Sources of variation in patient response to radiation treatment

Time-Dependent ROC Curve Analysis for Assessing the Capability of Radiation-Induced CD8 T-Lymphocyte Apoptosis to Predict Late Toxicities after Adjuvant Radiotherapy of Breast Cancer Patients

Late fibrosis can occur in breast cancer patients treated with curative-intent radiotherapy. Predicting this toxicity is of clinical interest in order to adapt the irradiation dose delivered. Radiation-induced CD8 T-lymphocyte apoptosis (RILA) had been proven to be associated with less grade ≥2 late radiation-induced toxicities in patients with miscellaneous cancers. Tobacco smoking status and adjuvant hormonotherapy were also identified as potential factors related to late-breast-fibrosis-free survival. This article evaluates the predictive performance of the RILA using a ROC curve analysis that takes into account the dynamic nature of fibrosis occurrence. This time-dependent ROC curve approach is also applied to evaluate the ability of the RILA combined with the other previously identified factors. Our analysis includes a Monte Carlo cross-validation procedure and the calculation of an expected cost of misclassification, which provides more importance to patients who have no risk of late fibrosis in order to be able to treat them with the maximal irradiation dose. Performance evaluation was assessed at 12, 24, 36 and 50 months. At 36 months, our results were comparable to those obtained in a previous study, thus underlying the predictive power of the RILA. Based on specificity and cost, RILA alone seemed to be the most performant, while its association with the other factors had better negative predictive value results.

Improving Patients’ Life Quality after Radiotherapy Treatment by Predicting Late Toxicities

Simple Summary

Over 50% of patients with cancer will receive radiotherapy treatment. Five to ten percent of patients who received radiotherapy will develop side effects. Identifying these patients before treatment start would allow for treatment modification to minimize these effects and improve the life quality of these patients. Our team developed a test, which allows predicting these secondary effects before starting the treatment. This will help in proposing personalized treatments to improve the outcome. This review presents how this test is performed, its results, as well as its modification in order to be used in hospitals.

Abstract

Personalized treatment and precision medicine have become the new standard of care in oncology and radiotherapy. Because treatment outcomes have considerably improved over the last few years, permanent side-effects are becoming an increasingly significant issue for cancer survivors. Five to ten percent of patients will develop severe late toxicity after radiotherapy. Identifying these patients before treatment start would allow for treatment adaptation to minimize definitive side effects that could impair their long-term quality of life. Over the last decades, several tests and biomarkers have been developed to identify these patients. However, out of these, only the Radiation-Induced Lymphocyte Apoptosis (RILA) assay has been prospectively validated in multi-center cohorts. This test, based on a simple blood draught, has been shown to be correlated with late radiation-induced toxicity in breast, prostate, cervical and head and neck cancer. It could therefore greatly improve decision making in precision radiation oncology. This literature review summarizes the development and bases of this assay, as well as its clinical results and compares its results to the other available assays.

Computational image features of immune architecture is associated with clinical benefit and survival in gynecological cancers across treatment modalities

BACKGROUND

We present a computational approach (ArcTIL) for quantitative characterization of the architecture of tumor-infiltrating lymphocytes (TILs) and their interplay with cancer cells from digitized H&E-stained histology whole slide images and evaluate its prognostic role in three different gynecological cancer (GC) types and across three different treatment types (platinum, radiation and immunotherapy).

METHODS

In this retrospective study, we included 926 patients with GC diagnosed with ovarian cancer (OC), cervical cancer, and endometrial cancer with available digitized diagnostic histology slides and survival outcome information. ArcTIL features quantifying architecture and spatial interplay between immune cells and the rest of nucleated cells (mostly comprised cancer cells) were extracted from the cell cluster graphs of nuclei within the tumor epithelial nests, surrounding stroma and invasive tumor front compartments on H&E-stained slides. A Cox proportional hazards model, incorporating ArcTIL features was fit on the OC training cohort (N=51), yielding an ArcTIL signature. A unique threshold learned from the training set stratified the patients into a low and high-risk group.

RESULTS

The seven feature ArcTIL classifier was found to significantly correlate with overall survival in chemotherapy and radiotherapy-treated validation cohorts and progression-free survival in an immunotherapy-treated validation cohort. ArcTIL features relating to increased density of TILs in the epithelium and invasive tumor front were found to be associated with better survival outcomes when compared with those patients with an increased TIL density in the stroma. A statistically significant association was found between the ArcTIL signature and signaling pathways for blood vessel morphogenesis, vasculature development, regulation of cell differentiation, cell-substrate adhesion, biological adhesion, regulation of vasculature development, and angiogenesis.

CONCLUSIONS

This study reveals that computationally-derived features from the spatial architecture of TILs and tumor cells are prognostic in GCs treated with chemotherapy, radiotherapy, and checkpoint blockade and are closely associated with central biological processes that impact tumor progression. These findings could aid in identifying therapy-refractory patients and further enable personalized treatment decision-making.

