George A. Tanteles

A genome wide association study (GWAS) providing evidence of an association between common genetic variants and late radiotherapy toxicity

BACKGROUND AND PURPOSE This study was designed to identify common single nucleotide polymorphisms (SNPs) associated with toxicity 2years after radiotherapy. MATERIALS AND METHODS A genome wide association study was performed in 1850 patients from the RAPPER study: 1217 received adjuvant breast radiotherapy and 633 had radical prostate radiotherapy. Genotype associations with both overall and individual endpoints of toxicity were tested via univariable and multivariable regression. Replication of potentially associated SNPs was carried out in three independent patient cohorts who had radiotherapy for prostate (516 RADIOGEN and 862 Gene-PARE) or breast (355 LeND) cancer. RESULTS Quantile-quantile plots show more associations at the P<5×10(-7) level than expected by chance (164 vs. 9 for the prostate cases and 29 vs. 4 for breast cases), providing evidence that common genetic variants are associated with risk of toxicity. Strongest associations were for individual endpoints rather than an overall measure of toxicity in all patients. However, in general, significant associations were not validated at a nominal 0.05 level in the replication cohorts. CONCLUSIONS This largest GWAS to date provides evidence of true association between common genetic variants and toxicity. Associations with toxicity appeared to be tumour site-specific. Future GWAS require higher statistical power, in particular in the validation stage, to test clinically relevant effect sizes of SNP associations with individual endpoints, but the required sample sizes are achievable.

A replicated association between polymorphisms near TNFα and risk for adverse reactions to radiotherapy

Background:Response to radiotherapy varies between individuals both in terms of efficacy and adverse reactions. Finding genetic determinants of radiation response would allow the tailoring of the treatment, either by altering the radiation dose or by surgery. Despite a growing number of studies in radiogenomics, there are no well-replicated genetic association results.Methods:We carried out a candidate gene association study and replicated the result using three additional large cohorts, a total of 2036 women scored for adverse reactions to radiotherapy for breast cancer.Results:Genetic variation near the tumour necrosis factor alpha gene is shown to affect several clinical endpoints including breast induration, telangiectasia and overall toxicity. In the combined analysis homozygosity for the rare allele increases overall toxicity (P=0.001) and chance of being in the upper quartile of risk with odds ratio of 2.46 (95% confidence interval 1.52–3.98).Conclusion:We have identified that alleles of the class III major histocompatibility complex region associate with overall radiotherapy toxicity in breast cancer patients by using internal replication through a staged design. This is the first well-replicated report of a genetic predictor for radiotherapy reactions.

Standardized total average toxicity score: a scale- and grade-independent measure of late radiotherapy toxicity to facilitate pooling of data from different studies.

PURPOSE The search for clinical and biologic biomarkers associated with late radiotherapy toxicity is hindered by the use of multiple and different endpoints from a variety of scoring systems, hampering comparisons across studies and pooling of data. We propose a novel metric, the Standardized Total Average Toxicity (STAT) score, to try to overcome these difficulties. METHODS AND MATERIALS STAT scores were derived for 1010 patients from the Cambridge breast intensity-modulated radiotherapy trial and 493 women from the University Hospitals of Leicester. The sensitivity of the STAT score to detect differences between patient groups, stratified by factors known to influence late toxicity, was compared with that of individual endpoints. Analysis of residuals was used to quantify the effect of these covariates. RESULTS In the Cambridge cohort, STAT scores detected differences (p < 0.00005) between patients attributable to breast volume, surgical specimen weight, dosimetry, acute toxicity, radiation boost to tumor bed, postoperative infection, and smoking (p < 0.0002), with no loss of sensitivity over individual toxicity endpoints. Diabetes (p = 0.017), poor postoperative surgical cosmesis (p = 0.0036), use of chemotherapy (p = 0.0054), and increasing age (p = 0.041) were also associated with increased STAT score. When the Cambridge and Leicester datasets were combined, STAT was associated with smoking status (p < 0.00005), diabetes (p = 0.041), chemotherapy (p = 0.0008), and radiotherapy boost (p = 0.0001). STAT was independent of the toxicity scale used and was able to deal with missing data. There were correlations between residuals of the STAT score obtained using different toxicity scales (r > 0.86, p < 0.00005 for both datasets). CONCLUSIONS The STAT score may be used to facilitate the analysis of overall late radiation toxicity, from multiple trials or centers, in studies of possible genetic and nongenetic determinants of radiotherapy toxicity.

7q11.23 Microduplication: a recognizable phenotype

Dixit A, McKee S, Mansour S, Mehta SG, Tanteles GA, Anastasiadou V, Patsalis PC, Martin K, McCullough S, Suri M, Sarkar A. 7q11.23 Microduplication: a recognizable phenotype.

Variation in Telangiectasia Predisposing Genes Is Associated With Overall Radiation Toxicity

