Background Colorectal cancer (CRC) diagnosed before age 50 years, or young-onset CRC, is increasing globally with undefined etiology. A sedentary lifestyle is an emerging risk factor for CRC after age 50 years, but its role in young-onset CRC is unknown. Methods We prospectively evaluated sedentary behaviors, primarily time watching television (TV), and risk of young-onset CRC among 89 278 women in the Nurses’ Health Study II ages 25–42 years at recruitment (1991–2011). We used Cox proportional hazards modelling to estimate relative risks (RR) and 95% confidence intervals (CIs). Statistical tests were two-sided. Results We documented 118 young-onset CRCs over 1 262 540 person-years. Sedentary TV viewing time was statistically significantly associated with increased risk of young-onset CRC, after adjusting for putative risk factors, including obesity and physical activity. Compared to no more than 7 hours per week, women with 7.1–14 hours per week of TV time had a multivariable relative risk (RR) of 1.12 (95% confidence interval [CI] = 0.72 to 1.75), further increased for greater than 14 hours per week (RR = 1.69, 95% CI = 1.07 to 2.67, Ptrend = .03). This association was observed among participants without a CRC family history and was more pronounced for rectal cancer (RR for >14 vs ≤7 hours per week 2.44, 95% CI = 1.03 to 5.78, Ptrend = .04). Overweight or obese participants may be more susceptible. Conclusion Independent of exercise and obesity, prolonged sedentary TV viewing time, a surrogate for a more inactive lifestyle, was associated with increased risk of young-onset CRC, particularly of the rectum. These findings provide further evidence on the importance of maintaining an active lifestyle.

ObjectiveFactors that lead to metabolic dysregulation are associated with increased risk of early-onset colorectal cancer (CRC diagnosed under age 50). However, the association between metabolic syndrome (MetS) and early-onset CRC remains unexamined.DesignWe conducted a nested case–control study among participants aged 18–64 in the IBM MarketScan Commercial Database (2006–2015). Incident CRC was identified using pathologist-coded International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes, and controls were frequency matched. MetS was defined as presence of ≥3 conditions among obesity, hypertension, hyperlipidaemia and hyperglycaemia/type 2 diabetes, based on ICD-9-CM and use of medications. Multivariable logistic regressions were used to estimate ORs and 95% CIs.ResultsMetS was associated with increased risk of early-onset CRC (n=4673; multivariable adjusted OR 1.25; 95% CI 1.09 to 1.43), similar to CRC diagnosed at age 50–64 (n=14 928; OR 1.21; 95% CI 1.15 to 1.27). Compared with individuals without a metabolic comorbid condition, those with 1, 2 or ≥3 conditions had a 9% (1.09; 95% CI 1.00 to 1.17), 12% (1.12; 95% CI 1.01 to 1.24) and 31% (1.31; 95% CI 1.13 to 1.51) higher risk of early-onset CRC (ptrend <0.001). No associations were observed for one or two metabolic comorbid conditions and CRC diagnosed at age 50–64. These positive associations were driven by proximal (OR per condition 1.14; 95% CI 1.06 to 1.23) and distal colon cancer (OR 1.09; 95% CI 1.00 to 1.18), but not rectal cancer (OR 1.03; 95% CI 0.97 to 1.09).ConclusionsMetabolic dysregulation was associated with increased risk of early-onset CRC, driven by proximal and distal colon cancer, thus at least in part contribute to the rising incidence of early-onset CRC.

BACKGROUND & AIMS: Vitamin D has been implicated in colorectal cancer (CRC) pathogenesis, but it remains unknown whether total vitamin D intake is associated with early-onset CRC and precursors diagnosed before age 50. METHODS: We prospectively examined the association between total vitamin D intake and risks of early-onset CRC and precursors among women enrolled in the Nurses' Health Study II. Multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for early-onset CRC were estimated with Cox proportional hazards model. Multivariable-adjusted odds ratios (ORs) and 95% CIs for early-onset conventional adenoma and serrated polyp were estimated with logistic regression model. RESULTS: We documented 111 incident cases of early-onset CRC during 1,250,560 person-years of follow-up (1991 to 2015). Higher total vitamin D intake was significantly associated with a reduced risk of early-onset CRC (HR for !450 IU/day vs <300 IU/day, 0.49; 95% CI, 0.26-0.93; P for trend ¼ .01). The HR per 400 IU/day increase was 0.46 (95% CI, 0.26-0.83). The inverse association was significant and appeared more evident for dietary sources of vitamin D (HR per 400 IU/day increase, 0.34; 95% CI, 0.15-0.79) than supplemental vitamin D (HR per 400 IU/day increase, 0.77; 95% CI, 0.37-1.62). For CRC precursors, the ORs per 400 IU/day increase were 0.76 (95% CI, 0.65-0.88) for conventional adenoma (n ¼ 1,439) and 0.85 (95% CI, 0.75-0.97) for serrated polyp (n ¼ 1,878). CONCLUSIONS: In a cohort of younger women, higher total vitamin D intake was associated with decreased risks of early-onset CRC and precursors.