The Possibility of Using Genotoxicity, Oxidative Stress and Inflammation Blood Biomarkers to Predict the Occurrence of Late Cutaneous Side Effects after Radiotherapy

Despite the progresses performed in the field of radiotherapy, toxicity to the healthy tissues remains a major limiting factor. The aim of this work was to highlight blood biomarkers whose variations could predict the occurrence of late cutaneous side effects. Two groups of nine patients treated for Merkel Cell Carcinoma (MCC) were established according to the grade of late skin toxicity after adjuvant irradiation for MCC: grade 0, 1 or 2 and grade 3 or 4 of RTOG (Radiation Therapy Oncology Group)/EORTC (European Organization for Research and Treatment of Cancer). To try to discriminate these 2 groups, biomarkers of interest were measured on the different blood compartments after ex vivo irradiation. In lymphocytes, cell cycle, apoptosis and genotoxicity were studied. Oxidative stress was evaluated by the determination of the erythrocyte antioxidant capacity (superoxide dismutase, catalase, glutathione peroxidase, reduced and oxidized glutathione) as well as degradation products (protein carbonylation, lipid peroxidation). Inflammation was assessed in the plasma by the measurement of 14 cytokines. The most radiosensitive patients presented a decrease in apoptosis, micronucleus frequency, antioxidant enzyme activities, glutathione and carbonyls; and an increase in TNF-a (Tumor Necrosis Factor a), IL-8 (Interleukin 8) and TGF-β1 (Transforming Growth Factor β1) levels. These findings have to be confirmed on a higher number of patients and before radiotherapy and could allow to predict the occurrence of late skin side effects after radiotherapy.

A Review of Radiation-Induced Lymphocyte Apoptosis as a Predictor of Late Toxicity After Breast Radiotherapy

BACKGROUND

Improved survivorship in patients with breast cancer means many are currently living with the late effects of radiotherapy, particularly fibrosis. Personalized treatment is not currently considered for patients with breast cancer. Radiation-induced lymphocyte apoptosis (RILA), a predictive assay, could offer a novel approach in predicting patients at a higher risk of developing this late toxicity and therefore improving informed decision-making.

MATERIALS AND METHODS

A systematic search of PubMed and Embase was performed and eight clinical trials were identified that investigate RILA as a predictor of late breast fibrosis after radiotherapy.

RESULTS

Median RILA scores were lower in patients who experienced ≥ grade 2 fibrosis than in patients who experienced ≥ grade 1. A clear inverse relationship between RILA scores and late toxicity was reported in the literature; however, there were several other confounding factors involved in the development of fibrosis. CD8 lymphocytes were reported to have superior sensitivity and specificity over CD4 lymphocytes.

CONCLUSION

RILA was reported to be an effective biomarker in predicting fibrosis in breast cancer but other factors also need to be considered before clinical implementation.

Intra-patient and inter-patient comparisons of DNA damage response biomarkers in Nasopharynx Cancer (NPC): analysis of NCC0901 randomised controlled trial of induction chemotherapy in locally advanced NPC

BACKGROUND

Inter-patient heterogeneity in radiation-induced DNA damage responses is proposed to reflect intrinsic variations in tumour and normal tissue radiation sensitivity, but the prediction of phenotype by a molecular biomarker is influenced by clinical confounders and assay reproducibility. Here, we characterised the intrapatient and inter-patient heterogeneity in biomarkers of DNA damage and repair and radiation-induced apoptosis.

METHODS

We enrolled 85 of 172 patients with locally advanced nasopharynx cancer from a randomised controlled phase II/III trial of induction chemotherapy added to chemo-radiotherapy. G0 blood lymphocytes were harvested from these patients, and irradiated with 1, 4, and 8 Gy ex vivo. DNA damage induction (1 Gy 0.5 h) and repair (4 Gy 24 h) were assessed by duplicate γH2AX foci assays in 50-100 cells. Duplicate FLICA assays performed at 48 h post-8 Gy were employed as surrogate of radiation-induced apoptosis; %FLICA-positive cells were quantified by flow cytometry.

RESULTS

We observed limited intrapatient variation in γH2AX foci and %FLICA readouts; median difference of duplicate foci scores was - 0.37 (IQR = - 1.256-0.800) for 1 Gy 0.5 h and 0.09 (IQR = - 0.685-0.792) for 4 Gy 24 h; ICC of ≥0.80 was observed for duplicate %FLICA0Gy and %FLICA8Gy assays of CD4+ and CD8+ T lymphocytes. As expected, we observed wide inter-patient heterogeneity in both assays that was independent of intrapatient variation and clinical covariates, with the exception of age, which was inversely correlated with %FLICAbackground-corrected (Spearman R = - 0.406, P < 0.001 [CD4+]; R = - 0.220, P = 0.04 [CD8+]). Lastly, an exploratory case-control analysis indicates increased levels of γH2AX foci at 4 Gy 24 h in patients with severe late radiotherapy-induced xerostomia (P = 0.05).

CONCLUSION

Here, we confirmed the technical reproducibility of DNA damage response assays for clinical implementation as biomarkers of clinical radiosensitivity in nasopharynx cancer patients.

Personalizing Breast Cancer Irradiation Using Biology: From Bench to the Accelerator

While adjuvant treatments of early breast cancers (BCs) had significantly improved patients’ overall survival, some of them will still develop locoregional relapses and/or severe late radio-induced toxicities. Here, we propose to review how to personalize locoregional treatment by identifying patients at high and low risk of locoregional relapse, patients at risk of late radio-induced side effects. We will, therefore, discuss how to enhance BC radiosensitivity. Finally, we will address how personalized radiotherapy could be implemented in prospective clinical trials.

