[Show abstract][Hide abstract] ABSTRACT: Only a fraction of colorectal cancer heritability is explained by known risk-conferring genetic variation. This study was designed to identify novel risk alleles in Europeans. We conducted a genome-wide association study (GWAS) meta-analysis of colorectal cancer in participants from a population-based case control study in Israel (n = 1,616 cases, 1,329 controls) and a consortium study from the Colon Cancer Family Registry (n=1,977 cases, 999 controls). We used a two-stage (discovery-replication) GWAS design, followed by a joint meta-analysis. A combined analysis identified a novel susceptibility locus that reached genome-wide significance on chromosome 4q32.2 (rs35509282, risk allele = T (minor allele frequency = 0.09); odds ratio per risk allele = 1.53; p-value = 8.2x10(-9); nearest gene = FSTL5). The direction of the association was consistent across studies. In addition, we confirmed that 14 of 29 previously identified susceptibility variants were significantly associated with risk of colorectal cancer in this study. Genetic variation on chromosome 4q32.2 is significantly associated with risk of colorectal cancer in Ashkenazi Jews and Europeans in this study.
[Show abstract][Hide abstract] ABSTRACT: Background:Familial Colorectal Cancer Type X (FCCTX) is defined as individuals with colorectal cancer (CRC) who families meet Amsterdam Criteria-1 (AC1), but whose tumours are DNA-mismatch-repair-proficient, unlike Lynch syndrome (LS). FCCTX does not have an increased risk of extra-colonic cancers. This analysis compares epidemiologic and clinicopathologic features among FCCTX, LS, and 'non-familial' (non-AC1) CRC cases.Methods:From the Colon Cancer Family Registry, FCCTX (n=173), LS (n=303), and non-AC1 (n=9603) CRC cases were identified. Questionnaire-based epidemiologic information and CRC pathologic features were compared across case groups using polytomous logistic regression.Results:Compared with LS, FCCTX cases were less likely to be current (vs never) smokers; have a proximal subsite (vs rectal) tumour; or have mucinous histology, poor differentiation, or tumour-infiltrating lymphocytes. There were no observed differences in co-morbidities or medication usage.Conclusions:FCCTX were less likely to be current tobacco users; other exposures were similar between these groups. Histopathologic differences highly suggestive of LS CRCs do not appear to be shared by FCCTX.British Journal of Cancer advance online publication, 10 June 2014; doi:10.1038/bjc.2014.309 www.bjcancer.com.
[Show abstract][Hide abstract] ABSTRACT: Dietary factors, including meat, fruits, vegetables and fiber, are associated with colorectal cancer; however, there is limited information as to whether these dietary factors interact with genetic variants to modify risk of colorectal cancer. We tested interactions between these dietary factors and approximately 2.7 million genetic variants for colorectal cancer risk among 9,287 cases and 9,117 controls from ten studies. We used logistic regression to investigate multiplicative gene-diet interactions, as well as our recently developed Cocktail method that involves a screening step based on marginal associations and gene-diet correlations and a testing step for multiplicative interactions, while correcting for multiple testing using weighted hypothesis testing. Per quartile increment in the intake of red and processed meat were associated with statistically significant increased risks of colorectal cancer and vegetable, fruit and fiber intake with lower risks. From the case-control analysis, we detected a significant interaction between rs4143094 (10p14/near GATA3) and processed meat consumption (OR = 1.17; p = 8.7E-09), which was consistently observed across studies (p heterogeneity = 0.78). The risk of colorectal cancer associated with processed meat was increased among individuals with the rs4143094-TG and -TT genotypes (OR = 1.20 and OR = 1.39, respectively) and null among those with the GG genotype (OR = 1.03). Our results identify a novel gene-diet interaction with processed meat for colorectal cancer, highlighting that diet may modify the effect of genetic variants on disease risk, which may have important implications for prevention.
[Show abstract][Hide abstract] ABSTRACT: To determine whether risk of endometrial cancer for women without a germline mutation in a DNA mismatch repair (MMR) gene depends on family history of endometrial or colorectal cancer.
We retrospectively followed a cohort of 79,166 women who were recruited to the Colon Cancer Family Registry, after exclusion of women who were relatives of a carrier of a MMR gene mutation. The Kaplan-Meier failure method was used to estimate the cumulative risk of endometrial cancer. Cox regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for association between family history of endometrial or colorectal cancer and risk of endometrial cancer.
