Pharmacogenetic analysis in neoadjuvant chemoradiation for rectal cancer: high incidence of somatic mutations and their relation with response

Methylenetetrahydrofolate reductase polymorphic variants C677T and A1298C in rectal cancer in Slavic population: significance for cancer risk and response to chemoradiotherapy

Background: Methylenetetrahydrofolate reductase (MTHFR) single nucleotide polymorphisms (SNPs) have been suggested as risk, prognostic, and predictive factors for colorectal cancer in various populations, but have not been validated so far. The aim of this study was to examine the association of MTHFR C677T (rs1801133) and A1298C (rs1801131) single nucleotide polymorphisms with the risk of rectal cancer as well as the response to neoadjuvant chemoradiotherapy (nCRT) based on 5-Fluorouracil (5-FU)/leucovorin (LV) in the locally advanced setting. Patients and methods: This case-control study included 119 healthy controls and 97 patients with locally advanced rectal cancer (LARC). For MTHFR genotyping, restriction fragment length polymorphism analysis (PCR-RFLP) was employed. Results: In silico analysis highlighted that SNPs C677T and A1298T correlate with MTHFR gene expression, and that gene expression profile correlates with cancer risk and stage. Using dominant and recessive models, it was found that the MTHFR 677CC vs. 677CT+677TT have increased risk of cancer development (odds ratio (OR): 2.27; 95% confidence interval (CI): 1.30-3.95, p = 0.002) as well as 677CC+677CT compared to 677TT (OR: 4.18, 95% CI: 1.16-14.99, p = 0.014). MTHFR 1298AA also shown increased risk for cancer development compared to 1298AC+1298CC (OR:2.0, 95% CI: 1.20-3.59, p = 0.035) Statistical analysis of combined genotypes highlighted the protective role of CT/AC combined genotype (OR: 3.15 95% CI: 1.576-6.279, p = 0.002) while the CC/AA genotype showed an increased risk for rectal cancer development (OR: 2.499, 95% CI: 1.246-5.081, p = 0.016) The carriers of the 677C/1298A haplotype had the highest risk for developing rectal cancer (OR: 1.74; 95% CI: 1.198-2.530, p = 0.002) while the 677T/1298C haplotype seems to provide a protective effect. (OR: 0.44; 95%CI 0.248-0.795, p = 0.003). No significant association with response to chemoradiotherapy was found. Conclusion: Our data point to MTHFR 667C allele and 1298A alleles as low-penetrance risk factors for rectal cancer in our population. To the best of our knowledge, this is the first study of this type performed on the Slavic population in the Western Balkan, as various population-based factors might also be significant our findings can be used for future meta-analyses and the construction of genetic cancer risk prediction panels.

Significant Association Between XRCC1 Expression and Its rs25487 Polymorphism and Radiotherapy-Related Cancer Prognosis

Background/Aims

XRCC1 (X-ray repair cross-complementing protein 1) expression and its single nucleotide polymorphism XRCC1 rs25487 (G>A) may be related to radiotherapy-related cancer prognosis or radiation-induced side effects. However, this association is controversial. We performed a bioinformatic analysis and a meta-analysis to obtain comprehensive results.

Results

Sixty nine articles with 10232 patients and 17 TCGA data sets with 2705 patients were included in the analysis. We observed that high XRCC1 expression was associated with an increased risk of minor treatment response and poor overall survival, XRCC1 rs25487 was associated with reduced risk of minor treatment response in esophageal cancer and an increased risk of high-grade side effects in head and neck cancer.

Conclusion

The results suggest that XRCC1 expression and rs25487 polymorphism are prognostic factors for patients receiving radiotherapy-related treatment. Considering the insufficient treatment parameters provided and the various sample sizes in most of the studies, we suggest that genetic association studies related to radiation-based treatment should include more cancer types with sufficient statistical power and more detailed clinical parameters.

Germline and Somatic Pharmacogenomics to Refine Rectal Cancer Patients Selection for Neo-Adjuvant Chemoradiotherapy

Neoadjuvant chemoradiotherapy (nCRT) followed by radical surgery is the standard of care for patients with Locally Advanced Rectal Cancer (LARC). Current selection for nCRT is based on clinical criteria regardless of any molecular marker. Pharmacogenomics may be a useful strategy to personalize and optimize nCRT in LARC. This review aims to summarize the most recent and relevant findings about the role of germline and somatic pharmacogenomics in the prediction of nCRT outcome in patients with LARC, discussing the state of the art of their application in the clinical practice. A systematic literature search of the PubMed database was completed to identify relevant English-language papers published up to January 2020. The chemotherapeutic backbone of nCRT is represented by fluoropyrimidines, mainly metabolized by DPD (Dihydro-Pyrimidine Dehydrogenase, DPYD). The clinical impact of testing DPYD*2A, DPYD*13, c.2846A > T and c.1236G > A-HapB3 before a fluoropyrimidines administration to increase treatment safety is widely acknowledged. Other relevant target genes are TYMS (Thymidylate Synthase) and MTHFR (Methylene-Tetrahydro-Folate Reductase), whose polymorphisms were mainly studied as potential markers of treatment efficacy in LARC. A pivotal role of a TYMS polymorphism in the gene promoter region (rs34743033) was reported and was pioneeringly used to guide nCRT treatment in a phase II study. The pharmacogenomic analysis of other pathways mostly involved in the cellular response to radiation damage, as the DNA repair and the activation of the inflammatory cascade, provided less consistent results. A high rate of somatic mutation in genes belonging to PI3K (Phosphatidyl-Inositol 3-Kinase) and MAPK (Mitogen-Activated Protein Kinase) pathways, as BRAF (V-raf murine sarcoma viral oncogene homolog B1), KRAS (Kirsten Rat Sarcoma viral oncogene homolog), NRAS (Neuroblastoma RAS viral (v-ras) oncogene homolog), PIK3CA (Phosphatidyl-Inositol-4,5-bisphosphate 3-Kinase, Catalytic Subunit Alpha), as well as TP53 (Tumor Protein 53) was reported in LARC. Their pharmacogenomic role, already defined in colorectal cancer, is under investigation in LARC with promising results concerning specific somatic mutations in KRAS and TP53, as predictors of tumor response and prognosis. The availability of circulating tumor DNA in plasma may also represent an opportunity to monitor somatic mutations in course of therapy.

