Abstract
To examine trends in colorectal cancer (CRC) incidence and colonoscopy history in adolescents and young adults (AYAs) aged 15-39 years in Western Australia (WA) from 1982 to 2007. Descriptive cohort study using population-based linked hospital and cancer registry data. Five-year age-standardized and age-specific incidence rates of CRC were calculated for all AYAs and by sex. Temporal trends in CRC incidence were investigated using Joinpoint regression analysis. The annual percentage change (APC) in CRC incidence was calculated to identify significant time trends. Colonoscopy history relative to incident CRC diagnosis was examined and age and tumor grade at diagnosis compared for AYAs with and without pre-diagnosis colonoscopy. CRC-related mortality within 5 and 10 years of incident diagnosis were compared for AYAs with and without pre-diagnosis colonoscopy using mortality rate ratios (MRRs) derived from negative binomial regression. Age-standardized CRC incidence among AYAs significantly increased in WA between 1982 and 2007, APC = 3.0 (95% CI 0.7-5.5). Pre-diagnosis colonoscopy was uncommon among AYAs (6.0%, 33/483) and 71% of AYAs were diagnosed after index (first ever) colonoscopy. AYAs with pre-diagnosis colonoscopy were older at CRC diagnosis (mean 36.7 ± 0.7 years) compared to those with no prior colonoscopy (32.6 ± 0.2 years), p < 0.001. At CRC diagnosis, a significantly greater proportion of AYAs with pre-diagnosis colonoscopy had well-differentiated tumors (21.2%) compared to those without (5.6%), p = 0.001. CRC-related mortality was significantly lower for AYAs with pre-diagnosis colonoscopy compared to those without, for both 5-year [MRR = 0.44 (95% CI 0.27-0.75), p = 0.045] and 10-year morality [MRR = 0.43 (95% CI 0.24-0.83), p = 0.043]. CRC incidence among AYAs in WA has significantly increased over the 25-year study period. Pre-diagnosis colonoscopy is associated with lower tumor grade at CRC diagnosis as well as significant reduction in both 5- and 10-year CRC-related mortality rates. These findings warrant further research into the balance in benefits and harms of targeted screening for AYA at highest risk.
Highlights
Australia and New Zealand have the highest rates of colorectal cancer (CRC) internationally [1]
We examined trends in CRC incidence and colonoscopy history among AYAs aged 15–39 years in Western Australia (WA) from 1982 to 2007, before implementation of the National Bowel Cancer Screening Program (NBCSP), using whole-population linked hospital and Cancer Registry data
A total of 517 incident cases of CRC among AYAs aged 15–39 years were registered with the WA Cancer Registry (WACR) between 1982 and 2007
Summary
Australia and New Zealand have the highest rates of colorectal cancer (CRC) internationally [1]. Current Australian guidelines recommend biennial CRC screening through fecal occult blood tests commencing from 50 years of age for all asymptomatic average-risk persons [3]. In the United States (US), CRC incidence and mortality in persons over 50 years have declined over the past decade owing in part to screening initiatives [4]. In direct contrast to trends in those over 50 years of age, an increasing incidence of CRC among adolescents and young adults (AYAs) has been reported internationally [11,12,13,14,15] as well as in Australia [16, 17] over the past two decades. There is currently a lack of empirical data on the impact of screening in age groups
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