proximal cancer than males (ORs ranged from 1.16 to 1.63). Patients over 60 years or olderexhibited increased likelihood for proximal tumor (ORs ranged from 1.20 to 1.78) comparedto younger cases. Over time, there was a stepwise increased likelihood in proximal tumorswith the time period of 2003-07 having the highest likelihood compared to the referentfirst five-year time period of 1973-77 (ORs ranged from 1.26 to 1.60). Discussion: Geographicvariation in the proportion of proximal CRC appears to be related to race/ethnicity, sex andage structures in the regions, which is consistent with our prior study reporting significantdemographic variation in frequency of proximal CRC. Further research is needed to determinespecific behavioral and clinical explanations underlying these demographic differences

Percent of CRC tumors by location for SEER-9 registries

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National Trends in Proximal vs. Distal Colorectal Cancer (CRC) ResectionRates in the US: Does Screening Colonoscopy Reduce Proximal CRC Risk?Parvathi A. Myer, Ajitha Mannalithara, Gurkirpal Singh, Uri Ladabaum

Introduction: Fecal occult blood testing (FOBT) and sigmoidoscopy decrease colorectalcancer (CRC) incidence and mortality, with sigmoidoscopy protecting only against distalCRC. Whether colonoscopy protects against proximal CRC has been questioned. CRCscreening guidelines and utilization have changed significantly in the last 2 decades in theUS. We analyzed trends in surgical CRC resection rates using the Nationwide InpatientSample (NIS) and evaluated the difference in proximal vs. distal CRC trends in the US.Methods: NIS, the largest U.S. inpatient database, is a 20% stratified probability sample ofUS hospitals.We identified all cases of CRC resection from 1993-2009, defined as hospitaliza-tions including an ICD-9 CM procedure code for colorectal resection and a diagnostic codefor colon/rectal cancer. Proximal and distal CRC were defined by a combination of procedureand diagnosis codes. Proximal CRC was defined as proximal to the splenic flexure. Surveymethods in SAS v9.2 were used to determine national estimates of CRC resection rates.Rates for all adults, age-adjusted to the 2000 US standard population, are expressed per100,000 persons (95% CI). Joinpoint regression program v3.5.2 was used to calculate annual% changes and to test for changes in trends over time. Results: The overall CRC resectionrate decreased from 71.1 (65.9-76.2) in 1993 to 47.3 (43.4-51.2) in 2009, with moremarked decreases after 2000 than before 2000 (Figure 1, Table 1). The distal CRC resectionrate decreased from 38.7 (35.4-42.0) in 1993 to 23.2 (20.9-25.5) in 2009, with a decreaseof 1.2%/year (0.1-2.3%) before 1999 accelerating to a decrease of 3.8%/year (3.3-4.3%)after 1999 (Figure 1, Table 1). In contrast, the proximal CRC resection rate per 100,000decreased from 30.0 (27.4-32.5) in 1993 to 22.7 (20.6-24.7) in 2009, but the decrease wasnot significant before 2002. The proximal CRC resection rate decreased by 3.1%/year (2.3-4.0%) only after 2002 (Figure 1, Table 1). Discussion: CRC surgical resection rates reflectCRC incidence rates since most CRC patients undergo resection. National distal CRC resectionrates have decreased significantly since 1993, with more dramatic decreases after 1999. Incontrast, national proximal CRC resection rates have decreased significantly only since 2002.The fraction of Americans screened has risen steadily over time, with colonoscopy becomingthe leading CRC screening test since 2001, when Medicare and then private insurers offeredcoverage. Our results are consistent with the hypothesis that decreases in distal CRC resectionrates are associated with CRC screening in general, but that the decreases in proximal CRCresection rates are associated with the implementation of screening colonoscopy specifically.Age-Adjusted Colorectal Cancer Resection Rates

S-513 AGA Abstracts

Colorectal Cancer Resection Rates in Adults

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Interval Cancers in a Colorectal Cancer Population Screening Fit-Based: Resultof Two RoundsSergio Crotta, Simona Paganin, Bruna Dagnes, Roberto Lolli