Radiogenomics: A systems biology approach to understanding genetic risk factors for radiotherapy toxicity?

Adverse reactions in normal tissue after radiotherapy (RT) limit the dose that can be given to tumour cells. Since 80% of individual variation in clinical response is estimated to be caused by patient-related factors, identifying these factors might allow prediction of patients with increased risk of developing severe reactions. While inactivation of cell renewal is considered a major cause of toxicity in early-reacting normal tissues, complex interactions involving multiple cell types, cytokines, and hypoxia seem important for late reactions. Here, we review 'omics' approaches such as screening of genetic polymorphisms or gene expression analysis, and assess the potential of epigenetic factors, posttranslational modification, signal transduction, and metabolism. Furthermore, functional assays have suggested possible associations with clinical risk of adverse reaction. Pathway analysis incorporating different 'omics' approaches may be more efficient in identifying critical pathways than pathway analysis based on single 'omics' data sets. Integrating these pathways with functional assays may be powerful in identifying multiple subgroups of RT patients characterised by different mechanisms. Thus 'omics' and functional approaches may synergise if they are integrated into radiogenomics 'systems biology' to facilitate the goal of individualised radiotherapy.

Rh factor is associated with individual radiosensitivity: A cytogenetic study

Introduction

Radiosensitivity is an inherent trait, associated with a raised reaction to ionizing radiation on the human body. In radiotherapy and radiation protection fields, individualization of the patient’s treatment is one of the main topics. With the goal of determining biomarkers capable of anticipating normal tissue side reactions, we studied the association between the Rh factor and radiosensitivity.

Methods

This experimental study was carried out from January to June 2014 among 50 normal responders with A blood group (25Rh+ and 25Rh−) between the ages of 22 and 23 in Babol, Iran. Human peripheral blood samples were taken from subjects and, using CBMN assay, the biological effects of gamma irradiation, including the frequency of micronuclei (MN) and nuclear division index (NDI), were measured. A data analysis was performed using SPSS version 18 to determine the independent and paired samples t-tests.

Results

A significant increment occurred in the frequency of MN in group Rh+ (196 ± 18.23) compared with Rh- (169 ± 17.11) following irradiation (p<0.001).

Conclusions

The Rh factor might be a predicting marker in an individual’s radiosensitivity to ionizing radiations. However, we believe that additional investigations are needed to prove this hypothesis.

Prediction of radiation-induced toxicity by in vitro radiosensitivity of lymphocytes in prostate cancer patients

Aim: To identify predictive assays for radiation-induced toxicity in prostate cancer patients. Patients & methods: Patients have been surveyed prospectively before and up to 16 months after radiotherapy using a validated questionnaire. Subgroups of 25 patients with minor and larger score changes, respectively, were selected for γ-H2AX, G2 and Annexin V assays. Results: A significantly higher spontaneous chromatid aberration yield (HR: 1.46 [95% CI: 1.02–2.09]; p = 0.04), higher levels of early apoptotic (HR: 1.12 [95% CI: 1.01–1.24]; p = 0.04) and late apoptotic and necrotic (HR: 1.10 [95% CI: 0.99–1.23]; p = 0.08) lymphocytes 24 h post-irradiation were found in patients with a bowel bother score decrease greater than 20 points more than 1 year after treatment. Conclusion: Chromatid aberration and apoptosis/necrosis assays appear to be suitable for the prediction of radiation-induced toxicity.

Apoptosis for prediction of radiotherapy late toxicity: lymphocyte subset sensitivity and potential effect of TP53 Arg72Pro polymorphism

We tested apoptosis levels in in vitro irradiated T-lymphocytes from breast cancer (BC) patients with radiotherapy-induced late effects. Previous results reported in the literature were revised. We also examined the effect of TP53 Arg72Pro polymorphism on irradiation-induced apoptosis (IA). Twenty BC patients, ten with fibrosis and/or telangiectasias and ten matched controls with no late reactions, were selected from those receiving radiotherapy between 1993 and 2007. All patients were followed-up at least 6 years after radiotherapy. Using the combination of both CD3 and CD8 antibodies the in vitro IA was measured in CD3, CD8 and CD4 T-lymphocytes, and CD8 natural killer lymphocytes (CD8 NK) by flow cytometry. The TP53 Arg72Pro genotype was determined by sequencing. Patients with late radiotherapy toxicity showed less IA for all T-lymphocytes except for the CD8 NK. CD8 NK showed the highest spontaneous apoptosis and the lowest IA. IA in patients with toxicity appears to be lower than the control patients only in TP53 Arg/Arg patients (P = 0.077). This difference was not present in patients carrying at least one Pro allele (P = 0.8266). Our data indicate that late side effects induced by radiotherapy of BC are associated to low levels of IA. CD8 NK cells have a different response to in vitro irradiation compared to CD8 T-lymphocytes. It would be advisable to distinguish the CD8 NK lymphocytes from the pool of CD8+ lymphocytes in IA assays using CD8+ cells. Our data suggest that the 72Pro TP53 allele may influence the IA of patients with radiotherapy toxicity.

