Predicting the effect of gonadotropin-releasing hormone (GnRH) analogue treatment on uterine leiomyomas based on MR imaging

Purpose. To test the hypothesis that the simple assessment of signal intens ity on T2-weighted MR images is predictive of the effect of hormonal treatm ent with gonadotropin-releasing hormone (GnRH) analogue. Material and Methods. The correlation between T2-weighted MR imaging of ute rine leiomyomas and histologic findings was evaluated using 85 leiomyomas f rom 62 females who underwent myomectomy or hysterectomy. We also correlated the pretreatment MR images features obtained in 110 women with 143 leiomyo mas with the effect of GnRH analogue treatment. The size (length < width x depth) of the leiomyoma was evaluated before and at 6 months after treatmen t by ultrasound. Results. The proportion of leiomyoma cell fascicles and that of extracellul ar matrix affected signal intensities of uterine leiomyomas on T2-weighted MR images. The amount of extracellular matrix was predominant in hypointens e leiomyomas on T2-weighted images, while diffuse intermediate signal leiom yomas were predominantly composed of leiomyoma cell fascicles. Marked degen erative changes were noted in leiomyomas with heterogenous hyperintensity. The homogeneously intermediate signal intensity leiomyomas showed significa nt size reduction after treatment (size ratio; posttreatment volume/pretrea tment volume 0.29 +/- 0.11). The size ratio for the hypointense tumors was 0.82 +/- 0.14, and 0.82 +/- 0.18 for the heterogeneously hyperintense tumor s. There was a significant difference in the response to treatment between the homogeneously intermediate signal intensity leiomyomas and the hypointe nse or heterogeneously hyperintense leiomyomas (both p < 0.01). Conclusion: Signal intensity on T2-weighted MR images depends on the amount of leiomyoma cell fascicles and extracellular matrix. Simple assessment of the MR signal intensity is useful in predicting the effect of GnRH analogu e on uterine leiomyomas.