Background Prompt detection of colorectal cancer under age 50 (early-onset CRC) is a clinical priority due to its alarming rise. Methods We conducted a matched case-control study of 5075 incident early-onset CRC among U.S. commercial insurance beneficiaries (113 million adults aged 18-64) with ≥2 years of continuous enrollment (2006-2015) to identify red-flag signs/symptoms between 3 months to 2 years before the index date among 17 pre-specified signs/symptoms. We assessed diagnostic intervals according to the presence of these signs/symptoms before and within 3 months of diagnosis. Results Between 3 months to 2 years before the index date, four red-flag signs/symptoms (abdominal pain, rectal bleeding, diarrhea, and iron deficiency anemia) were associated with an increased risk of early-onset CRC, with ORs ranging from 1.34 to 5.13. Having 1, 2, or ≥ 3 of these signs/symptoms were associated with a 1.94 (95% CI, 1.76 to 2.14), 3.59 (2.89 to 4.44), and 6.52 (3.78 to 11.23)-fold risk (Ptrend &lt; .001), with stronger associations for younger ages (Pinteraction &lt; .001) and rectal cancer (Pheterogenity=0.012). The number of different signs/symptoms was predictive of early-onset CRC beginning 18 months before diagnosis. About 19.3% of cases had their first sign/symptom occur between 3 months to 2 years before diagnosis (median diagnostic interval: 8.7 months), and around 49.3% had the first sign/symptom within 3 months of diagnosis (median diagnostic interval: 0.53 month). Conclusions Early recognition of red-flag signs and symptoms (abdominal pain, rectal bleeding, diarrhea, or iron-deficiency anemia) may improve early detection and timely diagnosis of early-onset CRC.

1571 Background: The etiology and contributors to the rising incidence of early-onset colorectal cancer (CRC diagnosed under age 50), driven largely by distal and rectal cancer, remain largely unknown. Metabolic syndrome is associated with higher risk of CRC diagnosed at older ages; however, its association with early-onset CRC remains unclear. Methods: We conducted a nested case-control study among participants aged 18-50 years with ≥2 years of enrollment and prescription drug coverage in the IBM MarketScan Commercial Databases (2006-2015). Incident CRC cases were identified using ICD-9-CM diagnosis codes. Controls without any cancer were identified using frequency matching on age, sex, geographical region, and duration of insurance enrollment. Metabolic syndrome was defined using either ICD-9-CM diagnosis codes or the presence of at least 3 of the following: obesity, hypertension, hyperlipidemia, and hyperglycemia/type 2 diabetes. In addition to ICD-9-CM codes, hypertension, hyperlipidemia, and hyperglycemia/type 2 diabetes were also defined based on regular use of medications. Multivariable logistic regressions were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Results: A total of 4,673 early-onset CRC and 40,832 controls were included. Metabolic syndrome was associated with increased risk of early-onset CRC (OR: 1.33, 95% CI 1.16-1.52), after adjusting for a range of potential confounders. The number of metabolic comorbid conditions was positively associated with risk of early-onset CRC in a dose-response fashion. Compared to individuals without any conditions, individuals with 1, 2, ≥3 metabolic conditions had a 13% (OR: 1.13, CI 1.04-1.22), 18% (OR: 1.18, CI 1.07-1.31), and 40% (OR: 1.40, CI 1.22-1.61) higher risk of early-onset CRC (Ptrend<0.001), respectively. These associations were driven by proximal (OR for ≥2 vs 0 metabolic comorbid conditions: 1.40, CI 1.15-1.69) and distal colon cancer, OR ≥2 vs 0: 1.25, CI 1.03-1.53), but not rectal cancer (OR≥2 vs 0: 1.07, CI 0.92-1.24). Conclusions: Metabolic syndrome and metabolic comorbid conditions were associated with increased risk of early-onset CRC, largely driven by proximal and distal colon cancer. Metabolic dysregulations may contribute to the rising incidence of early-onset CRC.