Efficacy and toxicity of adjuvant chemotherapy on colorectal cancer patients: how much influence from the genetics?

We studied the predictive value for response and toxicity of functional polymorphisms in genes involved in the oxaliplatin/fluorouracil pathway in colorectal cancer patients. One hundred and twenty-seven (127) patients were treated with curative intended surgery followed by adjuvant chemotherapy with FOLFOX (fluorouracil, leucovorin and oxaliplatin) regimen. The median age was 65.53 (27-80) years (66.9% male, 59.1% rectum). The median follow-up was 8.5 years (IQR, 4.1-9.4). At the end of follow-up, 59 patients (46.5%) had relapsed or died in the whole study population. We did find that XRCC1GG genotype is associated with a higher risk of developing haematologic toxicity. Furthermore, we report a significant association of the TS 3'UTR 6 bp/6 bp polymorphism and the XRCC1 rs25487 with a higher risk of developing anaemia and diarrhoea, respectively. On the other hand, none of the studied polymorphisms showed clinically relevant association with disease-free survival and overall survival or early failure to adjuvant FOLFOX therapy.

Variación somática intraindividual del polimorfismo rs669 del gen A2M en pacientes con cáncer colorrectal

La variación somática intraindividual (VSI) se describe como la diferencia genética entre los tejidos de un mismo individuo. La VSI se incrementa conforme avanza la edad y se asocia con alteraciones neurológicas, hematológicas e inmunes y, de manera especial, con cáncer, aunque puede no manifestar un fenotipo definido.1Para analizar la posible VSI en pacientes mexicanos con cáncer colorrectal (CCR), Yang et al.2 estudiaron el polimorfismo rs669 (c.2998 A>G, p.Ile1000Val) del gen A2M que codifica para la proteína alfa-2 macroglobulina, una inhibidora de proteasas involucrada en la progresión y proliferación del tumor. Esta variante se localiza cerca de un sitio tioéster, necesario para la función inhibidora de la proteína.

Single nucleotide polymorphism of <italic>GSTP1</italic> and pathological complete response in locally advanced rectal cancer patients treated with neoadjuvant concomitant radiochemotherapy

Purpose

Standard treatment for locally advanced rectal cancer consists of neoadjuvant radiochemotherapy with concomitant fluoropyrimidine or oxaliplatin and surgery with curative intent. Pathological complete response has shown to be predictive for better outcome and survival; nevertheless there are no biological or genetic factors predictive for response to treatment. We explored the correlation between the single nucleotide polymorphisms (SNPs) GSTP1 (A313G) and XRCC1 (G28152A), and the pathological complete response and survival after neoadjuvant radiochemotherapy in locally advanced rectal cancer patients.

Materials and Methods

Genotypes GSTP1 (A313G) and XRCC1 (G28152A) were determined by pyrosequencing technology in 80 patients affected by locally advanced rectal cancer.

Results

The overall rate of pathological complete response in our study population was 18.75%. Patients homozygous AA for GSTP1 (A313G) presented a rate of pathological complete response of 26.6% as compared to 8.5% of the AG+GG population (p = 0.04). The heterozygous comparison (AA vs. AG) showed a significant difference in the rate of pathological complete response (26.6% vs. 6.8%; p = 0.034). GSTP1 AA+AG patients presented a 5- and 8-year cancer-specific survival longer than GSTP1 GG patients (87.7% and 83.3% vs. 44.4% and 44.4%, respectively) (p = 0.014). Overall survival showed only a trend toward significance in favor of the haplotypes GSTP1 AA+AG. No significant correlations were found for XRCC1 (G28152A).

Conclusion

Our results suggest that GSTP1 (A313G) may predict a higher rate of pathological complete response after neoadjuvant radiochemotherapy and a better outcome, and should be considered in a more extensive analysis with the aim of personalization of radiation treatment.

