Genetic predictors of adverse radiotherapy effects: the Gene-PARE project

Radiation-induced lymphocyte apoptosis assay: Primetime for routine clinical use?

The impact of curative radiotherapy mainly depends on the total dose delivered to the tumor. However, despite recent technological advances, the dose delivered to surrounding healthy tissues may reduce the therapeutic ratio of many radiation treatments. In the same population treated at one center with the same technique, individual radiosensitivity clearly exists, particularly in terms of late side effects that are, in principle, non-reversible. This article details the history of the radiation-induced lymphocyte apoptosis assay, from preclinical data to multicenter clinical trials. It puts the performance of such assays into perspective to define the optimal clinical situations for its use in daily practice.

Does Gender Difference Effect Radiation-Induced Lung Toxicity? An Experimental Study by Genetic and Histopathological Predictors

Several studies have reported differences in radiation toxicity between the sexes, but these differences have not been tested with respect to histopathology and genes. This animal study aimed to show an association between histopathological findings of radiation-induced lung toxicity and the genes ATM, SOD2, TGF-β1, XRCC1, XRCC3 and HHR2. In all, 120 animals were randomly divided into 2 control groups (male and female) and experimental groups comprising fifteen rats stratified by sex, radiotherapy (0 Gy vs. 10 Gy), and time to sacrifice (6, 12, and 24 weeks postirradiation). Histopathological evaluations for lung injury, namely, intra-alveolar edema, alveolar neutrophils, intra-alveolar erythrocytes, activated macrophages, intra-alveolar fibrosis, hyaline arteriosclerosis, and collapse were performed under a light microscope using a grid system; the evaluations were semi quantitatively scored. Then, the alveolar wall thickness was measured. Real-time quantitative reverse transcription PCR (RT-qPCR) was used to determine gene expression differences in ATM, TGF-β1, XRCC1, XRCC3, SOD2 and HHR2L among the groups. Histopathological data showed that radiation-induced acute, subacute, and chronic lung toxicity were worse in male rats. The expression levels of the evaluated genes were significantly higher in females than males in the control group, but this difference was lost over time after radiotherapy. Less toxicity in females may be attributable to the fact that the expression of the evaluated genes was higher in normal lung tissue in females than in males and the changes in gene expression patterns in the postradiotherapy period played a protective role in females. Additional data related to pulmonary function, lung weights, imaging, or outcomes are needed to support this data that is based on histopathology alone.

Liquid biopsy in NSCLC: a new challenge in radiation therapy

Lung cancer is the most common cancer and the leading cause of cancer mortality worldwide. To date, tissue biopsy has been the gold standard for the diagnosis and the identification of specific molecular mutations, to guide choice of therapy. However, this procedure has several limitations. Liquid biopsy could represent a solution to the intrinsic limits of traditional biopsy. It can detect cancer markers such as circulating tumor DNA or RNA (ctDNA, ctRNA), and circulating tumor cells, in plasma, serum or other biological fluids. This procedure is minimally invasive, reproducible and can be used repeatedly. The main clinical applications of liquid biopsy in non-small cell lung cancer (NSCLC) patients are the early diagnosis, stratification of the risk of relapse, identification of mutations to guide application of targeted therapy and the evaluation of the minimum residual disease. In this review, the current role of liquid biopsy and associated markers in the management of NSCLC patients was analyzed, with emphasis on ctDNA and CTCs, and radiotherapy.

Low dose ionizing radiation effects on the immune system

Ionizing radiation interacts with the immune system in many ways with a multiplicity that mirrors the complexity of the immune system itself: namely the need to maintain a delicate balance between different compartments, cells and soluble factors that work collectively to protect, maintain, and restore tissue function in the face of severe challenges including radiation damage. The cytotoxic effects of high dose radiation are less relevant after low dose exposure, where subtle quantitative and functional effects predominate that may go unnoticed until late after exposure or after a second challenge reveals or exacerbates the effects. For example, low doses may permanently alter immune fitness and therefore accelerate immune senescence and pave the way for a wide spectrum of possible pathophysiological events, including early-onset of age-related degenerative disorders and cancer. By contrast, the so called low dose radiation therapy displays beneficial, anti-inflammatory and pain relieving properties in chronic inflammatory and degenerative diseases. In this review, epidemiological, clinical and experimental data regarding the effects of low-dose radiation on the homeostasis and functional integrity of immune cells will be discussed, as will be the role of immune-mediated mechanisms in the systemic manifestation of localized exposures such as inflammatory reactions. The central conclusion is that ionizing radiation fundamentally and durably reshapes the immune system. Further, the importance of discovery of immunological pathways for modifying radiation resilience amongst other research directions in this field is implied.

Radiogenomics Consortium Genome-Wide Association Study Meta-Analysis of Late Toxicity After Prostate Cancer Radiotherapy

BACKGROUND

A total of 10%-20% of patients develop long-term toxicity following radiotherapy for prostate cancer. Identification of common genetic variants associated with susceptibility to radiotoxicity might improve risk prediction and inform functional mechanistic studies.

METHODS

We conducted an individual patient data meta-analysis of six genome-wide association studies (n = 3871) in men of European ancestry who underwent radiotherapy for prostate cancer. Radiotoxicities (increased urinary frequency, decreased urinary stream, hematuria, rectal bleeding) were graded prospectively. We used grouped relative risk models to test associations with approximately 6 million genotyped or imputed variants (time to first grade 2 or higher toxicity event). Variants with two-sided Pmeta less than 5 × 10-8 were considered statistically significant. Bayesian false discovery probability provided an additional measure of confidence. Statistically significant variants were evaluated in three Japanese cohorts (n = 962). All statistical tests were two-sided.

