FDA panel clears microwave ablation device: menorrhagia treatment.
The unanimous decision by the nine voting members of the Food and Drug Administration's Obstetrics and Gynecology Devices Panel hinged largely on steps already taken by Microsulis, the Hampshire, England-based manufacturer of the device, to virtually eliminate the risk of transmural burns that occurred with commercial use of the device outside the United States. Such injuries involved uterine perforations and bowel wall damage, which in some cases required bowel resection.
The FDA usually follows the recommendations of its advisory panels.
If the device, known as the Microsulis Microwave Endometrial Ablation (MEA) system, is approved, women will most likely require an ultrasound before the procedure to determine the minimum thickness of their myometrium. Hysteroscopy after cervical dilation and before insertion of the applicator may also be required.
Physicians who want to use the device would be required to undergo training with an experienced doctor and to have experience in diagnostic hysteroscopy.
MEA is intended only for women who have completed childbearing.
The panel's decision was based on findings from a multicenter, U.S.-based, randomized controlled study of 324 patients showing no significant difference in successful treatment outcomes between MEA and rollerball endometrial ablation (REA). A successful outcome in this study was defined as a reduction in monthly bleeding, according to the pictorial blood loss assessment chart, from a score of at least 185 to a score of 75 or less at 12 months.
Among the 322 patients included in the intent-to-treat analysis, 87% of MEA patients and 83% of REA patients achieved successful outcomes, said Dr. Julia Corrado of the obstetrics/gynecology devices branch of the FDA's Office of Device Evaluation.
Posttreatment amenorrhea rates were 55% and 46% in the MEA and REA groups, respectively, said Dr. Corrado, who presented the results of the FDA's independent review of the study.
Success rates among patients without fibroids were even higher: 91% of MEA patients and 86% of REA patients were successfully treated. Those women with fibroids achieved success rates of 68% in the MEA group, compared with 77% in the REA group.
Women with small submucosal fibroids (3 cm) were included in the trial; there were no exclusion criteria based on the presence or size of subserosal and intramural fibroids.
Treatment outcomes were not stratified by fibroid type, said Dr. Ted Anderson of the Women's Hospital at Centennial, Nashville, Tenn., a coinvestigator in the trial. Dr. Anderson also cochaired the Microsulis clinical advisory panel that conducted follow-up investigations of the device's safety but has no financial interest in it.
In general, only about 25% of women who are symptomatic for menorrhagia have submucosal fibroids.
"And in these cases, I would estimate most fibroids in this group (about 75%) are smaller than 3 cm. This is why the approval of MEA represents a significant advance," Dr. Jay Cooper, a coinvestigator in the U.S trial, said in an interview. Dr. Cooper of the University of Arizona, Phoenix, also has no financial interest in the device.
Endometritis occurred in five MEA patients and one REA patient. One postablation pregnancy occurred in the REA group.
One patient in each group required a hysterectomy because of pain and a left adnexal mass in the MEA group and dissatisfaction with the outcome in the REA group.
Despite a greater use of anesthesia in the REA group, nausea was more common in the MEA group (22% vs. 17%), as were vomiting (13% vs. 4%) and uterine cramping (72% vs. 59%).
There were no unanticipated serious adverse events in the U.S. trial. However, out of more than 15,000 procedures that were performed after the device was released commercially in the United Kingdom, Canada, and Australia, 27 cases of uterine perforation and/or transmural thermal injury to the bowel occurred. In 24 of these cases, bowel resections were required.
The speculated causes of the uterine injuries, according to an FDA investigation, include ignored discrepancies between uterine cavity length estimates by uterine sounding and the depth of the device's penetration, pre-MEA mechanical preparation such as curettage leading to uterine wall thinning, preexisting abnormalities that would have been found on hysteroscopy had such screening been universally performed, ignored abnormalities found on hysteroscopy; failure to perform ultrasound as indicated by the patient's history, and a failure to heed protocol warnings against the reinsertion of the applicator for repeat treatment, Dr. Corrado said.
Most perplexing to the FDA reviewers was the occurrence of transmural thermal injuries to the bowel in the absence of uterine perforation.
Possible causes that explain some of the injuries include the creation of a false passage during uterine sounding or cervical dilation that misguided the applicator during insertion, uterine wall thinning from prior endometrial ablation, mechanical instrumentation, C-section, and prolonged use of Depo-Provera (medroxy-progesterone) leading to uterine wall thinning, and failure to follow instructions for use.
Overall, all but one of the injuries could have been avoided if the patient had been appropriately imaged before undergoing the procedure.
Proof of that fact is the absence of a single serious adverse event among the 3,600 patients treated since November 2002, when the company instituted a preceptor-training program for new users and modified instructions for use, Dr. Anderson said.
The fact that there have been no significant injuries since then "speaks highly of the device" and the steps the company has taken to correct user-related problems, said panelist Dr. Andrew I. Brill of the University of Illinois at Chicago.
Microwave Endometrial Ablation
After uterine assessment and cervical dilation, the physician positions the applicator midline in the fundus, then moves the applicator in a continuous lateral motion across the fundus, cornua, and corpus. Treatment lasts about 3-5 minutes for an average-size uterus.
Equipment used in the procedure
The reusable applicator is connected to the device by two cables, and a foot pedal is depressed to deliver the microwave energy. Treatment occurs at 70[degrees]-80[degrees] C. Beyond 85[degrees] C, an audible alarm is triggered; above 90[degrees] C the microwave power is cut off.
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|Title Annotation:||Clinical Rounds|
|Publication:||Internal Medicine News|
|Date:||Jul 15, 2003|
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