Aim: International studies have shown that most colon cancers are diagnosed among people with symptoms, but research is limited in the United States. Here, we conducted a retrospective study of adults aged 50-85 years diagnosed with stage I-IIIA colon cancer between 1995 and 2014 in two US healthcare systems.
Methods: Mode of detection (screening or symptomatic) was ascertained from medical records. We estimated unadjusted odds ratios (OR) and 95% confidence intervals (CI) comparing detection mode by patient factors at diagnosis (year, age, sex, race, smoking status, body mass index [BMI], Charlson score), prediagnostic primary care utilization, and tumour characteristics (stage, location).
Results: Of 1,675 people with colon cancer, 38.4% were screen-detected, while 61.6% were diagnosed following symptomatic presentation. Screen-detected cancer was more common among those diagnosed between 2010 and 2014 versus 1995-1999 (OR 1.65, 95% CI: 1.19-2.28), and those with a BMI of 25-<30 kg/m2 (OR 1.54, 95% CI: 1.21-1.98) or ≥30 kg/m2 (OR 1.52, 95% CI: 1.18-1.96) versus <25 kg/m2 . Screen-detected cancer was less common among people aged 76-85 (OR 0.50, 95% CI: 0.39-0.65) versus 50-64, those with comorbidity scores >0 (OR 0.71, 95% CI: 0.56-0.91 for score = 1, OR 0.34, 95% CI: 0.26-0.45 for score = 2+), and those with 2+ prediagnostic primary care visits (OR 0.53, 95% CI: 0.37-0.76) versus 0 visits. The odds of screen detection were lower among patients diagnosed with stage IIA (OR 0.33, 95% CI = 0.27-0.41) or IIB (OR 0.12, 95% CI: 0.06-0.24) cancers versus stage I.
Conclusions: Most colon cancers among screen-eligible adults were diagnosed following symptomatic presentation. Even with increasing screening rates over time, research is needed to better understand why specific groups are more likely to be diagnosed when symptomatic and identify opportunities for interventions.
Keywords: colon cancer; early detection; screening; signs and symptoms.
© 2022 Association of Coloproctology of Great Britain and Ireland. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.