A total of 628 endometrial cancer cases were observed, with mean age at diagnosis of 54.4 (standard deviation 15.7) years. The cumulative risk of endometrial cancer to age 70years was estimated to be 0.94% (95% CI 0.83-1.05) for women with no family history of endometrial cancer, and 3.80% (95% CI 2.75-4.98) for women with at least one first- or second-degree relative with endometrial cancer. Compared with women without family history, we found an increased risk of endometrial cancer for women with at least one first- or second-degree relative with endometrial cancer (HR 3.66, 95% CI 2.63-5.08), and for women with one first-degree relative with colorectal cancer diagnosed at age <50years (HR 1.48, 95% CI 1.15-1.91).
An increased risk of endometrial cancer is associated with a family history of endometrial cancer or early-onset colorectal cancer for women without a MMR gene mutation; indicating for potential underlying genetic and environmental factors shared by colorectal and endometrial cancers other than caused by MMR gene mutations.
[Show abstract][Hide abstract] ABSTRACT: To estimate risk of colorectal cancer (CRC) for first-degree relatives of CRC cases based on CRC molecular subtypes and tumour pathology features.
We studied a cohort of 33 496 first-degree relatives of 4853 incident invasive CRC cases (probands) who were recruited to the Colon Cancer Family Registry through population cancer registries in the USA, Canada and Australia. We categorised the first-degree relatives into four groups: 28 156 of 4095 mismatch repair (MMR)-proficient probands, 2302 of 301 MMR-deficient non-Lynch syndrome probands, 1799 of 271 suspected Lynch syndrome probands and 1239 of 186 Lynch syndrome probands. We compared CRC risk for first-degree relatives stratified by the absence or presence of specific tumour molecular pathology features in probands across each of these four groups and for all groups combined.
Compared with first-degree relatives of MMR-proficient CRC cases, a higher risk of CRC was estimated for first-degree relatives of CRC cases with suspected Lynch syndrome (HR 2.06, 95% CI 1.59 to 2.67) and with Lynch syndrome (HR 5.37, 95% CI 4.16 to 6.94), but not with MMR-deficient non-Lynch syndrome (HR 1.04, 95% CI 0.82 to 1.31). A greater risk of CRC was estimated for first-degree relatives if CRC cases were diagnosed before age 50 years, had proximal colon cancer or if their tumours had any of the following: expanding tumour margin, peritumoral lymphocytes, tumour-infiltrating lymphocytes or synchronous CRC.
Molecular pathology features are potentially useful to refine screening recommendations for first-degree relatives of CRC cases and to identify which cases are more likely to be caused by genetic or other familial factors.
[Show abstract][Hide abstract] ABSTRACT: Background: Individuals with a strong family history of colorectal cancer (CRC) have significant risk for CRC, though adherence to colonoscopy screening in these groups remains low. This study assessed whether a tailored, telephone counseling intervention can increase adherence to colonoscopy in members of high risk families in a randomized, controlled trial. Methods: Eligible participants were recruited from two national cancer registries if they had a first-degree relative with CRC under age 60 or multiple affected family members, which included families that met Amsterdam criteria for Hereditary Non-Polyposis Colon Cancer, and if they were due for colonoscopy within 24-months. Participants were randomized to receive a tailored, telephone intervention grounded in behavioral theory or a mailed packet with general information about screening. Colonoscopy status was assessed through follow-up surveys and endoscopy reports. Cox-proportional hazards models were used to assess intervention effect. Results: Of the 632 participants (aged 25-80), 60% were female, the majority were White, non-Hispanic, educated and had health insurance. Colonoscopy adherence increased 11 percentage points in the tailored, telephone intervention group, compared to no significant change in the mailed group. The telephone intervention was associated with a 32% increase in screening adherence compared to the mailed intervention (Hazard Ratio=1.32; p=0.01). Conclusions: A tailored, telephone intervention can effectively increase colonoscopy adherence in high risk persons. This intervention has the potential for broad dissemination to health-care organizations or other high risk populations. Impact: Increasing adherence to colonoscopy among persons with increased CRC risk could effectively reduce incidence and mortality from this disease.
