Association between adipose tissue thickness and fibroid shrinkage using ultrasound-guided-high-intensity focused ultrasound

Abstract

Background: Ultrasound-guided high frequency focused ultrasound (USgHIFU) is used to treat uterine fibroids that are symptomatic in a non-invasive way. A high frequency focused ultrasound beam (HIFU) can heat tissue within a fibroid to 65 - 85 degrees celsius where the cells within it denature. The treated fibroid decreases in size over the next 24 months (median follow up period 33.9 months, range 6 - 54 months). A greater thickness of adipose tissue that the HIFU beam travels through is thought to be associated with a decreased treatment effect, although the evidence for this is anecdotal. Objectives: This study aims to determine whether the thickness of adipose tissue that the HIFU beam travels through affects the percentage volume shrinkage of the uterine fibroid after treatment. Method: A retrospective study was performed at Chris Hani Baragwanath Academic Hospital (CHBAH) of patients who were treated with USgHIFU for symptomatic uterine fibroids between 11 October 2015 and 11 April 2018. Pre- and post-treatment MRI images were used to measure the adipose thickness that the HIFU beam traveled through, as well as the percentage volume shrinkage that the uterine fibroid underwent. Linear regression was used to determine whether there is an association between adipose thickness and the percentage volume shrinkage of the uterine fibroid after treatment. Results: The data of 71 female patients who attended the CHBAH HIFU clinic during a 30 month period were analysed. Mean adipose thickness was 17,49mm (95% CI 14,86-19,73). Mean pre-treatment volume of the fibroid was 176ml (95% CI 123,26-208,57). Mean post-treatment volume of the fibroid was 109ml (95% CI 71,75-141,73). Mean fibroid volume reduction was 44.68% (p < 0,0001). The analysis indicated that the relationship between adipose thickness and change in volume ratio is not significant. Conclusion: In our experience, the adipose thickness does not affect treatment outcome when symptomatic uterine fibroids are ablated using USgHIFU. This is of clinical value as women with an adipose tissue thickness of greater than 6cm are excluded from treatment at CHBAH. The study suggests that the exclusion criteria for USgHIFU treatment of uterine fibroids be reviewed