Abstract During the last decade, nearly 60 studies have addressed possible associations between various genetic sequence alterations and risk of adverse reactions after radiotherapy. We report here ...an overview of these studies with information on the genetic variants, tumour type, number of patients included, the endpoint studied, the mechanism(s) by which the candidate genes are involved in the pathogenesis of normal tissue toxicity, and odds ratios (ORs) for candidate variants. Though many positive results have been reported, inconsistent findings and non-replication of previous results have frequently occurred. This can presumably be attributed to certain methodological shortcomings including lack of statistical power to detect small effect sizes. Based on theoretical considerations and experiences from other scientific fields, we discuss how future studies should be designed in order to successfully unravel the genetics of normal tissue radiosensitivity. We propose a model of the allelic architecture that may underlie differences in normal tissue radiosensitivity. Genome wide association studies have proven a powerful tool to identify novel loci that affect various phenotypes. Nonetheless, genome wide association studies are extremely demanding in terms of sample size. Furthermore, certain limitations still relate to this kind of studies, emphasizing the need for international consortia such as the ESTRO GENEPI.
Abstract Background HPV/p16-positive head and neck cancers (HNSCC) show superior response to radiotherapy, compared with virus-negative tumours. Tumour hypoxia induces radioresistance and the ...randomised DAHANCA 5 trial found that the hypoxic cell radiosensitiser nimorazole significantly improved the outcome in HNSCC. Using p16-status as a retrospective stratification parameter, we aimed to assess the influence of p16-expression on the response to nimorazole in HNSCC. Materials and methods Pre-treatment tumour blocks were available from 331 of the 414 patients in the DAHANCA 5 trial and evaluated by immunohistochemistry for p16-expression. The influence of p16-expression on outcome was analysed as a function of treatment group (nimorazole/placebo) 5 years after radiotherapy. Results Overall, patients treated with nimorazole had significantly better loco-regional control than did those given placebo: hazard ratio (HR) 0.70 95% CI 0.52–0.93. Positive expression of p16 also significantly improved outcome after radiotherapy (0.41 0.28–0.61). In the subgroup of patients with p16-negative tumours, loco-regional failure was more frequent in the placebo group than in the nimorazole group (0.69 0.50–0.95). However, in the p16-positive group, patients treated with nimorazole had a loco-regional control rate similar to patients given placebo (0.93 0.45–1.91). Conclusions HPV/p16-expression significantly improved outcome after radiotherapy in HNSCC. Hypoxic modification improved outcome in HPV/p16-negative tumours but was of no significant benefit in HPV/p16-positive tumours, suggesting that hypoxic radioresistance may not be clinically relevant in these tumours.
•RT doses to heart and cardiac substructures differed markedly depending on laterality of irradiation.•The highest doses after left-sided RT were observed in the left ventricle and the left anterior ...descending coronary artery.•The highest doses after right-sided RT were observed in the right atrium and the right coronary artery.•Coronary artery disease tends to occur in the part of the heart with the highest radiation dose.•No significant difference in RT doses to the heart and cardiac substructures was observed in cases versus controls after 7 years follow-up.
Coronary artery disease (CAD) has been reported as a late effect following radiation therapy (RT) of early breast cancer (BC). This study aims to report individual RT doses to the heart and cardiac substructures in patients treated with CT-based RT and to investigate if a dose–response relationship between RT dose and CAD exists using modern radiation therapy techniques.
Patients registered in the Danish Breast Cancer Group database from 2005 to 2016 with CT-based RT were eligible. Among 15,765 patients, the study included 204 with CAD after irradiation (cases) and 408 matched controls. Individual planning CTs were retrieved, the heart and cardiac substructures were delineated and dose-volume parameters were extracted.
The median follow-up time was 7.3 years (IQR: 4.6–10.0). Among cases, the median mean heart dose was 1.6 Gy (IQR 0.2–6.1) and 0.8 Gy (0.1–2.9) for left-sided and right-sided patients, respectively (p < 0.001). The highest RT doses were observed in the left ventricle and left anterior descending coronary artery for left-sided RT and in the right atrium and the right coronary artery after right-sided RT. The highest left-minus-right dose-difference was located in the distal part of the left anterior descending coronary artery where also the highest left-versus-right ratio of events was observed. However, no significant difference in the distribution of CAD was observed by laterality. Furthermore, no significant differences in the dose-volume parameters were observed for cases versus controls.
CAD tended to occur in the part of the heart with the highest left-minus- right dose difference, however, no significant risk of CAD was observed at 7 years' median follow-up.
