Melbourne School of Population and Global Health - Research Publications
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ItemBody Mass Index, sex, non-steroidal anti-inflammatory drug medications, smoking and alcohol are differentially associated with World Health Organisation criteria and colorectal cancer risk in people with Serrated Polyposis Syndrome: an Australian case-control study(BMC, 2022-11-26)OBJECTIVE: The unknown aetiology of Serrated Polyposis Syndrome (SPS) impedes risk prediction and prevention. We investigated risk factors for SPS, overall and stratified by World Health Organization (WHO)2010 clinical criteria and by colorectal cancer (CRC). METHOD: A retrospective case-control study involving a cross-sectional analysis from 350 unrelated individuals with SPS from the Genetics of Colonic Polyposis Study and 714 controls from the Australasian Colorectal Cancer Family Registry. Univariate and multivariate logistic regression modelling was used to determine the association between risk factors and SPS and risk factors associated with CRC in SPS. RESULTS: Female biological sex (odds ratio (OR) = 4.54; 95%Confidence interval (CI) = 2.77-7.45), increasing body mass index (BMI) at age 20 years (OR = 1.09; 95%CI = 1.04-1.13), hormone replacement therapy (OR = 0.44; 95%CI = 0.20.98), and increasing weekly folate intake (OR = 0.82; 95%CI = 0.75-0.90) were associated with SPS by multivariate analysis. Increasing weekly calcium intake (OR = 0.79; 95%CI = 0.64-0.97) and smoking > 10 cigarettes daily (OR = 0.45; 95%CI = 0.23-0.86) were associated with WHO criterion I only. The consumption of 1-100 g of alcohol per week (OR = 0.39; 95%CI = 0.18-0.83) was associated with WHO criterion III only. Smoking 1-5 cigarettes daily (OR = 2.35; 95%CI = 1.09-5.05), weekly non-steroidal anti-inflammatory drug (NSAIDs) intake (OR = 0.88; 95%CI = 0.78-0.99), and increased height (OR = 1.09; 95% = 1.05-1.13), were associated with SPS fulfilling both WHO criteria I and III. Moreover, weekly NSAIDs intake (OR = 0.81; 95%CI = 0.67-0.98) was associated with a reduced likelihood of CRC in SPS. CONCLUSION: We identified novel risk and potential protective factors associated with SPS, some specific for certain WHO2010 criteria. Weekly use of NSAIDs may reduce the risk of CRC in people with SPS.
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ItemDo the risks of Lynch syndrome-related cancers depend on the parent-of-origin of the mutation?(Oxford University Press, 2021-09-01)Background Individuals who carry pathogenic mutations in DNA mismatch repair (MMR) genes have high risks of cancer, and small studies have suggested that these risks depend on the sex of the parent from whom the mutation was inherited. We have conducted the first large study of such a parent-of-origin effect (POE). Methods Our study was based on all MMR gene mutation carriers and their relatives in the Colon Cancer Family Registry, comprising 18,226 people. The POE was estimated as a hazard ratio (HR) using a segregation analysis approach that adjusted for ascertainment. HR = 1 corresponds to no POE and HR>1 corresponds to higher risks for maternal mutations. Results For all MMR genes combined, the estimated POE HRs were 1.02 (95% confidence interval (CI) 0.75-1.39, p = 0.9) for male colorectal cancer, 1.12 (95% CI 0.81-1.54, p = 0.5) for female colorectal cancer and 0.84 (95% CI 0.52-1.36, p = 0.5) for endometrial cancer. Separate results for each MMR gene were similar. Conclusions Despite being well-powered, our study did not find any evidence that cancer risks for MMR gene mutation carriers depend on the parent-of-origin of the mutation. Based on current evidence, we don’t recommend that POEs be incorporated into the clinical guidelines or advice for such carriers. Key messages MMR gene mutations inherited from the maternal and paternal side confer similar risks of developing colorectal and endometrial cancer.
