Association of single nucleotide polymorphisms in the genes ATM, GSTP1, SOD2, TGFB1, XPD and XRCC1 with risk of severe erythema after breast conserving radiotherapy

Radiosensitivity of radiotherapy patients: The effect of individual DNA repair capacity

Individual radiosensitivity is a critical problem in radiotherapy because of the treatment restrictions it imposes. We have tested whether induction/repair of genomic lesions correlates with the acute cutaneous effects of radiotherapy. Peripheral blood samples of 56 healthy volunteers and 18 patients with breast cancer were studied. DNA damage and DNA repair capacity were assessed in vitro (alkaline comet assay). Patients without skin reaction did not show significant differences from healthy individuals, with respect to either initial or radiation-induced DNA damage. Similar DNA repair kinetics, fitting a decreasing exponential response, were observed in both groups, and there were no significant differences in residual genotoxic damage. In contrast, patients exhibiting acute side effects showed significantly lower DNA repair ability and significantly more residual damage, compared to patients without radiotoxicity. This approach may help to identify patients who are at greater risk of radiotherapy side effects. However, many other factors, such as dosimetry, irradiated volume, and lifestyle should also be considered in the evaluation of individual radiosensitivity.

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.

Association Between Polymorphisms in DNA Damage Repair Genes and Radiation Therapy-Induced Early Adverse Skin Reactions in a Breast Cancer Population: A Polygenic Risk Score Approach

PURPOSE

Genetic variations in DNA damage repair (DDR) genes may influence radiation therapy (RT)-induced acute normal tissue toxicity in patients with breast cancer. Identifying an individual or multiple single-nucleotide polymorphisms (SNPs) associated with RT-induced early adverse skin reactions (EASR) is critical for precision medicine in radiation oncology.

METHODS AND MATERIALS

At the completion of RT, EASR was assessed using the Oncology Nursing Society scale (0-6) in 416 patients with breast cancer, and Oncology Nursing Society score ≥4 was considered RT-induced EASR. PLINK set-based tests and subsequent individual SNP association analyses were conducted to identify genes and SNPs associated with EASR among the 53 DDR genes and 1968 SNPs. A weighted polygenic risk score (PRS) model was constructed to ascertain the association between the joint effect of risk alleles and EASR.

RESULTS

The study population consisted of 264 Hispanic whites, 86 blacks or African Americans, 55 non-Hispanic whites, and 11 others. A total of 115 patients (27.6%) developed EASR. Five genes (ATM, CHEK1, ERCC2, RAD51C, and TGFB1) were significantly associated with RT-induced EASR. Nine SNPs within these 5 genes were further identified: ATM rs61915066, CHEK1 rs11220184, RAD51C rs302877, rs405684, TBFB1 rs4803455, rs2241714, and ERCC2 rs60152947, rs10404465, rs1799786. In a multivariable-adjusted PRS model, patients in a higher quartile of PRS were more likely to develop EASR compared with patients in the lowest quartile (OR_{q2 vs.q1} = 1.94, 95% CI, 0.86-4.39; OR_{q3 vs.q1} = 3.46, 95% CI, 1.57-7.63; OR_{q4 vs.q1} = 8.64, 95% CI, 3.92-19.02; and P_trend < .0001).

CONCLUSIONS

We newly identified the associations between 9 SNPs in ATM, CHEK1, RAD51C, TGFB1, and ERCC2 and RT-induced EASR. PRS modeling showed its potential in identifying populations at risk. Multiple SNPs in DDR genes may jointly contribute to interindividual variation in RT-induced EASR. Validation in an independent external cohort is required to determine the clinical significance of these predictive biomarkers.

Molecular Profiling for Predictors of Radiosensitivity in Patients with Breast or Head-and-Neck Cancer

Nearly half of all cancers are treated with radiotherapy alone or in combination with other treatments, where damage to normal tissues is a limiting factor for the treatment. Radiotherapy-induced adverse health effects, mostly of importance for cancer patients with long-term survival, may appear during or long time after finishing radiotherapy and depend on the patient’s radiosensitivity. Currently, there is no assay available that can reliably predict the individual’s response to radiotherapy. We profiled two study sets from breast (n = 29) and head-and-neck cancer patients (n = 74) that included radiosensitive patients and matched radioresistant controls.. We studied 55 single nucleotide polymorphisms (SNPs) in 33 genes by DNA genotyping and 130 circulating proteins by affinity-based plasma proteomics. In both study sets, we discovered several plasma proteins with the predictive power to find radiosensitive patients (adjusted p < 0.05) and validated the two most predictive proteins (THPO and STIM1) by sandwich immunoassays. By integrating genotypic and proteomic data into an analysis model, it was found that the proteins CHIT1, PDGFB, PNKD, RP2, SERPINC1, SLC4A, STIM1, and THPO, as well as the VEGFA gene variant rs69947, predicted radiosensitivity of our breast cancer (AUC = 0.76) and head-and-neck cancer (AUC = 0.89) patients. In conclusion, circulating proteins and a SNP variant of VEGFA suggest that processes such as vascular growth capacity, immune response, DNA repair and oxidative stress/hypoxia may be involved in an individual’s risk of experiencing radiation-induced toxicity.

