192PPROGNOSTIC BIOMARKERS IN MALIGNANT PLEURAL MESOTHELIOMA

ABSTRACT Aim: The standard of care for malignant pleural mesothelioma (MPM) includes combination of platinum compounds and pemetrexed. Despite this, the median survival of MPM patients is still bad (12 months). Excision Repair Cross Complementing Group 1 (ERCC1) acts removing DNA adducts formed by platinum compounds, whereas Pemetrexed inhibits Thymidylate Synthase (TS), a folic enzyme also involved in ex novo synthesis of DNA. This study aims to analyse retrospectively, in a large series of MPM specimens, the ERCC1 and TS gene and protein expression to investigate their prognostic and predictive role. Methods: Pleural biopsies were collected from140 consecutive MPM patients (98 males and 42 females, mean age 68 years, range 27-90). Histologic subtypes were: epithelioid (#103, 73%), sarcomatoid (#19, 14%) and biphasic (#18, 13%). At the end of the study 113 patients were died (average disease specific survival (DSS) 13 months; range 1-60); mRNA was extracted from formalin fixed paraffin embedded blocks and reverse transcribed in cDNA to perform gene expression assay by qRT-PCR. Immunohistochemistry was performed by anti-ERCC1 and anti-TS mAbs and the results were scored from 0 to 3 depending on the percentage of positive tumour cells and staining intensity. The results were statistically correlated with the clinical features and with the DSS of the patients respectively by Fisher's exact test and Logrank test. Results: Of 140 patients 102 received platinum and pemetrexed (in single or in combination), the remaining were untreated due to bad performance status, advanced age or refusing therapy. Statistically significant correlation was found between the lack of protein expression of ERCC1 and DSS in the whole cohort (P = .03). Low levels of TS mRNA were significantly correlated with the DSS in the whole cohort (P = .01) and in the untreated subgroup (including patients not receiving pemetrexed) (P = .04), whereas did not in the subgroup of pemetrexed treated patients Conclusions: ERCC1 protein expression, scored by IHC, and TS gene expression, evaluated by mRNA analysis, seem both important prognostic markers; we suggest their evaluation in routine biopsies from patients with MPM. Disclosure: All authors have declared no conflicts of interest.