Body size, physical activity, genetic variants in the insulin-like growth factor pathway and colorectal cancer risk

Physical activity, polygenic risk score, and colorectal cancer risk

INTRODUCTION

Whether and to what extent the relationship between physical activity (PA) and colorectal cancer (CRC) differs according to CRC-related genetic risk remains to be determined, and no studies to date have quantified how much genetically determined risk could be compensated for with active exercise.

METHODS

Genetic risk was quantified by a polygenic risk score (PRS) summarizing the estimated effect of 140 CRC-associated genetic variants. Associations of PA with CRC risk were estimated by multivariable logistic regression across PRS levels. We also compared the impact of PA and specific PA types to the PRS using "genetic risk equivalent (GRE)", a novel approach to enhance effective risk communication.

RESULTS

Among 5058 CRC patients and 4134 controls, we observed no significant association between overall PA level in quartiles and CRC risk. However, the highest versus lowest lifetime leisure time physical activity (LTPA) was associated with a 13% lower CRC risk [odds ratio 0.87, 95% confidence interval (CI) 0.77-1.00] independent of PRS levels (adjusted p value for interaction = 0.18). This effect was equivalent to the effect of having 11 percentiles lower PRS (GRE -10.6, 95% CI -20.7 to -0.6). The GRE (95% CI) for the highest lifetime sports tertile was -23.0 (-33.9 to -12.0).

CONCLUSIONS

LTPA was inversely associated with CRC risk irrespective of polygenic risk for CRC, which reinforces the importance of LTPA in CRC prevention among the general population. Adequate sports activity can compensate for a large share of polygenic risk for CRC.

Energy balance-related factors in childhood and adolescence and risk of colorectal cancer based on KRAS, PIK3CA, and BRAF mutations and MMR status

KRAS mutations (KRAS_mut ), PIK3CA_mut , BRAF_mut , and deficient DNA mismatch repair (dMMR) have been associated with the Warburg effect. We previously reported differential associations between early-life energy balance-related factors (height, energy restriction, body mass index [BMI]) and colorectal cancer (CRC) subtypes based on the Warburg effect. We now investigated associations of early-life energy balance-related factors and the risk of CRC subgroups based on mutation and MMR status. Data from the Netherlands Cohort Study was used. KRAS_mut , PIK3CA_mut, BRAF_mut, and MMR status were available for 2349 CRC cases, and complete covariate data for 1934 cases and 3911 subcohort members. Multivariable-adjusted Cox regression was used to estimate associations of height, energy restriction proxies (exposure to Dutch Hunger Winter, Second World War, Economic Depression), and early adult BMI (age 20 years) with risk of CRC based on individual molecular features and combinations thereof (all-wild-type+MMR-proficient [pMMR]; any-mutation/dMMR). Height was positively associated with any-mutation/dMMR CRC but not all-wild-type+pMMR CRC, with the exception of rectal cancer in men, and with heterogeneity in associations observed for colon cancer in men (p-heterogeneity = 0.049) and rectal cancer in women (p-heterogeneity = 0.014). Results on early-life energy restriction proxies in relation to the risk of CRC subgroups did not show clear patterns. Early adult BMI was positively, but not significantly, associated with KRAS_mut colon cancer in men and with BRAF_mut and dMMR colon cancer in women. Our results suggest a role of KRAS_mut , PIK3CA_mut , BRAF_mut , and dMMR in the etiological pathway between height and CRC risk. KRAS_mut might potentially play a role in associations of early adult BMI with colon cancer risk in men, and BRAF_mut and dMMR in women.

Adult-Attained Height and Colorectal Cancer Risk: A Cohort Study, Systematic Review, and Meta-Analysis

BACKGROUND

The influence of anthropometric characteristics on colorectal neoplasia biology is unclear. We conducted a systematic review and meta-analysis to determine if adult-attained height is independently associated with the risk of colorectal cancer or adenoma.

METHODS

We searched MEDLINE, EMBASE, the Cochrane Library, and Web of Science from inception to August 2020 for studies on the association between adult-attained height and colorectal cancer or adenoma. The original data from the Johns Hopkins (Baltimore, MD) Colon Biofilm study was also included. The overall HR/OR of colorectal cancer/adenoma with increased height was estimated using random-effects meta-analysis.