DNA double-strand break repair and induction of apoptosis in ex vivo irradiated blood lymphocytes in relation to late normal tissue reactions following breast radiotherapy

This study aimed to test whether induction of apoptosis following ex vivo X-irradiation of unstimulated blood lymphocytes correlated with clinical radiosensitivity and DNA double-strand break (DSB) repair in breast radiotherapy patients and healthy volunteers. Using small molecule inhibitors, the relationship between DSB repair and radiation-induced apoptosis was examined. Sixteen breast cancer patients with minimal (controls, n = 8) or extremely marked late radiation-induced change (cases, n = 8) and eight healthy volunteers were selected. DSBs were quantified by γH2AX/53BP1 immunofluorescence, and apoptosis was measured using a fluorogenic inhibitor of caspases assay. Mean γH2AX/53BP1 focus levels 24 h after exposure to 4 Gy were higher in cases (12.7 foci per cell) than in controls (10.3 foci per cell, p = 0.002). In contrast, the mean apoptotic fraction 48 h after 8 Gy was comparable, 37.2 % in cases and 34.7 % in controls (p = 0.442). Residual focus and apoptosis levels were not correlated within individuals (Spearman's R = -0.0059, p = 0.785). However, cells treated with DNA-PK inhibitor Nu7441 had higher focus and apoptosis levels 48 h after 1 Gy compared to mock-treated cells, suggesting that apoptosis induction following irradiation is modulated by DSB repair. This effect required functional ATM since cells treated simultaneously with Nu7441 and the ATM inhibitor Ku55933 were resistant to apoptosis despite high levels of residual foci. One clinical case displayed an impaired DNA-PK-dependent end-joining cellular phenotype. In summary, clinical radiosensitivity may be associated with impaired DSB repair in some patients. Although pharmaceutical inhibition of ATM and DNA-PK affected apoptosis induction and DSB repair, no association was observed between apoptosis and residual focus levels in patients and volunteers.

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.

Deoxyribonucleic acid damage-associated biomarkers of ionising radiation: current status and future relevance for radiology and radiotherapy

Diagnostic and therapeutic radiation technology has developed dramatically in recent years, and its use has increased significantly, bringing clinical benefit. The use of diagnostic radiology has become widespread in modern society, particularly in paediatrics where the clinical benefit needs to be balanced with the risk of leukaemia and brain cancer increasing after exposure to low doses of radiation. With improving long-term survival rates of radiotherapy patients and the ever-increasing use of diagnostic and interventional radiology procedures, concern has risen over the long-term risks and side effects from such treatments. Biomarker development in radiology and radiotherapy has progressed significantly in recent years to investigate the effects of such use and optimise treatment. Recent biomarker development has focused on improving the limitations of established techniques by the use of automation, increasing sensitivity and developing novel biomarkers capable of quicker results. The effect of low-dose exposure (0-100 mGy) used in radiology, which is increasingly linked to cancer incidences, is being investigated, as some recent research challenges the linear-no-threshold model. Radiotherapy biomarkers are focused on identifying radiosensitive patients, determining the treatment-associated risk and allowing for a tailored and more successful treatment of cancer patients. For biomarkers in any of these areas to be successfully developed, stringent criteria must be applied in techniques and analysis of data to reduce variation among reports and allow data sets to be accurately compared. Newly developed biomarkers can then be used in combination with the established techniques to better understand and quantify the individual biological response to exposures associated with radiology tests and to personalise treatment plans for patients.

Evaluation of different biomarkers to predict individual radiosensitivity in an inter-laboratory comparison--lessons for future studies

Radiotherapy is a powerful cure for several types of solid tumours, but its application is often limited because of severe side effects in individual patients. With the aim to find biomarkers capable of predicting normal tissue side reactions we analysed the radiation responses of cells from individual head and neck tumour and breast cancer patients of different clinical radiosensitivity in a multicentric study. Multiple parameters of cellular radiosensitivity were analysed in coded samples of peripheral blood lymphocytes (PBLs) and derived lymphoblastoid cell lines (LCLs) from 15 clinical radio-hypersensitive tumour patients and compared to age- and sex-matched non-radiosensitive patient controls and 15 lymphoblastoid cell lines from age- and sex- matched healthy controls of the KORA study. Experimental parameters included ionizing radiation (IR)-induced cell death (AnnexinV), induction and repair of DNA strand breaks (Comet assay), induction of yH2AX foci (as a result of DNA double strand breaks), and whole genome expression analyses. Considerable inter-individual differences in IR-induced DNA strand breaks and their repair and/or cell death could be detected in primary and immortalised cells with the applied assays. The group of clinically radiosensitive patients was not unequivocally distinguishable from normal responding patients nor were individual overreacting patients in the test system unambiguously identified by two different laboratories. Thus, the in vitro test systems investigated here seem not to be appropriate for a general prediction of clinical reactions during or after radiotherapy due to the experimental variability compared to the small effect of radiation sensitivity. Genome-wide expression analysis however revealed a set of 67 marker genes which were differentially induced 6 h after in vitro-irradiation in lymphocytes from radio-hypersensitive and non-radiosensitive patients. These results warrant future validation in larger cohorts in order to determine parameters potentially predictive for clinical radiosensitivity.

