In the last decade, PAE gained ground as an alternative minimally invasive procedure for LUTS / BPH, much based on its favorable safety profile, and the possibility of being performed in an outpatient basis (1–7).
In the present cohort, no NTE resulting in hematochezia, hematospermia, or penile ulcers was observed during follow-up, even when contrast reflux to important branches was visible during embolization (Fig. 3). The reflux-control mechanism of the microcatheter involves discharge of filtered contrast solution through small side fenestrate, creating a fluid-barrier that avoids the reflux of microspheres, which are delivered by the distal-end hole of the device. In that sense, reflux of contrast solution is expected and seen routinely during embolization using this microcatheter. The preserved non-target branches aspect during control DSAs after embolization suggests that the mechanism is effective to blockade the reflux of a relevant amount of embolic agent (Fig. 3D). In addition to that, a strict follow-up protocol including MRI showed that no subclinical NTE was observed, with normal aspect of the periprostatic structures in all patients. Is noteworthy that the microcatheter used potentially protects against contrast microspheres reflux to relevant arterial branches, however, high-flow anastomosis to relevant structures should still be coiled to protect against NTE. In fact, and protective embolization by coiling was performed in one patient in the present cohort (10%).
The grade III complication observed (ball-valve effect) occurred in a patient with a large prostate (130 cm3), and a 26 mm intraprostatic protrusion (grade III IPP) caused by a large, asymmetric medium lobe (Fig. 3). In fact, patients with a large medium lobe seem to be more frequently prone to complications after PAE. Meira et al. (18) recently reported the efficacy and safety of PAE in patients with different IPP grades, showing a higher overall incidence of complications in grade III IPP when compared with grade II (62.5% vs. 23.4% P ≤ 0.01). Also, all major complications observed in the cohort occurred in grade III IPP patients (3/32, 9.4%), which included ball-valve effect, hematuria needing cystoscopic management, and persistent urinary tract infection.
Using the 2.4-F reflux control microcatheter, bilateral embolization was possible in all 10 patients (100%), while a deeper, intraprostatic navigation into the prostatic branches (PErFecTED technique) was possible in 24/25 prostatic branches (96.0%). Also, even in the type I PAs (7/25, 28%), which are considered as of harder catheterization (17), no additional difficulty related to the material was observed. In one patient (10.0%), occlusion of the microcatheter was observed during the embolization of the first prostatic side with 300–500 micrometers Embospheres, and microcatheter exchange was necessary to resume PAE. After removing the microcatheter, occlusion of its distal end by impacted particles was observed, as well as exteriorization of embolic material through the damaged side holes during saline injection. Although we did not modify the dilution protocol after this episode, no other similar event was observed. It is possible that using a more diluted microsphere solution could help reducing the incidence of microcatheter occlusion and subsequent damage of the reflux control mechanism.
Regarding the efficacy outcomes, the improvements in IPSS/QoL scores and the objective endpoints such as Qmax, prostatic volume and PSA levels (Table 3) were somewhat greater than historically described in multiple single center series and metanalyses (2–7, 19–20) and lasted during the 12-month follow-up. Although these findings could be related to the small sample size, it is possible that a more aggressive embolization endpoint due to a lower risk of microspheres reflux could have also played an important role. Larger comparative trials are desirable to further explore this hypothesis.
In 2019, a clinical trial comparing the outcomes of PAE using conventional (cPAE) versus balloon-occlusion microcatheter (bPAE) showed no difference regarding efficacy outcomes between groups (11). Although coiling was employed as protective measure in both arms (8.7% in the bPAE group and 14.0% in the cPAE group, P = 0.51), NTE resulting in penile lesions (n = 3, 7.0%) and rectal bleeding (n = 2, 4.7%) occurred only in the cPAE group. Similarly, we did not observe any clinical or subclinical NTE event, despite employing protective embolization with coils in only 1/20 hemipelvis (5.0%). Finally, the efficacy outcomes seen in the present cohort were superior when compared to the bPAE arm of the aforementioned clinical trial: reduction of IPSS of -17.9 vs. -8.3; reduction of QoL of -4.3 vs. -1.63; reduction of prostatic volume of -43.2 cm3 vs. -6.15 cm3; reduction of PSA of -3.0 ng/mL vs. -0.22 ng/mL; and increase of Qmax of + 13.30 mL/s vs. + 3.12 mL/s), which could be due to the differences in the materials utilized and the employed techniques, as well as the small sample sizes.
Limitations of the present study include its small sample size, leading to higher variability of the results and possibly bias. Also, it does not allow a definitive conclusion about the extent of the protection against NTE. Even so, it was possible to obtain statistical significance for all the intended endpoints using non-parametric tests. Also, the findings obtained were exclusively compared to historic data, which populations are not necessarily similar regarding baseline aspects such as prostatic volume, arterial anatomy, technique utilized, among others. Larger prospective trials would be more suitable to address the efficacy of PAE using the reflux-control microcatheter. Also, no long-term data was obtained, although the short- and medium-term results presented were considered enough to attest the feasibility of the method, even using a 2.4-F microcatheter, which is often considered too large for PAE.
In conclusion, this initial experience suggests that PAE using the reflux control microcatheter is effective and safe for the treatment of LUTS / BPH. No NTE was observed during follow-up. High flow intraprostatic anastomosis still need coil protective embolization to avoid NTE even with the use of reflux-control microcatheters.