268 Early-Onset Colorectal Cancer Annual Percent Change Incidence Analysis in 20–29 and 30–39 Year-Olds Utilizing 2000–2016 SEER 18 Data and Stratified by Histology

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INTRODUCTION: SEER 9 analysis has revealed rising early-onset colorectal cancer (EOCRC) incidence. We seek to analyze SEER 18 EOCRC rates as this represents a greater percentage of the U.S. population compared to SEER 9 (28% vs. 9%). Furthermore, given evidence carcinoid (CN) rates are increasing and these tumors may potentially be broadly categorized as “colorectal cancer,” we aimed to substratify analysis by histology. METHODS: Age-specific CRC, colon only and rectal only incidence rates from SEER 18 (2000–2016) were generated in yearly intervals using SEER*Stat. Age 20–29 and 30–39 blocks were analyzed and Joinpoint regression was used to calculate annual percent changes (APC). Histologic categories included all CRCs, adenocarcinomas (AC), CNs and CRCs without CNs. RESULTS: Age 20–29 overall CRC APC was 3.39% from 2001–2013 and 14.55% from 2013–2016. Colon AC APCs (1.03% from 2000–2016) and rectal AC APCs (7.42% 2000–2006, −0.24% 2007–2016) in 20–29 year-olds were not statistically significant. However, colorectal combined ACs had a statistically significant, modest APC of 1.12%. In contrast, 2007–2016 age 20–29 colon CN APC was 41.05%. Rectal CN APCs were not significantly changed. Age 30–39 overall CRC APCs were 1.58% from 2000–2010 and 4.03% from 2010–2016. Age 30–39 2000–2016 colorectal AC APCs were 1.89% with a colon AC APC of 1.59% and rectal AC APC of 2.40%. Age 30–39 colonic CN APCs were 32.81% from 2010–2016. Rectal CN APCs were 2.90% from 2000–2016. CONCLUSION: Age 20–29 overall CRC rate increases in SEER 18 appear to be driven in large part by increasing CN incidence. Although there was a significant colorectal AC APC of 1.12% in 20–29 year-olds, there was no significant APC increase in colon ACs. There appeared to be an increased APC trend in rectal ACs from 2000–2006 (7.42%), however this was non-significant and there was a negative trend from 2006–2016. In contrast, colon and rectal ACs in the 30–39 age group have been steadily increasing. In both age groups, colon CNs have been increasing faster than rectal CNs. Reasons are unclear but could potentially represent increased use of colonoscopy which can detect proximal lesions. Study limitations include underreported age 20–29 CN rates from 2000–2006. Overall, findings support rises in CRC incidence in young adults, however this is less from ACs in 20–29 year-olds. Despite these findings, ACs are still present in 20–29 year-olds and concerning symptoms should trigger diagnostic evaluations.