Modulation of ionizing radiation-induced damage in human blood lymphocytes by in vivo treatment with resveratrol

Purpose: Radiotherapy is an effective tool for cancer control, but side effects on normal tissue limit its therapeutic effectiveness. Thus, the search for agents that may allow the use of high doses of radiation but exerting a differential protection to healthy tissue is of current concern. Resveratrol (3,5,4'-trihydroxy-trans-stilbene) (RSV) is a polyphenol with pleiotropic benefits for health due to its antioxidant and anti-inflammatory properties. Recent findings suggest that RSV could be promising in the fight against cancer since it inhibits the growth of tumor cells and optimizes radiotherapy. However, evidence in rodents and human beings is inconsistent. The aim of this study was to evaluate the radiomodulatory capacity of RSV on human lymphocytes. Materials and methods: To study these properties of RSV, human peripheral blood lymphocytes from 20 healthy women undergoing in vivo RSV treatment with 50 mg/day doses were irradiated. The genotoxic damage was assessed by the comet assay, also called single cell gel electrophoresis (it makes it possible to measure the extent of the DNA migration from individual cells, detecting the genomic damage present in each cell). Results: No differences were observed in basal clastogenic damage among samples without irradiation. There was only a slight radiation-induced clastogenic damage. The damage index (DI) value had a statistically significant increase in the exposed groups in comparison with the control groups (p < .0001), but a statistically significant decrease of the DI value was observed in samples irradiated after treatment with RSV compared to pretreatment samples (p < .0001). Conclusion: The RSV used as a dietary supplement had radioprotective properties, without exerting a cytotoxic effect. The potential utility of RSV to optimize the radiotherapeutic ratio in cancer treatments using radiotherapy should be considered.

A review of radiation genomics: integrating patient radiation response with genomics for personalised and targeted radiation therapy

Background

The success of radiation therapy for cancer patients is dependent on the ability to deliver a total tumouricidal radiation dose capable of eradicating all cancer cells within the clinical target volume, however, the radiation dose tolerance of the surrounding healthy tissues becomes the main dose-limiting factor. The normal tissue adverse effects following radiotherapy are common and significantly impact the quality of life of patients. The likelihood of developing these adverse effects following radiotherapy cannot be predicted based only on the radiation treatment parameters. However, there is evidence to suggest that some common genetic variants are associated with radiotherapy response and the risk of developing adverse effects. Radiation genomics is a field that has evolved in recent years investigating the association between patient genomic data and the response to radiation therapy. This field aims to identify genetic markers that are linked to individual radiosensitivity with the potential to predict the risk of developing adverse effects due to radiotherapy using patient genomic information. It also aims to determine the relative radioresponse of patients using their genetic information for the potential prediction of patient radiation treatment response.

Methods and materials

This paper reports on a review of recent studies in the field of radiation genomics investigating the association between genomic data and patients response to radiation therapy, including the investigation of the role of genetic variants on an individual’s predisposition to enhanced radiotherapy radiosensitivity or radioresponse.

Conclusion

The potential for early prediction of treatment response and patient outcome is critical in cancer patients to make decisions regarding continuation, escalation, discontinuation, and/or change in treatment options to maximise patient survival while minimising adverse effects and maintaining patients’ quality of life.

Association Between Inflammatory Biomarker C-Reactive Protein and Radiotherapy-Induced Early Adverse Skin Reactions in a Multiracial/Ethnic Breast Cancer Population

Purpose This study examined an inflammatory biomarker, high-sensitivity C-reactive protein (hsCRP), in radiotherapy (RT)-induced early adverse skin reactions or toxicities in breast cancer. Patients and Methods Between 2011 and 2013, 1,000 patients with breast cancer who underwent RT were evaluated prospectively for skin toxicities through the National Cancer Institute-funded Wake Forest University Community Clinical Oncology Program Research Base. Pre- and post-RT plasma hsCRP levels and Oncology Nursing Society skin toxicity criteria (0 to 6) were used to assess RT-induced skin toxicities. Multivariable logistic regression analyses were applied to ascertain the associations between hsCRP and RT-induced skin toxicities after adjusting for potential confounders. Results The study comprised 623 white, 280 African American, 64 Asian/Pacific Islander, and 33 other race patients; 24% of the patients were Hispanic, and 47% were obese. Approximately 42% and 15% of patients developed RT-induced grade 3+ and 4+ skin toxicities, respectively. The hsCRP levels differed significantly by race and body mass index but not by ethnicity. In multivariable analysis, grade 4+ skin toxicity was significantly associated with obesity (odds ratio [OR], 2.17; 95% CI, 1.41 to 3.34], post-RT hsCRP ≥ 4.11 mg/L (OR, 1.61; 95% CI, 1.07 to 2.44), and both factors combined (OR, 3.65; 95% CI, 2.18 to 6.14). Above-median post-RT hsCRP (OR, 1.93; 95% CI, 1.03 to 3.63), and change in hsCRP (OR, 2.80; 95% CI, 1.42 to 5.54) were significantly associated with grade 4+ skin toxicity in nonobese patients. Conclusion This large prospective study is the first to our knowledge of hsCRP as an inflammatory biomarker in RT-induced skin toxicities in breast cancer. We demonstrate that nonobese patients with elevated RT-related change in hsCRP levels have a significantly increased risk of grade 4+ skin toxicity. The outcomes may help to predict RT responses and guide decision making.

