Transrectal ultrasound-guided (TRUS) prostate biopsy poorly detects and rules out clinically significant prostate cancer, whereas multi-parametric magnetic resonance imaging (MP-MRI) can identify 27% of men who might safely avoid unnecessary biopsy, a study presented at the 2016 American Society of Clinical Oncology (ASCO) Annual Meeting showed.
"The current diagnosis pathway can result in various errors: clinically indolent cancers are identified by chance; clinically significant lesions are missed; important cancers are incorrectly classified as unimportant; and men undergo whole-gland treatment, which carries harm," said co-investigator and presenter Hashim Ahmed, PhD, an MRC clinician scientist at University College London Hospitals in the United Kingdom.
Because MP-MRI as a triage test might allow men to avoid unnecessary TRUS-biopsy, since men with an elevated PSA do not have clinically significant prostate cancer, researchers evaluated the accuracy of MP-MRI followed by TRUS-biopsy vs template prostate mapping biopsy (TPM-biopsy) as an accurate reference test.
For the prospective, paired-cohort confirmatory PROMIS study, investigators enrolled 740 men with an elevated PSA up to 15 ng/mL who had not undergone prior biopsy.
All men underwent MP-MRI followed by both TRUS-biopsy and TPM-biopsy. All patients and physicians were blinded to MP-MRI reports and radiologists were not present at the time of biopsy; pathologists reading biopsy reports were blinded to MP-MRI reports; and TPM-biopsy and TRUS-biopsy reports were sent to different expert uro-pathologists.
Among the 576 evaluable patients who underwent all 3 diagnostic tests, results showed that the reference TPM-biopsy detected clinically significant prostate cancer in 40% of patients. For MP-MRI, sensitivity was 93% (95% CI, 88-96), specificity was 41% (95% CI, 36-46), positive predictive value was 51% (95% CI, 46-56), and negative predictive value was 89% (95% CI, 83-94).
"MP-MRI can identify more than 90% of men with clinically significant prostate cancers," Dr Ahmed said.
In contrast, sensitivity for TRUS-biopsy was 48% (95% CI, 42-55), specificity was 96% (95% CI, 94-98), positive predictive value was 90% (95% CI, 83-94), and negative predictive value was 74% (95% CI, 69-78).
"TRUS-biopsy has poor attributes for a diagnostic test," Dr Ahmed noted.
Researchers found that TRUS-biopsy was significantly less sensitive than MP-MRI (OR, 0.06; 95% CI, 0.02-0.12; P≤.0001). Further, TRUS-biopsy had significant worse negative predictive value than MP-MRI (OR, 0.34; 95% CI, 0.21-0.55; P<.0001).
The investigators determined that using MP-MRI as a triage test would avoid a primary biopsy in 27% of men at the minimum but detect 18% more cases of clinically significant cancer than the standard TRUS-biopsy.
"The high sensitivity and negative predictive value of prostate MP-MRI at 1.5 Tesla justify its use as a triage test to identify those men who might avoid a primary biopsy," Dr Ahmed explained. "The low specificity and positive predictive value of prostate MP-MRI indicated that men with suspicious MP-MRI still require a biopsy."
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