Cancer Epidemiology Biomarkers & Prevention 02/2014; · 4.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Early-onset breast cancer (EOBC) causes substantial loss of life and productivity, creating a major burden among women worldwide. We analyzed 1,265,548 Hapmap3 SNPs among a discovery set of 3,523 EOBC incident case and 2,702 population control women aged <=51 years. The SNPs with smallest P-values were examined in a replication set of 3,470 EOBC case and 5,475 control women. We also tested EOBC association with 19,684 genes by annotating each gene with putative functional SNPs, and then combining their P-values to obtain a gene-based P-value. We examined the gene with smallest P-value for replication in 1,145 breast cancer case and 1,142 control women. The combined discovery and replication sets identified 72 new SNPs associated with EOBC (P<4x10-8) located in six genomic regions previously reported to contain SNPs associated largely with later-onset breast cancer (LOBC). SNP rs2229882 and 10 other SNPs on chromosome 5q11.2 remained associated (P<6x10-4) after adjustment for the strongest published SNPs in the region. Thirty-two of the 82 currently known LOBC SNPs were associated with EOBC (P<0.05). Low power is likely responsible for the remaining 50 unassociated known LOBC SNPs. The gene-based analysis identified an association between breast cancer and the phosphofructokinase-muscle (PFKM) gene on chromosome 12q13.11 that met the genomewide gene-based threshold of 2.5x10-In conclusion, EOBC and LOBC appear to have similar genetic etiologies; the 5q11.2 region may contain multiple distinct breast cancer loci; and the PFKM gene region is worthy of further investigation. These findings should enhance our understanding of the etiology of breast cancer.
Cancer Epidemiology Biomarkers & Prevention 02/2014; · 4.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We studied 2332 individuals with monoallelic mutations in MUTYH among 9504 relatives of 264 colorectal cancer (CRC) cases with a MUTYH mutation. We estimated CRC risks, through 70 y of age, of 7.2% for male carriers of monoallelic mutations (95% confidence interval [CI], 4.6%-11.3%) and 5.6% for female carriers of monoallelic mutations (95% CI, 3.6%-8.8%), irrespective of family history. For monoallelic MUTYH mutation carriers with a first-degree relative with CRC, diagnosed by 50 y of age who does not have the MUTYH mutation, risks of CRC were 12.5% for men and (95% CI, 8.6%-17.7%) and 10% for women (95% CI, 6.7%-14.4%). Risks of CRC for carriers of monoallelic mutations in MUTYH with a first-degree relative with CRC are sufficiently high to warrant more intensive screening than for the general population.
[Show abstract][Hide abstract] ABSTRACT: Telomeres are nucleoprotein structures that cap the end of chromosomes and shorten with sequential cell divisions in normal aging. Short telomeres are also implicated in the incidence of many cancers, but the evidence is not conclusive for colorectal cancer (CRC). Therefore, the aim of this study was to assess the association of CRC and telomere length.
In this case-control study, we measured relative telomere length from peripheral blood leukocytes (PBLs) DNA with quantitative PCR in 598 CRC patients and 2,212 healthy controls.
Multivariate analysis indicated that telomere length was associated with risk for CRC, and this association varied in an age-related manner; younger individuals (≤50 years of age) with longer telomeres (80-99 percentiles) had a 2-6 times higher risk of CRC, while older individuals (>50 years of age) with shortened telomeres (1-10 percentiles) had 2-12 times the risk for CRC. The risk for CRC varies with extremes in telomere length in an age-associated manner.
Younger individuals with longer telomeres or older individuals with shorter telomeres are at higher risk for CRC. These findings indicate that the association of PBL telomere length varies according to the age of cancer onset and that CRC is likely associated with at minimum two different mechanisms of telomere dynamics.
Clinical and translational gastroenterology. 01/2014; 5:e52.
[Show abstract][Hide abstract] ABSTRACT: The clinical classification of hereditary sequence variants identified in disease-related genes directly affects clinical management of patients and their relatives. The International Society for Gastrointestinal Hereditary Tumours (InSiGHT) undertook a collaborative effort to develop, test and apply a standardized classification scheme to constitutional variants in the Lynch syndrome–associated genes MLH1, MSH2, MSH6 and PMS2. Unpublished data submission was encouraged to assist in variant classification and was recognized through microattribution. The scheme was refined by multidisciplinary expert committee review of the clinical and functional data available for variants, applied to 2,360 sequence alterations, and disseminated online. Assessment using validated criteria altered classifications for 66% of 12,006 database entries. Clinical recommendations based on transparent evaluation are now possible for 1,370 variants that were not obviously protein truncating from nomenclature. This large-scale endeavor will facilitate the consistent management of families suspected to have Lynch syndrome and demonstrates the value of multidisciplinary collaboration in the curation and classification of variants in public locus-specific databases.