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ItemColorectal cancer incidences in Lynch syndrome: a comparison of results from the prospective lynch syndrome database and the international mismatch repair consortium(BMC, 2022-10-01)OBJECTIVE: To compare colorectal cancer (CRC) incidences in carriers of pathogenic variants of the MMR genes in the PLSD and IMRC cohorts, of which only the former included mandatory colonoscopy surveillance for all participants. METHODS: CRC incidences were calculated in an intervention group comprising a cohort of confirmed carriers of pathogenic or likely pathogenic variants in mismatch repair genes (path_MMR) followed prospectively by the Prospective Lynch Syndrome Database (PLSD). All had colonoscopy surveillance, with polypectomy when polyps were identified. Comparison was made with a retrospective cohort reported by the International Mismatch Repair Consortium (IMRC). This comprised confirmed and inferred path_MMR carriers who were first- or second-degree relatives of Lynch syndrome probands. RESULTS: In the PLSD, 8,153 subjects had follow-up colonoscopy surveillance for a total of 67,604 years and 578 carriers had CRC diagnosed. Average cumulative incidences of CRC in path_MLH1 carriers at 70 years of age were 52% in males and 41% in females; for path_MSH2 50% and 39%; for path_MSH6 13% and 17% and for path_PMS2 11% and 8%. In contrast, in the IMRC cohort, corresponding cumulative incidences were 40% and 27%; 34% and 23%; 16% and 8% and 7% and 6%. Comparing just the European carriers in the two series gave similar findings. Numbers in the PLSD series did not allow comparisons of carriers from other continents separately. Cumulative incidences at 25 years were < 1% in all retrospective groups. CONCLUSIONS: Prospectively observed CRC incidences (PLSD) in path_MLH1 and path_MSH2 carriers undergoing colonoscopy surveillance and polypectomy were higher than in the retrospective (IMRC) series, and were not reduced in path_MSH6 carriers. These findings were the opposite to those expected. CRC point incidence before 50 years of age was reduced in path_PMS2 carriers subjected to colonoscopy, but not significantly so.
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ItemSegregation analysis of 17,425 population-based breast cancer families: Evidence for genetic susceptibility and risk prediction(CELL PRESS, 2022-10-06)Rare pathogenic variants in known breast cancer-susceptibility genes and known common susceptibility variants do not fully explain the familial aggregation of breast cancer. To investigate plausible genetic models for the residual familial aggregation, we studied 17,425 families ascertained through population-based probands, 86% of whom were screened for pathogenic variants in BRCA1, BRCA2, PALB2, CHEK2, ATM, and TP53 via gene-panel sequencing. We conducted complex segregation analyses and fitted genetic models in which breast cancer incidence depended on the effects of known susceptibility genes and other unidentified major genes and a normally distributed polygenic component. The proportion of familial variance explained by the six genes was 46% at age 20-29 years and decreased steadily with age thereafter. After allowing for these genes, the best fitting model for the residual familial variance included a recessive risk component with a combined genotype frequency of 1.7% (95% CI: 0.3%-5.4%) and a penetrance to age 80 years of 69% (95% CI: 38%-95%) for homozygotes, which may reflect the combined effects of multiple variants acting in a recessive manner, and a polygenic variance of 1.27 (95% CI: 0.94%-1.65), which did not vary with age. The proportion of the residual familial variance explained by the recessive risk component was 40% at age 20-29 years and decreased with age thereafter. The model predicted age-specific familial relative risks consistent with those observed by large epidemiological studies. The findings have implications for strategies to identify new breast cancer-susceptibility genes and improve disease-risk prediction, especially at a young age.
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ItemGenetic Aspects of Mammographic Density Measures Associated with Breast Cancer Risk(MDPI, 2022-06)Cumulus, Altocumulus, and Cirrocumulus are measures of mammographic density defined at increasing pixel brightness thresholds, which, when converted to mammogram risk scores (MRSs), predict breast cancer risk. Twin and family studies suggest substantial variance in the MRSs could be explained by genetic factors. For 2559 women aged 30 to 80 years (mean 54 years), we measured the MRSs from digitized film mammograms and estimated the associations of the MRSs with a 313-SNP breast cancer polygenic risk score (PRS) and 202 individual SNPs associated with breast cancer risk. The PRS was weakly positively correlated (correlation coefficients ranged 0.05−0.08; all p < 0.04) with all the MRSs except the Cumulus-white MRS based on the “white but not bright area” (correlation coefficient = 0.04; p = 0.06). After adjusting for its association with the Altocumulus MRS, the PRS was not associated with the Cumulus MRS. There were MRS associations (Bonferroni-adjusted p < 0.04) with one SNP in the ATXN1 gene and nominally with some ESR1 SNPs. Less than 1% of the variance of the MRSs is explained by the genetic markers currently known to be associated with breast cancer risk. Discovering the genetic determinants of the bright, not white, regions of the mammogram could reveal substantial new genetic causes of breast cancer.
