A single baseline ultrasound assessment of fibroid presence and size is strongly predictive of future uterine procedure: 8-year follow-up of randomly sampled premenopausal women aged 35-49 years.

Abstract

How well can a single baseline ultrasound assessment of fibroid burden (presence or absence of fibroids and size of largest, if present) predict future probability of having a major uterine procedure? During an 8-year follow-up period, the risk of having a major uterine procedure was 2% for those without fibroids and increased with fibroid size for those with fibroids, reaching 47% for those with fibroids ≥ 4 cm in diameter at baseline. Uterine fibroids are a leading indication for hysterectomy. However, when fibroids are found, there are few available data to help clinicians advise patients about disease progression. Women who were 35-49 years old were randomly selected from the membership of a large urban health plan; 80% of those determined to be eligible were enrolled and screened with ultrasound for fibroids ≥ 0.5 cm in diameter. African-American and white premenopausal participants who responded to at least one follow-up interview (N = 964, 85% of those eligible) constituted the study cohort. During follow-up (5822 person-years), participants self-reported any major uterine procedure (67% hysterectomies). Life-table analyses and Cox regression (with censoring for menopause) were used to estimate the risk of having a uterine procedure for women with no fibroids, small (<2 cm in diameter), medium (2-3.9 cm), and large fibroids (≥ 4 cm). Differences between African-American and white women, importance of a clinical diagnosis of fibroids prior to study enrollment, and the impact of submucosal fibroids on risk were investigated. There was a greater loss to follow-up for African-Americans than whites (19 versus 11%). For those with follow-up data, 64% had fibroids at baseline, 33% of whom had had a prior diagnosis. Of those with fibroids, 27% had small fibroids (<2 cm in diameter), 46% had medium (largest fibroid 2-3.9 cm in diameter), and 27% had large fibroids (largest ≥ 4 cm in diameter). Twenty-one percent had at least one submucosal fibroid. Major uterine procedures were reported by 115 women during follow-up. The estimated risk of having a procedure in any given year of follow-up for those with fibroids compared with those without fibroids increased markedly with fibroid-size category (from 4-fold, confidence interval (CI) (1.4-11.1) for the small fibroids to 10-fold, CI (4.4-24.8) for the medium fibroids, to 27-fold, CI (11.5-65.2) for the large fibroids). This influence of fibroid size on risk did not differ between African-Americans and whites (P-value for interaction = 0.88). Once fibroid size at enrollment was accounted for, having a prior diagnosis at the time of ultrasound screening was not predictive of having a procedure. Exclusion of women with a submucosal fibroid had little influence on the results. The 8-year risk of a procedure based on lifetable analyses was 2% for women with no fibroids, 8, 23, and 47%, respectively, for women who had small, medium or large fibroids at enrollment. Given the strong association of fibroid size with subsequent risk of a procedure, these findings are unlikely to be due to chance. Despite a large sample size, the number of women having procedures during follow-up was relatively small. Thus, covariates such as BMI, which were not important in our analyses, may have associations that were too small to detect with our sample size. Another limitation is that the medical procedures were self-reported. However, we attempted to retrieve medical records when participants agreed, and 77% of the total procedures reported were verified. Our findings are likely to be generalizable to other African-American and white premenopausal women in their late 30s and 40s, but other ethnic groups have not been studied. Though further studies are needed to confirm and extend the results, our findings provide an initial estimate of disease progression that will be helpful to clinicians and their patients.