Predictive value of single nucleotide polymorphisms in XRCC1 for radiation-induced normal tissue toxicity

Purpose

X-Ray Repair Cross Complementing 1 (XRCC1) functioning in the base excision repair pathway plays an important role in the repair of DNA single-strand breaks caused by ionizing radiation. The relationship between XRCC1 polymorphisms and the risk of radiation-induced side effects on normal tissues remains controversial. Therefore, we performed a comprehensive meta-analysis to elucidate these associations.

Materials and methods

A systematic literature search was carried out in PubMed, Medline (Ovid), Embase, Web of Science, Cochrane database, and the references of relevant studies. The pooled odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were calculated to evaluate the strength of the association.

Results

A total of 40 studies including 6,682 patients were eventually identified in this meta-analysis. Pooled results suggested that rs25487 Arg399Gln polymorphism significantly increased the risk of acute radiation-induced side effects (OR=1.29, 95% CI: 1.10–1.52, P=0.002), especially acute mucositis (OR=1.91, 95% CI: 1.17–3.11, P=0.01) and acute gastrointestinal and genitourinary toxicity (OR=1.49, 95% CI: 1.04–2.11, P=0.03). Furthermore, patients who received head and neck irradiation with rs25487 Arg399Gln polymorphism were more likely to experience radiotherapy (RT)-induced side effects (OR=1.46, 95% CI: 1.12–1.90, P=0.005). However, no statistically significant correlations were identified between rs25487 polymorphism and any late side effects and other irradiation areas. Likewise, no significant associations were detected between rs25489, rs1799782, or rs3213245 polymorphism and RT-induced toxicity.

Conclusion

Our meta-analysis demonstrated that XRCC1 rs25487 Arg399Gln polymorphism had a significant predictive value and might predict a risk of severely acute RT-induced adverse effects, especially in acute mucositis and acute gastrointestinal and genitourinary toxicity, or in patients with head and neck irradiation. However, large-scale and well-designed studies are required to further evaluate the predictive value of XRCC1 variations on radiation-induced side effects in order to identify radiosensitive patients and predict radiotoxicity.

Association between XRCC1 single-nucleotide polymorphism and acute radiation reaction in patients with nasopharyngeal carcinoma: A cohort study

To explore the association of the X-ray repair cross-complementing gene 1 (XRCC1) codon 399 single-nucleotide polymorphism (SNP) with acute radiation dermatitis and oral mucositis in nasopharyngeal carcinoma (NPC) patients treated by intensity-modulated radiation therapy (IMRT).Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to detect the SNP of the XRCC1 codon 399 in 114 NPC patients before radiotherapy.The risk of patients with the Arg/Arg genotype suffering from acute radiation dermatitis Grade ≥2 was higher than the other 2 genotypes (P = .014, 95% CI: 1.182-4.582). No significant difference was observed in the degree of acute radiation oral mucositis injury among the patients with different genotypes (P = .449, 95% CI: 0.691-2.304). Multivariate analysis showed that N stage and genotype were significantly associated with acute radiation dermatitis of Grade ≥2 (OR = 3.221, P < .001, 95% CI: 1.669-6.216, OR = 2.860, P = .006, 95% CI: 1.354-6.043). T stage and smoking status were significantly associated with acute radiation oral mucositis with Grade ≥2 (OR = 2.508, P = .001, 95% CI: 1.427-4.408, OR = 6.355, P < .001, 95% CI: 2.533-15.841).The XRCC1 codon 399 genotype in NPC could be an important predicting factor in the risk of acute radiation dermatitis during IMRT.

GSTP1 polymorphism predicts treatment outcome and toxicities for breast cancer

This study aimed to investigate the association of the GSTP1 gene polymorphism with the outcomes and toxicities of treatments in breast cancer. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated for the association of GSTP1 polymorphism with tumour response and toxicities, and the hazard ratios (HRs) and 95% CIs were calculated for the association between GSTP1 polymorphism and overall survival (OS). The statistical analysis showed that the GSTP1 polymorphism was not associated with tumour response or OS. A significant increase in the incidence of toxicities was observed (GA vs. AA OR = 1.45, 95% CI = 1.04–2.01, P = 0.028; GG vs. AA OR = 1.47, 95% CI = 1.03–2.10, P = 0.036; recessive model OR = 1.54, 95% CI = 1.13–2.09, P = 0.006; and allele model OR = 1.35, 95% CI = 1.07–1.71, P = 0.011), especially in the chemotherapy ± surgery group (GA vs. AA OR = 1.64, 95% CI = 1.05–2.56, P = 0.030; recessive model OR = 1.72, 95% CI = 1.17–2.54, P = 0.006; and allele model OR = 1.57, 95% CI = 1.11–2.21, P = 0.010). Our results indicate that the GSTP1 polymorphism may be associated with increased toxicity, especially in patients treated with chemotherapy ± surgery.