RESULTS

Meta-analysis of the European ancestry cohorts identified three genomic signals: single nucleotide polymorphism rs17055178 with rectal bleeding (Pmeta = 6.2 × 10-10), rs10969913 with decreased urinary stream (Pmeta = 2.9 × 10-10), and rs11122573 with hematuria (Pmeta = 1.8 × 10-8). Fine-scale mapping of these three regions was used to identify another independent signal (rs147121532) associated with hematuria (Pconditional = 4.7 × 10-6). Credible causal variants at these four signals lie in gene-regulatory regions, some modulating expression of nearby genes. Previously identified variants showed consistent associations (rs17599026 with increased urinary frequency, rs7720298 with decreased urinary stream, rs1801516 with overall toxicity) in new cohorts. rs10969913 and rs17599026 had similar effects in the photon-treated Japanese cohorts.

CONCLUSIONS

This study increases the understanding of the architecture of common genetic variants affecting radiotoxicity, points to novel radio-pathogenic mechanisms, and develops risk models for testing in clinical studies. Further multinational radiogenomics studies in larger cohorts are worthwhile.

Developing more sensitive genomic approaches to detect radioresponse in precision radiation oncology: From tissue DNA analysis to circulating tumor DNA

Despite the common application and considerable efforts to achieve precision radiotherapy (RT) in several types of cancer, RT has not yet entered the era of precision medicine; the ability to predict radiosensitivity and treatment responses in tumors and normal tissues is lacking. Therefore, development of genome-based methods for individual prognosis in radiation oncology is urgently required. Traditional DNA sequencing requires tissue samples collected during invasive operations; therefore, repeated tests are nearly impossible. Intra- and inter-tumoral heterogeneity may undermine the predictive power of a single assay from tumor samples. In contrast, analysis of circulating tumor DNA (ctDNA) allows for non-invasive and near real-time sampling of tumors. By investigating the genetic composition of tumors and monitoring dynamic changes during treatment, ctDNA analysis may potentially be clinically valuable in prediction of treatment responses prior to RT, surveillance of responses during RT, and evaluation of residual disease following RT. As a biomarker for RT response, ctDNA profiling may guide personalized treatments. In this review, we will discuss approaches of tissue DNA sequencing and ctDNA detection and summarize their clinical applications in both traditional RT and in combination with immunotherapy.

Precision Radiotherapy and Radiation Risk Assessment: How Do We Overcome Radiogenomic Diversity?

Precision medicine is a rapidly developing area that aims to deliver targeted therapies based on individual patient characteristics. However, current radiation treatment is not yet personalized; consequently, there is a critical need for specific patient characteristics of both tumor and normal tissues to be fully incorporated into dose prescription. Furthermore, current risk assessment following environmental, occupational, or accidental exposures to radiation is based on population effects, and does not account for individual diversity underpinning radiosensitivity. The lack of personalized approaches in both radiotherapy and radiation risk assessment resulted in the current situation where a population-based model, effective dose, is being used. In this review article, to stimulate scientific discussion for precision medicine in both radiotherapy and radiation risk assessment, we propose a novel radiological concept and metric - the personalized dose and the personalized risk index - that incorporate individual physiological, lifestyle-related and genomic variations and radiosensitivity, outlining the potential clinical application for precision medicine. We also review on recent progress in both genomics and biobanking research, which is promising for providing novel insights into individual radiosensitivity, and for creating a novel conceptual framework of precision radiotherapy and radiation risk assessment.

Polymorphism of regulatory region of APEH gene (c.-521G>C, rs4855883) as a relevant predictive factor for radiotherapy induced oral mucositis and overall survival in head neck cancer patients

Background

The study purpose was to examine the correlation between SNP in the regulatory region (c.-521G>C, rs4855883) of APEH gene as well as the incidence and severity of radiotherapy (RTH) induced oral mucositis (OM) and overall survival (OS) in head and neck cancer (HNC) patients.

Methods

OM in 62 HNC patients subjected to irradiation was assessed using RTOG/EORTC scale. DNA was isolated from whole blood of HNC patients. Mini-sequencing method (SNaPshot PCR) was used to determine the genotype.

Results

The following frequency of occurrence of APEH gene was observed: CC: 37.1%, CG: 43.6% and GG: 19.3%. It was established that the presence of CC genotype reduced the risk of occurrence of grade 2 and 3 OM symptoms: 3-fold in RTH week 2 (in case of CC vs GC or GG it was: 26.8% vs 73.2% patients, respectively, OR = 0.27, 95 CI: 0.09–0.83; p = 0.0222), 6-fold in RTH week 3 (in case of CC vs GC or GG it was: 29.4% vs 70.6% patients, respectively, OR = 0.16, 95 CI: 0.04–0.67; p = 0.0125) and grade 3 OM symptoms 4-fold in RTH week 6 (in case of CC vs GC or GG it was: 19.2% vs 80.8% patients, respectively, OR = 0.23, 95 CI: 0.07–0.77; p = 0.0166). CC genotype was associated with lower OS (CC vs GG or GC: 29 months vs 38 months; HR = 2.48, 95% CI: 0.90–6.85; p = 0.0266).

Conclusion

CC genotype of APEH gene was correlated with the risk of more severe radiotherapy-induced OM in HNC patients and lower rates of survival.

