Targeted MRI-ultrasound is better than standard biopsy at detecting high-risk prostate cancer
Among men undergoing biopsy for suspected prostate cancer, targeted magnetic resonance (MR)/ultrasound fusion biopsy, compared with a standard biopsy technique, was associated with increased detection of high-risk prostate cancer and decreased detection of low-risk prostate cancer, according to a study in JAMA (2015; doi:10.1001/jama.2014.17942).
The current diagnostic procedure for men suspected of prostate cancer is a standard extended-sextant biopsy (ie, standard biopsy). Advances in imaging have led to the development of targeted magnetic resonance (MR)/ultrasound fusion biopsy (ie, targeted biopsy), which has been shown to detect prostate cancer. The implications of targeted biopsy alone compared with standard biopsy or the two methods combined are not well understood, according to background information in the article.
Peter A. Pinto, MD, and M. Minhaj Siddiqui, MD, of the National Cancer Institute (NCI), National Institutes of Health in Bethesda, Maryland, and colleagues examined the outcomes of 1,003 men who underwent an imaging procedure to identify regions of prostate cancer suspicion followed by targeted biopsy and concurrent standard biopsy from 2007 through 2014 at NCI. Patients were referred for elevated level of prostate-specific antigen (PSA) or abnormal digital rectal examination results, often with prior negative biopsy results.
Targeted biopsy diagnosed a similar number of cancer cases (461 patients) to standard biopsy (469 patients). There was exact agreement between targeted and standard biopsy in 690 men (69%) undergoing biopsy. However, the two approaches differed in that targeted biopsy diagnosed 30% more high-risk cancers than standard biopsy (173 vs 122 cases) and 17% fewer low-risk cancers (213 vs 258 cases).
Adding standard biopsy to targeted biopsy lead to 103 more cases of cancer (22%); however, of these, 83% were low risk while only 5% were high risk; 12% were intermediate risk. Thus, the usefulness of combining these methods was found to be limited. The number needed to biopsy by standard biopsy in addition to targeted biopsy to diagnose one additional high-risk tumor was 200 men.
The predictive ability of targeted biopsy for differentiating low-risk from intermediate- and high-risk disease in 170 men with whole-gland pathology after prostatectomy (surgical removal of the prostate gland) was greater than that of standard biopsy or the two approaches combined.
“This study demonstrated that targeted biopsy could significantly change the distribution of risk in men newly diagnosed with prostate cancer toward diagnosis of more highrisk disease,” wrote the authors. “Although these improvements in risk stratification could translate into substantial clinical benefits, it is important to recognize that this study is preliminary with regard to clinical end points such as recurrence of disease and prostate cancer-specific mortality. These findings provide a strong rationale for the conduct of randomized clinical trials to determine the effect of targeted biopsy on clinical outcomes.”