In vivo versus in vitro individual radiosensitivity analysed in healthy donors and in prostate cancer patients with and without severe side effects after radiotherapy

BACKGROUND

A high cellular radiosensitivity may be connected with a risk for development of severe side effects after radiotherapy and indicate cancer susceptibility. Hence, a fast and robust in vitro test is desirable to identify radiosensitive individuals.

MATERIALS AND METHODS

The study included 25 prostate cancer patients with severe side effects (S) and 25 patients without severe side effects (0) after radiotherapy as well as 23 male healthy age-matched donors. Blood samples were exposed to 0.5 Gy or 1 Gy of γ-rays. The initial level of double-strand breaks (dsb) and repair kinetics measured by phosphorylation of histone H2A (γ-H2AX-assay), apoptosis (Annexin V-assay) and the induction of chromatid aberrations after irradiation in the G2-phase of the cell cycle (G2-assay) were analysed.

RESULTS

A significant higher chromatid aberration yield was found in lymphocytes from prostate cancer patients when compared to healthy donors. We found no significant differences between patients S and patients 0.

CONCLUSIONS

There is no obvious correlation between clinical and cellular radiosensitivity in lymphocytes of prostate cancer patients when all chosen in vitro assays are considered. Although 25% of the patients showed both severe side effects and increased radiation-induced chromosomal sensitivity, predictive value of G2-assay is doubtful.

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.

Combined low initial DNA damage and high radiation-induced apoptosis confers clinical resistance to long-term toxicity in breast cancer patients treated with high-dose radiotherapy

Background

Either higher levels of initial DNA damage or lower levels of radiation-induced apoptosis in peripheral blood lymphocytes have been associated to increased risk for develop late radiation-induced toxicity. It has been recently published that these two predictive tests are inversely related. The aim of the present study was to investigate the combined role of both tests in relation to clinical radiation-induced toxicity in a set of breast cancer patients treated with high dose hyperfractionated radical radiotherapy.

Methods

Peripheral blood lymphocytes were taken from 26 consecutive patients with locally advanced breast carcinoma treated with high-dose hyperfractioned radical radiotherapy. Acute and late cutaneous and subcutaneous toxicity was evaluated using the Radiation Therapy Oncology Group morbidity scoring schema. The mean follow-up of survivors (n = 13) was 197.23 months. Radiosensitivity of lymphocytes was quantified as the initial number of DNA double-strand breaks induced per Gy and per DNA unit (200 Mbp). Radiation-induced apoptosis (RIA) at 1, 2 and 8 Gy was measured by flow cytometry using annexin V/propidium iodide.

Results

Mean DSB/Gy/DNA unit obtained was 1.70 ± 0.83 (range 0.63-4.08; median, 1.46). Radiation-induced apoptosis increased with radiation dose (median 12.36, 17.79 and 24.83 for 1, 2, and 8 Gy respectively). We observed that those "expected resistant patients" (DSB values lower than 1.78 DSB/Gy per 200 Mbp and RIA values over 9.58, 14.40 or 24.83 for 1, 2 and 8 Gy respectively) were at low risk of suffer severe subcutaneous late toxicity (HR 0.223, 95%CI 0.073-0.678, P = 0.008; HR 0.206, 95%CI 0.063-0.677, P = 0.009; HR 0.239, 95%CI 0.062-0.929, P = 0.039, for RIA at 1, 2 and 8 Gy respectively) in multivariate analysis.

Conclusions

A radiation-resistant profile is proposed, where those patients who presented lower levels of initial DNA damage and higher levels of radiation induced apoptosis were at low risk of suffer severe subcutaneous late toxicity after clinical treatment at high radiation doses in our series. However, due to the small sample size, other prospective studies with higher number of patients are needed to validate these results.

Radiation induced apoptosis and initial DNA damage are inversely related in locally advanced breast cancer patients

Background

DNA-damage assays, quantifying the initial number of DNA double-strand breaks induced by radiation, have been proposed as a predictive test for radiation-induced toxicity. Determination of radiation-induced apoptosis in peripheral blood lymphocytes by flow cytometry analysis has also been proposed as an approach for predicting normal tissue responses following radiotherapy. The aim of the present study was to explore the association between initial DNA damage, estimated by the number of double-strand breaks induced by a given radiation dose, and the radio-induced apoptosis rates observed.

Methods

Peripheral blood lymphocytes were taken from 26 consecutive patients with locally advanced breast carcinoma. Radiosensitivity of lymphocytes was quantified as the initial number of DNA double-strand breaks induced per Gy and per DNA unit (200 Mbp). Radio-induced apoptosis at 1, 2 and 8 Gy was measured by flow cytometry using annexin V/propidium iodide.

Results

Radiation-induced apoptosis increased in order to radiation dose and data fitted to a semi logarithmic mathematical model. A positive correlation was found among radio-induced apoptosis values at different radiation doses: 1, 2 and 8 Gy (p < 0.0001 in all cases). Mean DSB/Gy/DNA unit obtained was 1.70 ± 0.83 (range 0.63-4.08; median, 1.46). A statistically significant inverse correlation was found between initial damage to DNA and radio-induced apoptosis at 1 Gy (p = 0.034). A trend toward 2 Gy (p = 0.057) and 8 Gy (p = 0.067) was observed after 24 hours of incubation.

Conclusions

An inverse association was observed for the first time between these variables, both considered as predictive factors to radiation toxicity.

