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.

Patient reported outcome measures (PROMs) following forward planned field-in field IMRT: results from the Cambridge Breast IMRT trial.

BACKGROUND: The use of intensity-modulated radiotherapy (IMRT) in breast cancer reduces clinician-assessed breast tissue toxicity including fibrosis, telangectasia and sub-optimal cosmesis. Patient reported outcome measures (PROMs) are also important as they provide the patient's perspective. This longitudinal study reports on (a) the effect of forward planned field-in-field IMRT (∼simple IMRT) on PROMs compared to standard RT at 5 years after RT, (b) factors affecting PROMs at 5years after RT and (c) the trend of PROMs over 5 years of follow up. METHODS: PROMs were assessed at baseline (pre-RT), 6, 24 and 60 months after completion of RT using global health (EORTC QLQ C30) and 4 breast symptom questions (BR23). Also, 4 breast RT-specific questions were included at 6, 24 and 60 months: change in skin appearance, firmness to touch, reduction in breast size and overall change in breast appearance since RT. The benefits of simple IMRT over standard RT at 5 years after RT were assessed using standard t-test for global health and logistic regression analysis for breast symptom questions and breast RT-specific questions. Clinical factors affecting PROMs at 5 years were investigated using a multivariate analysis. A repeated mixed model was applied to explore the trend over time for each of PROMs. RESULTS: (89%) 727/815, 84%, 81% and 61% patients completed questionnaires at baseline, 6, 24 and 60 months respectively. Patients reported worse toxicity for all four BR23 breast symptoms at 6 months, which then improved over time (p<0.0001). They also reported improvement in skin appearance and breast hardness over time (p<0.0001), with no significant change for breast shrinkage (p=0.47) and overall breast appearance (p=0.13). At 5years, PROMs assessments did not demonstrate a benefit for simple IMRT over standard radiotherapy. Large breast volume, young age, baseline surgical cosmesis and post-operative infection were the most important variables to affect PROMs. CONCLUSIONS: This study was unable to demonstrate the benefits of IMRT on PROMs at 5years. PROMs are influenced by non-radiotherapy factors and surgical factors should be optimised to improve patients' outcome. Only a small proportion of patients report moderate-severe breast changes post radiotherapy, with most PROMs improving over time. The difference in clinician assessment and PROMs outcome requires further investigation.

Randomized controlled trial of intensity-modulated radiotherapy for early breast cancer: 5-year results confirm superior overall cosmesis.

PURPOSE: There are few randomized controlled trial data to confirm that improved homogeneity with simple intensity-modulated radiotherapy (IMRT) decreases late breast tissue toxicity. The Cambridge Breast IMRT trial investigated this hypothesis, and the 5-year results are reported. PATIENTS AND METHODS: Standard tangential plans of 1,145 trial patients were analyzed; 815 patients had inhomogeneous plans (≥ 2 cm(3) receiving 107% of prescribed dose: 40 Gy in 15 fractions over 3 weeks) and were randomly assigned to standard radiotherapy (RT) or replanned with simple IMRT; 330 patients with satisfactory dose homogeneity were treated with standard RT and underwent the same follow-up as the randomly assigned patients. Breast tissue toxicities were assessed at 5 years using validated methods: photographic assessment (overall cosmesis and breast shrinkage compared with baseline pre-RT photographs) and clinical assessment (telangiectasia, induration, edema, and pigmentation). Comparisons between different groups were analyzed using polychotomous logistic regression. RESULTS: On univariate analysis, compared with standard RT, fewer patients in the simple IMRT group developed suboptimal overall cosmesis (odds ratio [OR], 0.68; 95% CI, 0.48 to 0.96; P = .027) and skin telangiectasia (OR, 0.58; 95% CI, 0.36 to 0.92; P = .021). No evidence of difference was seen for breast shrinkage, breast edema, tumor bed induration, or pigmentation. The benefit of IMRT was maintained on multivariate analysis for both overall cosmesis (P = .038) and skin telangiectasia (P = .031). CONCLUSION: Improved dose homogeneity with simple IMRT translates into superior overall cosmesis and reduces the risk of skin telangiectasia. These results are practice changing and should encourage centers still using two-dimensional RT to implement simple breast IMRT.