Background and Aims: Stage distribution of screen-detected (SD) CRCs and the evaluationof interval CRCs (IC) represent important quality indicators in a screening program. Wereport preliminary descriptive data concerning the characteristics of CRCs diagnosed in ourscreened population, divided as screen-detected (SD) and interval cancer (IC). Methods:Between 2006 and 2010 two rounds of a biennial screening program for colorectal cancer(CRC) based on 1-day fecal immunochemical test (FIT; OC Sensor) offered every two yearswere carried out in Aosta Valley. ICs were defined as CRCs diagnosed within 2 years of anegative FIT. We compared the stage and site distribution of SD and interval CRCs. Results:In a target population of about 38,000 subjects the participation rate and the positivity ratein two rounds were on average 64% and 5%. As expected the number of SD CRCs droppedfrom 68 in the first to 34 in the second screening round. ICs made up 10.2% of the CRCsdetected among people screened in the first (8/76) and 22.7% of those detected amongpeople screened in the second round (10/44). The increased proportion of IC in the secondround is partly due to the decline in the number of SD CRCs. These findings are consistentwith the data from the Scottish screening program with guaiac-FOBT1, although the observedproportion of IC was higher with guaiac (31.2% in the first and 47.7% in the second round)than with FIT in our program. Compared to SD CRCs, IC had a worse stage distributionand were more likely to be right-sided (Table I). Conclusions: In two FIT screening roundsthe proportion of ICs increased, partly as a result of the decline of incident SD CRCs.Compared to SD CRCs, ICs had worse stage distribution and were more often right-sided.1Interval cancers in a FOBT-based colorectal cancer population screening programme:implications for stage, gender and tumour site. Steele RJ, McClements P, Watling C, etal.Gut. 2011 Sep 19. Epub ahead of printTable I: Stage distribution and site of IC and SD cancer in two rounds

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Population-Based Correlation Between Demographic Factors andHistopathologic Features in Colorectal Carcinoma CasesFeriyl Bhaijee, Dominique Pepper, Jessica E. Fleming, Grant Knutson, Alexandra S.Brown

Background: Various patient- and tumor- specific characteristics are used to approximaterisk and prognosis in patients with colorectal carcinoma (CRC). In this study, we assessedthe relationship between demographic factors, such as age, sex, and race, and specifichistopathology features in patients with CRC. Methods: We used a prospectively maintaineddatabase to identify all patients who underwent resection of a primary CRC between 2000and 2011 at a large academic medical center. We retrieved demographic data and pathologyreports from electronic medical records, and glass slides of formalin-fixed paraffin-embeddedtumor sections from pathology archives. For each patient, we obtained the following data:age; sex; race; tumor location, size, grade/differentiation, histologic heterogeneity, infiltratinglymphocytes, pathologic stage, lymphovascular invasion, perineural invasion, and lymphnode metastasis. Analyses were performed with STATA 10.1, using student-t tests and Fisherexact tests for univariate analyses and linear regression models for multivariate analyses.Results: Over an 11.5-year period, 400 patients underwent resection of a primary CRC(Table 1). In univariate analyses (Table 2), increasing age was associated with more proximallocation (P<0.001), higher pathologic stage (P=0.030), lymphovascular invasion (P=0.030),perineural invasion (P=0.027), and lymph nodemetastasis (P=0.017); male sex was associatedwith increasing pathologic stage (P=0.007) and perineural invasion (P=0.019); and African-American race was associated with lymphovascular invasion (P=0.037). In multivariateanalyses, increasing age was associated with more proximal location (odds ratio [OR] 4.95;

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s95% confidence interval [95CI] 2.65-9.27); female sex was associated with perineural inva-sion (OR 1.16; 95CI 1.02-1.32); and African-American race was associated with both lymph-ovascular invasion (OR 1.16; 95CI 1.04-1.30) and lower tumor grade (OR 0.84; 95CI 0.72-0.98). Conclusion: In our study of patients with CRC, we demonstrate that demographicfactors, such as age, sex, and race, are significantly associated with certain histopathologicfeatures: proximal tumors are more common in older patients, perineural invasion is moreoften seen in women, lymphovascular invasion is more common in African-Americans, andhigh-grade tumors are frequent amongst Caucasians. Population-based correlation betweendemographic factors and histopathologic features of CRC provides a better approximationof risk, which may be useful when delivering targeted interventions.Table 1. Demographic and histopathologic characteristics of colorectal carcinoma cases