RESULTS

We included 47 observational studies involving 280,644 colorectal cancer and 14,139 colorectal adenoma cases. Thirty-three studies reported data for colorectal cancer incidence per 10-cm increase in height; 19 yielded an HR of 1.14 [95% confidence interval (CI), 1.11-1.17; P < 0.001), and 14 engendered an OR of 1.09 (95% CI, 1.05-1.13; P < 0.001). Twenty-six studies compared colorectal cancer incidence between individuals within the highest versus the lowest height percentile; 19 indicated an HR of 1.24 (95% CI, 1.19-1.30; P < 0.001), and seven resulting in an OR of 1.07 (95% CI, 0.92-1.25; P = 0.39). Four studies reported data for assessing colorectal adenoma incidence per 10-cm increase in height, showing an overall OR of 1.06 (95% CI, 1.00-1.12; P = 0.03).

CONCLUSIONS

Greater adult attained height is associated with an increased risk of colorectal cancer and adenoma.

IMPACT

Height should be considered as a risk factor for colorectal cancer screening.

Polymorphisms in the mTOR-PI3K-Akt pathway, energy balance-related exposures and colorectal cancer risk in the Netherlands Cohort Study

BACKGROUND

The mTOR-PI3K-Akt pathway influences cell metabolism and (malignant) cell growth. We generated sex-specific polygenic risk scores capturing natural variation in 7 out of 10 top-ranked genes in this pathway. We studied the scores directly and in interaction with energy balance-related factors (body mass index (BMI), trouser/skirt size, height, physical activity, and early life energy restriction) in relation to colorectal cancer (CRC) risk in the Netherlands Cohort Study (NLCS) (n=120,852). The NLCS has a case-cohort design and 20.3 years of follow-up. Participants completed a baseline questionnaire on diet and cancer in 1986 when 55-69 years old. ~75% of the cohort returned toenail clippings used for DNA isolation and genotyping (n subcohort=3,793, n cases=3,464). To generate the scores, the dataset was split in two and risk alleles were defined and weighted based on sex-specific associations with CRC risk in the other dataset half, because there were no SNPs in the top-ranked genes associated with CRC risk in previous genome-wide association studies at a significance level p<1*10^-5.

RESULTS

Cox regression analyses showed positive associations between the sex-specific polygenic risk scores and colon but not rectal cancer risk in men and women, with hazard ratios for continuously modeled scores close to 1.10. There was no modifying effect observed of the scores on associations between the energy balance-related factors and CRC risk. However, BMI (in men), non-occupational physical activity (in women), and height (in men and women) were associated with the risk of CRC, in particular (proximal and distal) colon cancer, in the direction as expected in the lower tertiles of the sex-specific polygenic risk scores.

CONCLUSIONS

Current data suggest that the mTOR-PI3K-Akt pathway may be involved in colon cancer development. This study thereby sheds more light on colon cancer etiology through use of genetic variation in the mTOR-PI3K-Akt pathway.

Rectal Cancer in Adolescent and Young Adult Patients: Pattern of Clinical Presentation and Case-Matched Comparison of Outcomes

BACKGROUND

Rectal cancer in adolescents and young adults (age ≤39) is increasing. Early diagnosis is a challenge in this subset of patients.

OBJECTIVE

This study aims to analyze the presentation pattern and outcomes of sporadic rectal cancer in adolescents and young adults.

DESIGN

This is a retrospective study.

SETTING

This study was conducted at 3 European tertiary centers.

PATIENTS

Data on adolescents and young adults operated on for sporadic rectal cancer (January 2008 through October 2019) were analyzed. To compare outcomes, adolescents and young adults were matched to a group of patients aged ≥40 operated on during the same period.

MAIN OUTCOME MEASURES

The primary outcomes measured were clinical presentation and long-term outcomes.

