Multiparametric MRI: Standardizations Needed

摘要

The article by Gupta et al does a nice job of summarizing the role of multiparametric MRI (mpMRI) in the diagnosis and treatment of prostate cancer. Such an article is necessary because MRI of the prostate in 2013 is much different than it was even 5 or 10 years ago. For many years, the primary role of prostate MRI was to stage known disease-specifically, to determine whether carcinoma was confined to the gland in candidates for radical prostatectomy. The potential role of prostate MRI has in recent years expanded significantly, and there is great hope that mpMRI can help address two major problems encountered when treating prostate cancer: overtreatment and understaging. Prostate-specific antigen (PSA) level, the currently used screening tool for prostate cancer, is nonspecific and often leads to prostate biopsy Despite the fact that transrectal ultrasound (TRUS)-guided biopsy routinely misses and understages cancers, many patients are still unnecessarily treated for identified indolent cancers that will not kill them. The goal of a multiparametric approach to prostate MRI is to increase the accuracy of the identification of tumors within the prostate. Many recent publications have confirmed that a multiparameter approach achieves this goal, although with sensitivities ranging from 49% to 95%. The identification by mpMRI of tissue foci within the prostate suspicious for neoplasm has many potential benefits: it can identify lesions in patients with elevated PSA levels but negative prior TRUS biopsy, guide biopsies in patients who are candidates for active surveillance, provide serial information on the size of tumors under active surveillance, provide reassurance that low-risk patents do not harbor significant disease, and identify lesions for localized therapy. These uses should help us accurately stage and follow disease and reduce the incidence of unnecessary whole gland treatment. Recent studies have shown that MRI/US-guided biopsies diagnose significant cancers in patients with prior negative TRUS biopsy, independent of the number of prior negative biopsies. In addition, the degree of suspicion for focal neoplasm on mpMRI correlates with the likelihood of obtaining a positive targeted biopsy and the likelihood of Gleason 7 or greater disease, while the size of a tumor on MRI correlates with its actual size on histopathology. Finally, glands with no intermediate- or high-suspicion lesions on mpMRI are unlikely to harbor clinically significant disease.