Prognostic Study of Colorectal Cancer: Differences between Screen-Detected and Symptom-Diagnosed Patients

Background and objective: Colorectal cancer (CRC) is the leading cause of mortality in Spain, with screening programs, such as the faecal occult blood test and colonoscopy, having shown effectiveness in reducing CRC incidence and mortality. Despite these advancements, CRC screening uptake remains low in Spain, highlighting the need for studies comparing outcomes between screening-diagnosed and symptom-diagnosed patients to better understand the impact on overall survival and to quantify the clinical benefit in prognosis at diagnosis and at the end of follow-up. Methods: We conducted a retrospective cohort study with the following objectives: to compare stage at diagnosis, all-cause mortality, and disease-specific mortality among people diagnosed with CRC based on screening and based on symptoms; to identify the risk factors associated with mortality in this population; and to evaluate the effectiveness of screening on survival and early detection. Our study included people diagnosed with CRC in the public hospital of Elda (Spain) from 2014 to 2018; follow-up was until 2023 or death. Our primary outcome was all-cause mortality, which we analysed using Kaplan-Meier curves. We also investigated CRC-specific mortality and other-cause mortality. Results: Our sample included 315 people (186 with symptom-based diagnoses, 129 with screening-based diagnoses). The mean length of follow-up was 62.8 months. The screening group had a higher prevalence of a family history of CRC (p = 0.008), a distal tumour location (p = 0.002), and a cancer stage of 0 or I (p < 0.001). The symptoms group had a higher prevalence of a proximal CRC (p = 0.002), other chronic diseases (p < 0.001), and stages II, III, and IV (p < 0.001). Two variables were associated with mortality: stage IV at diagnosis and previous cancers. People with a symptom-based diagnosis had a higher prevalence of stage IV at diagnosis and a higher cumulative incidence of CRC mortality and all-cause mortality at the end of follow-up (p < 0.05). The Kaplan-Meier curves also showed a higher rate of all-cause mortality in the symptoms group throughout the follow-up. Conclusion: CRC screening enables an earlier diagnosis and improves survival. These findings support public health policies that promote accessible and effective screening.