Relevance of methylenetetrahydrofolate reductase gene variants C677T and A1298C with response to fluoropyrimidine-based chemotherapy in colorectal cancer: a systematic review and meta-analysis

Methylenetetrahydrofolate reductase (MTHFR) is a critical enzyme influencing the metabolism of fluoropyrimidines. The relevance of MTHFR polymorphisms with the clinical response to fluoropyrimidine-based chemotherapy has been explored, but the results remain controversial. Thus, a meta-analysis was performed to provide a comprehensive estimate in this account. Relevant studies were identified through PubMed, Embase and Web of Science databases from inception up to May 2017. Odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were applied to assess the strength of association. A total of 2118 colorectal cancer patients from 21 studies were included in the meta-analysis. Overall, there was no significant association between MTHFR C677T (rs1801133) or A1298C (rs1801131) polymorphisms and the clinical response to fluoropyrimidine-based chemotherapy under all of the three genetic models (allele model, dominant model, and recessive model) and stratification analysis, except for the retrospective study subgroup in the dominant model of MTHFR C677T and the “5-Fu + FA” treatment group in the allele contrast of MTHFR A1298C. No or moderate heterogeneity was observed in all genetic models. This meta-analysis suggested that MTHFR polymorphisms could not be considered as reliable factors for predicting the clinical response to fluoropyrimidine-based chemotherapy in colorectal cancer patients.

Potential Role of Single Nucleotide Polymorphisms of XRCC1, XRCC3, and RAD51 in Predicting Acute Toxicity in Rectal Cancer Patients Treated With Preoperative Radiochemotherapy

OBJECTIVES

To investigate the association between polymorphisms of DNA repair genes and xenobiotic with acute adverse effects in locally advanced rectal cancer patients treated with neoadjuvant radiochemotherapy.

METHODS

Sixty-seven patients were analyzed for the current study. Genotypes in DNA repair genes XRCC1 (G28152A), XRCC3 (A4541G), XRCC3 (C18067T), RAD51 (G315C), and GSTP1 (A313G) were determined by pyrosequencing technology.

RESULTS

The observed grade ≥3 acute toxicity rates were 23.8%. Chemotherapy and radiotherapy were interrupted for 46 and 14 days, respectively, due to critical complications. Four patients were hospitalized, 6 patients had been admitted to the ER, and 5 patients received invasive procedures (2 bladder catheters, 2 blood transfusions, and 1 growth factor therapy).RAD51 correlated with acute severe gastrointestinal toxicity in heterozygosity (Aa) and homozygosity (AA) (P=0.036). Grade ≥3 abdominal/pelvis pain toxicity was higher in the Aa group (P=0.017) and in the Aa+AA group (P=0.027) compared with homozygous (aa) patients. Acute skin toxicity of any grade occurred in 55.6% of the mutated patients versus 22.8% in the wild-type group (P=0.04) for RAD51. XRCC1 correlated with skin toxicity of any grade in the Aa+AA group (P=0.03) and in the Aa group alone (P=0.044). Grade ≥3 urinary frequency/urgency was significantly higher in patients with AA (P=0.01), Aa (P=0.022), and Aa+AA (P=0.031) for XRCC3 compared with aa group.

CONCLUSIONS

Our study suggested that RAD51, XRCC1, and XRCC3 polymorphisms may be predictive factors for radiation-induced acute toxicity in rectal cancer patients treated with preoperative combined therapy.

A meta-analysis identifies ERCC1 gene polymorphism as a predictor of better patient response to treatment with radiochemotherapy

PURPOSE

This meta-analysis aimed to evaluate whether an association exists between the ERCC1 rs11615 (C>T) polymorphism and patient response to platinum-based chemotherapy and radiation-based chemotherapy.

METHODS

Publications were selected from PubMed and MEDLINE. A meta-analysis was conducted to determine the association between genetic polymorphisms and response to platinum-based chemotherapy and radiation-based chemotherapy by checking the odds ratios (ORs) and 95 % confidence intervals (CIs).

RESULTS

In our overall analysis, the ERCC1 rs11615 (C>T) polymorphism was not associated with response to platinum-based chemotherapy in five comparison models. In the subgroup analyses by ethnicity, the ERCC1 rs11615 (C>T) polymorphism was shown to be significantly associated with objective response in Caucasian patients treated with platinum-based chemotherapy in the recessive model (TT vs.

CT/CC

OR 0.696, 95 % CI 0.508-0.954, heterogeneity = 0.330), but the association was not observed in the Asian population. The C allele was significantly associated with better response to radiochemotherapy in the recessive model comparison (TT vs.

CC/CT

OR 0.724, 95 % CI 0.585-0.869, heterogeneity = 0.008). Subgroup analysis by cancer type revealed that the C allele of ERCC1 rs11615 predicted a better response in esophageal cancers in two comparison models (T vs. C: OR 0.756, 95 % CI 0.648-0.880, heterogeneity = 0.653; TT vs.

TC/CC

OR 0.457, 95 % CI 0.306-0.684, heterogeneity = 0.723). Stratified analysis by ethnicity showed a better response in Caucasians in allelic comparison model (T vs. C: OR 0.895, 95 % CI 0.819-0.977, heterogeneity = 0.095).

CONCLUSION

Together, our results suggest that the ERCC1 rs11615 (C>T) polymorphism was associated with therapeutic response in Caucasian patients and C allele of ERCC1 rs11615 could represent a genetic molecular marker to predict better patient response to radiochemotherapy in recessive model. However, larger prospective randomized trials will be required.