GSTP1 Ile105Val polymorphism might be associated with the risk of radiation pneumonitis among lung cancer patients in Chinese population: A prospective study

Background: Growing data suggest that DNA damage repair and detoxification pathways play crucial roles in radiation-induced toxicities. To determine whether common functional single-nucleotide polymorphisms (SNPs) in candidate genes from these pathways can be used as predictors of radiation pneumonitis (RP), we conducted a prospective study to evaluate the associations between functional SNPs and risk of RP.

Methods: We recruited a total of 149 lung cancer patients who had received intensity modulated radiation therapy (IMRT). GSTP1 and XRCC1 were genotyped using the SurPlexTM-xTAG method in all patients. RP events were prospectively scored using the National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE), version 4.0. Kaplan-Meier analysis was used to determine the cumulative probability of RP of grade ≥ 2. Cox proportional hazard regression was performed to identify clinical variables and SNPs associated with risk of RP grade ≥ 2, using univariate and multivariate analysis, respectively.

Results: With a median follow-up of 9 months, the incidence of RP of grade ≥ 2 was 38.3%. A predicting role in RP was observed for the GSTP1 SNP (adjusted hazard ratio 3.543; 95% CI 1.770-7.092; adjusted P< 0.001 for the Ile/Val and Val/Val genotypes versus Ile/Ile genotype). Whereas, we found that patients with XRCC1 399Arg/Gln and Gln/Gln genotypes had a lower risk of RP compares with those carrying Arg/Arg genotype (adjusted HR 0.653; 95% CI 0.342-1.245), but with no statistical significance observed (adjusted P = 0.195).

Conclusions: Our results suggested a novel association between GSTP1 SNP 105Ile/Val and risk of RP development, which suggests the potential use of this genetic polymorphism as a predictor of RP. In addition, genetic polymorphisms of XRCC1 399Arg/Gln may also be associated with RP.

Compromized DNA repair as a basis for identification of cancer radiotherapy patients with extreme radiosensitivity

A small percentage of cancer radiotherapy patients develop abnormally severe side effects as a consequence of intrinsic radiosensitivity. We analysed the γ-H2AX response to ex-vivo irradiation of peripheral blood lymphocytes (PBL) and plucked eyebrow hair follicles from 16 patients who developed severe late radiation toxicity following radiotherapy, and 12 matched control patients. Longer retention of the γ-H2AX signal and lower colocalization efficiency of repair factors in over-responding patients confirmed that DNA repair in these individuals was compromised. Five of the radiosensitive patients harboured LoF mutations in DNA repair genes. An extensive range of quantitative parameters of the γ-H2AX response were studied with the objective to establish a predictor for radiosensitivity status. The most powerful predictor was the combination of the fraction of the unrepairable component of γ-H2AX foci and repair rate in PBL, both derived from non-linear regression analysis of foci repair kinetics. We introduce a visual representation of radiosensitivity status that allocates a position for each patient on a two-dimensional "radiosensitivity map". This analytical approach provides the basis for larger prospective studies to further refine the algorithm, ultimately to triage capability.

Meta-analysis of Genome Wide Association Studies Identifies Genetic Markers of Late Toxicity Following Radiotherapy for Prostate Cancer

Nearly 50% of cancer patients undergo radiotherapy. Late radiotherapy toxicity affects quality-of-life in long-term cancer survivors and risk of side-effects in a minority limits doses prescribed to the majority of patients. Development of a test predicting risk of toxicity could benefit many cancer patients. We aimed to meta-analyze individual level data from four genome-wide association studies from prostate cancer radiotherapy cohorts including 1564 men to identify genetic markers of toxicity. Prospectively assessed two-year toxicity endpoints (urinary frequency, decreased urine stream, rectal bleeding, overall toxicity) and single nucleotide polymorphism (SNP) associations were tested using multivariable regression, adjusting for clinical and patient-related risk factors. A fixed-effects meta-analysis identified two SNPs: rs17599026 on 5q31.2 with urinary frequency (odds ratio [OR] 3.12, 95% confidence interval [CI] 2.08-4.69, p-value 4.16×10(-8)) and rs7720298 on 5p15.2 with decreased urine stream (OR 2.71, 95% CI 1.90-3.86, p-value=3.21×10(-8)). These SNPs lie within genes that are expressed in tissues adversely affected by pelvic radiotherapy including bladder, kidney, rectum and small intestine. The results show that heterogeneous radiotherapy cohorts can be combined to identify new moderate-penetrance genetic variants associated with radiotherapy toxicity. The work provides a basis for larger collaborative efforts to identify enough variants for a future test involving polygenic risk profiling.

Single Nucleotide Polymorphism rs1801516 in Ataxia Telangiectasia-Mutated Gene Predicts Late Fibrosis in Cancer Patients After Radiotherapy: A PRISMA-Compliant Systematic Review and Meta-Analysis

