Purpose: DNA repair genes are potential biomarkers for chemotherapy in muscle-invasive bladder cancer (MIBC). O6-methylguanine methyltransferase (MGMT) is involved in DNA repair and is found to affect the efficacy of platinum-based chemotherapy. However, the prognostic or predictive value of MGMT expression in chemotherapy for MIBC is unknown.
Materials and methods: Immunohistochemical staining for MGMT was performed in paraffin-embedded tumor tissue of high-grade MIBC patients who underwent cystectomy in two independent cohorts [n = 74 for Fudan University Shanghai Cancer Center (FUSCC) cohort and n = 115 for Zhongshan Hospital (ZS) cohort]. MGMT messenger RNA (mRNA) analysis was conducted using patients' clinical and fragments per kilobase of exon model per million mapped fragments mRNA data from The Cancer Genome Atlas (TCGA) database (n = 245).
Results: In our cohorts, high MGMT expression was significantly correlated with shorter overall survival (OS) in patients with platinum-based adjuvant chemotherapy [hazard ratio (HR) 2.386, p = 0.048; HR 2.920, p = 0.007; HR 2.324, p = 0.004, respectively, in FUSCC, ZS, and combination sets], but not in patients without chemotherapy. These findings were corroborated by the TCGA set (HR 1.952 and 0.697 for patients with and without chemotherapy, respectively). The chemotherapy-MGMT interaction for OS was significant in both the surgery set (p = 0.045) and TCGA set (p = 0.034).
Conclusions: We demonstrated that high MGMT expression is an independent poor prognostic factor in MIBC patients with platinum-based adjuvant chemotherapy, but not in patients without chemotherapy. MGMT expression may be a potential predictor for administration of adjuvant chemotherapy.