Association of thymidylate synthase polymorphisms with the tumor response to preoperative chemoradiotherapy in rectal cancer: a systematic review and meta-analysis

Preoperative chemoradiotherapy (pCRT) followed by surgery is currently the standard therapy for patients with locally advanced rectal cancer. It is very important to develop biomarkers to prior identify the patients who have a higher likelihood of responding to pCRT. Recently, a series of studies have been conducted to investigate the association of thymidylate synthase (TYMS) polymorphisms with the tumor response to pCRT in rectal cancer, but the results were not consistent and conclusive. In the present study, we performed a systematic literature search for relevant studies up to 30 March 2015 and conducted a meta-analysis to summarize and clarify the association between the TYMS polymorphisms and the tumor response to pCRT in rectal cancer. Finally, 7 studies containing 892 cases for TYMS 2R/3R polymorphism, 7 studies involving 715 cases for TYMS 1494del6 polymorphism and 6 studies containing 616 cases for TYMS 5' untranslated region (UTR) expression allele polymorphism were analyzed in the meta-analysis. The results suggested that TYMS 2R/3R was associated with the response and the patients with 2R/2R or 2R/3R genotype with rectal cancer might benefit more from pCRT than others. On the contrary, neither 1494del6 nor 5'UTR expression allele polymorphisms was associated with the response to pCRT.

DNA repair gene polymorphisms do not predict response to radiotherapy-based multimodality treatment of patients with rectal cancer: a meta-analysis

BACKGROUND

: A number of association studies have been carried out to investigate the relationship between genetic polymorphisms in DNA repair genes and response to radiotherapy-based multimodality treatment of patients with rectal cancer. However, their conclusions were inconsistent. The objective of the present study was to assess the role of DNA repair gene genetic polymorphisms in predicting genetic biomarkers of the response in rectal cancer patients treated with neoadjuvant chemoradiation.

MATERIALS AND METHODS

Studies were retrieved by searching the PubMed database, Cochrane Library, Embase, and ISI Web of Knowledge. We conducted a meta-analysis to evaluate the association between genetic polymorphisms and the response in rectal cancer treated with neoadjuvant chemoradiation by checking odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Data were extracted from 5 clinical studies for this meta-analysis. The results showed that XRCC1 RS25487, XRCC1 RS179978, XRCC3 RS861539, ERCC1 RS11615 and ERCC2 RS13181 were not associated with the response in the radiotherapy-based multimodality treatment of patients with rectal cancer (p>0.05).

CONCLUSIONS

This study shows that DNA repair gene common genetic polymorphisms are not significantly correlated with the radiotherapy-based multimodality treatment in rectal cancer patients.

MTHFR C677T Polymorphism is Associated with Tumor Response to Preoperative Chemoradiotherapy: A Result Based on Previous Reports

BACKGROUND

Preoperative chemoradiotherapy (pRCT) followed by surgery has been widely practiced in locally advanced rectal cancer, esophageal cancer, gastric cancer and other cancers. However, the therapy also exerts some severe adverse effects and some of the patients show poor or no response. It is very important to develop biomarkers (e.g., gene polymorphisms) to identify patients who have a higher likelihood of responding to pRCT. Recently, a series of reports have investigated the association of the genetic polymorphisms in methylenetetrahydrofolate reductase (MTHFR) and epidermal growth factor receptor (EGFR) genes with the tumor response to pRCT; however, the results were inconsistent and inconclusive.

MATERIAL AND METHODS

A systematic review and meta-analysis was performed by searching relevant studies about the association of MTHFR and EGFR polymorphisms with the tumor regression grade (TRG) in response to pRCT in databases of PubMed, EMBAS, Web of science, Chinese National Knowledge Infrastructure, and Wanfang database up to March 30, 2015. The pooled odds ratios (ORs) with corresponding 95% confidence intervals (95% CIs) were calculated to assess the strength of the association under 5 genetic models.

RESULTS

A total of 11 eligible articles were included in the present meta-analysis, of which 8 studies were performed in rectal cancer and 3 studies were performed in esophageal cancer. We finally included 8 included studies containing 839 cases for MTHFR C677T, 5 studies involving 634 cases for MTHFR A1298C, 3 studies containing 340 cases for EGFR G497A, and 4 studies containing 396 cases for EGFR CA repeat. The pooled analysis results indicated that MTHFR C677T might be correlated with the tumor response to pRCT under the recessive model (CC vs. CTTT) in overall analysis (OR=1.426(1.074-1.894), P=0.014), rectal cancer (OR=1.483(1.102-1.996), P=0.009), and TRG 1-2 vs. 3-5 group (OR=1.423(1.046-1.936), P=0.025), while other polymorphism including MTHFR A1298C, EGFR G497A, and EGFR CA repeat polymorphisms exerted significant association under all genetic models in overall analysis or subgroup analysis.

CONCLUSIONS

MTHFR C677T might be correlated with the tumor response to pRCT. Further well-designed, larger-scale epidemiological studies are needed to validate our results.