Studies on associations between ataxia telangiectasia-mutated (ATM) polymorphisms and late radiotherapy-induced adverse events vary in clinical settings, and the results are inconsistent.We conducted the first meta-analysis following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines to investigate the role of the ATM polymorphism rs1801516 in the development of radiotherapy-induced late fibrosis.We searched PubMed, Embase, Web of Science, and Chinese National Knowledge Infrastructure databases to identify studies that investigated the effect of the ATM polymorphism rs1801516 on radiotherapy-induced late fibrosis before September 8, 2015. Summary odds ratios (ORs) and the corresponding 95% confidence intervals (CIs) were used to assess the association between late fibrosis and the rs1801516 polymorphism. Subgroup analyses were conducted to evaluate the influence of clinical features on the genetic association. Tests of interaction were used to compare differences in the effect estimates between subgroups.The overall meta-analysis of 2000 patients from 9 studies showed that the minor allele of the rs1801516 polymorphism was associated with a significantly increased risk of developing late fibrosis (OR = 1.78, 95% CI: 1.07, 2.94), with high between-study heterogeneity (I = 66.6%, P = 0.002). In subgroup analyses, we identified that the incidence of late fibrosis was a major source of heterogeneity across studies. The OR for patients with a high incidence of late fibrosis was 3.19 (95% CI: 1.86, 5.47), in contrast to 1.09 (95% CI: 1.01, 1.17) for those with a low incidence. There was a significant difference in the effect estimates between the 2 subgroups (ratio of OR = 2.94, 95% CI 1.70, 5.08, P = 0.031).This meta-analysis supported previously reported effect of the ATM polymorphism rs1801516 on radiotherapy-induced late fibrosis. This finding encouraged further researches to identify more genetic polymorphisms that were predictive for radiotherapy-induced adverse events. In addition, we showed that the inconsistency of the associations seen in these studies might be related to variations in the incidence of late fibrosis in the patients. This suggested that future studies should consider the incidence of radiotherapy-induced adverse events when investigating radiosensitivity signature genes.

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.

Incorporating Genetic Biomarkers into Predictive Models of Normal Tissue Toxicity

There is considerable variation in the level of toxicity patients experience for a given dose of radiotherapy, which is associated with differences in underlying individual normal tissue radiosensitivity. A number of syndromes have a large effect on clinical radiosensitivity, but these are rare. Among non-syndromic patients, variation is less extreme, but equivalent to a ±20% variation in dose. Thus, if individual normal tissue radiosensitivity could be measured, it should be possible to optimise schedules for individual patients. Early investigations of in vitro cellular radiosensitivity supported a link with tissue response, but individual studies were equivocal. A lymphocyte apoptosis assay has potential, and is currently under prospective validation. The investigation of underlying genetic variation also has potential. Although early candidate gene studies were inconclusive, more recent genome-wide association studies are revealing definite associations between genotype and toxicity and highlighting the potential for future genetic testing. Genetic testing and individualised dose prescriptions could reduce toxicity in radiosensitive patients, and permit isotoxic dose escalation to increase local control in radioresistant individuals. The approach could improve outcomes for half the patients requiring radical radiotherapy. As a number of patient- and treatment-related factors also affect the risk of toxicity for a given dose, genetic testing data will need to be incorporated into models that combine patient, treatment and genetic data.

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.

Targeting DNA repair pathways for cancer treatment: what's new?

Disruptions in DNA repair pathways predispose cells to accumulating DNA damage. A growing body of evidence indicates that tumors accumulate progressively more mutations in DNA repair proteins as cancers progress. DNA repair mechanisms greatly affect the response to cytotoxic treatments, so understanding those mechanisms and finding ways to turn dysregulated repair processes against themselves to induce tumor death is the goal of all DNA repair inhibition efforts. Inhibition may be direct or indirect. This burgeoning field of research is replete with promise and challenge, as more intricacies of each repair pathway are discovered. In an era of increasing concern about healthcare costs, use of DNA repair inhibitors can prove to be highly effective stewardship of R&D resources and patient expenses.

Immunological markers that predict radiation toxicity

Radiotherapy is a major modality of cancer treatment responsible for a large proportion of cancer that is cured. Radiation exposure induces an inflammatory response which can be influenced by genetic, epigenetic, tumour, health and other factors which can lead to very different treatment outcomes between individuals. Molecules involved in the immunological response provide excellent potential biomarkers for the prediction of radiation-induced toxicity. The known molecular and cellular immunological responses in relation to radiation and the potential to improve cancer treatment are presented in this review. In particular, immunological biomarkers of radiation-induced fibrosis and pneumonitis in cancer radiotherapy patients are discussed.

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.

Relationship between radiation-induced apoptosis of T lymphocytes and chronic toxicity in patients with prostate cancer treated by radiation therapy: a prospective study

PURPOSE

To assess the correlation of radiation-induced apoptosis in vitro of CD4 and CD8 T lymphocytes with late toxicity of prostate cancer patients treated with radiation therapy.

METHODS AND MATERIALS

214 patients were prospectively included in the study. Peripheral blood was drawn from patients before treatment and irradiated with 8 Gy. The percentage of CD4+ and CD8+ T lymphocytes that underwent radiation-induced apoptosis was assessed by flow cytometry. Toxicity and mortality were correlated in 198 cases with pretreatment apoptosis and clinical and biological variables by use of a Cox proportional hazards model.

RESULTS

The mean percentage of CD4+ and CD8+ T lymphocyte radiation-induced apoptosis was 28.58% (±14.23) and 50.76% (±18.9), respectively. Genitourinary (GU) toxicity was experienced by 39.9% of patients, while gastrointestinal (GI) toxicity was experienced by 19.7%. The probability of development of GU toxicity was nearly doubled (hazard ratio [HR] 1.99, P=.014) in those patients in whom the percentage of in vitro radiation-induced apoptosis of CD4+ T-lymphocytes was ≤28.58%. It was also almost double in patients who received doses ≥50 Gy in 65% of the bladder volume (V65 ≥50) (HR 1.92, P=.048). No correlation was found between GI toxicity and any of the variables studied. The probability of death during follow-up, after adjustment for different variables, was 2.7 times higher in patients with a percentage of CD8+ T lymphocyte apoptosis ≤50.76% (P=.022).