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).

Prediction of clinical toxicity in locally advanced head and neck cancer patients by radio-induced apoptosis in peripheral blood lymphocytes (PBLs)

Head and neck cancer is treated mainly by surgery and radiotherapy. Normal tissue toxicity due to x-ray exposure is a limiting factor for treatment success. Many efforts have been employed to develop predictive tests applied to clinical practice. Determination of lymphocyte radio-sensitivity by radio-induced apoptosis arises as a possible method to predict tissue toxicity due to radiotherapy. The aim of the present study was to analyze radio-induced apoptosis of peripheral blood lymphocytes in head and neck cancer patients and to explore their role in predicting radiation induced toxicity. Seventy nine consecutive patients suffering from head and neck cancer, diagnosed and treated in our institution, were included in the study. Toxicity was evaluated using the Radiation Therapy Oncology Group scale. Peripheral blood lymphocytes were isolated and irradiated at 0, 1, 2 and 8 Gy during 24 hours. Apoptosis was measured by flow cytometry using annexin V/propidium iodide. Lymphocytes were marked with CD45 APC-conjugated monoclonal antibody. Radiation-induced apoptosis increased in order to radiation dose and fitted to a semi logarithmic model defined by two constants: α and β. α, as the origin of the curve in the Y axis determining the percentage of spontaneous cell death, and β, as the slope of the curve determining the percentage of cell death induced at a determined radiation dose, were obtained. β value was statistically associated to normal tissue toxicity in terms of severe xerostomia, as higher levels of apoptosis were observed in patients with low toxicity (p = 0.035; Exp(B) 0.224, I.C.95% (0.060-0.904)). These data agree with our previous results and suggest that it is possible to estimate the radiosensitivity of peripheral blood lymphocytes from patients determining the radiation induced apoptosis with annexin V/propidium iodide staining. β values observed define an individual radiosensitivity profile that could predict late toxicity due to radiotherapy in locally advanced head and neck cancer patients. Anyhow, prospective studies with different cancer types and higher number of patients are needed to validate these results.

Multidisciplinary approach of early breast cancer: the biology applied to radiation oncology

Early breast cancer treatment is based on a multimodality approach with the application of clinical and histological prognostic factors to determine locoregional and systemic treatments. The entire scientific community is strongly involved in the management of this disease: radiologists for screening and early diagnosis, gynecologists, surgical oncologists and radiation oncologists for locoregional treatment, pathologists and biologists for personalized characterization, genetic counselors for BRCA mutation history and medical oncologists for systemic therapies.Recently, new biological tools have established various prognostic subsets of breast cancer and developed predictive markers for miscellaneous treatments.The aim of this article is to highlight the contribution of biological tools in the locoregional management of early breast cancer.

DNA and cytogenetic damage in white blood cells of postmenopausal breast cancer patients treated with radiotherapy

The primary and residual genome damage and its elimination rate were evaluated in peripheral blood lymphocytes of breast cancer patients treated with adjuvant radiotherapy after surgical removal of the tumor by mastectomy or quadrantectomy. The levels of DNA/chromosome damage were estimated before, throughout, as well as after six months, respectively one year after the radiotherapy, using the alkaline comet assay, the chromosome aberration analysis and the cytokinesis-block micronucleus assay. The marked individual differences in the baseline genome damage were observed in patients, which additionally increased until the end of the radiotherapy cycle. The levels of DNA/cytogenetic damage slowly declined during post-irradiation period; although in the majority of subjects they did not return to pre-therapy levels. In addition to the well-established comet parameters, the long-tailed nuclei were also proved as a useful indicator of individual DNA damage and response to radiation. One of the most important observation was that older breast cancer patients, irradiated after mastectomy, had higher values of almost all parameters evaluated. We found positive correlations between the comet assay parameters and the cytogenetic biomarkers that confirmed their complementary value in the assessment of the radiation sensitivity/susceptibility in elderly breast cancer patients. The specific patterns of DNA damage observed in the majority of subjects after a prolonged exposure to ionizing radiation indicate the possibility of adaptive response. Such results may also be linked to the hormesis theory and support previous observations, but the underlying mechanisms should be further investigated on a much larger population.

Prediction of clinical toxicity in localized cervical carcinoma by radio-induced apoptosis study in peripheral blood lymphocytes (PBLs)

Background

Cervical cancer is treated mainly by surgery and radiotherapy. Toxicity due to radiation is a limiting factor for treatment success. Determination of lymphocyte radiosensitivity by radio-induced apoptosis arises as a possible method for predictive test development. The aim of this study was to analyze radio-induced apoptosis of peripheral blood lymphocytes.

Methods

Ninety four consecutive patients suffering from cervical carcinoma, diagnosed and treated in our institution, and four healthy controls were included in the study. Toxicity was evaluated using the Lent-Soma scale. Peripheral blood lymphocytes were isolated and irradiated at 0, 1, 2 and 8 Gy during 24, 48 and 72 hours. Apoptosis was measured by flow cytometry using annexin V/propidium iodide to determine early and late apoptosis. Lymphocytes were marked with CD45 APC-conjugated monoclonal antibody.

