Ergebnisse und prädiktive Faktoren bei der Behandlung von Uterusmyomen mittels Magnetresonanztomographie- gesteuerten fokussierten Ultraschall

Abstract MRgFUS is a noninvasive, effective and relatively safe method for the treatment of uterine fibroids leading to symptom relief with rare side effects and complications. Due to technical improvements, MRgFUS is part of national and international treatment guidelines and is becoming accessible to an increasing number of patients. Nevertheless, the ideal selection of suitable patients is key to achieve maximal therapeutic effecacy. This study was able to demonstrate certain significant correlations between treatment effectivity. Hence, the therapy was effective with regard to the reductionof symptoms. The score in the survey questionnaire showed a correlation with the treatment effect. As already described before, treatment effectivity increased if the uterine fibroid was small in size and based on the hypointense signal intensity. The distance to the ultrasound source has not been previously described as a significant parameter. In our study, we could demonstrated that the distance of the acoustic path, especially to the dorsal wall of the uterine fibroid was a criterion for a higher therapeutic success, with best results at a length of less than 80 mm.  The distance of the fibroid to the os sacrum also seems to play a significant role in treatment effectivity. Herby we found, that distance is an independent risk factor related to thermal damage of the sacral plexus and bone, and caution of thermal loading of fibroids in this location, leading to significantly inferior therapeutic efficacy. As expected, a high correlation existed between the applied sonification density and the link between the computer-calculated sonified volume and the NPV. In our study, there was no significant correlation between patient age and therapy efficacy. Neither were the number of fibroids (greater than 2) and the thickness of the subcutaneous fat layer, which are known to be significant parameters for good therapeutic efficacy as confirmed in this study. Therefore, the two parameters should be included in the preselection process. The presence of a scar also had no influence on the efficacy of treatment, not excluding the group of pre-operated patients from therapy. Measures such as rectal or bladder filling, as well as the use of different pad sizes can be applied depending on the individual case without significant treatment outcome. Of the few documented cases in need of a secondary treatment, no risk factors were identified that are per se associated with a poor outcome. Symptomatology, as also seen by the 2019 expert meeting is leading and seems to dominate both the indication for uterine fibroid therapy and secondary interventions. Adenomyosis uteri appears to be effectively treatable with MRgFUS. Even fibroids with prior endocrine treatments (ulipristalacetate) do not have a significantly reduced therapeutic outcome. This study supports that the necrosis degrades over the years and that the growth of the vital residual fibroid volume over time poses a risk factor. In this regard, close monitoring and, if necessary, a second MRgFUS treatment should be considered to improve long-term efficacy.With regard to the location of the uterine fibroid, only descriptive results were found with more bleeding in the case of intracavitary fibroid location and reduced therapeutic s efficacy in the case of subserosal fibroid location. The duration of therapy, which highly depends on the size and location of the uterine fibroid and the optimal presentation of a sonic window, is a significant parameter for the efficacy of the MRgFUS treatment. One goal for the future, based on the results of further studies should be to summarize parameters that correlate directly with the efficacy of treatment in a survey for preselection, in order to provide patients and therapists with a predictive option for an improved selection of this or alternative therapies.   Parameters for feasibility also play a role, which may not have a direct effect on the efficacy of the treatment, but should nevertheless be taken into account in the treatment selection. The questionnaire used in our study mixed both selection criteria. Thus, only 3 parameters (proximity to the os sacrum, signal strength hyperintensity, heterogeneities) actually had a statistical association with therapy efficacy in our study. The other parameters were either too inaccurate (uterine fibroid size above 500 ml) or related to feasibility criteria (scar or intestinal interposition in the sonic window). Based on improved and more differentiated questionnaires, it should be possible to create a better individual concept for the treatment of uterine fibroids. Therefore, a re-evaluation of the selection criteria for MRgFUS seems to be one of the most important conclusions of this study.