Trends in incidence, mortality rates, and survival of colorectal cancer in Western Australia from 1990 to 2014: a retrospective whole-population longitudinal study.

Purpose: This study aimed to investigate the trends in colorectal cancer (CRC) incidence and mortality rates among the Western Australian (WA) population. This study further compared the trends with the timing of the implementation and rollout of the National Bowel Cancer Screening Program (NBCSP) and examined the survival predictors in CRC cases.
Methods: This study was a whole-population, retrospective longitudinal study and included all individuals with a confirmed histological diagnosis of primary invasive CRC diagnosed in WA from 1990 to 2014 (n = 25,932). The temporal trends were assessed by Joinpoint regression models and Kaplan-Meier survival curves were used to asses 5-year survival. Predictors of survival were examined using multivariable Cox proportional hazard regression models, adjusting for age of diagnosis.
Results: The overall CRC incidence showed an upward trend between 1990 and 2010 (annual percent change (APC) = 1.1%); then, there was a downward trend from 2010 to 2014 (APC = - 5.0%). In younger people (< 50 years), the incidence rate increased steadily (APC = 0.9%) over the study period. The overall CRC mortality trend increased from 1990 to 1999 (APC = 1.6%), decreasing after that (APC = - 2.1%). Younger people had better CRC-related 5-year survival than older people (HR = 0.81, 95%CI 0.75-0.87, p = < 0.001).
Conclusion: This study found that CRC incidence and mortality rates decreased among older people over the last 10 years in Western Australia. However, incidence continues to rise for younger people. Hence, more widespread adoption of the screening program, and potential preventive and early diagnostic strategies should become key priorities for the CRC control in WA.