The epidemiology of colorectal cancer: global implications for measuring incidence, with a focus on trends, risk factors, and screening uptake in Saudi Arabia

Colorectal cancer (CRC) is a global public health concern, imposing considerable health and economic burdens. While population-based studies worldwide closely monitor CRC incidence, variations in incidence methods hinder reliable interpretation and comparisons of rates. A description of variations in incidence calculation and the quality of reporting incidence methods is lacking. In Saudi Arabia, CRC is the second most common cancer; about one-third of cases present with a late-stage disease, resulting in poor prognosis. A comprehensive analysis of CRC rates, trends, and factors associated with late-stage diagnosis is currently lacking. The Ministry of Health recently launched a national CRC screening program, yet the public’s perceptions and acceptance of screening remain limited. This thesis aims to address the identified gaps by conducting five studies. Study One is a systematic review describing variations in the methods used in CRC incidence and the quality of their reporting. Variations in incidence calculation were identified, and recommendations were provided to enhance the reliability and reporting of incidence estimations. Study Two describes methods for estimating CRC incidence trends, highlighting the most common methods and the need for clarity and transparency in their reporting. Insights from studies One and Two informed methodological and reporting decisions in subsequent quantitative studies. Study Three is a retrospective analysis examining CRC incidence rates and trends in Saudi Arabia. Over time, CRC incidence rates increased across all age groups and stages at diagnosis, highlighting the critical need for cancer control policies and strategies. Study Four examines risk factors associated with late-stage CRC diagnosis in Saudi patients. Women under 50 had an increased risk, emphasizing the need for targeted preventive efforts. Study Five is a qualitative exploration of Saudi women’s perceptions and attitudes towards CRC screening. The interviews revealed multifaceted factors influencing screening uptake, underscoring the need for tailored health promotion interventions.