Genetic susceptibility to cutaneous radiation injury

The use of ionizing radiation is critical to cancer treatment and fluoroscopic procedures. However, despite efforts to minimize total radiation dose, many patients experience toxic cutaneous side-effects of ionizing radiation, ranging from mild erythema to subcutaneous fibrosis, telangiectasia formation, and ulceration. Extent of injury is highly variable among patients. Studying the genetic determinants of radiation injury can help develop protocols to reduce radiation toxicity, as well as drive research into effective modulators of the genes and gene products associated with radiation injury. Many studies in the past two decades have identified single-nucleotide polymorphisms that may be associated with susceptibility to cutaneous radiation injury, such as those in genes related to the following cellular responses to ionizing radiation: inflammation, DNA repair, oxidation and stress response, and cell-cycle and apoptosis. This review summarizes the current literature on potential major genes and polymorphisms, in the previously described damage response pathways, that are involved in susceptibility to cutaneous radiation injury. Potential pitfalls of current research and further avenues of discovery will be explored.

Predictive value of Xrcc1 gene polymorphisms for side effects in patients undergoing whole breast radiotherapy: a meta-analysis

Radiation-induced side effects on normal tissue are determined largely by the capacity of cells to repair radiation-induced DNA damage. X-ray repair cross-complementing group 1 (XRCC1) plays an important role in the repair of DNA single-strand breaks. Studies have shown conflicting results regarding the association between XRCC1 gene polymorphisms (Arg399Gln, Arg194Trp, -77T>C and Arg280His) and radiation-induced side effects in patients undergoing whole breast radiotherapy. Therefore, we conducted a meta-analysis to determine the predictive value of XRCC1 gene polymorphisms in this regard. Analysis of the 11 eligible studies comprising 2,199 cases showed that carriers of the XRCC1 399 Gln allele had a higher risk of radiation-induced toxicity than those with the 399 ArgArg genotype in studies based on high-quality genotyping methods [Gln vs. ArgArg: OR, 1.85; 95% CI, 1.20-2.86] or in studies with mixed treatment regimens of radiotherapy alone and in combination with chemotherapy [Gln vs. ArgArg: OR, 1.60; 95% CI, 1.09-2.23]. The XRCC1 Arg399Gln variant allele was associated with mixed acute and late adverse reactions when studies on late toxicity only were excluded [Gln allele vs. Arg allele: OR, 1.22; 95% CI, 1.00-1.49]. In contrast, the XRCC1 Arg280His variant allele was protective against radiation-induced toxicity in studies including patients treated by radiotherapy alone [His allele vs. Arg allele: OR, 0.58; 95% CI, 0.35-0.96]. Our results suggest that XRCC1 399Gln and XRCC1 280Arg may be independent predictors of radiation-induced toxicity in post-surgical breast cancer patients, and the selection of genotyping method is an important factor in determining risk factors. No evidence for any predictive value of XRCC1 Arg194Trp and XRCC1 -77T>C was found. So, larger and well-designed studies might be required to further evaluate the predictive value of XRCC1 gene variation on radiation-induced side effects in patients undergoing whole breast radiotherapy.

ERCC2 polymorphisms and radiation-induced adverse effects on normal tissue: systematic review with meta-analysis and trial sequential analysis

Background

The relationship between ERCC2 polymorphisms and the risk of radiotoxicity remains inconclusive. The aim of our study is to systematically evaluate the association between ERCC2 polymorphisms and the risk of radiotoxicity.

Methods

Publications were identified through a search of the PubMed and Web of Science databases up to August 15, 2015. The pooled odds ratios (ORs) with corresponding 95 % confidence intervals (CIs) were calculated to evaluate the association between ERCC2 polymorphisms and radiotoxicity. Trial sequential analysis (TSA) and power calculation were performed to evaluate the type 1 and type 2 errors.

Results

Eleven studies involving 2584 patients were ultimately included in this meta-analysis. Conventional meta-analysis identified a significant association between ERCC2 rs13181 polymorphism and radiotoxicity (OR = 0.71, 95 % CI: 0.55-0.93, P = 0.01), but this association failed to get the confirmation of TSA.

Conclusions

The minor allele of rs13181 polymorphism may confer a protect effect against radiotoxicity. To confirm this correlation at the level of OR = 0.71, an overall information size of approximate 2800 patients were needed.

Electronic supplementary material

The online version of this article (doi:10.1186/s13014-015-0558-6) contains supplementary material, which is available to authorized users.

Meta-analysis of associations between ATM Asp1853Asn and TP53 Arg72Pro polymorphisms and adverse effects of cancer radiotherapy

BACKGROUND

The ataxia telangiectasia mutated (ATM) protein and p53 play key roles in sensing and repairing radiation-induced DNA double strand breaks (DSBs). Accumulating epidemiological evidence indicates that functional genetic variants in ATM and TP53 genes may have an impact on the risk of radiotherapy-induced side effects. Here we performed a meta-analysis to investigate the potential interaction between ATM Asp1853Asn and TP53 polymorphisms and risk of radiotherapy-induced adverse effects quantitatively.

