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Letters to the Editor |
Department of Interventional Radiology, Delaware Valley Imaging, 301 City Avenue, Suite G1, Bala Cynwyd, PA 19004, e-mail: kirsch@dvirad.com, Department of Vascular and Interventional Radiology, Great Lakes Radiologists, Milwaukee, Wis, Department of Radiology, UCLA Medical Center, Los Angeles, Calif, Department of Radiology, University of British Columbia Hospital, Vancouver, British Columbia, Canada, Department of Radiology, Mease Hospitals, Safety Harbor, Fla, Department of Radiology, Guy’s and St. Thomas’ Hospital NHS Trust, London, England, Department of Radiology, Georgetown University Medical Center, Washington, DC, Department of Radiology, Royal Surrey County Hospital, Guildford, England
Editor:
We read with interest the recent article by Dr Pelage and colleagues in the May 2000 issue of Radiology (1) in which they presented midterm follow-up findings of the first cohort of women who underwent uterine artery embolization for fibroid disease. We believe that a comment is in order to clarify the choice of the size of polyvinyl alcohol (PVA) particles used in this procedure.
The patient data presented in this article represent the initial experience with uterine artery embolization for Dr Pelage and colleagues. The protocol they described for uterine artery embolization has evolved substantially since then. One of the most important changes has been in the choice of particle size for embolization.
Clinicians (2–5) with substantial experience with uterine artery embolization use PVA particles in either the 300–500- or 500–700-µm ranges. The use of 150–300-µm PVA particles has been abandoned, even by Dr Pelage and colleagues (Pelage JP, oral and written communication, 2000). These ranges have produced outcomes demonstrably similar to those of the smaller particles, and, at the same time, they provide occlusion at a somewhat more proximal level. We believe that the larger embolic particle size is safer, lowering the risk of both global uterine infarction and nontarget embolization through utero-ovarian collaterals.
We believe that it is important to comment on this issue, lest individuals who are just beginning to perform uterine artery embolization make an incorrect and possibly riskier choice of embolic particle size.
REFERENCES
Department of Vascular and Body Imaging, Hôpital Lariboisière, 2 rue Ambroise Paré, 75475, Paris Cedex 10, France, e-mail: jean-pierre.pelage@lrb.ap-hop-paris.fr,02064
We thank our overseas colleagues for their interest in our article (1). All of them have made great contribution to the field of uterine fibroid embolization; therefore, their comments are of real value.
The published study findings represent the initial results of uterine artery embolization in our center. The paper was first submitted to Radiology after the 1998 RSNA scientific assembly, in December 1998. Dr Worthington-Kirsch and colleagues are correct when they say that there have been numerous changes in the uterine artery embolization technique since that time.
We think that there are two main aspects of the article that are still interesting to report. The first is the problem of complications related to uterine artery embolization. We reported one case of extensive uterine necrosis after embolization, which was probably related to the size and location of the fibroids. The second is the frequency of amenorrhea after the procedure. These complications are now of primary consideration for all groups that are performing uterine artery embolization (2–4).
We still believe that there is a need to improve the procedure before the indications are extended to include young women with a desire of becoming pregnant. Even if the rate of complications from uterine artery embolization is low, especially when compared with rates of other therapeutic options (ie, multiple myomectomy or hysterectomy), it is the role of academic centers to carry out experimental studies and clinical trials to propose guidelines.
Concerning the size of the embolic agents, several comments are necessary. The use of small particles is potentially risky with regard to untargetted ovarian embolization and uterine necrosis (1,5). That is why most physicians who perform uterine artery embolization are now using PVA particles larger than 300 µm. However, even medium-sized PVA particles can be associated with uterine infection, as was reported in 1999 in a woman with large fibroids (6).
Recent experimental study findings (7) suggest that the level of arterial occlusion achieved is independent of the size of PVA particles mainly because of the irregular shape of the particles and their tendency to clump. This finding could be a potential explanation for the risk of complications encountered with all the sizes of PVA particles.
In addition, we have changed our end point of embolization to avoid occlusion of normal myometrial branches and cervicovaginal arteries. We know that there is a predominant blood flow to the fibroids at the beginning of the procedure. Fibroids are also more sensitive to ischemia than is normal myometrium. Currently, our end point of embolization includes the following criteria: (a) disappearance of hypervascularization related to fibroids, (b) reduction of the distal flow of the uterine artery, and (c) patency of the main uterine artery, including cervicovaginal branches, at the end of embolization.
One of the possible options to obtain more accurate arterial occlusion and tumor devascularization is the use of calibrated particles. In our clinical practice, we are currently evaluating the use of calibrated microspheres for uterine fibroid embolization. It is a new application of a well-known embolic agent that is widely used in Europe to perform embolization in the field of neuroradiology (8,9). Other groups are performing the same type of experimental or clinical studies with calibrated microspheres from various manufacturers (10).
Again, we thank Dr Worthington-Kirsch and colleagues for their constructive comments. Collaboration between the groups of physicians who have the most extensive experience with uterine fibroid embolization is the key to success in defining guidelines and improving the procedure.
REFERENCES
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