Expression of estrogen receptor beta (ERβ) and its prognostic value in pleural mesothelioma

Background: Overexpression of estrogen receptors in malignant pleural mesothelioma has shown an independent relation with a better prognosis of survival, and the use of selective estrogen receptor beta (ER beta) agonists increases the susceptibility to antitumor treatment. Methods: This was a retrospective single center study that analyzed the response of malignant pleural mesothelioma with an expression of ER beta to first-line chemotherapy. The study included patients with pleural mesothelioma pathologically confirmed between 2013 and 2016 at the National Institute for Respiratory Disease (INER), who underwent an immunohistochemistry assay for ER beta (mouse monoclonal antibody PPG5/10). The primary endpoint was the response to chemotherapy based on RECIST 1.1 according to the ER beta expression; secondary outcomes were the overall survival (OS) and progression-free survival (PFS). Results: We included 22 patients, regarding the expression of ER beta, 17 (77.2%) patients had high or moderate degree, while 5 (22.7%) had low degree or null expression. The response to treatment as by RECIST 1.1, 12 (54.5%) had partial response, 5 (22.7%) had stable disease, and 3 (13.6%) had progression. None of the patients had a complete response. Of those who had a partial response, 9 (75%) had a high or moderate degree of ER beta expression in tumor cells, and 3 (25%) had a low or null degree of expression. Conclusions: High and moderate expression of ER beta group with advanced clinical stage malignant pleural mesothelioma was associated with a tendency of higher OS and better response to chemotherapy treatment resulting in longer PFS although statistical significance was not achieved.