Growth of uterine leiomyomata among premenopausal black and white women

Abstract

Uterine leiomyomata (fibroids) are the leading cause of hysterectomy in the United States. Black women have a greater fibroid burden than whites, yet no study has systematically evaluated the growth of fibroids in blacks and whites. We prospectively tracked growth for 262 fibroids (size range: 1-13 cm in diameter) from 72 premenopausal participants (38 blacks and 34 whites). Fibroid volume was measured by computerized analysis of up to four MRI scans over 12 months. We used mixed effects models to identify factors that are associated with growth, and results were converted to percent change per 6 months for clinical relevance. The median growth rate was 9% (range: -89% to +138%). Seven percent of fibroids regressed (>20% shrinkage). Tumors from the same woman grew at different rates (within-woman component of variation was twice the component among women; both were significant, P < 0.001). Black and white women less than 35 years of age had similar fibroid growth rates. However, growth rates declined with age for whites but not for blacks (P = 0.05). The odds of a tumor growing more than 20% in 6 months also decreased with age for whites but not for blacks (P < 0.01). Growth rates were not influenced by tumor size, location, body mass index, or parity. We conclude that (i) spontaneous regression of fibroids occurs; (ii) fibroids from the same woman grow at different rates, despite a uniform hormonal milieu; (iii) fibroid size does not predict growth rate; and (iv) age-related differences in fibroid growth between blacks and whites may contribute to the higher symptom burden for black women.

Fig. 1.

Frequency distribution of growth rates for 262 fibroids from 72 premenopausal women, Fibroid Growth Study, enrollment 2001–2004.

Fig. 2.

Median (black circles) and range (vertical bars) of fibroid growth rates for each of 72 participants, ordered by each participant's median tumor growth rate. The horizontal hatch marks show the growth rate for each individual tumor, Fibroid Growth Study, enrollment 2001–2004.

Fig. 3.

Unadjusted mean fibroid growth rates by participant characteristics and fibroid characteristics, 258 fibroids (4 statistical outliers excluded) from 72 participants, Fibroid Growth Study, enrollment 2001–2004.