We compare outcomes in two large‐scale contemporaneously treated HPV‐positive (HPV+) oropharynx cancer (OPC) cohorts treated with definitive radiotherapy/chemoradiotherapy (RT/CRT). p16‐confirmed ...HPV+ OPC treated between 2007 and 2015 at PMH and DAHANCA were identified. Locoregional failure (LRF), distant metastasis (DM), and overall survival (OS) were compared. Multivariable analysis (MVA) calculated adjusted‐hazard‐ratio (aHR) with 95% confidence interval (95% CI), adjusting for cohort, age, gender, performance status, smoking pack‐years, T‐category and N‐category and chemotherapy. Compared to PMH (n = 701), DAHANCA (n = 1174) contained lower TNM‐8T‐categories (T1‐T2: 77% vs 56%), N‐categories (N0‐N1: 77% vs 67%) and stages (stage I: 63% vs 44% (all P < .001). PMH used standard‐fractionation CRT in 69% (481) while 31% (220) received hypofractionated or moderately accelerated RT‐alone. All DAHANCA patients were treated with moderately accelerated RT; 96% (1129) received nimorazole (NIM) and 73% (856) concurrent weekly cisplatin. DAHANCA had shorter overall‐treatment‐time (P < .001), lower gross tumor (66‐68 vs 70 Gy) and elective neck (50 vs 56 Gy) doses. Median follow‐up was 4.8 years. DAHANCA had higher 5‐year LRF (13% vs 7%, aHR = 0.47 0.34‐0.67), comparable DM (7% vs 12%, aHR = 1.32 0.95‐1.82), but better OS (85% vs 80%, aHR = 1.30 1.01‐1.68). CRT patients had a lower risk of LRF (aHR 0.56 0.39‐0.82), DM (aHR 0.70 0.50‐1.00) and death (aHR 0.39 0.29‐0.52) vs RT‐alone. We observed exemplary outcomes for two large‐scale trans‐Atlantic HPV+ OPC cohorts treated in a similar manner. Concurrent chemotherapy was a strong, independent prognostic factor for all endpoints. Our findings underscore the need for a very careful approach to de‐intensification of treatment for this disease.
What's new?
HPV‐positive oropharyngeal cancer (OPC) represents a unique subgroup which has very different epidemiology, molecular biology, and response to radiotherapy/chemo‐radiotherapy (RT/CRT) than HPV‐negative squamous cell carcinoma of the head and neck (HNSCC). In this study, the authors compared two large cohorts of HPV‐positive OPC, and found significantly better outcomes in patients that routinely received concurrent chemoradiotherapy with cisplatin compared with radiotherapy alone. The authors conclude that these findings underscore the need for a cautious approach to efforts aimed at de‐intensifying treatment for this disease.
Radiotherapy has been optimized over the last decades not only through technological advances, but also through the translation of biological knowledge into clinical treatment schedules. Optimization ...of fractionation schedules and/or the introduction of simultaneous combined systemic treatment have significantly improved tumour cure rates in several cancer types. With modern techniques, we are currently able to measure factors of radiation resistance or radiation sensitivity in patient tumours; the definition of new biomarkers is expected to further enable personalized treatments. In this Review article, we overview important translation paths and summarize the quality requirements for preclinical and translational studies that will help to avoid bias in trial results.
Translation of preclinical radiobiological research into clinical radiotherapy has largely improved treatment outcomes. Indicatively, based on the results of current biological research, fractionation schedules have been optimized, and combined treatments have been developed. In this Review, we discuss translation paths that have substantially improved radiotherapy and summarize what quality requirements within preclinical and translational studies will ensure the development of unbiased clinical trials.
Reliable methods for identification of hypoxia in radiotherapy-treated tumors have been a desirable aim in radiation oncology for decades. Hypoxia is a common feature of the microenvironment in solid ...tumors, and it is associated with increased aggressiveness, reduced therapeutic response, and a poorer clinical outcome. In head and neck squamous cell carcinomas, the negative effect of hypoxia on radiotherapeutic response can be counteracted and minimized by applying hypoxic modification to radiotherapy, which favors the clinical outcome after treatment. However, not all tumors are hypoxic, hence not all patients benefit from the addition of hypoxic modification. Therefore, predictive and clinically applicable methods for pretherapeutic hypoxic evaluation and categorization are needed. Hypoxia gene expression signatures are a developing strategy to approach this obstacle. This method has evolved along with the development of complementary DNA microarray analysis and classifies tumors in accordance to the expression of specific hypoxia-responsive genes in the tumor biopsy. Thus, tumors are classified and categorized in terms of the biological behavior to hypoxic conditions in the microenvironment. Until now, most of the developed hypoxia signatures have only been evaluated in terms of their prognostic impact; however, recently, a predictive impact for hypoxic modification of radiotherapy was verified. Here, we provide an overview of the hypoxic issue in radiotherapy and present the most promising hypoxia gene expression signatures developed to date.