[Show abstract][Hide abstract] ABSTRACT: Cigarette smoking (CS), hormone therapy (HT) and folate intake (FI) are each thought to influence colorectal cancer (CRC) risk, but the underlying molecular mechanisms remain incompletely defined. The TP53 (p53) protein, encoded by the TP53 tumor suppressor gene that is commonly mutated in CRC, can be readily assessed to differentiate biologically distinct CRC subtypes. In this prospective cohort study, we examined CS, HT, and FI -associated CRC risks by TP53 protein expression level among Iowa Women's Health Study (IWHS) participants. The IWHS recruited 41,836 randomly selected Iowa women, ages 55-69 years, with a valid driver's license at study entry in 1986. Self-reported exposure variables were assessed at baseline. Incident CRC cases were ascertained by annual linkage with the Iowa Cancer Registry. Archived, paraffin-embedded tissue specimens were collected and evaluated for TP53 protein expression by immunohistochemistry. Multivariate Cox regression models were fit to estimate relative risks (RRs) and 95% confidence intervals (CIs) for associations between CS, HT, or FI and TP53-defined CRC subtypes. Informative environmental exposure and protein expression data were available for 492 incident CRC cases: 222 (45.1%) TP53 negative, 72 (14.6%) TP53 low, and 198 (40.2%) TP53 high. Longer duration (> 5 years) of HT was inversely associated with TP53 high CRCs (RR = 0.50; 95% CI = 0.27-0.94). No other statistically significant associations were observed. These data support possible heterogeneous effects from HT on TP53-related pathways of colorectal carcinogenesis in older women.
Cancer Epidemiology Biomarkers & Prevention 12/2013; · 4.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background: It is widely accepted that chronic inflammation plays a role in the etiology of colorectal cancer. Using a two-stage design, we examined the associations between colorectal cancer and common variation in 37 key genes in the inflammation and innate immunity pathways. Methods: In the discovery stage, 2,322 discordant sibships (2,535 cases, 3,915 sibling controls) from the Colorectal Cancer Family Registry were genotyped for over 600 tagSNPs and 99 SNPs were selected for further examination based on strength of association. In the second stage, 351 SNPs tagging gene regions covered by the 99 SNPs were tested in 4,783 Multiethnic Cohort subjects (2,153 cases, 2,630 controls). Results: The association between rs9858822 in the PPARG gene and colorectal cancer was statistically significant at the end of the second stage (odds ratio per allele = 1.36, Bonferroni-adjusted P = 0.045), based on the "effective" number of markers in Stage 2 (n = 306). The risk allele C was common (frequency 0.3) in African Americans but rare (frequency < 0.03) in whites, Japanese Americans, Latinos and Native Hawaiians. No statistically significant heterogeneity of effects across race/ethnicity, BMI levels, regular aspirin use or pack-years of smoking was detected for this SNP. Suggestive associations were also observed for several SNPs in close vicinity to rs9858822. Conclusions: Our results provide new evidence of association between PPARG variants and colorectal cancer risk. Impact: Further replication in independent samples is warranted.
Cancer Epidemiology Biomarkers & Prevention 09/2013; · 4.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background: Both shorter and longer telomeres in peripheral blood leukocyte (PBL) DNA have been associated with cancer risk. However, associations remain inconsistent across studies of the same cancer type. This study compares DNA preparation methods to determine telomere length from colorectal cancer patients. Methods: We examined PBL relative telomere length (RTL) measured by quantitative PCR (qPCR) in 1,033 colorectal cancer patients and 2,952 healthy controls. DNA was extracted with Phenol/Chloroform, PureGene or QIAamp. Results: We observed differences in RTL depending on DNA extraction method (p<0.001). Phenol/Chloroform extracted DNA had a mean RTL (T/S ratio) of 0.78 (range 0.01-6.54) ) compared to PureGene extracted DNA (mean RTL of 0.75; range 0.00-12.33). DNA extracted by QIAamp yielded a mean RTL of 0.38 (range 0.02-3.69). We subsequently compared RTL measured by qPCR from an independent set of 20 colorectal cancer cases and 24 normal controls in PBL DNA extracted by each of the three extraction methods. The range of RTL measured by qPCR from QIAamp-extracted DNA (0.17-0.58-) was smaller than from either PureGene or Phenol/Chloroform (ranges: 0.04-2.67 and 0.32-2.81, respectively). Conclusions: RTL measured by qPCR from QIAamp-extracted DNA was smaller than from either PureGene or Phenol/Chloroform (p<0.001). Impact: Differences in DNA extraction method may contribute to the discrepancies between studies seeking to find an association between the risk of cancer or other diseases and RTL.
