies the volume or risk of approximately a third of cases of biopsy-detected PCa when compared with whole-mount pathology [13], [14], [15].

Advances in 3-T multiparametric magnetic resonance imaging (mpMRI) have improved image-based diagnosis [16], [17], [18]. Also, targeted magnetic resonance (MR)–guided biopsy (MRGB) has become an alternative approach to TRUSGB. MRGB uses fewer cores than TRUSGB and can be applied only in men with lesions suspicious for intermediate/high-risk PCa [19], [20], [21], [22]. Although selective MRGB is an appealing pathway, few data support its reliability. It is unknown what proportion and what type of PCa would be missed by omitting biopsy from men with normal mpMRI scans. With this in mind, we designed a prospective diagnostic study to compare selective MRGB and unselected TRUSGB in men with an elevated PSA.