RESULTS

Sporadic rectal cancers occurred in 101 adolescents and young adults (2.4%; mean age, 33.5; range, 18-39); 51.5% were male, and a smoking habit was reported by 17.8% of patients. The rate of a family history for colorectal cancer was 25.7%, and of these patients, 24.7% were obese. Diagnosis based on symptoms was reported in 92.1% patients, and the mean time from first symptoms to diagnosis was 13.7 months. The most common symptom at diagnosis was rectal bleeding (68.8%), and 12% and 34% of the adolescents and young adults presented with locally advanced or metastatic disease at diagnosis. Consequently, 68.3% and 62.4% adolescents and young adults received neoadjuvant and adjuvant treatments. The rate of complete pathological response was 24.1%; whereas 38.6% patients had stage IV disease, and 93.1% were microsatellite stable. At a mean follow-up of 5 years, no difference in cancer-specific survival, but a lower disease-free survival was reported in adolescents and young adults (p < 0.0001) vs the matched group. Adolescents and young adults with stages I to II disease had shorter cancer-specific survival and disease-free survival (p = 0.006; p < 0.0001); with stage III disease, they had a shorter disease-free survival (p = 0.01).

LIMITATIONS

This study was limited by its observational, retrospective design.

CONCLUSIONS

The significantly delayed diagnosis in adolescents and young adults may have contributed to the advanced disease at presentation and lower disease-free survival, even at earlier stages, suggesting a higher metastatic potential than in older patients. See Video Abstract at http://links.lww.com/DCR/B537.

CNCER DE RECTO EN PACIENTES ADOLESCENTES Y ADULTOS JVENES CUADRO DE PRESENTACIN CLNICA Y COMPARACIN DE DESENLACES POR CASOS EMPAREJADOS

ANTECEDENTES:El cáncer de recto en adolescentes y adultos jóvenes (edad ≤ 39) está aumentando. El diagnóstico temprano es un desafío en este subgrupo de pacientes.OBJETIVO:Analizar el cuadro de presentación y los desenlaces en adolescentes y adultos jóvenes con cáncer de recto esporádico.DISEÑO:Estudio retrospectivo.ÁMBITO:Tres centros europeos de tercer nivel.PACIENTES:Se analizaron los datos de adolescentes y adultos jóvenes operados de cáncer de recto esporádico (enero de 2008 - octubre de 2019). Para comparar los desenlaces se emparejó a adolescentes y adultos jóvenes con un grupo de pacientes mayores de 40 años operados en el mismo período de tiempo.PRINCIPALES VARIABLES ANALIZADAS:Cuadro clínico, resultados a largo plazo.RESULTADOS:Los cánceres de recto esporádicos en adolescentes y adultos jóvenes fueron 101 (2,4%, edad media: 33,5, rango 18-39). El 51,5% eran hombres, el 17,8% de los pacientes fumaba. El 25,7% tentía antecedentes familiares de cáncer colorrectal. El 24,7% eran obesos. El diagnóstico con base en los síntomas se informó en el 92,1% de los pacientes, el tiempo promedio desde los primeros síntomas hasta el diagnóstico fue de 13,7 meses. El síntoma más común en el momento del diagnóstico fue el sangrado rectal (68,8%). 12% y 34% de adolescentes y adultos jóvenes presentaron enfermedad localmente avanzada o metastásica en el momento del diagnóstico. Por lo tanto, el 68,3% y el 62,4% de adolescentes y adultos jóvenes recibieron neoadyuvancia y adyuvancia. La tasa de respuesta patológica completa fue del 24,1%; mientras que el 38,6% estaban en estadio IV. El 93,1% eran microsatelite estable. Con una media de seguimiento de 5 años, no se observaron diferencias en la sobrevida específica del cáncer, pero se informó una menor sobrevida libre de enfermedad en adolescentes y adultos jóvenes (p <0,0001) frente al grupo emparejado. Los adolescentes y adultos jóvenes en estadios I-II tuvieron una sobrevida específica por cáncer y una sobrevida libre de enfermedad más corta (p = 0,006; p <0,0001); el estadio III tuvo una sobrevida libre de enfermedad más baja (p = 0,01).LIMITACIONES:Diseño observacional y retrospectivo.CONCLUSIONES:El diagnóstico notablemente demorado en adolescentes y adultos jóvenes puede contribuir a la presentación de una enfermedad avanzada y a una menor sobrevida libre de enfermedad, incluso en estadios más tempranas, lo cual implica un mayor potencial metastásico en comparación con pacientes mayores. Consulte Video Resumen en http://links.lww.com/DCR/B537.

