Needle Biopsy Sampling Techniques and Role of Multiparametric-Magnetic Resonance Imaging Modality in Prostate Cancer Diagnosis and Management
The clinicopathological characteristics of newly diagnosed prostate cancer have significantly changed due to widespread prostate-specific antigen (PSA) screening after its introduction in the late 1980s. The most remarkable change has been “stage migration” toward smaller volume disease at a younger age. The diagnosis of prostate cancer now is mostly triggered by an elevated or rising PSA rather than an abnormal digital rectal examination, resulting in a significant increase in the percentage of nonpalpable cancers (stage T1C) between 1988 and 1996 from 10% to 73%. With this trend, the prostate biopsy application and sampling techniques have also rapidly evolved. In 1989, the transrectal ultrasound (TRUS)-guided sextant prostate biopsy was introduced and rapidly became the standard over directed biopsies of hypoechoic lesions and palpable nodules. In recent years, it has become increasingly evident that sextant biopsies could miss a significant number (up to 30%) of cancers because only a small percentage of prostates has a tumor distribution detectable with the paramedian template utilized by the sextant approach. Furthermore, sextant protocol tends to undersample certain areas of the prostate, such as “anterior horns” and the lateral aspects of the peripheral zone, where majority of prostate cancer arises. Recent studies suggested moving the biopsies more laterally to better sample the lateral aspects and anterior horns of the peripheral zones. This recommendation was supported by the zonal anatomy of the prostate as well as the origin of the tumor. Because approximately 80% of prostate cancers originate in the peripheral zone, extended biopsy templates that more extensively sample this region could improve the cancer detection rate.
The main disadvantage of TRUS-guided prostate biopsy, however, is that it misses a substantial proportion of clinically significant cancers (approximately 20%) because of sampling errors, especially in the anterior part of the prostate gland, and a high proportion of men are diagnosed with clinically insignificant disease, which may result in subsequent overtreatment. Owing to its high soft-tissue contrast, high resolution, and ability to simultaneously image functional parameters, multiparametric-magnetic resonance imaging (mp-MRI) provides the best visualization of the prostate compared to other imaging methods. Over the past years, mp-MRI use has shifted from staging purposes to detection and tumor localization and prediction of clinically significant cancers. This chapter discusses the application of various TRUS and MRI-guided sampling methods and their impact on day-to-day practice.
KeywordsProstate-specific antigen Nonpalpable cancers (stage T1C) Sextant biopsy Extended biopsy Saturation biopsy Transrectal biopsy Transperineal biopsy Multiparametric-magnetic resonance imaging, mp-MRI T2-weighted imaging, T2W Diffusion-weighted imaging, DWI Apparent diffusion coefficient, ADC Dynamic contrast-enhanced imaging, DCEI Magnetic resonance spectroscopy imaging, MRSI Targeted biopsy Fusion imaging Region of interest, ROI PI-RADS score
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