Key: MSI-H = microsatellite instability 1 data missing in 10 patientsTable 2. Univariate analysis showing the relationship between demographic factorsand histopathologic features in colorectal carcinoma cases

1 Student t-test; 2 Fisher exact test; 3 Male; 4 Female; 5 Caucasian; 6 African-American P-value significant if < 0.05

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Risk of Colorectal Cancer After Diagnosis of Uroepithelial Cancers: APopulation Based StudyHarminder Singh, Zoann Nugent, Alain Demers, Piotr Czaykowski, Salaheddin Mahmud

Background: It has been reported that individuals with a history of uroepithelial cancers(involving the renal pelvis, ureter and bladder) have an increased risk of CRC. Some authorshave suggested that the patients with specific urological cancers may benefit from CRCscreening at a younger age and with more frequent colonoscopic examinations. However,the prior analyses did not account for potential confounding by increased screening or forcompeting risks among cancer survivors. Methods: We conducted a historical cohort studyassembled by means of record linkage of several large longitudinal databases of routinelycollected health data from Manitoba, including the databases of the Manitoba Cancer Registryand those of Manitoba Health. Each individual diagnosed with a uroepithelial cancer astheir first cancer (cancer cohort) between 1987 and 2008 was age and gender matched withup to five individuals with no history of a uroepithelial cancer (control cohort) on the indexdate (date of diagnosis of uroepithelial cancer in the cancer cohort). All study subjects werefollowed up to the date of diagnosis of CRC or another primary invasive cancer of any type,death, migration out of the province, or study end-point (December 31, 2009), whichevercame first. Competing risk proportional hazard models were used to calculate the relativerisk (estimated by hazards ratio (HR)) and 95% confidence intervals (CI) contrasting CRCincidence rates among the cancer and control cohorts. The analysis had three mutuallyexclusive (and competing) outcomes (i) diagnosis of CRC, (ii) diagnosis of another primarycancer, and (iii) death and was adjusted for age, gender, history of lower gastrointestinalendoscopy six months prior to the end of follow-up time and socio-economic status. Results:26,708 individuals (median age 72 years; 74% men) were followed up for a total of 174,456person years (median follow-up 5.2 years). In the multivariate analysis there was no increasedrisk of CRC among individuals with uroepithelial cancers (HR 0.84; 95% CI: 0.67-1.06).In stratified analysis, there was no increased risk in the different age groups. In the non-competing risk analysis, there was a 20 percent increased risk of CRC after diagnosis ofuroepithelial cancers. Conclusion: This study suggests there is no real increased risk of CRCafter diagnosis of a uroepithial cancer. Survivors of uroepithelial cancers should undergoage appropriate CRC screening.

S-514AGA Abstracts

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Asians Have a Lower Risk of Advanced Colonic Neoplasm Compared toCaucasiansVivek Kumbhari, Jason Behary, Jason Hui

