Brigham and Women's Hospital researchers in Boston have shown that MR-guided focused ultrasound surgery reduces the painful symptoms of uterine leiomyomas for at least a year after treatment. Better technique and growing experience with the minimally invasive procedure have improved its effectiveness and safety while helping physicians with patient selection.
Dr. Fiona M. Fennessy and colleagues reported in the June issue of Radiology that the good results from their original focused ultrasound protocol got even better after they expanded the amount of lesion exposed to focused ultrasound ablation. The improvement reflected ongoing efforts by Brigham radiologists, in cooperation with the U.S. Food and Drug Administration to increase the allowable amount of tissue and the number of treatments that may be performed on individual patients, said second author Dr. Clare Tempany, a professor of radiology at Harvard University.
The changed protocol allows interventionalists to treat 50% of the fibroid volume and 150 cm3 per fibroid; the old protocol allowed 33% and 100 cm3 per fibroid. The FDA also increased treatment time to 180 minutes, up from 120 minutes, and allowed a second treatment within 14 days.
A year after treatment, 72% of patients in the original protocol group and 91% in the modified group reported significant improvement. The percentage of patients who reported no problems increased from 13% for those undergoing the original approach to 25% for patients in the modified treatment group.
Additional results, based on a retrospective analysis of a subset of 66 patients with 71 fibroids, were announced at the 2007 meeting of the International Society for Magnetic Resonance in Medicine and the European Society for Magnetic Resonance in Medicine and Biology in Berlin. Dr. Zsuzsanna Maria Lenard, formerly a research fellow at Brigham and now a radiologist at Semmelweis University in Budapest, reported that the presentation of uterine leiomyomas on T2-weighted MRI reveals the potential for successful treatment with MRI-guided focused ultrasound.
Lenard found that both signal intensity and the extent of the nonenhancing volume produced by sonification influenced fibroid volume reduction measured at 12 months post-treatment. According to her observations, the minimal nonenhancing volume needed to produce a high rate of fibroid shrinkage at one year post-treatment appeared to be about 20%. Twenty-two of 23 fibroids with nonenhancing volume of at least 20% after sonication had decreased in size when measured a year later. Mean volume reduction was 21%, with a range of 2% to 53%. However, the mean loss of volume was only 5% for fibroids with nonenhancing volumes of less than 20%.
Lenard's other finding suggests that predicting the likelihood of success for an MR-guided focused ultrasound procedure may be as simple as determining whether fibroids appear black or white on T2-weighted imaging. The mean nonenhancing volume of dark fibroids after ablation was 19.9 cm3 compared with 13.6 cm3 for bright fibroid. The difference suggested that fibroids that have a bright T2 presentation require much more power deposition than lesions that have a dark T2 presentation to achieve equivalent thermal ablation. These latest results may help to establish a guideline for selecting appropriate uterine leiomyoma patients for surgical treatment with MR-guided focused-ultrasound.
