Long-term treatment of residual or recurrent low-grade endometrial stromal sarcoma with aromatase inhibitors: A report of two cases and a review of the literature.

Endometrial stromal sarcoma (ESS) occurs rarely and accounts for only 0.2% of all uterine malignancies. ESS usually expresses estrogen and progesterone receptors, and is regarded as hormone-sensitive. Due to the rarity of these tumors, there are only few case series on the use of aromatase inhibitors in the treatment of low-grade ESS. The present study reports the cases of two patients with residual or recurrent low-grade ESS who experienced long-term disease-free survival following treatment with letrozole. The study also reviews the literature with regard to the data on aromatase inhibitors used in patients with low-grade ESS. In total, 30 patients with recurrent or residual low-grade ESS who were treated with aromatase inhibitors were identified, including the present cases. Among the 30 patients, the overall response rate of advanced low-grade ESS to aromatase inhibitors was 77.4% (complete response, 25.8%; partial response, 51.6%) and the disease control rate was 90.3%. The response rate of first-line treatment was similar to that of second-line therapy or higher (84.6 vs. 72.2%; P=0.453). Duration of aromatase inhibitor treatment ranged from 1.5 to 168 months (median, 26.5 months). The aromatase inhibitors showed minimal adverse effects. In conclusion, aromatase inhibitors, particularly third-generation drugs, are a well-tolerated class of medications that are effective in the treatment of advanced low-grade ESS, with a favorable toxicity profile.