Long-Term Outcome of Aromatase Inhibitor Therapy With Letrozole in Patients With Advanced Low-Grade Endometrial Stromal Sarcoma.

Background: There has been no consensus on the indications for the treatment of ad-vanced low-grade endometrial stromal sarcoma (LGESS), and the possible effects of hor-monal treatmentincludingprogestins andaromatase inhibitors havebeen reported.The aimofthis studywas toinvestigatetheefficacyofaromatase inhibitor therapywith letrozole forpatients with residual or recurrent LGESS.Methods: We retrospectively reviewed the clinical response of patients with advancedLGESS who had been treated with letrozole. We also analyzed the adverse effects after theadministration of letrozole. The expression levels of estrogen receptor and aromatase in thetumors were immunohistochemically examined.Results: In 5 patients who had been treated for unresectable LGESS lesions after initial orrepeat surgical procedures, residuallesions in 3patients andrecurrence lesions in 2patientswere the indications for hormonal therapy with letrozole. The median duration of letrozoleexposure at retrospective analysis was 53 (10 Y96) months. The clinical outcomes were classi-fied as complete response in 2 patients, partial response in 1 patient, and stable disease in 2patients.Myalgias,hotflashes,andarthralgi aswerenotobservedduringthefollow-upperiodinanypatients.ThemedianserumlevelsofestradiolwereG5.0(cutoffvalue,G0.5Y11.8)pg/mL.Themedianage-matchedbonemineraldensitieswere92%(79%Y123%).TheLGESStissuesin all 5 patients were positive for estrogen receptor and aromatase expression.Conclusions: Letrozole as well as progestins could be the first choice of treatment forpatients with recurrent or residual LGESS, which is difficult to resect surgically because ofits efficacy and minimal adverse effects.Key Words: Endometrial stromal sarcoma, Aromatase inhibitor, Letrozole, Estrogenreceptor, Hormonal treatmentReceived May 19, 2015, and in revised form July 12, 2015.Accepted for publication July 15, 2015.(Int J Gynecol Cancer 2015;25: 1645Y1651)