Citations

Abstract Background. Several recent studies have reported an inverse relationship between sun exposure and non-Hodgkin (NHL) risk. One hypothesis is that vitamin D mediates this effect. We evaluated the association of sun exposure at various ages and common variants in vitamin D related genes with risk of NHL and its major subtypes. Methods. Newly diagnosed NHL cases (N=1023) and frequency matched controls (N=1254) were enrolled in a clinic-based case-control study conducted at the Mayo Clinic. Thirty-eight single nucleotide polymorphisms (SNPs) from 5 candidate genes relevant to vitamin D metabolism and sun sensitivity (IRF4, RXR, VDR, CYP24A1, CYP27B1) were genotyped. Participants also completed a detailed questionnaire, including self-reported sun exposure at ages 13-21, 22-40, and 41+ years. Odds ratios (OR), 95% confidence intervals (CI), and tests for trend and effect modification were estimated using unconditional logistic regression adjusted for age and gender. ORs are reported for the highest vs. lowest exposure category or as the ordinal OR for SNPs. Results. The mean age of diagnosis/enrollment was 61 years for cases and 60 years for controls. The most common subtypes were chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL; 34%), follicular (FL; 24%), and diffuse large B-cell (DLBCL; 18%) lymphomas. There was a significant decrease in NHL risk with increased sun exposure at ages 13-21 years (OR=0.66, 95% CI 0.44-1.00; ptrend=0.04), which attenuated with increasing age at exposure. Exploratory analysis by NHL subtype indicated a trend toward a protective effect of sun exposure at ages 13-21 years for each of the major subtypes, though these estimates did not reach statistical significance. Of the 38 SNPs evaluated, there was a significant association for 3 SNPs in VDR and 1 SNP in CYP24A1: rs3819545 (OR=1.24, 95% CI 1.10-1.40, p=0.0004), rs2239186 (OR=1.22, 95% CI 1.05-1.41, p=0.009), and rs886441 (OR=0.82, 95% CI 0.70-0.96, p=0.02) for VDR and rs2762939 (OR=0.85, 95% CI 0.75-0.98, p=0.02) for CYP24A1. Both the VDR and CYP24A1 associations were observed for CLL/SLL, FL, but were attenuated for DLBCL. There was no evidence of any significant effect modification of sun exposure at ages 13-21 years by genotype in these four SNPs for NHL overall, or for NHL subtypes. Conclusions. We observed an inverse association between the frequency of sun exposure at ages 13-21 years and NHL risk, which attenuated for sun exposure at older ages, suggesting that early life exposure may be more relevant. While genetic variation in VDR and CYP24A1 were associated with NHL risk, there was no evidence for an interaction of sun exposure with these genes, suggesting that a sun association may not act through the vitamin D metabolism pathway. This would be consistent with a lack of association of circulating vitamin D with NHL risk recently published from the Cohort Consortium pooling project. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1894. doi:10.1158/1538-7445.AM2011-1894

Abstract Background: Folate intake (FI) appears to affect colorectal cancer (CRC) risk, but the molecular mechanism(s) involved are incompletely defined. In this study, we analyzed associations between FI and incident CRC, overall and by KRAS mutation status, in the population-based Iowa Women's Health Study (IWHS). Methods: The IWHS recruited 41,836 randomly selected Iowa women, ages 55-69 years, with a valid driver's license at study entry (1986). FI and other exposure variables were assessed at baseline, by self-report. Incident CRC cases were ascertained by annual linkage with the Iowa Cancer Registry. Archived, paraffin-embedded tissue specimens were recently collected from 732 representative CRC cases diagnosed through 12/31/2002. FI (including supplements) was categorized by quartiles. KRAS mutation status (wildtype [wt] vs. mutated [mut]) was determined by direct sequence analysis of codons 12 and 13 (exon 2). Multivariate Cox regression models were fit to estimate relative risks (RRs) and 95% confidence intervals (CIs). Results: Of the 732 available CRC cases, 470 (64%) had complete FI and KRAS data. FI was not associated with incident CRC overall (for quartile 4 vs. quartile 1, RR = 1.03; 95% CI = 0.82-1.28; p trend = 0.90), or with the KRAS-wt or KRAS-mut subtypes (see Table). Conclusions: These data do not support an association between FI and incident CRC, overall or by KRAS-defined subtypes, among older, predominately white, non-Hispanic women. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1892. doi:10.1158/1538-7445.AM2011-1892

Abstract Background: Cigarette smoking (CS) is an established, although relatively modest, colorectal cancer (CRC) risk factor. Emerging data suggest that CS might affect distinct pathways of colorectal carcinogenesis. In this study, we examined CS-associated CRC risks by KRAS mutation status in the population-based Iowa Women's Health Study (IWHS). Methods: The IIWHS recruited 41,836 randomly selected Iowa women, ages 55-69 years, with a valid driver's license at study entry (1986). CS and other exposure variables were assessed at baseline, by self-report. Incident CRC cases were ascertained by annual linkage with the Iowa Cancer Registry. Archived, paraffin-embedded tissue specimens were collected from 732 representative CRC cases diagnosed through 12/31/2002. CS was categorized by smoking status (current, former), average number of cigarettes per day (1-19, 20-39, > 40) and pack-years (1-19, 20-39, > 40); never smokers were defined as the reference group. KRAS mutation status (wildtype [wt] vs. mutated [mut]) was determined by direct sequence analysis of codons 12 and 13 (exon 2). Multivariate Cox regression models were fit to estimate relative risks (RRs) and 95% confidence intervals (CIs). Results: Of the 732 available CRC cases, 507 (69%) had complete CS and KRAS data. Each of the CS-related variables was more strongly associated with KRAS-wt vs. KRAS-mut tumors (see Table). However, event rates were relatively small in some cells, and tests for heterogeneity between KRAS-defined subtypes were not statistically significant (p > 0.05 for each comparison). Conclusions: These findings suggest that CS may affect colorectal carcinogenesis through KRAS-independent pathways, but additional data are needed from larger, more diverse study populations. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1891. doi:10.1158/1538-7445.AM2011-1891