ABSTRACT
Title
Radiogenetics and the outcome of radiation-treated prostate cancer patients
Authors
C. Zanusso1, E. Cecchin1, R. Bortolus2, P. Biason1, E. De Mattia1, S. Boffo1, M.G. Trovò2, and G. Toffoli1
1CRO, Experimental and Clinical Pharmacology, Aviano (Pn), 33081, Italy, 2CRO, Radiation Oncology, Aviano (Pn), 33081, Italy
1CRO, Experimental and Clinical Pharmacology, Aviano (Pn), 33081, Italy, 2CRO, Radiation Oncology, Aviano (Pn), 33081, Italy
Abstract
Prostate cancer (CA) is the third most common cause of cancer deaths in men of all ages and is a major health problem worldwide. Radiotherapy is an important weapon in the treatment of prostate cancer, but substantial variability is shown among patients. Although several clinicopathologic indicators, such as prostate-specific antigen level (PSA), Gleason score, pathologic stage, and surgical margin status, are currently used to predict therapy outcome, there is a need to find new biomarkers to improve the prediction of disease recurrence. There is evidence that in addition to patient-related factors, the heterogeneity in response to treatment is attributable to a genetic basis.
The objective of this study is to determine whether an association exists between a set of genetic markers and tumor response to radiotherapy (in term of time to biochemical recurrence, TTR, of the disease). Radiosensitivity can be considered as a complex, polygenic trait, which results from the interaction of a number of genes in different cellular pathways. A pathway-based approach was adopted selecting genetic variants impacting DNA repair, phase I and II metabolism, apoptosis, angiogenesis, and cellular transport pathways. 917 prostate cancer patients treated with radiation therapy (adjuvant: dose 6000-7000 Gy, cycles 30-35; or radical: dose 7000-8000 Gy, cycles 35-40) in association or not with surgery (radical prostatectomy or lymphadenectomy) and/or hormone therapy were enrolled at the National Cancer Institute of Aviano (CRO), 809 of them resulted eligible for TTR evaluation. TTR was calculated as the period between the first PSA analysis (3 months after the end of radiotherapy) and the first PSA biochemical recurrence (at least 2-unit increase) or last contact. We analyzed 53 polymorphisms in 37 genes (XRCC1, XRCC3, hMSH6, PARP1, MGMT, hEXO1, hOGG1, XPD, ERCC1, hMSH2, hMLH1, APE1, RAD51, GSTP1, GSTA1, GSTT1, GSTM1, GSTM3, SOD2, SOD3, CYP3A4, CYP3A5, CYP2B6I, CYP17, ABCC2, ABCB1, TP53, ATM, MDM2, P21, P22, MTHFR, TLR4, VEGF, NOS2, NOS3, IL6). Genomic DNA was extracted from whole blood. After PCR amplification, genetic tests were performed by Pyrosequencing, TaqMan allelic discrimination, and automated fragment analysis technologies. To assess the relative excess risk of recurrence between patients with different genotypes and to control for confounding factors, proportional hazards models (including Gleason, diagnosis PSA, radical surgery, hormone therapy and radiotherapy intent) were fitted. Median TTR were compared among genotypes by the Log-Rank test. Significant associations with the TTR in prostate cancer patients after radiotherapy were found for VEGF-1154G>A (rs1570360) (vascular endothelial growth factor), an important hypoxia-related angiogenesis stimulating factor, and P22phox-Ex4+11C>T (rs4673), a subunit of NAD(P)H oxidase, a major source of production of oxygen free radicals (ROS). The 1154AA genotype of the VEGF-rs1570360 polymorphism was associated with a lower risk (HR=0.35; 95%CI 0.13-0.97; P=0.044) of PSA biochemical recurrence than the wild type genotype. Patients with AA and GA genotypes showed a longer TTR if compared to GG genotype patients (median survival=not reached vs 96 months; P=0.037 by Log-Rank test). Concerning P22phox Ex4+11C>T, the presence of at least one variant allele conferred a lower risk of PSA biochemical recurrence (HR=0.57; 95%CI 0.40-0.81; P=0.002). The median TTR was 105 months for patients with CT or TT genotypes, and it was 96 months for patients with CC genotype (P=0.028 by Log-Rank test). In conclusion, this study allowed the identification of two polymorphisms, VEGF-1154G>A (rs1570360) and P22phox-Ex4+11C>T (rs4673) that may have a substantial impact on PSA recurrence after radiation therapy in prostate cancer.
The objective of this study is to determine whether an association exists between a set of genetic markers and tumor response to radiotherapy (in term of time to biochemical recurrence, TTR, of the disease). Radiosensitivity can be considered as a complex, polygenic trait, which results from the interaction of a number of genes in different cellular pathways. A pathway-based approach was adopted selecting genetic variants impacting DNA repair, phase I and II metabolism, apoptosis, angiogenesis, and cellular transport pathways. 917 prostate cancer patients treated with radiation therapy (adjuvant: dose 6000-7000 Gy, cycles 30-35; or radical: dose 7000-8000 Gy, cycles 35-40) in association or not with surgery (radical prostatectomy or lymphadenectomy) and/or hormone therapy were enrolled at the National Cancer Institute of Aviano (CRO), 809 of them resulted eligible for TTR evaluation. TTR was calculated as the period between the first PSA analysis (3 months after the end of radiotherapy) and the first PSA biochemical recurrence (at least 2-unit increase) or last contact. We analyzed 53 polymorphisms in 37 genes (XRCC1, XRCC3, hMSH6, PARP1, MGMT, hEXO1, hOGG1, XPD, ERCC1, hMSH2, hMLH1, APE1, RAD51, GSTP1, GSTA1, GSTT1, GSTM1, GSTM3, SOD2, SOD3, CYP3A4, CYP3A5, CYP2B6I, CYP17, ABCC2, ABCB1, TP53, ATM, MDM2, P21, P22, MTHFR, TLR4, VEGF, NOS2, NOS3, IL6). Genomic DNA was extracted from whole blood. After PCR amplification, genetic tests were performed by Pyrosequencing, TaqMan allelic discrimination, and automated fragment analysis technologies. To assess the relative excess risk of recurrence between patients with different genotypes and to control for confounding factors, proportional hazards models (including Gleason, diagnosis PSA, radical surgery, hormone therapy and radiotherapy intent) were fitted. Median TTR were compared among genotypes by the Log-Rank test. Significant associations with the TTR in prostate cancer patients after radiotherapy were found for VEGF-1154G>A (rs1570360) (vascular endothelial growth factor), an important hypoxia-related angiogenesis stimulating factor, and P22phox-Ex4+11C>T (rs4673), a subunit of NAD(P)H oxidase, a major source of production of oxygen free radicals (ROS). The 1154AA genotype of the VEGF-rs1570360 polymorphism was associated with a lower risk (HR=0.35; 95%CI 0.13-0.97; P=0.044) of PSA biochemical recurrence than the wild type genotype. Patients with AA and GA genotypes showed a longer TTR if compared to GG genotype patients (median survival=not reached vs 96 months; P=0.037 by Log-Rank test). Concerning P22phox Ex4+11C>T, the presence of at least one variant allele conferred a lower risk of PSA biochemical recurrence (HR=0.57; 95%CI 0.40-0.81; P=0.002). The median TTR was 105 months for patients with CT or TT genotypes, and it was 96 months for patients with CC genotype (P=0.028 by Log-Rank test). In conclusion, this study allowed the identification of two polymorphisms, VEGF-1154G>A (rs1570360) and P22phox-Ex4+11C>T (rs4673) that may have a substantial impact on PSA recurrence after radiation therapy in prostate cancer.