MATERIALS AND METHODS

Relevant articles were retrieved from PubMed, ISI Web of Science and the China National Knowledge Infrastructure (CNKI) databases. Eligible studies were selected according to specific inclusion and exclusion criteria. Odds ratios (ORs) and 95% confidence intervals (CIs) were pooled to estimate the association between ATM Asp1853Asn and TP53 Arg72Pro polymorphisms and risk of radiotherapy adverse effects. All analyses were performed using the Stata software.

RESULTS

A total of twenty articles were included in the present analysis. In the overall analysis, no significant associations between ATM Asp1853Asn and TP53 Arg72Pro polymorphisms and the risk of radiotherapy adverse effects were found. We conducted subgroup analysis stratified by type of cancer, region and time of appearance of side effects subsequently. No significant association between ATM Asp1853Asn and risk of radiotherapy adverse effects was found in any subgroup analysis. For TP53 Arg72Pro, variant C allele was associated with decreased radiotherapy adverse effects risk among Asian cancer patients in the stratified analysis by region (OR=0.71, 95%CI: 0.54-0.93, p=0.012). No significant results were found in the subgroup analysis of tumor type and time of appearance of side effects.

CONCLUSIONS

The TP53 Arg72Pro C allele might be a protective factor of radiotherapy-induced adverse effects among cancer patients from Asia. Further studies that take into consideration treatment-related factors and patient lifestyle including environmental exposures are warranted.

Association between Single Nucleotide Polymorphisms in XRCC3 and Radiation-Induced Adverse Effects on Normal Tissue: A Meta-Analysis

The X-ray repair cross-complementing group 3 (XRCC3) protein plays an important role in the repair of DNA double-strand breaks. The relationship between XRCC3 polymorphisms and the risk of radiation-induced adverse effects on normal tissue remains inconclusive. Thus, we performed a meta-analysis to elucidate the association between XRCC3 polymorphisms and radiation-induced adverse effects on normal tissue. All eligible studies up to December 2014 were identified through a search of the PubMed, Embase and Web of Science databases. Seventeen studies involving 656 cases and 2193 controls were ultimately included in this meta-analysis. The pooled odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were calculated to evaluate the association between XRCC3 polymorphisms and the risk of radiation-induced normal tissue adverse effects. We found that the XRCC3 p.Thr241Met (rs861539) polymorphism was significantly associated with early adverse effects induced by radiotherapy (OR = 1.99, 95%CI: 1.31-3.01, P = 0.001). A positive association lacking statistical significance with late adverse effects was also identified (OR = 1.28, 95%CI: 0.97-1.68, P = 0.08). In addition, the rs861539 polymorphism was significantly correlated with a higher risk of adverse effects induced by head and neck area irradiation (OR = 2.41, 95%CI: 1.49-3.89, p = 0.0003) and breast irradiation (OR = 1.41, 95%CI: 1.02-1.95, p = 0.04), whereas the correlation was not significant for lung irradiation or pelvic irradiation. Furthermore, XRCC3 rs1799794 polymorphism may have a protective effect against late adverse effects induced by radiotherapy (OR = 0.47, 95%CI: 0.26-0.86, P = 0.01). Well-designed large-scale clinical studies are required to further validate our results.

Ataxia telangiectasia-mutated gene polymorphisms and acute normal tissue injuries in cancer patients after radiation therapy: a systematic review and meta-analysis

PURPOSE

Studies of the association between ataxia telangiectasia-mutated (ATM) gene polymorphisms and acute radiation injuries are often small in sample size, and the results are inconsistent. We conducted the first meta-analysis to provide a systematic review of published findings.

METHODS AND MATERIALS

Publications were identified by searching PubMed up to April 25, 2014. Primary meta-analysis was performed for all acute radiation injuries, and subgroup meta-analyses were based on clinical endpoint. The influence of sample size and radiation injury incidence on genetic effects was estimated in sensitivity analyses. Power calculations were also conducted.

RESULTS

The meta-analysis was conducted on the ATM polymorphism rs1801516, including 5 studies with 1588 participants. For all studies, the cut-off for differentiating cases from controls was grade 2 acute radiation injuries. The primary meta-analysis showed a significant association with overall acute radiation injuries (allelic model: odds ratio = 1.33, 95% confidence interval: 1.04-1.71). Subgroup analyses detected an association between the rs1801516 polymorphism and a significant increase in urinary and lower gastrointestinal injuries and an increase in skin injury that was not statistically significant. There was no between-study heterogeneity in any meta-analyses. In the sensitivity analyses, small studies did not show larger effects than large studies. In addition, studies with high incidence of acute radiation injuries showed larger effects than studies with low incidence. Power calculations revealed that the statistical power of the primary meta-analysis was borderline, whereas there was adequate power for the subgroup analysis of studies with high incidence of acute radiation injuries.

CONCLUSIONS

Our meta-analysis showed a consistency of the results from the overall and subgroup analyses. We also showed that the genetic effect of the rs1801516 polymorphism on acute radiation injuries was dependent on the incidence of the injury. These support the evidence of an association between the rs1801516 polymorphism and acute radiation injuries, encouraging further research of this topic.