A preliminary study of cytokine gene polymorphism effects on Saudi patients with colorectal cancer

OBJECTIVE

 To determine the possible associations of polymorphisms in interleukin (IL)-8 (rs4073 T/A), IL-10 (rs1800896 A/G), IL-22 (rs1179251 C/G and rs2227485 C/T), IL-27 (rs17855750 T/G), and transforming growth factor beta 1 (TGFß1) (rs1800469 C/T) with colorectal cancer (CRC) susceptibility in Saudi patients.

METHODS

The case-control study was carried out between July 2019 and January 2020 in King Khaled University Hospital, Riyadh, Saudi Arabia. A total of 70 patients with CRC and 70 healthy controls were included  in  the  study.  Single nucleotide polymorphisms of promoter regions were determined using TaqMan genotyping assays.

RESULTS

 A statistically significant reduction in CRC risk was identified for carriers of the IL-10 (rs1800896 A/G) AG genotype, IL-22 (rs1179251 C/G) G allele, IL-27 (rs17855750 T/G) G allele and TGFß1 (rs1800469 C/T) CT and TT genotype. While IL-10 (rs1800896 A/G) AA genotype and TGFß1 (rs1800469 C/T) CC genotype were significantly associated with increased susceptibility to CRC. No significant associations were identified between the cytokine polymorphisms of IL-8 (rs4073 T/A) and IL-22 (rs2227485 C/T), and CRC risk. Conclusion: Our findings indicate a significant impact of IL-10 (rs1800896 A/G), IL-22 (rs1179251 C/G), IL-27 (rs17855750 T/G) and TGF-ß1 (rs1800469 C/T) polymorphisms on risk of CRC; while the IL-8 (rs4073 T/A) and IL-22 (rs2227485 C/T) and polymorphisms were not associated with CRC risk.

Does long-term use of antidiabetic drugs changes cancer risk?

Antidiabetic medications are commonly used around the world, but their safety is still unclear. The aim of this study was to investigate whether long-term use of insulin and oral antidiabetic medications is associated with cancer risk.We conducted a well-designed case-control study using 12 years of data from Taiwan's National Health Insurance Research Database and investigated the association between antidiabetic medication use and cancer risk over 20 years. We identified 42,500 patients diagnosed with cancer and calculated each patient's exposure to antidiabetic drugs during the study period. We matched cancer and noncancer subjects matched 1:6 by age, gender, and index date, and used Cox proportional hazard regression and conditional logistic regression, adjusted for potential confounding factors, that is, medications and comorbid diseases that could influence cancer risk during study period.Pioglitazone (adjusted odds ratio [AOR], 1.20; 95% confidence interval [CI], 1.05-1.38); and insulin and its analogs for injection, intermediate or long acting combined with fast acting (AOR, 1.22; 95% CI, 1.05-1.43) were significantly associated with a higher cancer risk. However, metformin (AOR, 1.00; 95% CI, 0.93-1.07), glibenclamide (AOR, 0.98; 95% CI, 0.92-1.05), acarbose (AOR, 1.06; 95% CI, 0.96-1.16), and others do not show evidence of association with cancer risk. Moreover, the risk for specific cancers among antidiabetic users as compared with nonantidiabetic medication users was significantly increased for pancreas cancer (by 45%), liver cancer (by 32%), and lung cancer (by 18%).Antidiabetic drugs do not seem to be associated with an increased cancer risk incidence except for pioglitazone, insulin and its analogs for injection, intermediate or long acting combined with fast acting.