Results

Radiation-induced apoptosis (RIA) increased with radiation dose and time of incubation. Data strongly fitted to a semi logarithmic model as follows: RIA = βln(Gy) + α. This mathematical model was defined by two constants: α, is the origin of the curve in the Y axis and determines the percentage of spontaneous cell death and β, is the slope of the curve and determines the percentage of cell death induced at a determined radiation dose (β = ΔRIA/Δln(Gy)). Higher β values (increased rate of RIA at given radiation doses) were observed in patients with low sexual toxicity (Exp(B) = 0.83, C.I. 95% (0.73-0.95), p = 0.007; Exp(B) = 0.88, C.I. 95% (0.82-0.94), p = 0.001; Exp(B) = 0.93, C.I. 95% (0.88-0.99), p = 0.026 for 24, 48 and 72 hours respectively). This relation was also found with rectal (Exp(B) = 0.89, C.I. 95% (0.81-0.98), p = 0.026; Exp(B) = 0.95, C.I. 95% (0.91-0.98), p = 0.013 for 48 and 72 hours respectively) and urinary (Exp(B) = 0.83, C.I. 95% (0.71-0.97), p = 0.021 for 24 hours) toxicity.

Conclusion

Radiation induced apoptosis at different time points and radiation doses fitted to a semi logarithmic model defined by a mathematical equation that gives an individual value of radiosensitivity and could predict late toxicity due to radiotherapy. Other prospective studies with higher number of patients are needed to validate these results.

Single nucleotide polymorphisms, apoptosis, and the development of severe late adverse effects after radiotherapy

PURPOSE

Evidence has accumulated in recent years suggestive of a genetic basis for a susceptibility to the development of radiation injury after cancer radiotherapy. The purpose of this study was to assess whether patients with severe radiation-induced sequelae (RIS; i.e., National Cancer Institute/CTCv3.0 grade, > or =3) display both a low capacity of radiation-induced CD8 lymphocyte apoptosis (RILA) in vitro and possess certain single nucleotide polymorphisms (SNP) located in candidate genes associated with the response of cells to radiation.

EXPERIMENTAL DESIGN

DNA was isolated from blood samples obtained from patients (n = 399) included in the Swiss prospective study evaluating the predictive effect of in vitro RILA and RIS. SNPs in the ATM, SOD2, XRCC1, XRCC3, TGFB1, and RAD21 genes were screened in patients who experienced severe RIS (group A, n = 16) and control subjects who did not manifest any evidence of RIS (group B, n = 18).

RESULTS

Overall, 13 and 21 patients were found to possess a total of <4 and > or =4 SNPs in the candidate genes. The median (range) RILA in group A was 9.4% (5.3-16.5) and 94% (95% confidence interval, 70-100) of the patients (15 of 16) had > or =4 SNPs. In group B, median (range) RILA was 25.7% (20.2-43.2) and 33% (95% confidence interval, 13-59) of patients (6 of 18) had > or =4 SNPs (P < 0.001).

CONCLUSIONS

The results of this study suggest that patients with severe RIS possess 4 or more SNPs in candidate genes and low radiation-induced CD8 lymphocyte apoptosis in vitro.

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

PURPOSE

The development of adverse effects resulting from the radiotherapy of cancer limits the use of this treatment modality. The validation of a test capable of predicting which patients would be most likely to develop adverse responses to radiation treatment, based on the possession of specific genetic variants, would therefore be of value. The purpose of the Genetic Predictors of Adverse Radiotherapy Effects (Gene-PARE) project is to help achieve this goal.

METHODS AND MATERIALS

A continuously expanding biorepository has been created consisting of frozen lymphocytes and DNA isolated from patients treated with radiotherapy. In conjunction with this biorepository, a database is maintained with detailed clinical information pertaining to diagnosis, treatment, and outcome. The DNA samples are screened using denaturing high performance liquid chromatography (DHPLC) and the Surveyor nuclease assay for variants in ATM, TGFB1, XRCC1, XRCC3, SOD2, and hHR21. It is anticipated that additional genes that control the biologic response to radiation will be screened in future work.

RESULTS

Evidence has been obtained that possession of variants in genes, the products of which play a role in radiation response, is predictive for the development of adverse effects after radiotherapy.

CONCLUSIONS

It is anticipated that the Gene-PARE project will yield information that will allow radiation oncologists to use genetic data to optimize treatment on an individual basis.

Inter-relation of apoptosis and DNA double-strand breaks in patients with multiple primary cancers

Since the development of multiple primary cancers in an individual is considered an unlikely event, it is suspected that a defect in DNA repair or apoptosis is the underlying cause for some of these patients. Therefore, this study was based on the hypothesis that such patients have increased remaining DNA double-strand breaks (DSBs) and reduced levels of apoptosis after in vitro irradiation. To investigate these mechanisms in cancer patients, 19 with multiple primary cancers were selected out of 25 121 cancer patients. For inclusion in this study, patients had to present with first malignancy at an early age, have a positive family history of cancer and no risk factors. The exclusion criteria were recurrence of cancer or metastasis, haematological tumours and tumours possibly connected to a patient risk factor such as smoking or drinking. Their peripheral blood lymphocytes were tested for proper repair of DNA DSBs and apoptosis after in vitro irradiation. DSBs were measured using constant field gel electrophoresis at 0, 8 and 24 h after irradiation. Apoptotic rates were determined at 24, 48 and 72 h after irradiation using the TUNEL assay. We found that patients' lymphocytes had significantly more initial DNA DSBs compared with controls, but there was no difference in the number of remaining DNA DSBs. Apoptotic rates of lymphocytes were only slightly lower in patients than in controls. These findings show that there are limited differences between patients with multiple cancers and healthy individuals. However, we found a trend towards an inverse correlation between remaining DNA DSBs and apoptotic rates in patients' lymphocytes. This is indicative of DNA DSBs persisting in patients' cells, presumably leading to a higher level of stable chromosomal aberrations that may contribute to tumour formation.