CONCLUSIONS

In conclusion, our study shows, in the largest prospective cohort of prostate cancer patients undergoing radiation therapy, that in vitro radiation-induced apoptosis of CD4+ T lymphocytes assessed before radiation therapy was associated with the probability of developing chronic GU toxicity. In addition, the radiation dose received in the urinary bladder (V65 ≥50) affected the occurrence of GU toxicity. Finally, we also demonstrate that radiation-induced apoptosis of CD8+ T lymphocytes was associated with overall survival, although larger series are needed to confirm this finding.

A novel high-throughput irradiator for in vitro radiation sensitivity bioassays

This paper describes the development and characterization of a fully automated in vitro cell irradiator using an electronic brachytherapy source to perform radiation sensitivity bioassays. This novel irradiator allows complex variable dose and dose rate schemes to be delivered to multiple wells of 96-well culture plates used in standard biological assays. The Xoft Axxent® eBx™ was chosen as the x-ray source due to its ability to vary tube current up to 300 µA for a 50 kVp spectrum using clinical surface applicators. Translation of the multiwell plate across the fixed radiation field is achieved using a precision motor driven computer controlled positioning system. A series of measurements was performed to characterize dosimetric performance of the system. Measurements have shown that the radiation output measured with an end window ionization chamber is stable between operating currents of 50-300 µA. In addition, radiochromic film was used to characterize the field flatness and symmetry. The average field flatness in the in-plane and cross-plane direction was 2.9 ± 1.0% and 4.0 ± 1.7%, respectively. The average symmetry in the in-plane and cross-plane direction was 1.8 ± 0.9% and 1.6 ± 0.5%, respectively. The optimal focal spot resolution at the cellular plane was determined by measuring sequential irradiations on radiochromic film for three different well spacing schemes. It was determined that the current system can irradiate every other well with negligible impact on the radiation field characteristics. Finally, a performance comparison between this system and a common cabinet irradiator is presented.

Radiogenomics: using genetics to identify cancer patients at risk for development of adverse effects following radiotherapy

Normal-tissue adverse effects following radiotherapy are common and significantly affect quality of life. These effects cannot be accounted for by dosimetric, treatment, or demographic factors alone, and evidence suggests that common genetic variants are associated with radiotherapy adverse effects. The field of radiogenomics has evolved to identify such genetic risk factors. Radiogenomics has two goals: (i) to develop an assay to predict which patients with cancer are most likely to develop radiation injuries resulting from radiotherapy, and (ii) to obtain information about the molecular pathways responsible for radiation-induced normal-tissue toxicities. This review summarizes the history of the field and current research.

SIGNIFICANCE

A single-nucleotide polymorphism–based predictive assay could be used, along with clinical and treatment factors, to estimate the risk that a patient with cancer will develop adverse effects from radiotherapy. Such an assay could be used to personalize therapy and improve quality of life for patients with cancer.

Will SNPs be useful predictors of normal tissue radiosensitivity in the future?

The ability to predict individual risk of radiation-induced normal tissue complications is a long sought goal in radiobiology. The last decade saw increasing interest in identifying associations between single nucleotide polymorphisms (SNPs) and normal tissue complication risk. Nevertheless, it remains controversial whether SNPs will be useful predictors of normal tissue radiosensitivity. This paper provides a summary of a scientific debate held at the 31st ESTRO conference in which four scientists argued in favor or against the motion that SNPs will be useful predictors of normal tissue radiosensitivity in the future.

Cerebral radiation necrosis: a review of the pathobiology, diagnosis and management considerations

Radiation therapy forms one of the building blocks of the multi-disciplinary management of patients with brain tumors. Improved survival following radiation therapy may come with a cost, including the potential complication of radiation necrosis. Radiation necrosis impacts the quality of life in cancer survivors, and it is essential to detect and effectively treat this entity as early as possible. Significant progress in neuro-radiology and molecular pathology facilitate more straightforward diagnosis and characterization of cerebral radiation necrosis. Several therapeutic interventions, both medical and surgical, may halt the progression of radiation necrosis and diminish or abrogate its clinical manifestations, but there are still no definitive guidelines to follow explicitly that guide treatment of radiation necrosis. We discuss the pathobiology, clinical features, diagnosis, available treatment modalities, and outcomes in the management of patients with intracranial radiation necrosis that follows radiation used to treat brain tumors.

Gastrointestinal radiation injury: Symptoms, risk factors and mechanisms

Ionising radiation therapy is a common treatment modality for different types of cancer and its use is expected to increase with advances in screening and early detection of cancer. Radiation injury to the gastrointestinal tract is important factor working against better utility of this important therapeutic modality. Cancer survivors can suffer a wide variety of acute and chronic symptoms following radiotherapy, which significantly reduces their quality of life as well as adding an extra burden to the cost of health care. The accurate diagnosis and treatment of intestinal radiation injury often represents a clinical challenge to practicing physicians in both gastroenterology and oncology. Despite the growing recognition of the problem and some advances in understanding the cellular and molecular mechanisms of radiation injury, relatively little is known about the pathophysiology of gastrointestinal radiation injury or any possible susceptibility factors that could aggravate its severity. The aims of this review are to examine the various clinical manifestations of post-radiation gastrointestinal symptoms, to discuss possible patient and treatment factors implicated in normal gastrointestinal tissue radiosensitivity and to outline different mechanisms of intestinal tissue injury.

