Table 1.

STROGAR – 18-item checklist for reporting radiogenomics studies.

	Item number	Recommendation
Title and abstract
Title and abstract	1	Include the primary outcome(s) and type of study (whether GWAS or gene-specific); provide an informative summary of the study including study design, whether discovery or validation, sample size, main endpoints, and major results.
Introduction
Background/rationale	2	Note if the study is a GWAS or a candidate gene/SNP study and, if candidate gene study, rationale for choice of genes/SNPs; give a general description of the study setting.
Objectives	3	Define the primary/main outcome(s) of interest; describe the overall/long-term goal of the study; note if it is a discovery, validation, or multi-stage study. Use terminology and definitions from National Cancer Institute biomarker study guidelines [42], where applicable.
Methods
Study design	4	Specify the study design (case-control, cohort); whether data were collected under a controlled trial setting; whether data were collected retrospectively or prospectively. Report power and sample size considerations.
Patient population	5	Specify the source(s) of the patients and, if multiple sources, whether they are pooled or treated as separate cohorts; define inclusion/exclusion criteria; report whether co-morbidities and medications were assessed by self-report or medical records; define methods/system used for tumour staging; describe the larger patient population from which the study sample was drawn; define how major changes in treatment protocol were handled in the analysis.
Radiation exposure	6	Specify details of radiation treatment parameters including: organ(s)-at-risk, dose–time-fractionation; dose-rate, target volume selection [ex: breast + boost], dose to critical substructures, dose–volume metric used, the type of treatment and treatment setting, radiation modality [ex: external beam vs. brachytherapy], whether single or combined treatment modalities were used, whether primary treatment or salvage therapy, imaging & planning details, ICRU recommendations followed and note relaxation of criteria, note any changes in dose or treatment protocol over the time course of enrolment and whether there were any interruptions in treatment.
Phenotype(s)	7	Specify how intra-patient or pre-treatment assessment was made and whether it is accounted for in defining phenotype(s); note whether patient reported outcomes or physician-assessed outcomes are being used to define phenotype(s); note which toxicity scoring system was used (if using a common/standard system); define the grading scales used and whether the phenotype(s) is/are defined as continuous, dichotomous or categorical; describe frequency of follow-up scheduling and diagnostic intensity; define the post-treatment timeframe for assessment of toxicity outcomes; describe whether outcome(s) is/are based on a single time point or the maximum/worst time point out of a series of follow-up assessments; note if/how competing risks were handled (such as non-radiation related manifestation of the phenotype); note any medical intervention that may influence study outcome(s).
Genotyping strategy and QC	8	Specify DNA source and isolation methods; note the methods/platform used for genotyping; specify whether genotyping was done in one stage or multiple stages; note whether genotyping was done in more than one lab or batch, and if so, how batch effects were handled; describe methods for genotype calling and cite the algorithm used; note whether genotype calling was done for the whole study sample together or in batches; describe quality control (QC) methods including concordance between duplicates, control samples, and checks for cryptic relatedness; describe methods for assessing population structure; describe SNP/CNP filtering methods including filtering on per-sample call rate, per-SNP call rate, minor allele frequency and Hardy–Weinberg equilibrium; note whether imputation was used and, if so, describe methods.
Data analysis and statistical methods	9	Define the statistical methods and models used for association testing; cite the software and settings used; describe how censoring was handled; define model selection methods used for multivariable models; describe whether all samples are analysed together or sequentially if the study involves multiple cohorts; for multi-stage studies, define methods for selecting variants to follow up in subsequent stages; describe how missing data were handled; if multiple cohorts were included, describe data harmonisation methods; note whether gene–gene interaction or gene–environment interaction was investigated; describe methods used to adjust for population structure; describe methods used to correct for multiple comparisons and/or control for risk of false-positive findings.
Results
Patient characteristics	10	Report number of individuals at each stage of the study (e.g. numbers examined for eligibility, numbers confirmed eligible, included in study, completed follow-up, successfully genotyped and analysed). Give reasons for nonparticipation at each stage. Give description of the included patient sample regarding demographic (e.g. age at start of therapy, sex, race/ethnicity) and clinical characteristics (e.g. site and stage of primary tumour, chemotherapy, hormone therapy), details of radiation exposure, where appropriate (e.g. type, dose, boost) and potential confounders and effect modifiers (e.g. life-style related factors, co-morbidities, and medications), including missing data; report length of follow-up and number of events and number of patients at risk at various follow-up times e.g. yearly. It is recommended to include a flow diagram of patients included/excluded from the study, as proposed by the CONSORT statement
Phenotype(s)	11	Report baseline function (if relevant); report numbers of responders and non-responders for dichotomous outcomes, descriptive statistics for quantitative outcome(s), or distributions for categorical outcomes.
Genotypes	12	Report call rates; numbers of samples and numbers of SNPs excluded on the basis of QC filters; if imputation was used, note which variants are imputed and which are genotyped directly; report genetically determined racial/ethnic groups or other population clusters; report genomic inflation factor as well as corrected genomic inflation factor after controlling for population structure.
Primary associations	13	For each SNP/CNP, report: common identifier (such as dbSNP rs number), minor allele identity and frequency, phenotype by genotype category, effect size (with 95% confidence interval) and p-value; genetic inheritance model(s) used; for multivariable analyses, report unadjusted and adjusted estimate and note which covariates were included in the model(s).
Secondary analyses	14	Report sub-group analyses and/or secondary outcomes of interest.
Discussion
Key results	15	Summarise key results in the context of the study objectives given in the Introduction.
Limitations	16	Discuss limitations of the study in the context of bias (noting both direction and size), confounding, sample size and power, and representativeness of study population.
Interpretation	17	Provide an overall interpretation of the findings in the context of previous clinical studies, genetic association studies, and biological studies of radiation response.
Generalisability and clinical utility	18	Comment on the potential clinical utility of the findings in the context of the patient populations to which the results may apply.