Long Survival and Severe Toxicity Under 5-Fluorouracil-Based Therapy in a Patient With Colorectal Cancer Who Harbors a Germline Codon-Stop Mutation in TYMS

We report the first clinical description of a patient with cancer with a heterozygous germline codon-stop mutation in the TYMS gene. The mutation g.657795_657826del, c.53_84del (NM_001071.2), p.Gln18Argfs*42 causes loss of function of one of the TYMS alleles, resulting in a truncated protein. This gene codifies for the target enzyme of 5-fluorouracil (5-FU), the basic treatment in colorectal cancer. The patient, diagnosed with metastatic colorectal cancer, had diarrhea and neutropenia grade 4 and mucositis and neurological toxicity grade 3 under 5-FU-based therapy and exceeded by more than 50% the average survival after metastasectomy. On the basis of the patient's characteristics and the key role of TYMS in 5-FU activity, we hypothesize that this mutation may contribute to the drug response and toxicities suffered by the patient.

Delimiting Allelic Imbalance of TYMS by Allele-Specific Analysis

Allelic imbalance of thymidylate synthase (TYMS) is attributed to polymorphisms in the 5'- and 3'-untranslated region (UTR). These polymorphisms have been related to the risk of suffering different cancers, for example leukemia, breast or gastric cancer, and response to different drugs, among which are methotrexate glutamates, stavudine, and specifically 5-fluorouracil (5-FU), as TYMS is its direct target. A vast literature has been published in relation to 5-FU, even suggesting the sole use of these polymorphisms to effectively manage 5-FU dosage. Estimates of the extent to which these polymorphisms influence in TYMS expression have in the past been based on functional analysis by luciferase assays and quantification of TYMS mRNA, but both these studies, as the association studies with cancer risk or with toxicity or response to 5-FU, are very contradictory. Regarding functional assays, the artificial genetic environment created in luciferase assay and the problems derived from quantitative polymerase chain reactions (qPCRs), for example the use of a reference gene, may have distorted the results. To avoid these sources of interference, we have analyzed the allelic imbalance of TYMS by allelic-specific analysis in peripheral blood mononuclear cells (PBMCs) from patients.Allelic imbalance in PBMCs, taken from 40 patients with suspected myeloproliferative haematological diseases, was determined by fluorescent fragment analysis (for the 3'-UTR polymorphism), Sanger sequencing and allelic-specific qPCR in multiplex (for the 5'-UTR polymorphisms).For neither the 3'- nor the 5'-UTR polymorphisms did the observed allelic imbalance exceed 1.5 fold. None of the TYMS polymorphisms is statistically associated with allelic imbalance.The results acquired allow us to deny the previously established assertion of an influence of 2 to 4 fold of the rs45445694 and rs2853542 polymorphisms in the expression of TYMS and narrow its allelic imbalance to 1.5 fold, in our population. These data circumscribe the influence of these polymorphisms in the clinical outcome of 5-FU and question their use for establishing 5-FU dosage, above all when additional genetic factors are not considered.

Germline and somatic genetic predictors of pathological response in neoadjuvant settings of rectal and esophageal cancers: systematic review and meta-analysis

Oncologists have pointed out an urgent need for biomarkers that can be useful for clinical application to predict the susceptibility of patients to preoperative therapy. This review collects, evaluates and combines data on the influence of reported somatic and germline genetic variations on histological tumor regression in neoadjuvant settings of rectal and esophageal cancers. Five hundred and twenty-seven articles were identified, 204 retrieved and 61 studies included. Among 24 and 14 genetic markers reported for rectal and esophageal cancers, respectively, significant associations in meta-analyses were demonstrated for the following markers. In rectal cancer, major response was more frequent in carriers of the TYMS genotype 2 R/2 R-2 R/3 R (rs34743033), MTHFR genotype 677C/C (rs1801133), wild-type TP53 and KRAS genes. In esophageal cancer, successful therapy appeared to correlate with wild-type TP53. These results may be useful for future research directions to translate reported data into practical clinical use.

Germ line polymorphisms as predictive markers for pre-surgical radiochemotherapy in locally advanced rectal cancer: a 5-year literature update and critical review

PURPOSE

Locally advanced rectal cancer is currently treated with pre-surgical radiotherapy and chemotherapy. Approximately one-half of patients obtain a relevant shrinkage/disappearance of tumour, with major clinical advantages. The remaining patients, in contrast, show no benefit and possibly need alternative treatment. To provide the best therapeutic option for each individual patient, predictive markers have been widely researched. This review was undertaken to evaluate recent progress made in this field.

METHODS

A systematic literature search was performed using PubMed and Scopus database, focused on germ line gene polymorphisms as biomarkers and response and toxicity as outcomes. Because an exhaustive previous review was available describing findings up to 2008, we restricted our analysis to the last 5 years.

RESULTS

Ten original research articles were found, reporting promising results for some candidate genes in drug metabolism (TYMS, MTHFR), DNA repair (XRCC1, OGG1, CCND1) and inflammation (SOD2, TGFB1)/immunity (IL13) pathways, but with no firm conclusion. All the studies had small sample size and were defined as exploratory. This review highlights pivotal molecular, clinical, genetic and statistical issues in the investigation of genetic polymorphisms as outcome predictors for rectal cancer and offers suggestions for future development.

CONCLUSIONS

What emerges is a clear need for new proposals, especially in view of the increasing evidence for tumour-host and gene-gene interactions during anticancer treatment, together with stronger adherence to proper methodological requirements.