During the last decade, a number of studies have supported the hypothesis that there is an important genetic component to the observed interpatient variability in normal tissue toxicity after ...radiotherapy. This review summarizes the candidate gene association studies published so far on the risk of radiation-induced morbidity and highlights some recent successful whole-genome association studies showing feasibility in other research areas. Future genetic association studies are discussed in relation to methodological problems such as the characterization of clinical and biological phenotypes, genetic haplotypes, and handling of confounding factors. Finally, candidate gene studies elucidating the genetic component of radiation-induced morbidity and the functional consequences of single nucleotide polymorphisms by studying intermediate phenotypes will be discussed.
Single nucleotide polymorphisms (SNPs) in genes related to the biological response to radiation injury may affect clinical normal tissue radiosensitivity. This study investigates whether seven ...selected SNPs in five candidate genes influence risk of subcutaneous fibrosis and telangiectasia after radiotherapy.
The 41 patients included in this study were given post-mastectomy radiotherapy in 1978–1982 and subsequently evaluated in detail with regard to several different normal tissue reactions. SNPs in
TGFB1 (codons 10, 25 and position −509),
SOD2 (codon 16),
XRCC3 (codon 241),
XRCC1 (codon 399) and
APEX (codon 148) were analyzed by PCR and single nucleotide primer extension. Dose–response curves were established for subcutaneous fibrosis and telangiectasia in patients with different genotypes. Differences in radiosensitivity were quantified in terms of ED
50 values and enhancement ratios.
For
TGFB1, the Pro/Pro genotype in codon 10 and the T/T genotype in position −509 correlated positively with risk of subcutaneous fibrosis. The
SOD 2 codon 16 Val/Ala genotype was associated with increased risk of subcutaneous fibrosis when compared to the Val/Val genotype. The Thr/Thr genotype in
XRCC3 codon 241 correlated with increased risk of subcutaneous fibrosis as well as telangiectasia. The Arg/Arg genotype in
XRCC1 codon 399 was associated with increased risk of radiation-induced subcutaneous fibrosis. For these polymorphisms, enhancement ratios between 1.09 and 1.25 were found. Combined analysis of multiple SNPs demonstrated that the risk of subcutaneous fibrosis correlated with the number of risk alleles in such a manner that patients with few risk alleles exhibited a remarkable degree of radioresistance.
The present study established significant correlations between five SNPs and risk of radiation-induced normal tissue reactions. These findings support the assumption that clinical normal tissue radiosensitivity should be regarded as a phenomenon dependent on the combined effect of variation in several genes and indicate that models based on multiple genetic markers may have the potential to predict normal tissue responses after radiotherapy.
The tumor microenvironment is characterized by regions of hypoxia and acidosis which are linked to poor prognosis. This occurs due to an aberrant vasculature as well as high rates of glycolysis and ...lactate production in tumor cells even in the presence of oxygen (the Warburg effect), which weakens the spatial linkage between hypoxia and acidosis.
Five different human squamous cell carcinoma cell lines (SiHa, FaDuDD, UTSCC5, UTSCC14 and UTSCC15) were treated with hypoxia, acidosis (pH 6.3), or a combination, and gene expression analyzed using microarray. SiHa and FaDuDD were chosen for further characterization of cell energetics and protein synthesis. Total cellular ATP turnover and relative glycolytic dependency was determined by simultaneous measurements of oxygen consumption and lactate synthesis rates and total protein synthesis was determined by autoradiographic quantification of the incorporation of 35S-labelled methionine and cysteine into protein.
Microarray analysis allowed differentiation between genes induced at low oxygen only at normal extracellular pH (pHe), genes induced at low oxygen at both normal and low pHe, and genes induced at low pHe independent of oxygen concentration. Several genes were found to be upregulated by acidosis independent of oxygenation. Acidosis resulted in a more wide-scale change in gene expression profiles than hypoxia including upregulation of genes involved in the translation process, for example Eukaryotic translation initiation factor 4A, isoform 2 (EIF4A2), and Ribosomal protein L37 (RPL37). Acidosis suppressed overall ATP turnover and protein synthesis by 50%. Protein synthesis, but not total ATP production, was also suppressed under hypoxic conditions. A dramatic decrease in ATP turnover (SiHa) and protein synthesis (both cell lines) was observed when hypoxia and low pHe were combined.
We demonstrate here that the influence of hypoxia and acidosis causes different responses, both in gene expression and in de novo protein synthesis, depending on whether the two factors induced alone or overlapping, and as such it is important for in vivo studies to take this into account.
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