Detection and quantification of a radiation-associated mitochondrial DNA deletion by a nested real-time PCR in human peripheral lymphocytes

In this study we implemented a new assay using a nested real-time polymerase chain reaction (PCR) to detect radiation-induced common deletion (CD) in mitochondrial DNA (mtDNA) of human peripheral lymphocytes. A standard curve for real-time PCR was established by applying a plasmid DNA containing human normal mtDNA or mutated mtDNA. Human peripheral lymphocyte DNA was amplified and quantified by real-time PCR using primer sets for total damaged or mutated mtDNA, plus probes labeled with the fluorescent dyes. The first-round PCR generated multiple products were used as the template for a second-round PCR. We herein describe a nested real-time PCR assay capable of quantifying mtDNA bearing the CD in human peripheral lymphocytes following exposure (in vitro) to (137)Cs γ-rays in a dose range of 0.5 up to 5Gy. The reproducibility of this assay was evident for both unirradiated and irradiated samples by examining human blood lymphocytes from 14 donors. This technique was sensitive enough to detect deletions in mtDNA at low dose levels, as low as 0.5Gy, and higher levels of CD mtDNA were evident at higher doses (≥1Gy), however, there was no consistent dose-response relationship.

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.

Antioxidant enzyme polymorphisms and neuropsychological outcomes in medulloblastoma survivors: a report from the Childhood Cancer Survivor Study

Psychological or neurocognitive impairment is often seen in medulloblastoma survivors after craniospinal radiation; however, significant variability in outcomes exists. This study investigated the role of antioxidant enzyme polymorphisms in moderating this outcome and hypothesized that patients who had polymorphisms associated with lower antioxidant enzyme function would have a higher occurrence of impairment. From the Childhood Cancer Survivor Study (CCSS) cohort, 109 medulloblastoma survivors and 143 siblings were identified who completed the CCSS Neurocognitive Questionnaire (NCQ) and the Brief Symptom Inventory-18 (BSI-18) and who provided buccal DNA samples. Real-time polymerase chain reaction (PCR) allelic discrimination was used for SOD2 (rs4880), GPX1 (rs1050450), and GSTP1 (rs1695 and rs1138272) genotyping and PCR for GSTM1 and GSTT1 gene deletions. Outcomes on NCQ and BSI-18 subscale scores were examined in association with genotypes and clinical factors, including age at diagnosis, sex, and radiation dose, using univariate and multivariate analysis of variance. Patients <7 years of age at diagnosis displayed more problems with task efficiency (P < .001) and fewer problems with somatic complaints (P = .004) than did patients ≥7 years of age. Female patients reported more organization problems than did male patients (P = .02). Patients with homozygous GSTM1 gene deletion reported higher anxiety (mean null genotype = 47.3 ± 9.2, non-null = 43.9 ± 7.8; P = .04), more depression (null = 51.0 ± 9.8, non-null = 47.0 ± 9.4; P = .03), and more global distress (null = 50.2 ± 9.7, non-null = 45.2 ± 9.9; P = .01). All associations for the GSTM1 polymorphism remained statistically significant in a multivariate model controlling for age, sex, and radiation dose. Homozygous GSTM1 gene deletion was consistently associated with greater psychological distress in medulloblastoma survivors across multiple domains, suggesting that this genotype may predispose patients for increased emotional late effects.

Biochemical markers predicting response to radiation- and radiochemo-therapy in cancer patients

In last years there is increasing interest in radiogenomics and the characterization of DNA array molecular profiles that can predict tumor and no tumor tissues radioresponse. Ongoing studies carried out worldwide in the banking of tumor and no tumor samples give evidence that perspective markers for response prediction in individual patient to intended radiation therapy can be some apoptotic indexes, spectrum a number of specific proteins, and DNA-based microarray molecular profiling analysis as well determination of single nucleotide polymorphisms in genome of the patients. So far there are only a few robust reports of molecular markers predicting tumor and no tumor tissues response to radiation. The results of new studies, which in future should be validated in larger definitive trials, are likely to see in nearest years. It is needed to determine technologies of methods and to define more precisely areas of its applications.

Prediction of normal tissue toxicity as part of the individualized treatment with radiotherapy in oncology patients

Normal tissue toxicity caused by radiotherapy conditions the success of the treatment and the quality of life of patients. Radiotherapy is combined with surgery in both the preoperative or postoperative setting for the treatment of most localized solid tumour types. Furthermore, radical radiotherapy is an alternative to surgery in several tumour locations. The possibility of predicting such radiation-induced toxicity would make possible a better treatment schedule for the individual patient. Radiation-induced toxicity is, at least in part, genetically determined. From decades, several predictive tests have been proposed to know the individual sensitivity of patients to the radiotherapy schedules. Among them, initial DNA damage, radiation-induced apoptosis, gene expression profiles, and gene polymorphisms have been proposed. We report here an overview of the main studies regarding to this field. Radiation-induced apoptosis in peripheral blood lymphocytes seem to be the most promising assay tested in prospective clinical trials, although they have to be validated in large clinical studies. Other promising assays, as those related with single nucleotide polymorphisms, need to be validated as well.

Genetics and genomics of radiotherapy toxicity: towards prediction

Radiotherapy is involved in many curative treatments of cancer; millions of survivors live with the consequences of treatment, and toxicity in a minority limits the radiation doses that can be safely prescribed to the majority. Radiogenomics is the whole genome application of radiogenetics, which studies the influence of genetic variation on radiation response. Work in the area focuses on uncovering the underlying genetic causes of individual variation in sensitivity to radiation, which is important for effective, safe treatment. In this review, we highlight recent advances in radiotherapy and discuss results from four genome-wide studies of radiotoxicity.