Cancer Epidemiology Biomarkers & Prevention 09/2013; · 4.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Genome-wide association studies have identified a large number of single nucleotide polymorphisms (SNPs) associated with a wide array of cancer sites. Several of these variants demonstrate associations with multiple cancers, suggesting pleiotropic effects and shared biological mechanisms across some cancers. We hypothesised that SNPs previously associated with other cancers may additionally be associated with colorectal cancer. In a large-scale study, we examined 171 SNPs previously associated with 18 different cancers for their associations with colorectal cancer.
We examined 13 338 colorectal cancer cases and 40 967 controls from three consortia: Population Architecture using Genomics and Epidemiology (PAGE), Genetic Epidemiology of Colorectal Cancer (GECCO), and the Colon Cancer Family Registry (CCFR). Study-specific logistic regression results, adjusted for age, sex, principal components of genetic ancestry, and/or study specific factors (as relevant) were combined using fixed-effect meta-analyses to evaluate the association between each SNP and colorectal cancer risk. A Bonferroni-corrected p value of 2.92×10(-4) was used to determine statistical significance of the associations.
Two correlated SNPs-rs10090154 and rs4242382-in Region 1 of chromosome 8q24, a prostate cancer susceptibility region, demonstrated statistically significant associations with colorectal cancer risk. The most significant association was observed with rs4242382 (meta-analysis OR=1.12; 95% CI 1.07 to 1.18; p=1.74×10(-5)), which also demonstrated similar associations across racial/ethnic populations and anatomical sub-sites.
This is the first study to clearly demonstrate Region 1 of chromosome 8q24 as a susceptibility locus for colorectal cancer; thus, adding colorectal cancer to the list of cancer sites linked to this particular multicancer risk region at 8q24.
[Show abstract][Hide abstract] ABSTRACT: Background: The effects of low-dose medical radiation on breast cancer risk are uncertain, and few studies have included genetically susceptible women, such as those who carry germline BRCA1 and BRCA2 mutations. Methods: We studied 454 BRCA1 and 273 BRCA2 mutation carriers aged <50 years from three breast cancer family registries in the USA, Canada, and Australia/New Zealand. We estimated breast cancer risk associated with diagnostic chest x-rays by comparing mutation carriers with breast cancer (cases) with those without breast cancer (controls). Exposure to chest x-rays was self-reported. Mammograms were not considered in the analysis. Results: After adjusting for known risk factors for breast cancer, the odds ratio (OR) for a history of diagnostic chest x-rays, excluding those for tuberculosis or pneumonia, was 1.16 (95% confidence interval (CI) = 0.64-2.11) for BRCA1 mutations carriers and 1.22 (95% CI=0.62-2.42) for BRCA2 mutations carriers. The OR was statistically elevated for BRCA2 mutation carriers with 3-5 diagnostic chest x-rays (p = 0.01), but not for those with 6 or more chest x-rays. Few women reported chest fluoroscopy for tuberculosis or chest x-rays for pneumonia; the OR estimates were elevated, but not statistically significant, for BRCA1 mutation carriers. Conclusions: Our findings do not support a positive association between diagnostic chest x-rays and breast cancer risk before age 50 years for BRCA1 or BRCA2 mutation carriers. Impact: Given the increasing use of diagnostic imaging involving higher ionizing radiation doses, further studies of genetically predisposed women are warranted.