CD4 and CD8 T-lymphocyte apoptosis can predict radiation-induced late toxicity: a prospective study in 399 patients

PURPOSE

Predicting late effects in patients treated with radiation therapy by assessing in vitro radiation-induced CD4 and CD8 T-lymphocyte apoptosis can be useful in individualizing treatment.

EXPERIMENTAL DESIGN

In a prospective study, 399 curatively irradiated patients were tested using a rapid assay where fresh blood samples were in vitro irradiated with 8 Gy X-rays. Lymphocytes were collected and prepared for flow cytometric analysis. Apoptosis was assessed by associated condensation of DNA. The incidences of late toxicities were compared for CD4 and CD8 T-lymphocyte apoptoses using receiver-operating characteristic curves and cumulative incidence.

RESULTS

No association was found between early toxicity and T-lymphocyte apoptosis. Grade 2 and 3 late toxicities were observed in 31% and 7% of patients, respectively. More radiation-induced T-lymphocyte apoptosis was significantly associated with less grade 2 and 3 late toxicity (Gray's test, P < 0.0001). CD8 (area under the curve = 0.83) was more sensitive and specific than CD4. No grade 3 late toxicity was observed for patients with CD4 and CD8 values greater than 15% and 24%, respectively. The 2-year cumulative incidence for grade 2 or 3 late toxicity was 70%, 32%, and 12% for patients with absolute change in CD8 T-lymphocyte apoptosis of < or =16, 16 to 24, and >24, respectively.

CONCLUSIONS

Radiation-induced T-lymphocyte apoptosis can significantly predict differences in late toxicity between individuals. It could be used as a rapid screen for hypersensitive patients to radiotherapy. In future dose escalation studies, patients could be selected using the apoptosis assay.

Intrinsic susceptibility to radiation-induced apoptosis of human lymphocyte subpopulations

PURPOSE

With the aim to evaluate intrinsic radiosensitivity, the susceptibility of lymphocyte subpopulations to radiation-induced apoptosis was determined. The investigated parameters included measurement reliability, phenotypic variance, intra- and inter-individual variability, and correlations between radiation-induced and spontaneous apoptosis.

METHODS AND MATERIALS

Quiescent lymphocytes of 63 healthy volunteers, sampled up to four times over a 1-year period were gamma-irradiated in vitro. Subsequent apoptosis (annexin V) was measured for T4-, T8-, and B-lymphocyte subpopulations using 6-color flow cytometry. Spontaneous apoptosis was measured and radiosensitivity was quantified from the dose-effect curves.

RESULTS

After thawing and short-term culture, both spontaneous apoptosis as well as radiation-induced apoptosis (radiosensitivity) differed among the three lymphocyte subpopulations, with T4 being most resistant, and B most sensitive. Spontaneous and radiation-induced apoptosis were correlated in all cell types, and variance between individuals was considerably higher than variance within individuals for both. A small but highly significant increase of both spontaneous and radiation-induced apoptosis was observed with age for T8, but not for T4 and B. Radiosensitivity of T8 and B proved to be sex-independent, whereas female T4 lymphocytes were less radiosensitive than those from males. T4 and T8 radiosensitivities were loosely correlated, and neither of them was related to B radiosensitivity.

CONCLUSION

Tendency to spontaneous and radiation-induced apoptosis of lymphocyte subpopulations differs among individuals. In addition, depending on the cell types, age and sex are factors influencing these parameters.

Chromosome instability and nibrin protein variants in NBS heterozygotes

The frequency of spontaneous chromosome abnormalities in peripheral blood lymphocytes and the X-ray G2 sensitivity in lymphoblastoid cell lines (LCL) have been evaluated in heterozygous subjects from three unrelated Nijmegen Breakage Syndrome (NBS) families, characterised by different mutations in the NBS1 gene. In all the 13 NBS heterozygotes analysed, we found spontaneous chromosome instability consisting in chromosome and chromatid breakages and rearrangements, while radiosensitivity was similar to that of control LCLs in seven out of eight tested NBS heterozygotes. The densitometric analysis of nibrin by immunoblotting indicated only a slight reduction in some of the LCLs from NBS carriers, whereas the immunoprecipitation assay appears a more reliable tool to detect NBS carriers. By means of immunoprecipitation, we investigated two homozygous and four heterozygous subjects. In the cells of the NBS patient 668, with the mutation 900del25, an alternative form of nibrin with a molecular weight of approximately 55 kDa has been detected. This variant protein, together with the normal p95, was also found in the LCL 34 established from a carrier of the same family. Signals of nibrin with a molecular weight lower than 95 kDa, but higher than that observed in LCLs 668 and 34, were detected also in three carriers from the family with mutation 835del4.