A Gene Signature for Selecting Benefit from Hypoxia Modification of Radiotherapy for High Risk Bladder Cancer Patients

Purpose: Hypoxia modification improves overall survival in muscle invasive bladder cancer patients who undergo radiotherapy. There is evidence that hypoxic tumors benefit most from hypoxia modification. The study aimed to identify or derive a hypoxia gene signature that predicts benefit from hypoxia-modifying treatment in bladder cancer.<br /><br />Experimental Design: Published hypoxia signatures were tested and a new one derived by analyzing bladder cancer transcriptomic data from public databases. Tumor samples were available from the BCON phase III randomized trial of radiotherapy alone or with carbogen and nicotinamide (CON). Gene expression data were generated for 151 tumors using Affymetrix Human 1.0 Exon ST arrays and used for independent validation. <br /><br />Results: A 24-gene signature was derived, which was prognostic in four out of six independent surgical cohorts (n=679, meta HR 2·32, 95% CI 1·73-3·12, P<0·0001). The signature was also prognostic in BCON patients receiving radiotherapy alone (n=75, HR for local relapse free survival 2·37, 95% CI 1·26-4·47, P=0·0076). The signature predicted benefit from CON (n=76, HR 0·47, 95% CI 0·26-0·86, P=0·015). Prognostic (P=0·017) and predictive (P=0·058) significance remained after adjusting for clinicopathological variables. A test for interaction between hypoxia status and treatment arms was significant (P=0·0094).<br /><br />Conclusions: A 24-gene hypoxia signature has strong and independent prognostic and predictive value for muscle invasive bladder cancer patients.  The signature can aid identification of patients likely to benefit from the addition of carbogen and nicotinamide to radiotherapy.

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