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ItemFamilial Aspects of Mammographic Density Measures Associated with Breast Cancer Risk(MDPI, 2022-03)Cumulus, Cumulus-percent, Altocumulus, Cirrocumulus, and Cumulus-white are mammogram risk scores (MRSs) for breast cancer based on mammographic density defined in effect by different levels of pixel brightness and adjusted for age and body mass index. We measured these MRS from digitized film mammograms for 593 monozygotic (MZ) and 326 dizygotic (DZ) female twin pairs and 1592 of their sisters. We estimated the correlations in relatives (r) and the proportion of variance due to genetic factors (heritability) using the software FISHER and predicted the familial risk ratio (FRR) associated with each MRS. The ρ estimates ranged from: 0.41 to 0.60 (standard error [SE] 0.02) for MZ pairs, 0.16 to 0.26 (SE 0.05) for DZ pairs, and 0.19 to 0.29 (SE 0.02) for sister pairs (including pairs of a twin and her non-twin sister), respectively. Heritability estimates were 39% to 69% under the classic twin model and 36% to 56% when allowing for shared non-genetic factors specific to MZ pairs. The FRRs were 1.08 to 1.17. These MRSs are substantially familial, due mostly to genetic factors that explain one-quarter to one-half as much of the familial aggregation of breast cancer that is explained by the current best polygenic risk score.
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ItemRisk factors for melanoma by anatomical site: an evaluation of aetiological heterogeneity(WILEY, 2021-06)BACKGROUND: Melanoma aetiology has been proposed to have two pathways, which are determined by naevi and type of sun exposure and related to the anatomical site where melanoma develops. OBJECTIVES: We examined associations with melanoma by anatomical site for a comprehensive set of risk factors including pigmentary and naevus phenotypes, ultraviolet radiation exposure and polygenic risk. METHODS: We analysed harmonized data from 2617 people with incident first invasive melanoma and 975 healthy controls recruited through two population-based case-control studies in Australia and the UK. Questionnaire data were collected by interview using a single protocol, and pathway-specific polygenic risk scores were derived from DNA samples. We estimated adjusted odds ratios using unconditional logistic regression that compared melanoma cases at each anatomical site with all controls. RESULTS: When cases were compared with control participants, there were stronger associations for many naevi vs. no naevi for melanomas on the trunk, and upper and lower limbs than on the head and neck (P-heterogeneity < 0·001). Very fair skin (vs. olive/brown skin) was more weakly related to melanoma on the trunk than to melanomas at other sites (P-heterogeneity = 0·04). There was no significant difference by anatomical site for polygenic risk. Increased weekday sun exposure was positively associated with melanoma on the head and neck but not on other sites. CONCLUSIONS: We found evidence of aetiological heterogeneity for melanoma, supporting the dual pathway hypothesis. These findings enhance understanding of risk factors for melanoma and can guide prevention and skin examination education and practices.