Diabetes mellitus, genetic variants in the insulin-like growth factor pathway and colorectal cancer risk

Genetic variation in the insulin‐like growth factor (IGF) pathway may further increase the risk of colorectal cancer (CRC) associated with type 2 diabetes mellitus (T2DM). Joint effects of T2DM and genetic variation in the IGF pathway on CRC risk can increase mechanistic insights. Participants from the Netherlands Cohort Study (n = 120, 852) completed a baseline questionnaire in 1986 when 55–69 years old (case–cohort, n_subcohort = 5,000, n_cases = 3,441 after 16.3 years follow‐up). Self‐reported DM at baseline with onset at ≥30 years was classified as T2DM. Eighteen single nucleotide polymorphisms (SNPs) from the IGF pathway were aggregated in a genetic risk score (GRS). Cox proportional hazard ratios (HRs) for CRC were estimated according to combinations of T2DM status with GRS tertiles and categories of an IGF1 19‐CA repeat polymorphism. Baseline T2DM prevalence was 3.1% in subcohort members and 3.8% in CRC cases. Comparison of combined categories with non‐T2DM individuals in the lowest GRS tertile as reference showed that those in the highest GRS tertiles with and without T2DM had significantly increased CRC risks, particularly those with T2DM (HR = 2.28, 95% CI: 1.11, 4.66). As compared to IGF1 19‐CA wild‐type carriers without T2DM, carrying two IGF1 19‐CA variant repeat alleles were associated with a significantly decreased CRC risk in those without T2DM (HR = 0.76, 95% CI: 0.63–0.91). This association was absent when T2DM was present. Our study of joint effects indicated that the presence of unfavorable alleles in the IGF pathway may further increase the risk of CRC associated with T2DM.

What's new?

Colorectal cancer (CRC) and type‐2 diabetes mellitus (T2DM) have several risk factors in common (high BMI, physical inactivity, etc.). In this study, the authors identified several SNPs in the insulin‐like growth factor (IGF) pathway that further increase CRC risk, particularly in people with T2DM. These results support the hypothesis that T2DM increases CRC risk by influencing the IGF pathway. Screening for these unfavorable genetic variations in the IGF pathway may also help to improve the assessment of personalized CRC risk.

Sirtuin 1 genetic variation, energy balance and colorectal cancer risk by sex and subsite in the Netherlands Cohort Study

Sirtuin 1 (SIRT1) is an energy-sensing protein, which may affect tumorigenesis. We used SIRT1 variants as time-independent indicators of SIRT1 involvement in carcinogenesis and we studied two tagging SIRT1 variants in relation to colorectal cancer (CRC) risk. We also evaluated known energy balance-related CRC risk factors within SIRT1 genotype strata. The Netherlands Cohort Study includes 120,852 individuals and has 20.3 years follow-up (case-cohort: n_subcohort = 5000; n_{CRC cases} = 4667). At baseline, participants self-reported weight, weight at age 20, height, trouser/skirt size reflecting waist circumference, physical activity, and early life energy restriction. SIRT1 rs12778366 and rs10997870 were genotyped in toenail DNA available for ~75% of the cohort. Sex- and subsite-specific Cox hazard ratios (HRs) showed that the rs12778366 CC versus TT genotype decreased CRC and colon cancer risks in women (HR_CRC = 0.53, 95% confidence interval: 0.30–0.94) but not men. Multiplicative interactions were observed between SIRT1 variants and energy balance-related factors in relation to CRC endpoints, but the direction of associations was not always conform expectation nor specific to one genotype stratum. In conclusion, these results support SIRT1 involvement in colon cancer development in women. No conclusions could be made regarding a modifying effect of SIRT1 variants on associations between energy balance-related factors and CRC risk.

Interaction between physical activity, PITX1 rs647161 genetic polymorphism and colorectal cancer risk in a Korean population: a case-control study

This study assessed the interaction between physical activity and colorectal cancer (CRC) risk based on a polymorphism in the paired-like homeodomain 1 (PITX1) gene in Koreans. In total, 923 cases and 1,846 controls were enrolled at the National Cancer Center, Korea. Subjects who did regular exercise showed a significantly reduced risk of CRC than those did not exercise regularly (OR = 0.37, 95% CI = 0.30-0.45). Subjects in the highest tertile of metabolic equivalents of task (MET)-minutes per week showed a significantly lower risk of CRC (OR = 0.62, 95% CI = 0.48-0.79, p-trend < 0.001). In the dominant model, minor allele carriers showed a significantly higher risk of CRC than subjects homozygous for the major allele (OR = 1.46, 95% CI = 1.18-1.80). The PITX1 genetic variant showed significant interactions with regular exercise and CRC risk (p-interaction = 0.018) and colon cancer risk (p-interaction = 0.029) among all subjects. Subjects who carried at least one minor allele and did not regularly exercise showed a greater risk of CRC (OR = 1.81, 95% CI = 1.37-2.41). Subjects who were homozygous for the major allele with high physical activity showed a significantly reduced risk of CRC (OR = 0.56, 95% CI = 0.38-0.82). Thus, individuals with PITX1 genetic variants can have benefit from physical activity regarding prevention of CRC risk in a Korean population.

