This small retrospective study summarizing our initial experience using HydroPearl Microspheres (Terumo Interventional Systems) as the embolic agent for UAE for the treatment of symptomatic uterine fibroids found that 81.3% of patients with menorrhagia experienced improvement in symptoms at follow-up an average of 136.6 days post-procedure (SD 77.4 days), or 4.6 months. For patients initially presenting with bulk-type symptoms, 92.3% experienced symptom improvement at an average of 141.1 days post-procedure (SD 71.4 days), or 4.7 months. The observed rate of clinical response that we observed, for both menorrhagia and bulk symptoms, for HydroPearl Microsphere particles was overall similar to other previously studied embolic agents for UAE. These include polyvinyl alcohol with or without gelfoam, polyphosphazene- coated hydrogel microspheres (Embozene, Varian Medical, Palo Alto, CA), tris-acryl gelatin spheres (Embospheres and Embogold, Merit Medical, South Jordan, UT), and gelatin sponge particles/porous gelatin particles (Toda et al., 2016; Salehi et al., 2015; Stampfl et al., 2011; Joffre et al., 2004; Lohle et al., 2006).
No major complications attributable to the UAE procedure were identified in this small series. The only complication documented in the EMR was the precipitation of amenorrhea in 4 of the 18 treated patients (22.2%). This is a known complication of UAE, particularly for older patients (Hamoda et al., 2015; Wozniakowska et al., 2013; Goodwin et al., 2008). These patients had an average age of 51 years, which is the average age of the onset of menopause for women in the United States (Bain et al., 2018).
HydroPearl Microsphere particles (Terumo Interventional Systems) have several unique characteristics that could prove beneficial for the treatment of symptomatic uterine fibroids with UAE. The particles are tightly calibrated, with at least 90% of the particles falling within the size range described. Compared to other spherical embolic particles such as Embosphere and Embozene, the tightly calibrated size distribution of HydroPearl Microspheres have demonstrated numerous benefits in in-vivo animal experiments. First, embolization with the HydroPearl Microspheres resulted in tighter luminal packing, ultimately causing greater tissue necrosis (Dasnurkar, 2015). The precisely calibrated size of these particles could also decrease non-target embolization, resulting in decreased damage to healthy tissues (Dasnurkar, 2015). HydroPearl Microspheres were found to be compressible, maintaining their spherical shape even after being pushed through a microcatheter, allowing for predictable embolization (Dasnurkar, 2015). This compressibility also allows for larger particles, such as 1100-μm particles, to be successfully delivered through a 2.8-Fr microcatheter if needed. We utilized the technique of administering 1100-μm HydroPearl particles through a 2.8 french Progreat microcatheter (Terumo Interventional Systems) in this small series, which was successful, but required frequent flushing of the microcatheter. Each size of the HydroPearl Microspheres has a unique particle color to ensure that the interventionalist is using the desired size. The color of the particles also allows for easy visualization to ensure adequate suspension of the particles prior to embolization, which could help to achieve an ideal embolization endpoint.
This retrospective study has limitations. The sample size of the study was small, and thus a determination of the safety and efficacy of this embolic agent for UAE for the treatment of symptomatic uterine fibroids cannot be made. The data reported in this study were obtained from EMR documentation of clinical follow-up either by telephone or in clinic. Standardized questions were not posed to each patient during these interactions, which could have introduced bias into this small study. Symptom questionnaires were not utilized in these clinical visits. Another major weakness of this study is that there was no control group, which would have allowed for direct comparison to other embolic agents. While all patients were initially scheduled for 1- and 3-month in-person clinic follow-up visits, many patients canceled or rescheduled their appointments, resulting in follow-up at variable times post-procedure and a few follow-up visits being conducted over the telephone. Some, but not all, patients had a documented 6-month or later follow-up, at the physician’s discretion. An additional limitation is that there were no specific inclusion criteria, as all patients that underwent embolization for fibroids using HydroPearl Microspheres within a certain time period were included. Consequently, patients had variable morphologies of their uterine fibroids (both size and location) that may have impacted the results.