MRI-Guided Targeted and Systematic Prostate Biopsies as Prognostic Indicators for Prostate Cancer Treatment Decisions

Abstract

The standard procedure for the diagnosis of prostate carcinoma involves the collection of 10-12 systematic biopsies (SBx) from both lobes. MRI-guided targeted biopsies (TBx) from suspicious foci increase the detection rates of clinically significant (cs) PCa. We investigated the extent to which the results of the TBx predicted the tumor board treatment decisions. SBx and TBx were acquired from 150 patients. Risk stratifications and recommendations for interventional therapy (prostatectomy and radiotherapy) or active surveillance were established by interdisciplinary tumor boards. We analyzed how often TBx alone were enough to correctly classify the tumors as well as to indicate interventional therapy and how often the findings of SBx were crucial for therapy decisions. A total of 28/39 (72%) favorable risk tumors were detected in TBx, of which 11/26 (42%) very-low-risk tumors were not detected and 8/13 (62%) low-risk tumors were undergraded. A total of 36/44 (82%) intermediate-risk PCa were present in TBx, of which 4 (9%) were underdiagnosed as a favorable risk tumor. A total of 12/13 (92%) high-risk carcinomas were detected and correctly grouped in TBx. The majority of csPCa were identified by the sampling of TBx alone. The tumor size was underestimated in a proportion of ISUP grade 1 tumors. Systematic biopsy sampling is therefore indicated for the next AS follow-up in these cases.

Keywords: MRI-guided targeted biopsies; clinically significant prostate cancer; prostate cancer.

Figure 1

Biopsy protocols. (A): Protocol for systematic biopsy (SBx) sampling—a total of 12 biopsies were taken evenly from apical, central, and basal sections of both prostate lobes. In this scheme, the largest and most dorsally located tumor site (red lesions) was captured in one biopsy, while the smaller and more anteriorly located tumor sites were not encountered. (B): Multimodal MRI showed a tumor-suspicious lesion in the right dorsolateral prostate apex with concomitant diffusion distortion (PIRADS 4 lesion). The remaining tissue had signs of nodular hypertrophy and increased or decreased signal intensity. For this study, one or more biopsies (black circles) were taken specifically from the target region (TBx), depending on the size of the lesions on MRI. Additionally, one biopsy was taken from each of the remaining sites according to the standard procedure (numbered zones) for systematic biopsies (SBx), avoiding the tumor-suspicious lesion.

Figure 2

Cancer detection rates of the PIRADS groups. In higher PIRADS groups, both the rate of tumors detected and the proportion of diseases requiring therapy increased.

Figure 3

Cancer detection rates of the risk groups in targeted biopsies (Tbx) and systematic biopsies (SBx). TBx achieved high detection rates and correct stratifications in intermediate- and high-risk cancer groups. Low-grade cancers were impeccably detected but often undergraded. Nearly half of the VL-risk cancers were missed in TBx. TBX and SBx showed comparable detection rates in all risk groups, but TBx showed slightly better results in high-grade cancers.