The annual American Urological Society meeting (AUA 2015, May 15-19) has more presentations than ever on multiparametric MRI detection of prostate cancer, MRI targeted biopsies, MRI/ultrasound fusion, and MRI-guided focal therapies. The urologic world is sitting up and taking notice as advanced imaging is changing the prostate cancer landscape. I will be sharing selected presentations from this year’s meeting, starting with an interesting report from the National Institutes of Health titled “The Natural History of Targeted Biopsy Negative Lesions Identified on Multiparametric Magnetic Resonance Imaging.”[i]
Natural history simply refers to what happens with cells over time. The authors of this paper are asking an interesting question: When a suspicious lesion seen on multiparametric MRI (mpMRI) is biopsied but comes back negative, and the patient goes on active surveillance (AS), does that area ever become cancerous? If so, will it be low-risk or high-risk? Their purpose was to determine if there are ways to predict how biopsy-negative areas will continue to behave. They point to the fact that previous studies have demonstrated that small lesions seen on mpMRI tend to be either non-malignant or low-risk PCa.
They studied 72 patients on AS how had at least to mpMRI and fusion-guided targeted biopsies. Originally, in that group 112 lesions were found to be biopsy-negative and were later re-biopsied because after an interval averaging 19 months, the mpMRI showed clinical characterics such as change in lesion size or worse features on one or more parameters. A total of 15 lesions in 13 patients proved to be positive for PCa, but over 90% of them were < Gleason 3+4 which did not meet their significance definition of Gleason 4+3 or greater. They found that lesion growth as seen on mpMRI correlated most with positive re-biopsy results.
Perhaps most importantly, the majority of re-biopsy findings of the original identified lesion were almost always benign, and for those 13 men whose later biopsy was positive, almost all were low-risk. This suggests that benign tissue tends to stay benign, even if the targeted area seems to be growing. However, depending on the rate of enlargement within two years, lesion growth may serve as a trigger for a re-biopsy. More research is needed.
While I find these results encouraging for AS patients who have access to mpMRI monitoring (along with PSA), I would have been happier had the targeted biopsies been done under real-time MRI rather than MRI/ultrasound fusion. Still, I respect the work with mpMRI that is being done at NIH, University College London, and other top-flight research centers. Exploring the natural history of biopsy-negative lesions is a valuable addition to our understanding of prostate cancer risk factors.
[i] Presented by Raju Chelluri http://www.urotoday.com/index.php?Itemid=2460&option=com_content&view=article&catid=1655&id=80713&utm_source=newsletter_2671&utm_medium=email&utm_campaign=aua-2015-day-2-morning-exclusives-051515