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.

Independent validation of genes and polymorphisms reported to be associated with radiation toxicity: a prospective analysis study.

BACKGROUND: Several studies have reported associations between radiation toxicity and single nucleotide polymorphisms (SNPs) in candidate genes. Few associations have been tested in independent validation studies. This prospective study aimed to validate reported associations between genotype and radiation toxicity in a large independent dataset. METHODS: 92 (of 98 attempted) SNPs in 46 genes were successfully genotyped in 1613 patients: 976 received adjuvant breast radiotherapy in the Cambridge breast IMRT trial (ISRCTN21474421, n=942) or in a prospective study of breast toxicity at the Christie Hospital, Manchester, UK (n=34). A further 637 received radical prostate radiotherapy in the MRC RT01 multicentre trial (ISRCTN47772397, n=224) or in the Conventional or Hypofractionated High Dose Intensity Modulated Radiotherapy for Prostate Cancer (CHHiP) trial (ISRCTN97182923, n=413). Late toxicity was assessed 2 years after radiotherapy with a validated photographic technique (patients with breast cancer only), clinical assessment, and patient questionnaires. Association tests of genotype with overall radiation toxicity score and individual endpoints were undertaken in univariate and multivariable analyses. At a type I error rate adjusted for multiple testing, this study had 99% power to detect a SNP, with minor allele frequency of 0·35, associated with a per allele odds ratio of 2·2. FINDINGS: None of the previously reported associations were confirmed by this study, after adjustment for multiple comparisons. The p value distribution of the SNPs tested against overall toxicity score was not different from that expected by chance. INTERPRETATION: We did not replicate previously reported late toxicity associations, suggesting that we can essentially exclude the hypothesis that published SNPs individually exert a clinically relevant effect. Continued recruitment of patients into studies within the Radiogenomics Consortium is essential so that sufficiently powered studies can be done and methodological challenges addressed. FUNDING: Cancer Research UK, The Royal College of Radiologists, Addenbrooke's Charitable Trust, Breast Cancer Campaign, Cambridge National Institute of Health Research (NIHR) Biomedical Research Centre, Experimental Cancer Medicine Centre, East Midlands Innovation, the National Cancer Institute, Joseph Mitchell Trust, Royal Marsden NHS Foundation Trust, Institute of Cancer Research NIHR Biomedical Research Centre for Cancer.

Randomized controlled trial of forward-planned intensity modulated radiotherapy for early breast cancer: interim results at 2 years.

PURPOSE: This single-center randomized trial was designed to investigate whether intensity-modulated radiotherapy (IMRT) reduces late toxicity in patients with early-stage breast cancer. METHODS AND MATERIALS: The standard tangential plans of 1,145 nonselected patients were analyzed. The patients with inhomogeneous plans were randomized to a simple method of forward-planned IMRT or standard radiotherapy (RT). The primary endpoint was serial photographic assessment of breast shrinkage. RESULTS: At 2 years, no significant difference was found in the development of any photographically assessed breast shrinkage between the patients randomized to the interventional or control group (odds ratio, 1.51; 95% confidence interval, 0.83-1.58; p = .41). The patients in the control group were more likely to develop telangiectasia than those in the IMRT group (odds ratio, 1.68; 95% confidence interval 1.13-2.40; p = .009). Poor baseline surgical cosmesis resulted in poor overall cosmesis at 2 years after RT. In patients who had good surgical cosmesis, those randomized to IMRT were less likely to deteriorate to a moderate or poor overall cosmesis than those in the control group (odds ratio, 0.63; 95% confidence interval, 0.39-1.03, p = .061). CONCLUSIONS: IMRT can lead to a significant reduction in telangiectasia at comparatively early follow-up of only 2 years after RT completion. An important component of breast induration and shrinkage will actually result from the surgery and not from the RT. Surgical cosmesis is an important determinant of overall cosmesis and could partially mask the longer term benefits of IMRT at this early stage.