High signal intensity on T1-weighted magnetic resonance images (MRI) and low diffusion coefficient values can accurately differentiate uterine leiomyosarcoma from benign leiomyoma, according to a meta-analysis in the Journal of the Belgium Society of Radiology.
However, although leiomyosarcoma had a higher pooled sensitivity for T2-weighted increased signal intensity compared to benign leiomyoma, the difference was not statistical significance.1
“Despite current advances in imaging, there remains a lack of consensus regarding which MRI features are useful for differentiating leiomyosarcoma from benign leiomyoma,” wrote the authors.
The purpose of the analysis was to compare the diagnostic performance of increased signal intensity on T1- and T2-weighted magnetic resonance images and apparent diffusion coefficient (ADC) values in differentiating the two types of tumors.
Diffusion-weighted imaging, which is based on the diffusion motion of water molecules, is widely employed to distinguish between malignant and benign tumors by measuring the ADC value. In essence, a low ADC value correlates with malignant lesions because their higher cellularity and total nuclear area restrict water diffusion.
The analysis consisted of eight studies with 795 patients by searching PubMed/Medline, the Cochrane Library, Embase and Web of Science for all available literature published in English through December 2019.
For leiomyosarcoma (60 patients), increased signal on T1-weighted imaging had a pooled sensitivity of 56.8% (95% confidence interval [CI]: 20% to 87.4%), which was significantly higher than 7.6% (95% CI: 2.2% to 22.7%) for benign leiomyoma (1,272 patients) (P = 0.0094).
However, increased signal analysis on T2-weighted imaging had pooled sensitivities of 93.2% and 93.2% (95% CI: 45.7% to 99.6% and 42.9% to 99.6%) for leiomyosarcoma (90 patients), which were not significantly different from the 54.5% and 53.9% (95% CI: 33.6% to 74% and 32% to 74%) for benign leiomyoma (215 patients) (P = 0.102 and 0.112).
Conversely, for ADC, leiomyosarcoma (43 patients) had a weighted mean and standard deviation of 0.896 ± 0.19 10-3 mm2/s and 0.929 ± 0.182 10-3 mm2/s, respectively, which were significantly lower than 1.258 ± 0.303 10-3 mm2/s and 1.304 ± 0.303 10-3 mm2/s, respectively, for benign leiomyoma (159 patients) (P = < 0.0001, < 0.0001).
The findings of the analysis for ADC values agree with most previous studies, according to the authors, which have also concluded that the weighted mean and standard deviation for leiomyosarcoma are significantly lower than for benign leiomyoma.
Overall, “The results of our meta-analysis indicate that increased signal intensity on T1 weighted image and low ADC values can provide accurate differentiation,” wrote the authors.
Nonetheless, three limitations of the analysis are the small number of included studies; combining data from studies without standardized protocols or techniques that may have resulted in bias and yielded outcomes that are challenging to interpret and translate to clinical practice; and sparse data on lesion size, benign leiomyoma type, uterine sarcoma type, interreader variability in MRI reporting and temporal parameters that can impact the diagnostic performance of MRI.
The authors recommend prospective studies with larger cohorts to advance the consensus on the significant MRI features of leiomyosarcoma and benign leiomyoma.