Background
The usefulness of long-term, low-dose gonadotropin-releasing hormone agonist (GnRHa; buserelin acetate) therapy, so-called draw-back therapy, for the treatment of adenomyosis was investigated not.
Material and Method
A retrospective observational study was conducted covering the period between January 2003 and March 2008. The subjects consisted of 12 patients with adenomyosis who underwent draw-back therapy for 2 years and had previously received GnRHa. GnRHa was initiated at 900 microg/day (6 nasal sprays/day). When the CA-125 level normalized, the GnRHa dosage was adjusted to 150-750 microg/day to achieve a plasma estradiol (E2) concentration of 20-50 pg/ml (i.e., the therapeutic window). Pain during withdrawal bleeding and chronic pelvic pain were assessed using a visual analogue scale. In addition, bone mineral density (BMD) of the lumbar vertebrae was measured using dual-energy X-ray absorptiometry.
Results
The mean GnRHa dose during draw-back therapy was 435 microg/day (2.9 nasal sprays/day). The mean E2 level during draw-back therapy was 36.3+/-14.3 pg/ml. The intensity of chronic pelvic pain was significantly lower during draw-back therapy than before draw-back therapy, and was nearly eliminated in many patients (4.8+/-1.2 vs. 0.6+/-0.7, respectively [p=0.000]). Compared to the severity of vasomotor symptoms during previous regular GnRHa therapy, the severity of vasomotor symptoms during draw-back therapy was significantly lower (3.8+/-0.7 vs 1.1+/-0.7, respectively [p=0.000]). The decrease in BMD during a 6-month course of treatment was 0.96+/-0.9%.
Conclusions
GnRHa draw-back therapy allowed maintenance of plasma E2 levels within the therapeutic window. GnRHa can thus be administered for long periods of time while maintaining therapeutic effects on adenomyosis and suppressing adverse events.

Keywords: Lumbar Vertebrae - chemistry, Gonadotropin-Releasing Hormone - agonists, Endometriosis - drug therapy, Estrogens - blood, Dose-Response Relationship, Drug, CA-125 Antigen - blood, Buserelin - therapeutic use, Bone Density, Analysis of Variance, Absorptiometry, Photon