In a study reported in JAMA, M. Minhaj Siddiqui, MD, currently of the University of Maryland School of Medicine, and colleagues found that targeted magnetic resonance imaging (MRI)/ultrasound fusion–guided prostate biopsy increased diagnosis of high-risk prostate cancer and reduced detection of low-risk disease compared with standard (extended-sextant) ultrasound-guided biopsy.1
Study Details
In the study, 1,003 men underwent multiparametric prostate MRI to identify regions suspicious for prostate cancer followed by both targeted and standard biopsy at the National Cancer Institute between 2007 and 2014. Patients had elevated prostate-specific antigen (PSA) levels or abnormal digital rectal examinations, most with prior negative biopsy results.
The primary objective was to compare targeted and standard biopsy for detection of high-risk prostate cancer (Gleason score ≥ 4 + 3). Secondary outcomes included detection of low-risk prostate cancer (Gleason score 3 + 3 or low-volume 3 + 4) and biopsy ability to predict whole-gland pathology at prostatectomy.
In total, 196 patients had no prior biopsy and 170 ultimately underwent prostatectomy. Among all patients: mean age was 62 years; median PSA level was 6.7 ng/mL; median prostate volume was 49 cm3; cancer suspicion score on multiparametric MRI was low for 18%, moderate for 72%, and high for 11%; tumor stage was T1c in 89% and T2a in 9%; 44% had anterior lesions; mean number of lesions on multiparametric MRI was 2.7; mean number of targeted MR/ultrasound biopsy cores was 5.3; and mean number of standard biopsy cores was 12.3.
Compared with patients with a prior biopsy, those with no prior biopsy had lower prebiopsy PSA level (median, 5.3 vs 7.1 ng/mL; P = .002), smaller prostate volume (median, 42 vs 52 cm3; P < .001), lower proportion with anterior lesions (34% vs 47%, P = .001), and more MRI lesions to biopsy (mean, 2.9 vs 2.6; P = .001).
Compared with all patients who underwent study biopsy, those who ultimately underwent prostatectomy were younger (mean age, 60.2 vs 62.1 years; P < .001), had smaller prostate volume (median, 39 vs 49 cm3; P < .001), and had more MRI lesions (mean, 3.1 vs 2.7; P < .001).
Diagnosis and Risk Categories
Targeted MR/ultrasound fusion biopsy diagnosed 461 prostate cancer cases, and standard biopsy diagnosed 469 cases. There was agreement between targeted and standard biopsy in 690 cases (69%).
Targeted biopsy diagnosed 30% more high-risk cancers vs standard biopsy (173 vs 122 cases, P < .001) and 17% fewer low-risk cancers (213 vs 258 cases, P = .002). Higher risk category was indicated by targeted biopsy in 167 cases (17%) and by standard biopsy in 146 cases (15%). Among the targeted biopsy cases, 112 (67%) were upgraded to intermediate- or high-risk compared with 60 cases (41%) on standard biopsy (P < .001).
Combining standard biopsy and targeted biopsy led to diagnosis of 103 more cancer cases (22%); of these, 86 (83%) were low-risk and only 5 (5%) were high-risk. On this approach, the number needed to biopsy with standard biopsy plus targeted biopsy was 200 to diagnose 1 additional high-risk cancer; for each additional case of high-risk cancer diagnosed, 17 additional cases of low-risk cancer would be diagnosed.
Combining standard and targeted biopsy led to no change in Gleason score risk stratification in 857 cases (85%). Of those with a change in risk category, 86 (9%) increased from no cancer to low-risk cancer, whereas only 19 (2%) increased from no cancer or low- or intermediate-risk disease to high-risk disease.
Biopsy Diagnosis vs Whole-Mount Pathology
Among the 170 patients who underwent radical prostatectomy, 17 patients were diagnosed with cancer only on standard biopsy; of these, 3 (18%) had intermediate- or high-risk cancer on whole-mount pathology. Of 20 patients diagnosed only on targeted biopsy, 12 (60%) had intermediate- or high-risk cancer on whole-mount pathology.
Overall, targeted vs standard biopsy had a sensitivity of 77% vs 53% and a specificity of 68% vs 66% for whole-gland pathology findings. The area under the receiver operator characteristic curve for targeted biopsy was 0.73, significantly greater than that for standard biopsy (0.59, P = .005) or combined biopsy (0.67, P = .04).
Patients With No Prior Biopsy
Among the 196 patients with no prior biopsy, cancer was diagnosed in 110; of these, 42% had low-risk, 16% had intermediate-risk, and 42% had high-risk disease. There was no significant difference between targeted biopsy risk distribution in this group compared with patients with prior biopsies (P = .52). The standard biopsy risk distribution was higher among patients without prior biopsy and did not differ significantly from the targeted biopsy distribution in the group.
Combining standard and targeted biopsy in this group resulted in no change in risk status for 85%, the same proportion as in the total study group. Combined biopsy use resulted in upgrading to high-risk disease in 7 patients without prior biopsy (4%).
The investigators concluded: “Among men undergoing biopsy for suspected prostate cancer, targeted [MRI]/ultrasound fusion biopsy, compared with standard extended-sextant ultrasound-guided biopsy, was associated with increased detection of high-risk prostate cancer and decreased detection of low-risk prostate cancer. Future studies will be needed to assess the ultimate clinical implications of targeted biopsy.” ■
Disclosure: For full disclosures of the study authors, visit jama.jamanetwork.com.
Reference
1. Siddiqui MM, Rais-Bahrami S, Turkbey B, et al: Comparison of MR/ultrasound fusion–guided biopsy with ultrasound-guided biopsy for the diagnosis of prostate cancer. JAMA 313:390-397, 2015.