Clinical and pathological significance of N-Myc downstream-regulated gene 2 (NDRG2) in diverse human cancers

Human N-Myc downstream-regulated gene 2 (NDRG2), located at chromosome 14q11.2, has been reported to be down-regulated and associated with the progression and prognosis of diverse cancers. Collectively, previous studies suggest that NDRG2 functions as a candidate tumor-suppressor gene; thus, up-regulation of NDRG2 protein might act as a promising therapeutic strategy for malignant tumors. The aim of this review was to comprehensively present the clinical and pathological significance of NDRG2 in human cancers.

Dietary components that counteract the increased risk of colorectal cancer related to red meat consumption

Western-style diets are associated with an increased risk of colorectal cancer (CRC). In particular, a strong correlation has been documented between CRC and the consumption of large amounts of red meat, especially processed red meat. Compared with white meat, red meat contains high levels of haem iron, a molecule that can exert a variety of genotoxic and other adverse effects on the colonic epithelium. According to current international guidelines, the reduction of red meat intake combined with the consumption of food containing antioxidant and chemoprotective substances may significantly reduce the risk of developing CRC. The dietary strategies that can help to contrast the harmful effects of haem iron are reported and discussed in this review.

Association of interleukin-22 polymorphisms with the colon cancer: A case-control study

INTRODUCTION

Interleukin-22 (IL-22), an IL-10 family cytokine produced by T cells and innate lymphoid cells, is implicated in inflammation and tumorigenesis. In this study, we aimed to investigate the association of IL-22 polymorphisms with the colon cancer in a Chinese population.

MATERIALS AND METHODS

Five hundred forty colon cancer cases and 540 healthy controls were recruited in the case-control study. The fluorogenic 5' exonuclease assays were used for genotype analysis of three common polymorphisms (-429C/T, +1046T/A and +1995A/C) of the IL-22 gene.

RESULTS

Colon cancer cases had a significantly higher frequency of IL-22-429 TT genotype [odds ratio (OR)=1.69, 95% confidence interval (CI)=1.24, 2.30; P=0.001] and -429T allele (OR=1.35, 95% CI=1.14, 1.60; P=0.001) than healthy controls. The findings are still emphatic by the Bonferroni correction (P<0.017). When stratifying by the differentiation of colon cancer, we found that colon cancer cases with poor differentiation had a significantly higher frequency of IL-22-429 TT genotype (OR=1.45, 95% CI=1.02, 2.07; P=0.04). When stratifying by the tumor location, tumor size, growth pattern and TNM stage of colon cancer, we found no statistical association. The IL-22 +1046T/A and IL-22 +1995A/C gene polymorphisms were not associated with colon cancer.

CONCLUSION

Our findings suggested that the IL-22 -429C/T gene polymorphisms might be associated with colon cancer.

Molecular pathological epidemiology: new developing frontiers of big data science to study etiologies and pathogenesis

