ERCC1 and Thymidylate Synthase as Prognostic Biomarkers in Malignant Mesothelioma

The standard of care for malignant pleural mesothelioma (MPM) is a combination of platinum compounds and Pemetrexed. Still, the median survival of MPM patients is low (about 12 months). Excision Repair Cross Complementing Group 1 (ERCC1) acts by removing DNA adducts formed by platinum compounds, whereas Pemetrexed inhibits Thymidylate Synthase (TS), which is involved in DNA synthesis. Pleural biopsies were collected from 140 MPM patients (98 males and 42 females, mean age 68 years) before treatment initiation. Average disease specific survival was 13 months (range 1‐60). mRNA was extracted from formalin fixed paraffin blocks, reverse transcribed and assayed by qRT‐PCR. Immunohistochemistry with anti‐ERCC1 and anti‐TS mAbs was scored semi‐quantitatively. Of 140 patients, 102 were treated, the remaining were not because of bad performance status or advanced age. Patients with low ERCC1 protein expression survived longer (24.3 vs 12.5 months, P=.03). Likewise, patients with low levels of TS mRNA had better survival (P=.01); there was no advantage, however, in the treated sub‐group, suggesting that Pemetrexed treatment and low TS expression had no additive value. ERCC1 protein expression and TS gene expression both seem important prognostic markers; we suggest their evaluation in routine biopsies from MPM patients.