The XPD Lys751Gln polymorphism has predictive value in colorectal cancer patients receiving oxaliplatin-based chemotherapy: a systemic review and meta-analysis

BACKGROUND

The predictive value of the xeroderma pigmentosum group D (XPD) Lys751Gln polymorphism regarding clinical outcomes of patients with colorectal cancer (CRC) receiving oxaliplatin-based chemotherapy has been evaluated in numerous published studies, but the results remain inconclusive. Therefore, we performed a meta-analysis to determine the precise role of the XPD Lys751Gln polymorphism in this clinical situation and optimize individual chemotherapy.

MATERIALS AND METHODS

A multiple search strategy was used to identify eligible studies. Pooled odds ratios (ORs), generalized odds ratio (ORG) and their 95% confidence intervals (CIs) were used to estimate the objective response, while hazard ratios (HRs) with 95%CIs were used for progression-free survival (PFS) and overall survival (OS).

RESULTS

A total of 17 studies including 2,286 patients met the inclusion criteria. Overall, the XPD 751Gln allele was associated with a non-significant reduced objective response to oxaliplatin-based chemotherapy in all patients or in the Asian and Caucasian subgroups. However, poor PFS and OS of CRC patients treated with oxaliplatin-based regimens were significantly related to the XPD 751Gln allele in the dominant model (PFS: HR=2.10, 95%CI: 1.65-2.67; OS: HR=3.18, 95%CI: 1.57-6.47). On stratified analysis by ethnicity, these relationships were more pronounced in Asians (PFS: HR=2.49, 95%CI: 1.79-3.47; OS: HR=5.25, 95%CI: 3.46-7.94) than in Caucasians (PFS: HR=1.73, 95%CI: 1.22-2.46; OS: HR=1.78, 95%CI: 1.06-2.99).

CONCLUSIONS

The XPD Lys751Gln polymorphism may have prognostic value in patients with CRC undergoing oxaliplatin-based chemotherapy.

Concordance of genotype for polymorphisms in DNA isolated from peripheral blood and colorectal cancer tumor samples

Background & aim: Results from different pharmacogenetic association studies in colorectal cancer are often conflicting. Both peripheral blood and formalin-fixed, paraffin-embedded (FFPE) tissue are routinely used as DNA source. This could cause bias due to somatic alterations in tumor tissue, such as loss of heterozygosity. We therefore compared genotypes in DNA from peripheral blood and FFPE colorectal tumor samples for SNPs with putative influence on the cytotoxicity of chemotherapy. Materials & methods: Eleven SNPs in nine genes involved in anticancer drug metabolism or efficacy were determined in matched samples from blood and FFPE tissue of colorectal tumors by pyrosequencing and TaqMan® techniques. The κ-statistic was calculated to assess concordance. Results: A total of 149 paired FFPE tissue and EDTA blood DNA samples were available for comparison. Overall, 20 out of 1418 genotypes were discordant (1.4%); in ten cases, loss of heterozygosity could not be ruled out. Only GSTP1 showed significant discordance between FFPE tissue and blood genotype (κ = 0.947; 95% CI: 0.896–0.998). Conclusion: FFPE tissue-derived DNA can be used as a valid proxy for germline DNA for a selection of SNPs in (retrospective) pharmacogenetic association studies in colorectal cancer. However, for future studies, genotyping of blood-derived DNA is preferred.

Original submitted 29 May 2013; Revision submitted 23 August 2013

MTHFR Glu429Ala and ERCC5 His46His polymorphisms are associated with prognosis in colorectal cancer patients: analysis of two independent cohorts from Newfoundland

Introduction

In this study, 27 genetic polymorphisms that were previously reported to be associated with clinical outcomes in colorectal cancer patients were investigated in relation to overall survival (OS) and disease free survival (DFS) in colorectal cancer patients from Newfoundland.

Methods

The discovery and validation cohorts comprised of 532 and 252 patients, respectively. Genotypes of 27 polymorphisms were first obtained in the discovery cohort and survival analyses were performed assuming the co-dominant genetic model. Polymorphisms associated with disease outcomes in the discovery cohort were then investigated in the validation cohort.

Results

When adjusted for sex, age, tumor stage and microsatellite instability (MSI) status, four polymorphisms were independent predictors of OS in the discovery cohort MTHFR Glu429Ala (HR: 1.72, 95%CI: 1.04–2.84, p = 0.036), ERCC5 His46His (HR: 1.78, 95%CI: 1.15–2.76, p = 0.01), SERPINE1 −675indelG (HR: 0.52, 95%CI: 0.32–0.84, p = 0.008), and the homozygous deletion of GSTM1 gene (HR: 1.4, 95%CI: 1.03–1.92, p = 0.033). In the validation cohort, the MTHFR Glu429Ala polymorphism was associated with shorter OS (HR: 1.71, 95%CI: 1.18–2.49, p = 0.005), although with a different genotype than the discovery cohort (CC genotype in the discovery cohort and AC genotype in the validation cohort). When stratified based on treatment with 5-Fluorouracil (5-FU)-based regimens, this polymorphism was associated with reduced OS only in patients not treated with 5-FU. In the DFS analysis, when adjusted for other variables, the TT genotype of the ERCC5 His46His polymorphism was associated with shorter DFS in both cohorts (discovery cohort: HR: 1.54, 95%CI: 1.04–2.29, p = 0.032 and replication cohort: HR: 1.81, 95%CI: 1.11–2.94, p = 0.018).