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ItemGenome-wide association study and meta-analysis in Northern European populations replicate multiple colorectal cancer risk loci(WILEY, 2018-02-01)Genome-wide association studies have been successful in elucidating the genetic basis of colorectal cancer (CRC), but there remains unexplained variability in genetic risk. To identify new risk variants and to confirm reported associations, we conducted a genome-wide association study in 1,701 CRC cases and 14,082 cancer-free controls from the Finnish population. A total of 9,068,015 genetic variants were imputed and tested, and 30 promising variants were studied in additional 11,647 cases and 12,356 controls of European ancestry. The previously reported association between the single-nucleotide polymorphism (SNP) rs992157 (2q35) and CRC was independently replicated (p = 2.08 × 10-4 ; OR, 1.14; 95% CI, 1.06-1.23), and it was genome-wide significant in combined analysis (p = 1.50 × 10-9 ; OR, 1.12; 95% CI, 1.08-1.16). Variants at 2q35, 6p21.2, 8q23.3, 8q24.21, 10q22.3, 10q24.2, 11q13.4, 11q23.1, 14q22.2, 15q13.3, 18q21.1, 20p12.3 and 20q13.33 were associated with CRC in the Finnish population (false discovery rate < 0.1), but new risk loci were not found. These results replicate the effects of multiple loci on the risk of CRC and identify shared risk alleles between the Finnish population isolate and outbred populations.
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ItemAssociations of alcohol intake, smoking, physical activity and obesity with survival following colorectal cancer diagnosis by stage, anatomic site and tumor molecular subtype(WILEY, 2018-01-15)The influence of lifestyle factors on survival following a diagnosis of colorectal cancer (CRC) is not well established. We examined associations between lifestyle factors measured before diagnosis and CRC survival. The Melbourne Collaborative Cohort Study collected data on alcohol intake, cigarette smoking and physical activity, and body measurements at baseline (1990-1994) and wave 2 (2003-2007). We included participants diagnosed to 31 August 2015 with incident stages I-III CRC within 10-years post exposure assessment. Information on tumor characteristics and vital status was obtained. Tumor DNA was tested for microsatellite instability (MSI) and somatic mutations in oncogenes BRAF (V600E) and KRAS. We estimated hazard ratios (HRs) for associations between lifestyle factors and overall and CRC-specific mortality using Cox regression. Of 724 eligible CRC cases, 339 died (170 from CRC) during follow-up (average 9.0 years). Exercise (non-occupational/leisure-time) was associated with higher CRC-specific survival for stage II (HR = 0.25, 95% CI: 0.10-0.60) but not stages I/III disease (p for interaction = 0.01), and possibly for colon and KRAS wild-type tumors. Waist circumference was inversely associated with CRC-specific survival (HR = 1.25 per 10 cm increment, 95% CI: 1.08-1.44), independent of stage, anatomic site and tumor molecular status. Cigarette smoking was associated with lower overall survival, with suggestive evidence of worse survival for BRAF mutated CRC, but not with CRC-specific survival. Alcohol intake was not associated with survival. Survival did not differ by MSI status. We have identified pre-diagnostic predictors of survival following CRC that may have clinical and public health relevance.
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ItemMendelian randomisation implicates hyperlipidaemia as a risk factor for colorectal cancer(WILEY, 2017-06-15)While elevated blood cholesterol has been associated with an increased risk of colorectal cancer (CRC) in observational studies, causality is uncertain. Here we apply a Mendelian randomisation (MR) analysis to examine the potential causal relationship between lipid traits and CRC risk. We used single nucleotide polymorphisms (SNPs) associated with blood levels of total cholesterol (TC), triglyceride (TG), low-density lipoprotein (LDL), and high-density lipoprotein (HDL) as instrumental variables (IV). We calculated MR estimates for each risk factor with CRC using SNP-CRC associations from 9,254 cases and 18,386 controls. Genetically predicted higher TC was associated with an elevated risk of CRC (odds ratios (OR) per unit SD increase = 1.46, 95% confidence interval [CI]: 1.20-1.79, p = 1.68 × 10-4 ). The pooled ORs for LDL, HDL, and TG were 1.05 (95% CI: 0.92-1.18, p = 0.49), 0.94 (95% CI: 0.84-1.05, p = 0.27), and 0.98 (95% CI: 0.85-1.12, p = 0.75) respectively. A genetic risk score for 3-hydoxy-3-methylglutaryl-coenzyme A reductase (HMGCR) to mimic the effects of statin therapy was associated with a reduced CRC risk (OR = 0.69, 95% CI: 0.49-0.99, p = 0.046). This study supports a causal relationship between higher levels of TC with CRC risk, and a further rationale for implementing public health strategies to reduce the prevalence of hyperlipidaemia.