Positron emission tomography imaging of oestrogen receptor-expression in endometrial stromal sarcoma supports oestrogen receptor-targeted therapy: Case report and review of the literature

Although the majority of endometrial stromal sarcomas (ESSs) express oestrogen receptor (ER), data on the efficacy of ER-targeted therapies are scarce. Using PubMed search engine we identified nine case reports and small series in a total of 25 patients reporting on the efficacy of palliative ER-targeted therapies. Literature supports the efficacy of aromatase inhibitors after the failure of progestins, but not of the partial ER-antagonist tamoxifen. Fulvestrant is a pure ER-antagonist with a distinct mechanism, of which efficacy has not yet been reported in ESS. We present a patient that underwent positron emission tomography and computed tomography (PET/CT) of ER-expression with the tracer 18F-fluoroestradiol (FES). High levels of ER-expression provided a rationale for fulvestrant therapy. FES-PET/CT was repeated after 6 months and indicated a strong decrease in tumour FES-uptake, and 15% reduction in tumour diameters according to Response Evaluation Criteria in Solid Tumours (RECIST) criteria.