MRI may add value in monitoring men on surveillance

Vancouver, BC-Multiparametric MRI (mpMRI) of the prostate with subsequent targeted biopsy shows promise for improving the identification of men on active surveillance (AS) for low-risk prostate cancer who require definitive treatment, according to researchers from the Vancouver Prostate Centre, Vancouver, BC.

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The role of mpMRI in altering management of patients on AS was investigated in a retrospective study led by Larry Goldenberg, MD, and Peter Black, MD, both of the University of British Columbia, Vancouver. It included 111 men who underwent the imaging technique as part of their AS protocol.

During a median follow-up of about 2.5 years, mpMRI detected a total of 118 suspicious lesions (defined by a Prostate Imaging Reporting and Data Systems [PIRADS] score ≥3) in 68 men. All 68 men underwent systematic and targeted biopsies; the targeted biopsy was directed by transrectal ultrasound-magnetic resonance fusion software in 39 men and visually guided (“cognitive fusion”) in 29 men.

During follow-up, 27 (24.3%) of the 111 men stopped AS and went on to receive definitive treatment. The decision to stop AS was based on the MRI findings in 17 men (15.3%) and was independent of the MRI results in the other 10 (9.0%). The MRI findings that led to termination of AS included pathologic disease progression in targeted biopsies (16 men) and lesion size increase on MRI (one man). Among the 10 men who went on to definitive treatment for reasons independent of findings on mpMRI, the reasons included pathologic disease progression in standard biopsies (six men), patient choice (three), and PSA rise (one), reported first author Hamidreza Abdi, MD, clinical fellow at Vancouver Prostate Centre.

“Active surveillance is a way to address concerns pertaining to overdiagnosis and overtreatment of prostate cancer, but there remains a risk for missing tumor progression due to the limitations of biopsy sampling techniques,” said Dr. Abdi.

“We believe our study shows mpMRI has potential value for enhancing monitoring of men on active surveillance. However, our findings must be viewed as preliminary, and it should be emphasized that subsequent targeted biopsy needs to be improved to minimize errors.”

The 118 lesions identified by mpMRI had a median size of 12 mm. The radiologic grading showed the majority (71 lesions, 60.2%) were PIRADS 3, 37 lesions (31.4%) were PIRADS 4, and 10 (8.4%) were PIRADS 5.

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Lesion score could predict AS termination

PIRADS score was examined as a possible predictor of termination of AS in a multivariate analysis, and the results showed that men with a PIRADS 4 or 5 lesion were approximately sixfold more likely than men with a PIRADS 3 lesion to terminate active surveillance (p=.0003), Dr. Abdi reported.

Other variables investigated included PSA density (≤0.15 vs. >0.15), number of lesions (1-2 vs. >2), apparent diffusion coefficient value (≤890 vs. >890), and lesion size (≤10 vs. >10 mm), but with the chosen cut-offs, none of those factors significantly predicted termination of AS.

“A prospective study with a larger sample size and longer follow-up will be needed to determine whether mpMRI adds benefit in following men on active surveillance and what role these other features have in predicting progression,” Dr. Abdi said.

Results from the study were presented at the 2014 AUA annual meeting in Orlando, FL.

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