Photodynamic endometrial ablation in the nonhuman primate

OBJECTIVE: To test the effectiveness of 5-aminolevulinic acid (ALA)-induced photodynamic endometrial ablation ill the rhesus monkey under varying cond itions of light delivery (fractionated versus continuous) and steroid primi ng. METHODS: Photodynamic endometrial ablation was carried out iii 17 rhesus mo nkeys that were either postmenopausal or in the early proliferative phase. Four hours after intralumenal injection of ALA (250 mg in 1 mL hyskon), a q uartz fiber with a diffusing tip was inserted. A KTP tunable dye laser deli vered 300 mW of light (635 nm) for 60 minutes in either continuous or fract ionated fashion (20 minutes on, 5 minutes off, and 40 minutes on). In some experiments, thermistors were used to monitor. temperature iii the lumen an d myometrium during light treatment. Hysterectomy uns performed 3 or 4 days after treatment, and endometrial damage was assessed histologically. Two a dditional monkeys (one rhesus and one cynomolgus monkey) were exposed to th e same protocol, except hyskon was substituted for ALA to control for poten tial ablative effects due to light treatment alone. RESULTS: Endometrial ablation was evident in all ALA-photosensitized specim ens. The degree of ablation around the light fiber ranged from moderate to complete. The depth of ablation ranged from 1.14 +/- 0.54 to 2.15 +/- 1.62 mm (mean +/- standard deviation). Ablation was most complete in uteri of me nopausal monkeys. Light treatment after. ALA increased lumenal temperature from 36C to 50C, whereas temperature was not significantly increased by lig ht treatment in the controls. CONCLUSION: This is the first report of endometrial destruction in the prim ate using a photodynamic approach. Whereas clinical application of photodyn amic therapy (PDT) requires complete endometrial ablation to produce long-l asting amenorrhea, our results suggest that PDT may offer a simple office-b ased approach to endometrial ablation. Copyright (C) 2000 by the Society fo r Gynecologic Investigation.