Prospective study validating inter- and intraobserver variability of tissue compliance meter in breast tissue of healthy volunteers: potential implications for patients with radiation-induced fibrosis of the breast

PURPOSE

Accurate detection of radiation-induced fibrosis (RIF) is crucial in management of breast cancer survivors. Tissue compliance meter (TCM) has been validated in musculature. We validate TCM in healthy breast tissue with respect to interobserver and intraobserver variability before applying it in RIF.

METHODS AND MATERIALS

Three medical professionals obtained three consecutive TCM measurements in each of the four quadrants of the right and left breasts of 40 women with no breast disease or surgical intervention. The intraclass correlation coefficient (ICC) assessed interobserver variability. The paired t test and Pearson correlation coefficient (r) were used to assess intraobserver variability within each rater.

RESULTS

The median age was 45 years (range, 24-68 years). The median bra size was 35C (range, 32A-40DD). Of the participants, 27 were white (67%), 4 black (10%), 5 Asian (13%), and 4 Hispanic (10%). ICCs indicated excellent interrater reliability (low interobserver variability) among the three raters, by breast and quadrant (all ICC ≥ 0.99). The paired t test and Pearson correlation coefficient both indicated low intraobserver variability within each rater (right vs. left breast), stratified by quadrant (all r ≥ 0.94, p < 0.0001).

CONCLUSIONS

The interobserver and intraobserver variability is small using TCM in healthy mammary tissue. We are now embarking on a prospective study using TCM in women with breast cancer at risk of developing RIF that may guide early detection, timely therapeutic intervention, and assessment of success of therapy for RIF.

Genetic polymorphisms in XRCC1 associated with radiation therapy in prostate cancer

Radiation therapy is a potentially curative, important treatment option in localized prostate cancer. However, at 8 years after radiation therapy, even in the best risk subset of patients, approximately 10% of patients will experience clinical disease recurrence. The identification of molecular markers of treatment success or failure may allow for the development of strategies to further improve treatment outcomes. Herein, we investigated five molecular markers of DNA repair. 513 patients with castrate-resistant prostate cancer (CRPC), including 284 patients who received radiotherapy, 229 patients without radiotherapy and 152 healthy individuals were genotyped for five polymorphisms in DNA excision repair genes:ERCC1 N118N (500C>T), XPD K751Q (2282A>C), XRCC1 R194W (685C>T), XRCC1 R399Q (1301G>A) and PARP1 V762A(2446T>C). The distribution of genetic polymorphisms in the patients with CRPC and in healthy controls was compared,and the association between the polymorphisms and overall survival was investigated. The polymorphisms evaluated did not show differences between the patient group and the healthy controls, nor did they show a trend toward an association with survival. However, in the radiation treated subgroup, the median survival time was associated with the XRCC1 haplotype. The median survival time was 11.75 years for patients with the R399Q AA /R194W CC haplotype,12.17 years for patients with the R399Q AG/R194W CC haplotype, 6.665 years for patients with the R399Q AG/R194WCT haplotype, and 6.21 years for patients with the R399Q GG/R194W CT haplotype (p = 0.034). This association was not found when all patients were investigated. We conclude that the genetic polymorphisms in XRCC1 may affect the outcome in patients who received radiotherapy for localized prostate cancer.

Molecular biology: the key to personalised treatment in radiation oncology?

We know considerably more about what makes cells and tissues resistant or sensitive to radiation than we did 20 years ago. Novel techniques in molecular biology have made a major contribution to our understanding at the level of signalling pathways. Before the "New Biology" era, radioresponsiveness was defined in terms of physiological parameters designated as the five Rs. These are: repair, repopulation, reassortment, reoxygenation and radiosensitivity. Of these, only the role of hypoxia proved to be a robust predictive and prognostic marker, but radiotherapy regimens were nonetheless modified in terms of dose per fraction, fraction size and overall time, in ways that persist in clinical practice today. The first molecular techniques were applied to radiobiology about two decades ago and soon revealed the existence of genes/proteins that respond to and influence the cellular outcome of irradiation. The subsequent development of screening techniques using microarray technology has since revealed that a very large number of genes fall into this category. We can now obtain an adequately robust molecular signature, predicting for a radioresponsive phenotype using gene expression and proteomic approaches. In parallel with these developments, functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) can now detect specific biological molecules such as haemoglobin and glucose, so revealing a 3D map of tumour blood flow and metabolism. The key to personalised radiotherapy will be to extend this capability to the proteins of the molecular signature that determine radiosensitivity.

Loose stools lead to fecal incontinence among gynecological cancer survivors

BACKGROUND

Many patients treated with radiotherapy to the pelvic region report a change in bowel habits. Loose stools, urgency and fecal incontinence may have a significant impact on daily life and social functioning.

MATERIAL AND METHODS

We attempted to follow up 789 women, treated with pelvic radiotherapy for a gynecological cancer during 1991 to 2003 at two departments of gynecological oncology in Sweden. A control group of 478 women from the Swedish Population Registry was also included. As a preparatory study, we made in-depth interviews with 26 women previously treated for gynecological cancer. Based on their narratives, we constructed a study-specific questionnaire including 351 questions and validated it face-to-face. The questionnaire covered questions of physical symptoms originating in the pelvis, demographics, psychological and quality of life factors. In relation to bowel symptoms, 60 questions were asked.