Radiogenomics helps to achieve personalized therapy by evaluating patient responses to radiation treatment

Radiogenomics is the whole genome application of radiogenetics, which focuses on uncovering the underlying genetic causes of individual variation in sensitivity to radiation. There is a growing consensus that radiosensitivity is a complex, inherited polygenic trait, dependent on the interaction of many genes involved in multiple cell processes. An understanding of the genes involved in processes such as DNA damage response and oxidative stress response, has evolved toward examination of how genetic variants, most often, single nucleotide polymorphisms (SNPs), may influence interindividual radioresponse. Many experimental approaches, such as candidate SNP association studies, genome-wide association studies and massively parallel sequencing are being proposed to address these questions. We present a review focusing on recent advances in association studies of SNPs to radiotherapy response and discuss challenges and opportunities for further studies. We also highlight the clinical perspective of radiogenomics in the future of personalized treatment in radiation oncology.

Normal tissue studies in radiation oncology: A systematic review of highly cited articles and citation patterns

Radiation therapy is one of the cornerstones of modern multidisciplinary cancer treatment. Normal tissue tolerance is critical as radiation-induced side effects may compromise organ function and quality of life. The importance of normal tissue research is reflected by the large number of scientific articles, which have been published between 2006 and 2010. The present study identified important areas of research as well as seminal publications. The article citation rate is among the potential indicators of scientific impact. Highly cited articles, arbitrarily defined as those with ≥15 citations, were identified via a systematic search of the citation database, Scopus. Up to 608 articles per year were published between 2006 and 2010, however, <10% of publications in each year accumulated ≥15 citations. This figure is notably low, when compared with other oncology studies. A large variety of preclinical and clinical topics, including toxicity prediction, the dose-volume relationship and radioprotectors, accumulated ≥15 citations. However, clinical prevention or mitigation studies were underrepresented. The following conclusion may be drawn from the present study; despite the improved technology that has resulted in superior dose distribution, clinical prevention or mitigation studies are critical and must receive higher priority, funding and attention.

Inflammatory biomarker C-reactive protein and radiotherapy-induced early adverse skin reactions in patients with breast cancer

BACKGROUND

Breast cancer is the most frequently diagnosed cancer and the second leading cause of cancer death in American women. Postsurgery adjuvant radiotherapy (RT) significantly reduced the local recurrence rate. However, many patients develop early adverse skin reactions (EASR) that impact quality of life and treatment outcomes.

METHODS

We evaluated an inflammatory biomarker, C-reactive protein (CRP), in predicting RT-induced EASRs in 159 patients with breast cancer undergoing RT. In each patient, we measured pre- and post-RT plasma CRP levels using a highly sensitive ELISA CRP assay. RT-induced EASRs were assessed at weeks 3 and 6 using the National Cancer Institute Common Toxicity Criteria (v3.0). Associations between EASRs and CRP levels were assessed using logistic regression models after adjusting for potential confounders.

RESULTS

RT-induced grade 2+ EASRs were observed in 8 (5%) and 80 (50%) patients at weeks 3 and 6 (end of RT), respectively. At the end of RT, a significantly higher proportion of African Americans developed grade 3 EASRs (13.8% vs. 2.3% in others); grade 2+ EASRs were significantly associated with: change of CRP > 1 mg/L [odds ratio (OR), 2.51; 95% confidence interval (CI), 1.06-5.95; P = 0.04], obesity (OR, 2.08; 95% CI, 1.03-4.21; P = 0.04), or combined both factors (OR, 5.21; 95% CI, 1.77-15.38; P = 0.003).

CONCLUSION

This is the first study to demonstrate that an inflammatory biomarker CRP is associated with RT-induced EASRs, particularly combined with obesity.

IMPACT

Future larger studies are warranted to validate our findings and facilitate the discovery and development of anti-inflammatory agents to protect normal tissue from RT-induced adverse effects and improve quality of life in patients with breast cancer undergoing RT.

Finding the genetic determinants of adverse reactions to radiotherapy

Individual variation in radiosensitivity is thought to be at least partly determined by genetic factors. The remaining difference between individuals is caused by comorbidities, variation in treatment, body habitus and stochastic factors. Evidence for the heritability of radiosensitivity comes from rare genetic disorders and from cell-based studies. To what extent common and rare genetic variants might explain the genetic component of radiosensitivity has not been fully elucidated. If the genetic variants accounting for this heritability were to be determined, they could be incorporated into any future predictive statistical model of adverse reactions to radiotherapy. With the evolution of DNA sequencing and bioinformatics, radiogenomics has emerged as a new research field with the aim of finding the genetic determinants of adverse reactions to radiotherapy. Similar to the investigation of other complex genetic disease traits, early studies in radiogenomics involved candidate gene association studies--many plagued by false associations caused by low sample sizes and problematic experimental design. More recently, some promising genetic associations (e.g. with tumour necrosis factor) have emerged from large multi-institutional cohorts with built-in replication. At the same time, several small- to medium-sized genome-wide association studies (GWAS) have been or are about to be published. These studies will probably lead to an increasing number of genetic polymorphisms that may predict adverse reactions to radiotherapy. The future of the field is to create large patient cohorts for multiple cancer types, to validate the genetic loci and build reliable predictive models. For example, the REQUITE project involves multiple groups in Europe and North America. For further discovery studies, larger GWAS will be necessary to include rare sequence variants through next generation sequencing. Ultimately, radiogenomics seeks to predict which cancer patients will show radiosensitivity or radioresistance, so oncologists and surgeons can alter treatment accordingly to lower adverse reactions or increase the efficacy of radiotherapy.