Conclusions

In this study, associations of the MTHFR Glu429Ala polymorphism with OS and the ERCC5 His46His polymorphism with DFS were identified in two colorectal cancer patient cohorts. Our results also suggest that the MTHFR Glu429Ala polymorphism may be an adverse prognostic marker in patients not treated with 5-FU.

Progress in rectal cancer treatment

The dramatic improvement in local control of rectal cancer observed during the last decades is to be attributed to attention to surgical technique and to the introduction of neoadjuvant therapy regimens. Nevertheless, systemic relapse remains frequent and is currently insufficiently addressed. Intensification of neoadjuvant therapy by incorporating chemotherapy with or without targeted agents before the start of (chemo)radiation or during the waiting period to surgery may present an opportunity to improve overall survival. An increasing number of patients can nowadays undergo sphincter preserving surgery. In selected patients, local excision or even a "wait and see" approach may be feasible following active neoadjuvant therapy. Molecular and genetic biomarkers as well as innovative imaging techniques may in the future allow better selection of patients for this treatment option. Controversy persists concerning the selection of patients for adjuvant chemotherapy and/or targeted therapy after neoadjuvant regimens. The currently available evidence suggests that in complete pathological responders long-term outcome is excellent and adjuvant therapy may be omitted. The results of ongoing trials will help to establish the ideal tailored approach in resectable rectal cancer.

Can population differences in chemotherapy outcomes be inferred from differences in pharmacogenetic frequencies?

Inter-ethnic differences in drug handling and frequencies of pharmacogenetic variants are increasingly being characterized. In this study, we systematically assessed the feasibility of inferring ethnic trends in chemotherapy outcomes from inter-ethnic differences in pharmacogenetic variant frequencies. Frequencies of 51 variants and chemotherapy outcomes of East Asian and Caucasian colorectal cancer patients on standard chemotherapy regimens were summarized by meta-analyses, and variant frequencies were validated by MassARRAY analysis. Inferences of relative chemotherapy outcomes were made by considering minor allele function and population differences in their frequency. Significant population differences in genotype distributions were observed for 13/23 (60%) and 27/35 (77%) variants in the meta-analyses and validation series, respectively. Across chemotherapy regimens, East Asians had lower rates of grade 3/4 toxicity for diarrhea and stomatitis/mucositis than Caucasians, which was correctly inferred from 13/18 (72%, P=0.018) informative genetic variants. With appropriate variant selection, inferring relative population toxicity rates from population genotype differences may be relevant.

The value of genetic polymorphisms to predict toxicity in metastatic colorectal patients with irinotecan-based regimens

PURPOSE

We are trying to identify predictive factors of high risk of toxicity by analyzing candidate genes in the irinotecan pathways in order to identify useful tools to improve mCRC patient management under real practice conditions.

METHODS

Genomic DNA was genotyped for UGT1A1 (*28, *60 and *93) from all 101 patients, and irinotecan dose was 180 mg/m(2) every second week. Clinical data were obtained by retrospective chart review. The primary endpoint is to find out whether the pharmacogenetic test in the clinical practice may predict toxicity.

RESULTS

Grade 3/4 diarrhea occurred in twelve patients and required dose reduction in six patients, and neutropenia reached grade 3/4 in 19 patients (only one patient with *28/*28 genotype). The UGT1A1*93 seemed to relate with grade 3/4 neutropenia but only in the heterozygote state (G/A), p = 0.071, and UGT1A*60 showed no association with neutropenia. Twenty-eight percentage of patients required the use of G-CSF; 64.3% of them harbored *1/*28 or *28/*28 genotypes, p = 0.003. Thirty-seven (36.6%) patients required dose reduction of irinotecan and/or 5-FU owing to toxicity, mainly neutropenia and diarrhea. No significant association was detected between *28, *60 and *93 UGT1A variants and severe irinotecan-associated hematologic or GI toxicity.

CONCLUSION

The impact of increased risk of toxicity attributed to the UGT1A variants may be offset by irinotecan in clinical practice by dose reduction or the use of colony-stimulating factor.

Methylenetetrahydrofolate reductase genetic polymorphisms and toxicity to 5-FU-based chemoradiation in rectal cancer

BACKGROUND

There is a large degree of variation in tumour response and host toxicities associated with neoadjuvant chemoradiation for rectal cancer patients. We performed a complimentary pharmacogenetic study to investigate germline polymorphisms of genes involved in 5-fluorouracil (5-FU) and irinotecan pathways and their potential association with clinical outcomes and toxicities from neoadjuvant chemoradiation in patients with rectal cancer treated in a prospective genotype-directed study.

METHODS

The germline DNA of 131 patients was genotyped for 10 variants in TYMS, MTHFR, DPYD, UGT1A1, ABCC1 and SLCO1B1 genes. Ninety-six patients were treated with 5-FU/radiotherapy (RT) and 35 received 5-FU/RT/irinotecan. Relationships between genetic variants and adverse events, tumour response, overall and disease-free survivals were assessed.

RESULTS

MTHFR 1298A>C and MTHFR diplotypes (for 677C>T and 1298A>C) were associated with chemoradiation-related toxicity when 5-FU was used alone. MTHFR haplotypes (677C-1298C) and diplotypes (CA-TA and TA-TA) showed, respectively, a protective and a negative effect on the incidence of severe diarrhoea or mucositis. No association was observed between genetic markers and drug response.