RESULTS

Six-hundred and sixteen (78%) gynecological cancer survivors and 344 (72%) control women participated. Two-hundred and twenty-six (37%) cancer survivors reported loose stools at least once a week. Eighty-three percent of the survivors with loose stools every day reported defecation urgency with fecal leakage, compared to 20% of cancer survivors without loose stools. Cancer survivors with loose stools at least once a week were 7.7 times more likely to suffer from defecation urgency with fecal leakage (95% CI 4.4-13.3) compared to those who had loose stools once a month or less. In order to avoid loose stools affected survivors with loose stools often skipped meals (13%), made an active choice of food (47%) and preferentially used prescribed medication (36%).

DISCUSSION

There is a relation between loose stools and defecation urgency with fecal leakage among long-term gynecological cancer survivors treated with pelvic radiotherapy. Targeting loose stools can possibly help survivors to decrease frequency of fecal leakage.

Reduction of radiation pneumonitis by V20-constraints in breast cancer

Introduction

Adjuvant local-regional radiotherapy (LRRT) is routinely recommended for breast cancer patients. It is well known being related to pulmonary side-effects. We studied post-RT radiological changes on X-ray and CT, and correlated the findings with Quality of Life (QoL), common dosimetric factors and co-variates. The results were compared with a previously reported cohort of 137 irradiated women.

Methods

88 women underwent chest X-ray and CT pre-and 4-5 months after 3-D planned LRRT, minimizing the dose to the ipsilateral lung to V₂₀ < 30%. The lung field was divided into 3 regions and the development of post-RT density changes were graded (0-3). Patients with radiological changes were compared with non-responders. Clinical symptoms were registered and data on patient and treatment related co-variates were gathered prospectively. The ipsilateral lung dosimetric factors V₁₃, V₂₀, V₃₀ and mean dose were calculated and QoL was assessed before and 4 months after RT.

Results

The use of dose-volume constraints significally reduced moderate-severe radiological changes on chest X-ray compared with our earlier study (Chi square trend test: p < 0.001). Symptomatic pneumonitis was also rare in the present study. No agreement was found between CT and chest X-ray as diagnostic tools for post-RT pneumonitis. V₁₃ correlated independently with radiological changes on CT (logistic regression: p = 0.04; ROC area: 0.7). The Co-variates smoking habits, age, chemotherapy, endocrine or trastuzumab therapy did not influence the outcome on multivariate analysis. QoL changes in physical function, i.e. fatigue, dyspnoea were not detected but there was a trend for a worse recovery after chemotherapy in patients with high V₁₃ (Spearman Rank Correlation: p < 0.05).

Conclusions

The use of dose-volume constraints significantly reduced post-RT radiological changes on chest X-ray in LRRT for BC. The lung changes on CT were also generally limited when we used this strategy and was not always picked up on chest X-ray. Variation in V₁₃ alone was correlated with occurrence of lung changes on CT.

The impact of individual in vivo repair of DNA double-strand breaks on oral mucositis in adjuvant radiotherapy of head-and-neck cancer

PURPOSE

To evaluate the impact of individual in vivo DNA double-strand break (DSB) repair capacity on the incidence of severe oral mucositis in patients with head-and-neck cancer undergoing adjuvant radiotherapy (RT) or radiochemotherapy (RCT).

PATIENTS AND METHODS

Thirty-one patients with resected head-and-neck cancer undergoing adjuvant RT or RCT were examined. Patients underwent RT of the primary tumor site and locoregional lymph nodes with a total dose of 60-66 Gy (single dose 2 Gy, five fractions per week). Chemotherapy consisted of two cycles of cisplatin and 5-fluorouracil. To assess DSB repair, γ-H2AX foci in blood lymphocytes were quantified before and 0.5 h, 2.5 h, 5 h, and 24 h after in vivo radiation exposure (the first fraction of RT). World Health Organization scores for oral mucositis were documented weekly and correlated with DSB repair.

RESULTS

Sixteen patients received RT alone; 15 patients received RCT. In patients who developed Grade≥3 mucositis (n=18) the amount of unrepaired DSBs 24 h after radiation exposure and DSB repair half-times did not differ significantly from patients with Grade≤2 mucositis (n=13). Patients with a proportion of unrepaired DSBs after 24 h higher than the mean value + one standard deviation had an increased incidence of severe oral mucositis.

CONCLUSIONS

Evaluation of in vivo DSB repair by determination of γ-H2AX foci loss is feasible in clinical practice and allows identification of patients with impaired DSB repair. The incidence of oral mucositis is not closely correlated with DSB repair under the evaluated conditions.

Identifying patients at risk for late radiation-induced toxicity

The impact of curative radiotherapy depends mainly on the total dose delivered in the targeted volume. Nevertheless, the dose delivered to the surrounding healthy tissues may reduce the therapeutic ratio of many treatments. Two different side effects (acute and late) can occur during and after radiotherapy. Of particular interest are the radiation-induced late complications (LC) due to their irreversibility and the potential impact on quality of life. In one population treated with the same technique, it appears that individual radiosensitivity clearly exists. In the hypothesis that genetic is involved in this area of research, low CD4 and CD8 lymphocyte apoptosis were shown to be correlated with high grade of LC. In addition, recent data suggest that patients with severe radiation-induced LC possess 4 or more single nucleotide polymorphisms (SNPs) in candidate genes and low radiation-induced CD8 lymphocyte apoptosis in vitro. On-going studies are being analyzing the entire genome using a genome-wide association study (GWAS).