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Active surveillance (AS) is an alternative which can be proposed to these patients, requiring an annual re-evaluation of the tumor by a PSA assay and prostate biopsies. Radical treatment is only proposed if signs of tumor progression occur. This management is a source of anxiety, because of the risk of tumor progression, and a source of infection related to yearly repeat transrectal prostate biopsies. As a result, more than a third of patients included in AS protocols ask to be discharged in the mid-term and to be treated by a radical treatment.

Between these two extremes, focal laser ablation (FLA) of the most aggressive tumor site (index tumor), while sparing the rest of the prostate tissue, is a treatment which is gaining more and more widespread acceptance. FLA is an intermediate option between AS and radical treatments aiming to suppress the risk of progression and to provide a high quality of life after treatment (1).

How to guide the ablative energy to the tumor?

FLA has been made possible thanks to the ability of prostate MRI to consistently detect and localize tumor foci of PCa (2). Two different techniques are available to have access to the tumor. The first is direct in-bore MRI guidance which is an accurate technique (3), but with no wide availability, related to the limited access to interventional MRI, the cost of the examination and the complexity of the technique.

The alternative is ultrasound guidance, especially with the use of a very high frequency probe (microUS), operating at 29 MhZ (ExactVu, Exact Imaging, Canada). MicroUS can detect PCa in virtually 100% of cases, once the location of the lesion is known by MRI (4). The very high spatial resolution of the device allows a good visualization of tumor contours and of the treated area during FLA.

How to proceed?

The two patients treated at Clinique de l’Alma, July 3 2020, had a tumor anteriorly located, within the transition zone (patient #2 is shown on figure 1) and had the criteria of eligibility for FLA (1). The treatment consisted in a focal thermo-ablation by a laser fiber transperineally placed within the tumor, monitored in real time by transrectal microUS. The patients were discharged a few hours after treatment. Follow-up will be done in a routine standard of care recommended after treatment of PCa

FLA fig.1

Figure 1 . 64 y/o man. Gleason score 3+4, 20% grade 4, no cribriform pattern. PSA level : 7.4ng/ml. A-C : T2 weighted images of prostate MRI. The tumor (arrows) is located anteriorly, in the mid sextant, on the midline. B-D : overlay with diffusion weighted images (DWI) increases tumor visibility (arrow).

FLA fig.2

Figure 2 : MicroUS during treatment. Two ablations were performed, one on each side, given the location of the tumor

Right side (RT). Pretreatment sagittal view. The tumor is visible behind the anterior fibromuscular stroma. After treatment (RT post), the tumor has a hyperechoic appearance (arrows) related to the coagulative necrosis induced by the laser fiber (arrowhead)

Left side (LT). Pretreatment sagittal view (LT pre). The tumor is visible behind the anterior fibromuscular stroma. The laser fiber is in place (arrowhead). After treatment (LT post), the tumor has a hyperechoic appearance (arrows) and bubbles consecutive to vaporization, are visible (arrows).

FLA fig.3

Figure 3 : MRI three days after treatment. A-C : T2 weighted images. The bright focus visible (arrow) corresponds to cavitation. B-D: Dynamic Contrast Enhanced (DCE) image overlaid on T2W image: the devascularized area (*) is well delineated with a large safety margin around the tumor.

 

References

1.         van Luijtelaar A, Greenwood BM, Ahmed HU, Barqawi AB, Barret E, Bomers JGR, et al. Focal laser ablation as clinical treatment of prostate cancer: report from a Delphi consensus project. World J Urol. 2019;37(10):2147-53.

2.         Padhani AR, Barentsz J, Villeirs G, Rosenkrantz AB, Margolis DJ, Turkbey B, et al. PI-RADS Steering Committee: The PI-RADS Multiparametric MRI and MRI-directed Biopsy Pathway. Radiology. 2019;292(2):464-74.

3.         Walser E, Nance A, Ynalvez L, Yong S, Aoughsten JS, Eyzaguirre EJ, et al. Focal Laser Ablation of Prostate Cancer: Results in 120 Patients with Low- to Intermediate-Risk Disease. J Vasc Interv Radiol. 2019;30(3):401-9 e2.

4.         Cornud F, Lefevre A, Flam T, Dumonceau O, Galiano M, Soyer P, et al. MRI-directed high-frequency (29MhZ) TRUS-guided biopsies: initial results of a single-center study. Eur Radiol. 2020. 10.1007/s00330-020-06882-x

Figures

Figure 1 . 64 y/o man. Gleason score 3+4, 20% grade 4, no cribriform pattern. PSA level : 7.4ng/ml. A-C : T2 weighted images of prostate MRI. The tumor (arrows) is located anteriorly, in the mid sextant, on the midline. B-D : overlay with diffusion weighted images (DWI) increases tumor visibility (arrow).

Figure 2 : MicroUS during treatment. Two ablations were performed, one on each side, given the location of the tumor

Right side (RT). Pretreatment sagittal view. The tumor is visible behind the anterior fibromuscular stroma. After treatment (RT post), the tumor has a hyperechoic appearance (arrows) related to the coagulative necrosis induced by the laser fiber (arrowhead)

Left side (LT). Pretreatment sagittal view (LT pre). The tumor is visible behind the anterior fibromuscular stroma. The laser fiber is in place (arrowhead). After treatment (LT post), the tumor has a hyperechoic appearance (arrows) and bubbles consecutive to vaporization, are visible (arrows).

Figure 3 : MRI three days after treatment. A-C : T2 weighted images. The bright focus visible (arrow) corresponds to cavitation. B-D: Dynamic Contrast Enhanced (DCE) image overlaid on T2W image: the devascularized area (*) is well delineated with a large safety margin around the tumor.