PURPOSE In patients receiving radiotherapy for breast cancer where the heart is within the radiation field, cutaneous telangiectasiae could be a marker of potential radiation-induced heart disease. We hypothesized that single nucleotide polymorphisms (SNPs) in genes known to cause heritable telangiectasia-associated disorders could predispose to such late, normal tissue vascular damage. METHODS AND MATERIALS The relationship between cutaneous telangiectasia as a late normal tissue radiation injury phenotype in 633 breast cancer patients treated with radiotherapy was examined. Patients were clinically assessed for the presence of cutaneous telangiectasia and genotyped at nine SNPs in three candidate genes. Candidate SNPs were within the endoglin (ENG) and activin A receptor, type II-like 1 (ACVRL1) genes, mutations in which cause hereditary hemorrhagic telangiectasia and the ataxia-telangiectasia mutated (ATM) gene associated with ataxia-telangiectasia. RESULTS A total of 121 (19.1%) patients exhibited a degree of cutaneous telangiectasiae on clinical examination. Regression was used to examine the associations between the presence of telangiectasiae in patients who underwent breast-conserving surgery, controlling for the effects of boost and known brassiere size (n=388), and individual geno- or haplotypes. Inheritance of ACVRL1 SNPs marginally contributed to the risk of cutaneous telangiectasiae. Haplotypic analysis revealed a stronger association between inheritance of a ATM haplotype and the presence of cutaneous telangiectasiae, fibrosis and overall toxicity. No significant association was observed between telangiectasiae and the coinheritance of the candidate ENG SNPs. CONCLUSIONS Genetic variation in the ATM gene influences reaction to radiotherapy through both vascular damage and increased fibrosis. The predisposing variation in the ATM gene will need to be better defined to optimize it as a predictive marker for assessing radiotherapy late effects.

Can cutaneous telangiectasiae as late normal-tissue injury predict cardiovascular disease in women receiving radiotherapy for breast cancer?

Background:Overall, ∼5% of patients show late normal-tissue damage after radiotherapy with a smaller number having a risk of radiation-induced heart disease. Although the data are conflicting, large studies have shown increased risks of cardiovascular disease (CVD) for irradiated patients compared with non-irradiated ones, or for those treated to the left breast or chest wall compared with those treated to the right. Cutaneous telangiectasiae as late normal-tissue injury have so far only been regarded as a cosmetic burden.Methods:The relationship between late normal-tissue radiation injury phenotypes in 149 irradiated breast cancer patients and the presence of cardiovascular disease were examined.Results:A statistically significant association between the presence of skin telangiectasiae and the long-term risk of CVD was shown in these patients (P=0.017; Fishers exact test).Interpretation:This association may represent initial evidence that telangiectasiae can be used as a marker of future radiation-induced cardiac complications. It could also suggest a common biological pathway for the development of both telangiectasiae and CVD on the basis of a genetically predisposed endothelium. To our knowledge this is the first reported study looking at this association.

Association between single nucleotide polymorphisms in the DNA repair gene LIG3 and acute adverse skin reactions following radiotherapy

Many genes have been associated with radiotherapy toxicity, but most have only been found in a single study. Using our cohort of 480 breast cancer patients, we provide replicated evidence that a polymorphism near the LIG3 gene is associated with acute skin toxicity following radiotherapy.

Haploinsufficiency of the miR-873/miR-876 microRNA cluster is associated with craniofacial abnormalities.

MicroRNA haploinsufficiency has been associated with developmental defects in only a limited number of cases. Here we report a de novo genomic microdeletion that includes the LINGO2 gene as well as two microRNA genes, MIR873 and MIR876, in a patient with craniofacial abnormalities - in particular macrocephaly and hypertelorism - and learning difficulties. Subsequent analysis revealed that the microRNAs affected by this de novo microdeletion form a mammalian-lineage, neuronal tissue-enriched cluster. In addition, bioinformatic analysis and experimental data indicate that miR-873 is involved in the regulation of the Hedgehog signaling, an essential pathway involved in craniofacial patterning and differentiation. Collectively these observations are consistent with a role of the miR-873/miR-876 microRNA cluster in physiological cranial bone development and indicate that mutations affecting these microRNAs could be a rare cause of developmental defect in humans.

Familial Mediterranean fever associated with MEFV mutations in a large cohort of Cypriot patients.

Familial Mediterranean fever (FMF) is caused by mutations in the MEFV gene and the spectrum of mutations among Greek–Cypriots with FMF‐related symptoms was examined. Sequence analysis for exons 2, 3, 5, and 10 of the MEFV gene was performed in a cohort of 593 patients. A total of 70 patients carried mutations in the homozygote or compound heterozygote state, 128 were identified with one MEFV mutation and 395 had no mutations. Of the 268 identified alleles, p.Val726Ala (27.61%) was the most frequent followed by p.Met694Val (19.40%). The missense mutations p.Arg761His (3.73%) and p.Ala744Ser (2.24%) were identified as the rarest. An interesting finding is the high frequency (18.28%) of the complex p.Phe479Leu–p.Glu167Asp that was identified in 49 of the mutated alleles. The MEFV genotypes did not follow a binomial distribution and proved not to satisfy the HWE (P < 0.001). The high percentage (66.61%) of patients with unidentified mutations could be due to mutations in the rest of the coding or noncoding MEFV gene or due to mutations in other genes that are also causing Hereditary Recurrent Fevers. Results from this work indicate the high incidence of FMF in Cyprus and describe the spectrum of the mutations which occur in the country.

Partial MEF2C deletion in a Cypriot patient with severe intellectual disability and a jugular fossa malformation: Review of the literature

Deletions or intragenic mutations involving the MEF2C gene on chromosome 5q14.3 have generally been associated with a relatively uniform phenotype characterized by severe developmental delay, absent speech, stereotypies, absent or limited gait abilities, lack of a typical facial gestalt and scarcity of major malformations. We report on a patient of Cypriot descent with a de novo, approximately 147 kb in size, partial MEF2C deletion removing exons 1 to 3. He had a history of severe intellectual disability with absent speech, poor eye contact, hand stereotypies and a wide‐based gait. A broad‐based, shallow jugular pit with an overlying vascular malformation was also present. Partial MEF2C deletions have only been reported in a very small number of patients and have on occasion been associated with relatively milder phenotypes. We present a patient of Cypriot descent with such a deletion and review previously published literature on partial MEF2C gene deletions postulating a key role of the first few exons in the pathogenesis of the disease.