Cancer Epidemiology Biomarkers & Prevention 07/2013; · 4.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Genome-wide association studies of colorectal cancer (CRC) in Europeans and Asians have identified 21 risk susceptibility regions (29 index SNPs). Characterizing these risk regions in diverse racial groups with different linkage disequilibrium (LD) structure can help localize causal variants. We examined associations between CRC and all 29 index SNPs in 6,597 African Americans (1,894 cases and 4,703 controls). Nine SNPs in 8 regions (5q31.1, 6q26-q27, 8q23.3, 8q24.21, 11q13.4, 15q13.3, 18q21.1, 20p12.3) formally replicated in our data with one-sided p-values<0.05 and the same risk directions as reported previously. We performed fine-mapping of the 21 risk regions (including 250kb on both sides of the index SNPs) using genotyped and imputed markers at the density of the 1000 Genomes Project to search for additional or more predictive risk markers. Among the SNPs correlated with the index variants, two markers, rs12759486 (or rs7547751, a putative functional variant in perfect LD with it) in 1q41 and rs7252505 in 19q13.1, were more strongly and statistically significantly associated with CRC (P<0.0006). The average per allele risk was improved using the replicated index variants and the two new markers (odds ratio=1.14, P=6.5×10(-16)) in African Americans, compared to using all index SNPs (odds ratio=1.07, P=3.4×10(-10)). The contribution of the two new risk SNPs to CRC heritability was estimated to be 1.5% in African Americans. This study highlights the importance of fine-mapping in diverse populations.
Human Molecular Genetics 07/2013; · 7.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Purpose
Women who receive chemotherapy for a first primary breast cancer have been observed to have a reduced risk of contralateral breast cancer (CBC), however, whether the genetic profile of a patient modifies this protective effect is currently not understood. The purpose of this study is to investigate the impact of germline genetic variation in genes coding for drug metabolizing enzymes, transporters, and targets on the association between chemotherapy and risk of CBC.
From the population-based Women’s Environment Cancer and Radiation Epidemiology (WECARE) Study, we included 636 Caucasian women with CBC (cases) and 1,224 women with unilateral breast cancer (controls). The association between common chemotherapeutic regimens, CMF and FAC/FEC, and risk of CBC stratified by genotype of 180 single nucleotide polymorphisms in 14 genes selected for their known involvement in metabolism, action, and transport of breast cancer chemotherapeutic agents, were determined using conditional logistic regression.
CMF (RR = 0.5, 95 % CI 0.4, 0.7) and FAC/FEC (RR = 0.7, 95 % CI 0.4, 1.0) are associated with lower CBC risk relative to no chemotherapy in multivariable-adjusted models. Here we show that genotype of selected genes involved in the metabolism and uptake of these therapeutic agents does not significantly alter the protective effect of either CMF or FAC/FEC on risk of CBC.
The results of this study show that germline genetic variation in selected gene does not significantly alter the protective effect of CMF, FAC, and FEC on risk of CBC.
Cancer Causes and Control 06/2013; 24(8). · 3.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: BACKGROUND: Women with germline BRCA1 or BRCA2 (BRCA1/BRCA2) mutations are at very high risk of developing breast cancer, including asynchronous contralateral breast cancer (CBC). BRCA1/BRCA2 genes help maintain genome stability and assist in DNA repair. We examined whether the risk of CBC associated with radiation treatment was higher among women with germline BRCA1/BRCA2 mutations than among non-carriers. METHODS: A population-based, nested case-control study was conducted within a cohort of 52,536 survivors of unilateral breast cancer (UBC). Cases were 603 women with CBC and controls were 1199 women with UBC individually matched on age at diagnosis, race, year of first diagnosis and cancer registry. All women were tested for BRCA1 and BRCA2 mutations. Radiation absorbed dose from the initial radiotherapy (RT) to the CBC location within the contralateral breast was reconstructed from measurements in a tissue-equivalent phantom and details available in the therapy records. FINDINGS: Among women treated with radiation, the mean radiation dose was 1.1Gy (range=0.02-6.2Gy). Risk of developing CBC was elevated among women who carried a deleterious BRCA1/BRCA2 mutation (rate ratio, RR=4.5, confidence interval, CI=3.0-6.8), and also among those treated with RT (RR=1.2, CI=1.0-1.6). However, among mutation carriers, an incremental increase in risk associated with radiation dose was not statistically significant. INTERPRETATION: Multiplicative interaction of RT with mutation status would be reflected by a larger association of RT with CBC among carriers than among non-carriers, but this was not apparent. Accordingly, there was no clear indication that carriers of deleterious BRCA/BRCA2 mutations were more susceptible to the carcinogenic effects of radiation than non-carriers. These findings are reassuring and have important clinical implications for treatment decisions and the clinical management of patients harbouring deleterious BRCA1/BRCA2 mutations. FUNDING: All work associated with this study was supported by the U.S. National Cancer Institute [R01CA097397, U01CA083178].
European journal of cancer (Oxford, England: 1990) 05/2013; · 4.12 Impact Factor