CONCLUSION

MTHFR polymorphisms can potentially predict toxicity in patients treated with 5-FU as a single chemotherapeutic drug.

Use of a comprehensive panel of biomarkers to predict response to a fluorouracil-oxaliplatin regimen in patients with metastatic colorectal cancer

AIM

Polymorphisms in the metabolism, detoxification or DNA repair pathways have been proposed as potential predictors of response to 5-fluorouracil and oxaliplatin. We have studied the predictive value of a set of germline genetic polymorphisms in metastatic colorectal cancer patients treated with mFolfox-6.

MATERIALS & METHODS

A total of 72 patients, comprising 50 men (69.4%) and 22 women (30.6%), were included after the signing of an informed consent form. Median age was 65.5 years (range: 32-80). All participants received mFolfox-6. DNA was extracted from peripheral blood samples and genotyped by direct sequencing, SnapShot(®) and multiplex PCR techniques. Eight polymorphisms within six genes were investigated: TS 5´-UTR (variable number tandem repeat + G/C), TS 3´-UTR (TS1494del6); MTHFR C677T and A1298C; GSTP1 I105V; ERCC1 C118T; XPD Lys751Gln and XRCC1 Arg399Gln. Association was evaluated by univariate analysis, and Cox regression and Kaplan-Meier assessed survival. The local ethics committee approved the pharmacogenetic study protocol and all subjects signed an informed consent before participating in the study.

RESULTS

The sample was in Hardy-Weinberg equilibrium. Only XPD Lys751Gln was found to be significantly associated with a favorable progression-free survival (PFS). Median PFS for XPD Lys751Gln patients (n = 33) was 16 months (95% CI: 9.2-22.7), 10 months (95% CI: 6.1-13.9) for Gln/Gln (n = 11) and 8 months (95% CI: 5.8-10.2) for Lys/Lys (n = 28), p = 0.019. The increased risk of progression was: 1.93 (95% CI: 1.13-13.30; p = 0.017) for Lys/Lys and 2.1 (95% CI: 1.01-4.22; p = 0.047) for Gln/Gln. Patients with one or two Val alleles of GSTP1 tended to a lower risk of progression compared with Ile/Ile homozygotes, p = 0.067. When XPD Lys751Gln and GSTP1 were analyzed jointly, patients who carried one or two favorable genotypes, XPD Lys751Gln and Val, had a longer median PFS: 11 months (95% CI: 7.4-14.6) compared with six (95% CI: 4.6-7.4) with unfavorable genotypes, p < 0.001.

CONCLUSION

In metastatic colorectal cancer patients treated with mFolfox-6, the combination of haplotype XPD Lys751Gln-GSTP1 105Val seems to predict the risk of progression.

Pharmacogenetic study in rectal cancer patients treated with preoperative chemoradiotherapy: polymorphisms in thymidylate synthase, epidermal growth factor receptor, GSTP1, and DNA repair genes

PURPOSE

Several studies have been performed to evaluate the usefulness of neoadjuvant treatment using oxaliplatin and fluoropyrimidines for locally advanced rectal cancer. However, preoperative biomarkers of outcome are lacking. We studied the polymorphisms in thymidylate synthase, epidermal growth factor receptor, glutathione S-transferase pi 1 (GSTP1), and several DNA repair genes to evaluate their usefulness as pharmacogenetic markers in a cohort of 128 rectal cancer patients treated with preoperative chemoradiotherapy.

METHODS AND MATERIALS

Blood samples were obtained from 128 patients with Stage II-III rectal cancer. DNA was extracted from the peripheral blood nucleated cells, and the genotypes were analyzed by polymerase chain reaction amplification and automated sequencing techniques or using a 48.48 dynamic array on the BioMark system. The germline polymorphisms studied were thymidylate synthase, (VNTR/5'UTR, 2R G>C single nucleotide polymorphism [SNP], 3R G>C SNP), epidermal growth factor receptor (Arg497Lys), GSTP1 (Ile105val), excision repair cross-complementing 1 (Asn118Asn, 8092C>A, 19716G>C), X-ray repair cross-complementing group 1 (XRCC1) (Arg194Trp, Arg280His, Arg399Gln), and xeroderma pigmentosum group D (Lys751Gln). The pathologic response, pathologic regression, progression-free survival, and overall survival were evaluated according to each genotype.

RESULTS

The ∗3/∗3 thymidylate synthase genotype was associated with a greater response rate (pathologic complete remission and microfoci residual tumor, 59% in ∗3/∗3 vs. 35% in ∗2/∗2 and ∗2/∗3; p=.013). For the thymidylate synthase genotype, the median progression-free survival was 103 months for the ∗3/∗3 patients and 84 months for the ∗2/∗2 and ∗2/∗3 patients (p=.039). For XRCC1 Arg399Gln SNP, the median progression-free survival was 101 months for the G/G, 78 months for the G/A, and 31 months for the A/A patients (p=.048).

CONCLUSIONS

The thymidylate synthase genotype and XRCC1 Arg399Gln polymorphism might help to identify Stage II-III rectal cancer patients with a better outcome after preoperative concomitant chemoradiotherapy.