BERKELEY, CA (UroToday.com) - The last decade was marked by a widespread use of PSA-based prostate cancer screening and an exponential rise in the number of prostate biopsies, in terms of patients and of biopsies per patient. Some of these biopsies were unnecessarily performed while others missed significant prostate cancers. In addition, more men with low-risk prostate cancer had been diagnosed and some were also unnecessarily treated. The limited specificity of PSA and the low detection rate of prostate cancer on TRUS-guided biopsy generated much of the controversy existing about prostate cancer screening. Furthermore, the poor sampling of cancers under 2D TRUS and the underestimation of Gleason score widely opened the door for the development of more accurate strategies for the diagnosis of prostate cancer.
One of these promising strategies is multiparametric MRI and fusion-guided biopsy. At present, studies have demonstrated no, or only minimal benefit, to subjecting a man with a normal prostate MRI to a biopsy. In men with a PSA ≤ 10ug/L, a normal MRI was associated with a NPV of 93.7 - 97.5% for clinically significant disease (Numao N, et al., J Urol 2013). Moreover, an MRI-based strategy correctly identified more men with significant disease and more men without disease in 86% of a probabilistic sensitivity analysis published recently (Willis S et al., BMJ 2014). Thus, MRI followed by MRI-targeted biopsy will result in fewer but better biopsies. Several studies have demonstrated a more homogenous mapping and a precise targeting of the index lesion in contemporary series. This had resulted in an increased cancer length per biopsy core, a better detection of high-grade cancers and clinically significant cancer, and an improved clinico-pathological correlation. The number of men diagnosed having microfocal cancer lesions that may be clinically insignificant had consequently decreased. Despite available high-level evidence, there is still much to do to demonstrate its clinical utility and its value among various patient populations (biopsy naïve men, prior negative biopsies, active surveillance, suspected digital rectal exam, etc.).
In our study, we targeted the biopsy naïve patient. We had already reported, in a previous study of biopsy-naïve men, higher detection rate using the 3D system of Medison/koelis urostation without MRI fusion compared to standard protocol (50% vs. 33%, p < 0.05). This probably stems from a better distribution of prostate cores inside the prostate. Afterwards, we had integrated MRI-targeted biopsy using the same system into our practice. This had yielded an overall cancer detection rate of 62.7%, which is higher than most of the studies reporting on standard biopsy. In addition, in our study, TAR protocol improved prostate cancer detection rate compared to STD protocol and demonstrated higher detection rate of clinically significant disease with fewer tissue samples removed from lesions. The yield of targeted biopsies was significantly higher than standard biopsies with a ratio of 28.9% of cancer on TAR cores vs 9.8% of cancer on STD cores. Our data are even more encouraging when comparing clinically significant prostate cancer detection rate between the 2 protocols; 20 patients with clinically significant disease on TAR cores had either no cancer or clinically insignificant disease on STD cores, and 11 patients with no cancer on TAR protocol had clinically insignificant disease on standard cores. In contrast, one patient with clinically significant disease on STD protocol had a negative biopsy from a low suspicious lesion on the TAR protocol, and 5 patients with no cancer on STD protocol had a clinically insignificant cancer on TAR protocol.
At present, we are offering MRI for every patient presenting with a clinical suspicion of prostate cancer, and in the case of a suspected lesion, an MRI-targeted biopsy follows. Could we generalize these findings to a population-based scenario and integrate this approach for a better screening of prostate cancer? Enthusiasm for such screening is high, in part because it will
- Avoid unnecessary biopsies and their complication in a subset of patients,
- detect more patients with cancer,
- miss fewer patient with clinically significant cancer, and
- differentiate more accurately low-risk from intermediate- and high-risk prostate cancer.
However, some limitations needed to be mentioned before implementing this strategy on a large scale. First, data are needed on a community or nationwide population. Second, the issue of costs and health care value should be considered. Third, education of physicians and an extensive training and recruitment for radiologists is indeed needed in developed countries. Fourth, the time consuming nature of the procedure could also limit its widespread diffusion. From our personal point of view, we do think that advances in genetics will play an important role in understanding the biological behavior of the index lesion and could also be incorporated in future screening strategies.
Fouad Aoun, MD, MSc as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.
Jules Bordet Institute, Brussels, Belgium
Jules Bordet Institute, Brussels, Belgium