Effects of Magnetic Resonance Imaging Targeting on Overdiagnosis and Overtreatment of Prostate Cancer

Abstract

BackgroundIt has been suggested that targeting prostate lesions identified on magnetic resonance imaging (MRI) will improve the sensitivity of prostate biopsy for high-grade disease. The clinical significance of high-grade tumors found on MRI but missed on systematic biopsy is open to question. ObjectiveTo determine the risk of mortality for high-grade cancers identified by MRI targeting in men who had benign systematic biopsy findings. Design, setting, and participantsWe used data from 999 men with negative systematic biopsy and concurrent MRI-targeted biopsy in the National Cancer Institute MRI study. The comparison group consisted of 3056 men followed for 11 yr after negative sextant biopsy in the European Randomized Trial of Screening for Prostate Cancer (ERSPC). Outcome measurements and statistical analysisWe calculated the number of patients needed to be diagnosed (NND) and treated (NNT) following targeted biopsy in order to prevent one prostate cancer death at 11 yr. We used a simple modeling approach that involved several assumptions, such as the proportion of the deaths in ERSPC preventable by earlier detection with MRI-guided biopsy. We then varied these assumptions to assess the effects on the results. Results and limitationsNND and NNT were 89 and 57 for the scenario involving assumptions favorable to MRI, and 169 and 127 for a more neutral set of assumptions, respectively. Results were only more encouraging for MRI targeting under unlikely scenarios, such as 100% sensitivity for MRI and a cure rate of 100% for treatment. ConclusionsAlthough MRI may be of benefit overall, considering the decrease in overdiagnosis among men with negative MRI findings, targeting biopsy needles to MRI-detected lesions results in a large number of men diagnosed and treated per death prevented. Consideration should be given to changing guidelines on grading of MRI cores and those regarding treatment of MRI-detected high-grade prostate cancer. Patient summaryWe carried out a modeling study to assess how magnetic resonance imaging (MRI) scan results used to target prostate cancer lesions during biopsy can affect outcomes. The model results show that if MRI-visible tumors are targeted during prostate biopsy, a large number of men need to be diagnosed and treated for prostate cancer in order to avoid just one prostate cancer death.