DNA-damage foci to detect and characterize DNA repair alterations in children treated for pediatric malignancies

Purpose

In children diagnosed with cancer, we evaluated the DNA damage foci approach to identify patients with double-strand break (DSB) repair deficiencies, who may overreact to DNA-damaging radio- and chemotherapy. In one patient with Fanconi anemia (FA) suffering relapsing squamous cell carcinomas of the oral cavity we also characterized the repair defect in biopsies of skin, mucosa and tumor.

Methods and Materials

In children with histologically confirmed tumors or leukemias and healthy control-children DSB repair was investigated by counting γH2AX-, 53BP1- and pATM-foci in blood lymphocytes at defined time points after ex-vivo irradiation. This DSB repair capacity was correlated with treatment-related normal-tissue responses. For the FA patient the defective repair was also characterized in tissue biopsies by analyzing DNA damage response proteins by light and electron microscopy.

Results

Between tumor-children and healthy control-children we observed significant differences in mean DSB repair capacity, suggesting that childhood cancer is based on genetic alterations affecting DNA repair. Only 1 out of 4 patients with grade-4 normal-tissue toxicities revealed an impaired DSB repair capacity. The defective DNA repair in FA patient was verified in irradiated blood lymphocytes as well as in non-irradiated mucosa and skin biopsies leading to an excessive accumulation of heterochromatin-associated DSBs in rapidly cycling cells.

Conclusions

Analyzing human tissues we show that DSB repair alterations predispose to cancer formation at younger ages and affect the susceptibility to normal-tissue toxicities. DNA damage foci analysis of blood and tissue samples allows one to detect and characterize DSB repair deficiencies and enables identification of patients at risk for high-grade toxicities. However, not all treatment-associated normal-tissue toxicities can be explained by DSB repair deficiencies.

Current concepts in clinical radiation oncology

Based on its potent capacity to induce tumor cell death and to abrogate clonogenic survival, radiotherapy is a key part of multimodal cancer treatment approaches. Numerous clinical trials have documented the clear correlation between improved local control and increased overall survival. However, despite all progress, the efficacy of radiation-based treatment approaches is still limited by different technological, biological, and clinical constraints. In principle, the following major issues can be distinguished: (1) The intrinsic radiation resistance of several tumors is higher than that of the surrounding normal tissue, (2) the true patho-anatomical borders of tumors or areas at risk are not perfectly identifiable, (3) the treatment volume cannot be adjusted properly during a given treatment series, and (4) the individual heterogeneity in terms of tumor and normal tissue responses toward irradiation is immense. At present, research efforts in radiation oncology follow three major tracks, in order to address these limitations: (1) implementation of molecularly targeted agents and 'omics'-based screening and stratification procedures, (2) improvement of treatment planning, imaging, and accuracy of dose application, and (3) clinical implementation of other types of radiation, including protons and heavy ions. Several of these strategies have already revealed promising improvements with regard to clinical outcome. Nevertheless, many open questions remain with individualization of treatment approaches being a key problem. In the present review, the current status of radiation-based cancer treatment with particular focus on novel aspects and developments that will influence the field of radiation oncology in the near future is summarized and discussed.

XRCC1 R399Q polymorphism and risk of normal tissue injury after radiotherapy in breast cancer patients

Radiotherapy is an important weapon in the treatment of breast cancer, but normal tissue injury after radiotherapy can be a threat for patients. Genetic markers conferring the ability to identify hyper-sensitive patients at risk of normal tissue injury in advance would considerably improve therapy. Association studies on genetic variation and occurrence of normal tissue injury can help us identify such markers, but previous studies on the association between XRCC1 R399Q polymorphism and risk of normal tissue injury after radiotherapy in breast cancer patients report conflicting findings. We performed a meta-analysis to comprehensively evaluate the association between XRCC1 R399Q polymorphism and risk of normal tissue injury after radiotherapy in breast cancer patients. The pooled odds ratios (ORs) with their 95% confidence interval (95% CIs) were calculated to assess the strength of the association. Fourteen case-control studies with a total of 2,448 breast cancer cases were finally included into the meta-analysis. Overall, XRCC1 R399Q polymorphism was significantly associated with increased risk of normal tissue injury after radiotherapy under all three models (for QQ versus RR: fixed-effects OR = 1.06, 95% CI 1.00-1.13, P = 0.050; for RQ versus RR: fixed-effects OR = 1.05, 95% CI 1.00-1.10, P = 0.047; for QQ/RQ versus RR: fixed-effects OR = 1.26, 95% CI 1.01-1.58, P = 0.041). The meta-analysis suggests that XRCC1 R399Q polymorphism was significantly associated with increased risk of normal tissue injury after radiotherapy in breast cancer patients, and XRCC1 R399Q polymorphism is a genetic marker of normal tissue injury after radiotherapy in breast cancer patients.