Background and Aims: Colonic adenomas and sessile serrated adenomas (SSA) are themost common pre-malignant polyps identified at colonoscopy. There is limited data whichcompare the prevalence of neoplastic polyps in Asians compared with Caucasians. Interpreta-tion of the published data is difficult because of the variability in adenoma detection ratesby different endoscopists. We conducted a study to compare the prevalence of neoplasticpolyps in Asians compared with Caucasians in a single ethnically mixed community practiceinNew SouthWales, Australia.Methods:This is a prospective study of consecutive unselectedcolonoscopies performed for standard clinical indications by a single experienced endoscopist(JMH). All polyps detected were measured, resected and sent for histopathology. The preval-ence of adenoma, advanced adenoma, SSA and cancer in the Asian and Caucasian cohortswere compared. Advanced adenomas were defined as either adenomas >10mm, villoushistology or high-grade dysplasia. Results: Over a 13-month period, 1060 colonoscopieswere performed, of which 60 were excluded (prior colonic resection n= 21, inflammatorybowel disease n= 28, polyposis syndrome n= 2, incomplete colonoscopy n= 3, others n=6). The study included 34.6% (n=346) Asians and 65.4% (n=654) Caucasians. There wasno significant difference in the baseline characteristics including age, gender and indicationsof colonoscopy. The prevalence of neoplastic polyp is summarised in the table below. Theprevalence of adenomatous polyps was similar in both Caucasians and Asians. Advancedadenomas and SSA were significantly more common in Caucasians compared with Asians.Multivariate analysis showed that Caucasian ethnicity (OR: 2.3, 95% CI: 1.6 - 3.6) or thepresence of a SSA (OR: 4.4, 95% CI: 2.3 - 8.6) were independent predictors for the detectionof an advanced adenoma. Conclusions: The prevalence of significant colorectal lesionsincluding advanced adenomas, large adenomas and SSA is lower in Asians compared withCaucasians. These findings may influence the interval for surveillance colonoscopy. Publishedguidelines for surveillance colonoscopy using data from Western countries may not beapplicable to Asian patients. The presence of a SSA is associated with an increased risk ofadvanced adenoma.Frequency of Neoplastic Polyps by Race (frequency,%)

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Osteoporosis and Osteopenia are Not Associated With an Increased Risk ofColorectal Cancer: Analysis of the SEER-Medicare DatabaseJennifer LoSavio, Chuanhong Liao, David T. Rubin, Sonia Kupfer

Background: Calcium, vitamin D and estrogen are believed to be protective against colorectalcancer (CRC). These factors are also known to play important roles in bone mineral density(BMD) and development of osteoporosis. Studies have suggested that normal BMD is associ-ated with decreased risk of CRC; however, osteoporosis has not been studied as a risk factorfor CRC. Using the population-based Surveillance, Epidemiology and End Results (SEER)-Medicare database, we sought to determine if osteoporosis, osteopenia or osteoporoticfractures were associated with an increased risk of CRC. Methods: The SEER programprovides cancer data from 17 US cancer registries which includes data from 1973-2008 andis linked to Medicare claims. A case-control analysis was performed utilizing data from the2004 SEER-Medicare database. Cases included all of those over the age of 65 with CRCand no other known cancer diagnosis. The control group was a random sample of Medicarebeneficiaries living in SEER regions without any type of cancer. Medicare claims werelinked to the selected cases and controls to identify those with osteoporosis, osteopenia, orosteoporotic fractures (hip, vertebral or Colles' fractures). The prevalence of osteoporosis,osteopenia, or fracture was compared between cases and controls; subgroup analysis wasperformed to examine prevalence by age, gender, race, tumor location, and stage. Multivari-able logistic regression analysis was then performed to identify variables independentlyassociated with CRC risk. Results: A total of 241,625 individuals (11,481 CRC cases witha mean±SD age of 78.2±7 years and 61% female vs. 230,144 cancer-free subjects with amean±SD age of 76.9±7 years and 54% female) were included (81% White, 7% Black, 5%Asian, 3% Hispanic). 73,638 cases of osteoporosis or osteopenia and 8,774 osteoporoticfractures were identified in the entire population. The prevalence of osteoporosis, osteopeniaor osteoporotic fracture was significantly lower in CRC patients compared to cancer-freecontrol subjects (26.7% vs. 31.9%; p<0.001). This trend was observed regardless of age,gender, race, or tumor location (colon versus rectum). Results of multivariable logisticregression analysis are shown in Table 1. Osteoporosis or osteopenia were independentlyassociated with decreased CRC risk; while age, male gender and Black race compared toCaucasian were associated with increased CRC risk. Conclusion: Osteoporosis or osteopeniawas not associated with an increased incidence of CRC. On the contrary, osteoporosis orosteopenia had a negative association or protective effect in relation to CRC. Reasons forthese findings could be due to confounding variables, such as the possibility that patientsbeing screened for bone disease were also more likely to have successful CRC screening, orthat osteoporosis treatment reduces CRC risk.Table 1: Results of multivariable logistic regression analysis for risk of colorectal cancer