- Despite being FDA-approved for more than 20 years, adoption of focused ultrasound to treat uterine fibroids has been slow.
- Researchers examined long-term clinical outcomes and established a new metric for predicting treatment success.
- A novel variable based on total fibroid load turned out to be a key parameter.
Although FDA-approved more than 20 years ago in the United States, adoption of MRI-guided focused ultrasound (MRgFUS) to ablate uterine fibroids has been hampered by questions around treatment durability. Using data from a multicenter clinical trial that was completed in 2017, researchers from Stanford University, Mayo Clinic, the University of California, Los Angeles, the University of Virginia, Duke University, Brigham and Women’s Hospital, Ohio Health, and the University of California, San Francisco, examined long-term clinical outcomes and established a new metric for predicting treatment success when using focused ultrasound to treat uterine fibroids.
Out of 99 women aged 43.7 ± 5.7 years with symptomatic uterine fibroids treated with MRgFUS, 75 patients completed the uterine fibroid quality of life survey (UFS-QOL), which produces a symptom severity score (SSS), at baseline and at the 1- and 2-year time follow up time points. The uterine fibroids were considered to be symptomatic if the UFS-QOL SSS was equal to or greater than 40 out of 100. The researchers defined durable clinical success as a 30-point-or-more decline in SSS from baseline to follow up.
To determine which factors might best determine clinical success, the group evaluated:
- Patient demographics
- Fibroid characteristics (location and MRI signal intensity)
- Intervening subcutaneous fat thickness
- Distance from skin to the posterior margin of the fibroid
- Energy per sonication
- Total energy delivered per treatment
- Maximum temperature achieved
- A novel variable: the ratio of nonperfused volume to total fibroid load (NPV/TFL), to measure what percent of the total fibroid burden in the uterus was treated by MRgFUS
MRgFUS proved to be a durable and effective noninvasive treatment for uterine fibroids by providing significant relief from abnormal bleeding and bulk symptoms. Interestingly, the novel variable, NPV/TFL, turned out to be a key parameter for predicting durable clinical success.
The team also learned that (1) most of the participants responded to treatment at six months, one year, and continued to be responders at two years; (2) participants with T2 isointense fibroids responded well; and (3) the total volume of fibroids, not just the largest or most symptomatic one, should be factored in to predict durable success. For the best, longest lasting symptom relief, consideration of ablating a large portion of the total amount of fibroids is warranted.
“The NPV/TFL ratio robustly predicted treatment efficacy and correlated with SSS,” said Rachelle Bitton, PhD, clinical assistant professor of radiology at Stanford University School of Medicine and the study’s lead author. “We found that the higher the NPV/TFL ratio (especially greater than 80%), the greater the improvement in symptom relief.”
The study suggests that for durable response, patient selection should include the ability to target a large proportion of the total fibroid volume, not just the largest or most symptomatic fibroid. Future research studies could also incorporate NPV/TFL as a metric of efficacy.
“It is important to improve patient selection criteria and increase the efficacy of using focused ultrasound for uterine fibroids,” said Suzanne LeBlang, MD, the Foundation’s director of clinical relationships. “These important advancements could also lead to the creation of more affordable and faster devices that could help so many women that suffer from fibroids and offers an incisionless treatment option compared to surgery and other more invasive procedures.”