Molecular pathological epidemiology (MPE) is an integrative field that utilizes molecular pathology to incorporate interpersonal heterogeneity of a disease process into epidemiology. In each individual, the development and progression of a disease are determined by a unique combination of exogenous and endogenous factors, resulting in different molecular and pathological subtypes of the disease. Based on "the unique disease principle," the primary aim of MPE is to uncover an interactive relationship between a specific environmental exposure and disease subtypes in determining disease incidence and mortality. This MPE approach can provide etiologic and pathogenic insights, potentially contributing to precision medicine for personalized prevention and treatment. Although breast, prostate, lung, and colorectal cancers have been among the most commonly studied diseases, the MPE approach can be used to study any disease. In addition to molecular features, host immune status and microbiome profile likely affect a disease process, and thus serve as informative biomarkers. As such, further integration of several disciplines into MPE has been achieved (e.g., pharmaco-MPE, immuno-MPE, and microbial MPE), to provide novel insights into underlying etiologic mechanisms. With the advent of high-throughput sequencing technologies, available genomic and epigenomic data have expanded dramatically. The MPE approach can also provide a specific risk estimate for each disease subgroup, thereby enhancing the impact of genome-wide association studies on public health. In this article, we present recent progress of MPE, and discuss the importance of accounting for the disease heterogeneity in the era of big-data health science and precision medicine.

Energy restriction at young age, genetic variants in the insulin-like growth factor pathway and colorectal cancer risk in the Netherlands Cohort Study

The energy restriction (ER)-colorectal cancer (CRC) association is inconsistent in literature. To strengthen the biological plausibility of the ER-CRC association, we investigated whether genetic variation in the insulin-like growth factor (IGF) pathway, a putative underlying mechanism, modulated this association in the Netherlands Cohort Study. Participants completed a questionnaire (n = 120,852) and provided toenail clippings for DNA (∼75%) at baseline. Individuals living in a Western city during the Hunger Winter (1944-45) or Western rural versus non-Western area were exposed to (severe) ER at young age. Genotyping was performed for 3,768 subcohort members and 2,580 CRC cases (case-cohort with 16.3 years follow-up). Cox hazard ratios for CRC were estimated across combined categories of ER and a genetic sum score of unfavorable alleles based on 18 single nucleotide polymorphisms in IGF-related genes and ER and an IGF1 19-CA repeat polymorphism. The reference included ER exposed individuals, so that increased hazard ratios were expected in higher combined categories for calculating relative excess risks due to interaction (additive interactions). Wald tests for multiplicative interactions were also performed. Multiplicative and additive interactions were nonsignificant. Combined ER-genetic sum score categories showed increasing CRC risks in men, but confidence intervals were wide. Women carrying two variant IGF1 19-CA repeat alleles versus those carrying two wild type IGF1 19-CA repeat alleles were at an ∼50% decreased CRC risk, irrespective of ER exposure. In conclusion, data indicate that the IGF pathway might be involved in the ER-CRC association in men, but not women, although interactions were nonsignificant, hampering definite conclusions.

Physical Activity and Cancer Outcomes: A Precision Medicine Approach

There is increasing interest in applying a precision medicine approach to understanding exercise as a potential treatment for cancer. We aimed to inform this new approach by appraising epidemiologic literature relating postdiagnosis physical activity to cancer outcomes overall and by molecular/genetic subgroups. Across 26 studies of breast, colorectal, and prostate cancer patients, a 37% reduction was seen in risk of cancer-specific mortality, comparing the most versus the least active patients (pooled relative risk = 0.63; 95% confidence interval: 0.54-0.73). Risks of recurrence or recurrence/cancer-specific death (combined outcome) were also reduced based on fewer studies. We identified ten studies of associations between physical activity and cancer outcomes by molecular or genetic markers. Two studies showed statistically significant risk reductions in breast cancer mortality/recurrence for the most (versus least) physically active estrogen receptor-positive/progesterone receptor-positive (ER⁺/PR⁺) patients, while others showed risk reductions among ER^-PR^- and triple-negative patients. In colorectal cancer, four studies showed statistically significant risk reductions in cancer-specific mortality for patients with high (versus low) physical activity and P21 expression, P27 expression, nuclear CTNNB1^-, PTGS2 (COX-2)⁺, or IRS1 low/negative status. One prostate cancer study showed effect modification by Gleason score. As a means to enhance this evidence, future observational studies are needed that will measure physical activity objectively before and after diagnosis, use standardized definitions for outcomes, control for competing risks, assess nonlinear dose-response relations, and consider reverse causality. Ultimately, randomized controlled trials with clinical cancer outcomes and a correlative component will provide the best evidence of causality, relating exercise to cancer outcomes, overall and for molecular and genetic subgroups. Clin Cancer Res; 22(19); 4766-75. ©2016 AACR.