Genetic biomarkers for predicting Patological response in Chemoradiotherapy treated rectal Cancer Patients

Backgroundneo-adjuvant 5-fluorouracil-based chemoradiotherapy (CRT) for locally advanced rectal adenocarcinoma is effective in downstaging more than half of patients before surgery. Interindividual variations in DNA repair and metabolism of pyrimidine nucleotides and folates may be important mechanisms of resistance to radio and chemotherapy and often their associations with anticancer treatment cannot be revealed by classical statistics, due to epistasis.The Multifactor Dimensionality Reduction (MDR) method was designed to identify and model gene to gene interactions. The aim of our study was to verify if genetic variants in DNA repair and pyrimidine/folate metabolism are associated with rectal cancer response to CRT, comparing different statistical approaches.Material and MethodsSeventy patients with stage II and III rectal cancer were enrolled and treated for 5 weeks with concurrent 300 mg/m2/die of 5-fluorouracil protracted venous infusion and 56 Gy radiation, followed by surgical resection. Response was directly evaluated on surgical specimens and scored according to tumor residual mass as in TNM classification. PT0-2 were defined as major response. Genomic DNA was extracted from peripheral blood lymphocytes and ERCC1, XPD, XPC, XPA, XRCC1, XRCC3, UMPS, MTHFR and TYMS polymorphisms were analyzed by PCR-RFLP. Genotypes were associated with tumor outcomes to CRT using Chi square test and the MDR method.Resultspatients’ response to CRT was as follows: pT0 in 25.7%, pT1-2 in 34.3% and pT3-4 in 40%. Chi square test found no significant relationship between genotypes and local pathological response. Using the MDR method, we showed a significant association between the combination of XPC/TYMS/XRCC3 genetic variants and major response (P = 0.0001) that was correctly predicted in 81.8% of patients (VPP, 80.7%; 95% CI, 62.1–91.5; VPN, 86.4%; 95% CI, 73.3–93.6; sensibility, 77.8%; specificity, 88.4%).ConclusionsMDR proved to be an easy and valid method to detect genetic combinations identifying rectal cancer patients with a high probability of chemoradiotherapy response.Funded by LILT (Italy). Backgroundneo-adjuvant 5-fluorouracil-based chemoradiotherapy (CRT) for locally advanced rectal adenocarcinoma is effective in downstaging more than half of patients before surgery. Interindividual variations in DNA repair and metabolism of pyrimidine nucleotides and folates may be important mechanisms of resistance to radio and chemotherapy and often their associations with anticancer treatment cannot be revealed by classical statistics, due to epistasis.The Multifactor Dimensionality Reduction (MDR) method was designed to identify and model gene to gene interactions. The aim of our study was to verify if genetic variants in DNA repair and pyrimidine/folate metabolism are associated with rectal cancer response to CRT, comparing different statistical approaches. neo-adjuvant 5-fluorouracil-based chemoradiotherapy (CRT) for locally advanced rectal adenocarcinoma is effective in downstaging more than half of patients before surgery. Interindividual variations in DNA repair and metabolism of pyrimidine nucleotides and folates may be important mechanisms of resistance to radio and chemotherapy and often their associations with anticancer treatment cannot be revealed by classical statistics, due to epistasis. The Multifactor Dimensionality Reduction (MDR) method was designed to identify and model gene to gene interactions. The aim of our study was to verify if genetic variants in DNA repair and pyrimidine/folate metabolism are associated with rectal cancer response to CRT, comparing different statistical approaches. Material and MethodsSeventy patients with stage II and III rectal cancer were enrolled and treated for 5 weeks with concurrent 300 mg/m2/die of 5-fluorouracil protracted venous infusion and 56 Gy radiation, followed by surgical resection. Response was directly evaluated on surgical specimens and scored according to tumor residual mass as in TNM classification. PT0-2 were defined as major response. Genomic DNA was extracted from peripheral blood lymphocytes and ERCC1, XPD, XPC, XPA, XRCC1, XRCC3, UMPS, MTHFR and TYMS polymorphisms were analyzed by PCR-RFLP. Genotypes were associated with tumor outcomes to CRT using Chi square test and the MDR method. Seventy patients with stage II and III rectal cancer were enrolled and treated for 5 weeks with concurrent 300 mg/m2/die of 5-fluorouracil protracted venous infusion and 56 Gy radiation, followed by surgical resection. Response was directly evaluated on surgical specimens and scored according to tumor residual mass as in TNM classification. PT0-2 were defined as major response. Genomic DNA was extracted from peripheral blood lymphocytes and ERCC1, XPD, XPC, XPA, XRCC1, XRCC3, UMPS, MTHFR and TYMS polymorphisms were analyzed by PCR-RFLP. Genotypes were associated with tumor outcomes to CRT using Chi square test and the MDR method. Resultspatients’ response to CRT was as follows: pT0 in 25.7%, pT1-2 in 34.3% and pT3-4 in 40%. Chi square test found no significant relationship between genotypes and local pathological response. Using the MDR method, we showed a significant association between the combination of XPC/TYMS/XRCC3 genetic variants and major response (P = 0.0001) that was correctly predicted in 81.8% of patients (VPP, 80.7%; 95% CI, 62.1–91.5; VPN, 86.4%; 95% CI, 73.3–93.6; sensibility, 77.8%; specificity, 88.4%). patients’ response to CRT was as follows: pT0 in 25.7%, pT1-2 in 34.3% and pT3-4 in 40%. Chi square test found no significant relationship between genotypes and local pathological response. Using the MDR method, we showed a significant association between the combination of XPC/TYMS/XRCC3 genetic variants and major response (P = 0.0001) that was correctly predicted in 81.8% of patients (VPP, 80.7%; 95% CI, 62.1–91.5; VPN, 86.4%; 95% CI, 73.3–93.6; sensibility, 77.8%; specificity, 88.4%). ConclusionsMDR proved to be an easy and valid method to detect genetic combinations identifying rectal cancer patients with a high probability of chemoradiotherapy response.Funded by LILT (Italy). MDR proved to be an easy and valid method to detect genetic combinations identifying rectal cancer patients with a high probability of chemoradiotherapy response.