Acute skin toxicity in Korean breast cancer patients carrying BRCA mutations

PURPOSE

In contrast to in vitro studies, most clinical trials testing the radiosensitivity of BRCA (Breast cancer susceptibility gene) mutations do not find a correlation between BRCA status and enhanced radiosensitivity. These trials include different ethnicities, and there is a lack of clinical data on BRCA1/2 mutation carriers and radiosensitivity in non-Caucasian patients. The goal of this study was to investigate acute skin toxicity, as a part of radiosensitivity, in breast cancer patients with BRCA1/2 mutations.

MATERIAL AND METHODS

BRCA mutation analysis was performed for 213 patients who underwent breast-conserving therapy using radiotherapy. Skin toxicity was scored according to the Radiation Therapy Oncology Group (RTOG) criteria during treatment and during one-month follow-up after radiation therapy.

RESULTS

Forty-six patients had BRCA1/2 mutations and 57 patients showed higher than grade 2 (RTOG) skin toxicity. In multivariate analysis, significant associations were found between mean breast volume and acute skin toxicity. BRCA mutation status, however, failed to show a significant correlation.

CONCLUSIONS

Our results indicate that carriers of BRCA1/2 mutations among non-Caucasian breast cancer patients showed no enhancement in radiation sensitivity. Multiple genetic markers may be correlated with normal tissue responses after radiotherapy. Further studies are needed to identify genetic predispositions to normal tissue responses after radiotherapy.

Association between polymorphisms of XRCC1 Arg399Gln and XPD Lys751Gln genes and prognosis of colorectal cancer in a Chinese population

We conducted this study to detect associations between XRCC1 Arg399Gln and XPD Lys751Gln genotypes and survival of colorectal cancer patients treated with 5-FU/oxalipatin chemotherapy. We included 289 Chinese patients with advanced colorectal cancer, who had received 5-FU/oxalipatin chemotherapy as first-line treatment from January 2005 to January 2007. All patients were followed up till Nov. 2011. Genotyping for XRCC1 Arg399Gln and XPD Lys751Gln polymorphisms was based upon duplex polymerase-chain-reaction with the PCR-RFLP method. In our study, we found the XRCC1 399 Gln/Gln genotype to confer significantly higher rates of response to chemotherapy when compared to the Arg/Arg genotype [OR (95% CI)=2.56(1.57-2.55)]. patients with the XPD 751 Gln/Gln genotype had significantly higher rates of response to chemotherapy [OR (95% CI)=1.54(0.87-2.65)] and those with the XRCC1 399 Gln/Gln genotype had a longer average survival time and significantly lower risk of death than did those with the Arg/Arg genotype [HR (95% CI)=0.66(0.36-0.95)]. Similarly, those carrying the XPD 751Gln/Gln genotype had 0.51-fold the risk of death of those with XPD 751Lys/Lys [HR (95% CI)=0.51(0.33-0.94)]. In conclusion, it is suggested that the XRCC1 Arg399Gln and XPD Lys751Gln polymorphisms should be routinely assessed to determine colorectal patients who are more likely to benefit from 5-FU/oxalipatin chemotherapy.

ATM polymorphisms predict severe radiation pneumonitis in patients with non-small cell lung cancer treated with definitive radiation therapy

PURPOSE

The ataxia telangiectasia mutated (ATM) gene mediates detection and repair of DNA damage. We investigated associations between ATM polymorphisms and severe radiation-induced pneumonitis (RP).

METHODS AND MATERIALS

We genotyped 3 potentially functional single nucleotide polymorphisms (SNPs) of ATM (rs1801516 [D1853N/5557G>A], rs189037 [-111G>A] and rs228590) in 362 patients with non-small cell lung cancer (NSCLC), who received definitive (chemo)radiation therapy. The cumulative severe RP probabilities by genotypes were evaluated using the Kaplan-Meier analysis. The associations between severe RP risk and genotypes were assessed by both logistic regression analysis and Cox proportional hazard model with time to event considered.

RESULTS

Of 362 patients (72.4% of non-Hispanic whites), 56 (15.5%) experienced grade ≥3 RP. Patients carrying ATM rs189037 AG/GG or rs228590 TT/CT genotypes or rs189037G/rs228590T/rs1801516G (G-T-G) haplotype had a lower risk of severe RP (rs189037: GG/AG vs AA, adjusted hazard ratio [HR] = 0.49, 95% confidence interval [CI], 0.29-0.83, P=.009; rs228590: TT/CT vs CC, HR=0.57, 95% CI, 0.33-0.97, P=.036; haplotype: G-T-G vs A-C-G, HR=0.52, 95% CI, 0.35-0.79, P=.002). Such positive findings remained in non-Hispanic whites.

CONCLUSIONS

ATM polymorphisms may serve as biomarkers for susceptibility to severe RP in non-Hispanic whites. Large prospective studies are required to confirm our findings.