Targeted Biopsy Identifies Prostate Cancer Better than Standard Biopsy
In a recent study of men undergoing biopsy for suspected prostate cancer, targeted magnetic resonance imaging (MRI)/ultrasound fusion biopsy detected a greater number of high-risk cancers but fewer low-risk cancers when compared with standard extended-sextant ultrasound-guid- ed biopsy [JAMA. 2015;313(4):390-397].
Although standard biopsy remains the current diagnostic procedure for suspected cases of prostate cancer, advances in imaging have given way to targeted biopsies, in which multiparametric (MP)-MRI images are electronically superimposed on transrectal ultrasound images.
Peter Pinto, MD, National Institutes of Health, and colleagues conducted a prospective clinical trial that included 1034 men to compare targeted versus standard biopsy as well as the 2 approaches com- bined in the diagnosis of intermediate-to high-risk prostate cancer. The researchers' hypothesized that targeted biopsy had a higher rate of high-risk prostate cancer detection compared with standard biopsy.
Patients were enrolled between August 2007 and February 2014 and were included in the study if they had an elevated prostate-specific antigen or abnormal digital rectal examination and a MP-MRI demonstrating at least 1 lesion in the prostate. All patients underwent MP-MRI with 4 sequences: (1) triplanar T2-weighted; (2) dynamic contrast-enhanced; (3) diffusion-weighted imaging; and (4) MRI spectroscopy. All were pathologically risk-stratified as low, intermediate, and high risk.
A total of 1003 patients were ultimately included in the final analysis. Results showed that targeted biopsy diagnosed a similar number of cancers (461 patients) as standard biopsy (469 patients). There was exact agreement between the 2 approaches in 690 patients (69%). The combination of both approaches, however, yielded a difference in detecting high-and low-risk cancers: targeted biopsy detected 30% more high-risk cancers compared with standard biopsy (173 vs 122; P<.001) and 17% fewer low-risk cancers (213 vs 258; P=.002). Targeted biopsy also demonstrated a higher risk category in 167 cases (17%), while standard biopsy demonstrated a higher risk category in 146 cases (15%). In cases of targeted biopsy that indicated a higher risk category, 112 (67%) were upgraded to intermediate- or high-risk pathology by targeted biopsy, but in cases of standard biopsy that demonstrated a higher risk category, only 60 (41%) were upgraded to intermediate- or high-risk pathology by standard biopsy (P<.001).
Additionally, the researchers compared targeted biopsy alone with targeted and standard biopsy combined. The combined approach led to 103 more cancers being detected (22%), of which 83% were low risk and 5% were high risk. These results translated to 1 additional high-risk cancer being detected for every 200 men undergoing both standard and targeted biopsy; and for every additional case of high-risk cancer detected, 17 cases of low-risk cancer would be diagnosed. Among patients whose risk category changed, 86 (9%) increased from no cancer to low-risk cancer and 19 (2%) increased from no cancer or low- or intermediate-risk cancer to high-risk cancer.
In order to predict whole-gland pathology, the researchers also studied a subset of 170 patients who underwent radical prostatectomy. Among the 170 patients, 17 were diagnosed with preprostatectomy with prostate cancer on standard biopsy, and of those, 3 (18%) had intermediate- or high-risk cancer on whole-mount pathology. There were 20 patients in this group diagnosed with prostate cancer on targeted biopsy only; of these, 12 (60%) had intermediate- or high-risk cancer on whole-mount pathology. These results translated to a sensitivity of targeted biopsy of 77% versus 53% for standard biopsy; specificities were similar at 68% and 66%, respectively.
The majority of the total study population had at least 1 previous biopsy, which can be noted as a study limitation, according to the authors.—Mary Mihalovic
