Oestrogen receptors are prognostic factors in malignant peritoneal mesothelioma

Malignant peritoneal mesothelioma (MPM) is a rare and fatal cancer. Females are found to survive longer than males after treatment, suggesting a possible involvement of hormonal factors. Estradiol is involved in cellular proliferation of a number of cancers and acts mainly through oestrogen receptors (ERs). Hence, we examined the expression of oestrogen receptors with correlation to prognosis. Oestrogen receptors expression was examined using immunohistochemistry on 42 paraffin-embedded sections of MPM tumours. Kaplan-Meier survival curves were analysed to determine the significance of ER expression in relation to prognosis. ER-beta (nuclear) was detected in 33 (79 %) patients. ER-beta was also detected in the cellular cytoplasm of 9 (21 %) patients. Presence of ER-beta (nuclear) was associated with favourable survival (univariate analysis, P = 0.001), whereas the presence of ER-beta (cytoplasm) was associated with a poor survival (P = 0.014). Multivariate Cox regression analysis revealed the absence of ER-beta (nuclear) and the presence of ER-beta (cytoplasm) to be independent predictive factors for poor disease outcome (hazard ratio 5.4, 95 % confidence interval 1.86-15.75; P = 0.002 and hazard ratio 8.0, 95 % confidence interval 1.8-34; P = 0.005), respectively. ER-alpha (nuclear) was detected in only 4 (9 %) of patients and not statistically significant (univariate analysis, P = 0.066). The presence of ER-beta (cytoplasm) is associated with poor prognosis. The favourable survival association observed in patients with ER-beta (nuclear) raises a question about the molecular mechanisms of the tumorigenic roles of ER-beta in each cellular compartment and requires further studies.