Uterine fibroids reduce the sensitivity of ultrasound to detect endometrioid and serous endometrial cancer: a retrospective cohort study.

BACKGROUND

Transvaginal ultrasound (TVUS) is a guideline-approved stand-alone method to assess the risk of endometrial cancer (EC) for an episode of postmenopausal bleeding (PMB). However, the studies informing this guideline did not assess non-endometrioid histology which have a lower prevalence of abnormally thickened endometrium (EM), or account for uterine fibroids which may disproportionately obscure non-endometrioid histology. This study aims to assess whether fibroids reduce the sensitivity of TVUS for endometrioid and serous EC.

METHODS

This study is a retrospective cohort of pathology-confirmed endometrioid and serous EC of diagnosed between January 2012 and October 2022 at Montefiore Medical Center, an urban academic hospital system. Univariate analysis was completed with Fisher's exact tests for categorical data and Student's t-test for continuous variables. Multivariate logistic regression was used to model dichotomous outcomes.

RESULTS

Of 330 people who met eligibility criteria, 41% of the cohort had serous histology, and 25% had stage III-IV cancer. Large fibroid burden was present in 52% of serous EC vs. 29% of endometrioid EC, and in 55% of Black people vs. 26% of White people. Those with larger fibroid burden had EM visualized 15.9% less (73.8% vs. 89.7%, P<0.001), identification of thickened EM 3.6% less (87.5% vs. 91.1%, P=0.40). They had identification of any TVUS feature suspicious for malignancy 10.9% less (86.1% vs. 97.0%, P<0.001), and identification of focal TVUS features suspicious for malignancy 14.6% less (48.1% vs. 62.7%, P=0.01). Non-visualized EM (16.2% of TVUSs) was associated with total fibroid diameter >5 centimeters [adjusted odds ratio (aOR) 0.99, 95% confidence interval (CI): 0.36-1.61, P=0.002] and inversely associated with body mass index (BMI) ≥35 kg/m2 (aOR -1.15, 95% CI: -2.06 to -0.25, P=0.01). Larger fibroid burden reduced the sensitivity of TVUS to detect any feature suspicious for malignancy 3.2% more for serous than endometrioid histology (P=0.02).

CONCLUSIONS

Uterine fibroid burden is associated with lower sensitivity of TVUS to detect features of EC, especially for serous than endometrioid histology. This highlights an important limitation to guidelines for the evaluation of PMB.