1. Diseño
1.17 Mitos y leyendas
Incorporation of MP-MRI and MRGB in patients on AS may be useful as it results in early additional risk re-stratification and radical treatment of patients with intermediate to high-risk PCa, who were undersampled by initial TRUS-guided biopsy. Standardized MP-MRI interpretation using PI-RADS reveals that MP-MRI is a promising technique for differentiation
Discussion
Our initial results show that the application of MP-MRI and MRGB in an AS protocol may contribute in early identification of patients with Gleason grade 4 and/or 5 PCa, while also improving the selection of AS suitable patients. Our initial risk re-stratification rate using MP-MRI and MRGB at 3 months (24%) is comparable to risk re-stratification rates (17-27%) in studies on repeated TRUS-guided biopsy within 3 months after initial diagnosis10,22.
At 12 months of follow-up, combined MP-MRI and MRGB added little to repeat systematic TRUS-guided biopsy, as MRGB only additionally risk re-stratified 3 patients (21% (3/14)) due to PCa multifocality. Most patients, which were risk re-stratified by MRGB also were risk re-stratified by TRUS-guided biopsy. Due to TRUS-guided systematic sampling of Gleason grade 2 and/or 3 PCa23 or
of smal(ler) volume Gleason grade 4 and/or 5 PCa, which may have been missed on initial and/or repeat MR imaging, repeated TRUS-guided biopsy may have risk re-stratified a similar amount of patients compared with MRGB. Fourteen patients with risk re-stratification at repeat examinations were missed on initial combined MP-MRI and MRGB. Missing cancers on initial MP-MR imaging may be caused by low tumor Gleason grade and/or a small volume Gleason grade 4 and/or 5 components23. In general, detected
cancers at 12 months of follow-up had a lower cancer volume (5.0mm MCCL) compared with cancers detected at 3 months of follow-up (6.9mm MCCL). MP-MRI had a sensitivity of 92% for detection of Gleason grade 4 and/or 5 PCa in case of higher PI- RADS scores (≥4) and a NPV of 100% for detection of Gleason grade 4 and/or 5 PCa in case of lower PI-RADS scores (≤2)). Furthermore, an initial cancer-negative MRGB specimen had a NPV of 79% for risk re-stratification at 12 months follow-up. These results are comparable to those of Vargas et al., who reported an NPV of 96-100% and a sensitivity of 87-96% for biopsy upgrading in case of an MR imaging score ≤2 and ≥5 for PCa presence13. While both scoring systems predicted presence of cancer from
highly unlikely to highly likely on a 5-point scale, the system used by Vargas et al. was based on lower signal intensity on T2-weighted MR imaging and/or restricted diffusion on ADC maps, while the PI-RADS system also took shape and invasion of surrounding structures into account.
Our results for PCa detection accuracy using MP-MRI and MRGB in patients on AS are difficult to compare to literature. Other studies on MRI implementation
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Ch ap te r 3 Pr os ta te b io ps y f or p ro st at e c an ce r d ia gn os is a n d r is k s tr at if ic at io nReferences
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between AS suitable patients and patients with Gleason grade 4 and/or 5 PCa, the latter needing radical treatment. However, smaller cancers may be missed by MP-MRI and MRGB. Follow-up of our preliminary results of initial cancer-negative MRGB specimens showed a NPV of 79% of an initial cancer- negative MRGB specimen for risk re- stratification after 12 months. This finding shows that a cancer-negative initial MRGB may be a promising prognostic parameter for active surveillance patient selection. In conclusion, application of MP-MRI and MRGB biopsy in AS may contribute in early identification of patients with Gleason grade 4 and/or 5 PCa, while also selecting AS suitable patients.
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