Researchers have created novel scoring tools for predicting actual risk of colon cancer and advanced precancerous polyps for patients at average for the disease. The work was led by Dr Thomas F Imperiale from the Regenstrief Institute and US Department of Veterans Affairs research scientist and Indiana University School of Medicine professor of medicine.
The tools may be most useful in countries where colonoscopy is not routinely used for screening average risk individuals, and include Canada, the United Kingdom, Italy, Netherlands, Australia and others which typically screen average risk individuals with less invasive sigmoidoscopy and the many countries which use no imaging tests for colon cancer screening. The findings were reported in the paper, ‘New scoring systems for predicting advanced proximal neoplasia in asymptomatic adults with or without knowing distal colorectal findings’, published in European Journal of Cancer Prevention.
The new weighted models are based on scoring various factors such as age, gender, smoking history, co-habitation history, nonsteroidal anti-inflammatory drug (for example ibuprofen) and aspirin use, and moderate physical activity over the past year in average risk individuals. These tools weigh the importance of each factor to determine an individual's personalised risk.
"We need to more precisely measure risk of individuals and populations, so good, scientifically-based decisions about when and how to be screened for colorectal cancer can be made by patients, clinicians and public health officials," explained Imperiale, a practicing gastroenterologist who has researched colon cancer risks and screening for two decades. "Our composite, weighted scoring methods enable simple risk stratification to determine an individual's risk, for example, of a precancerous polyp with certain ominous features or of colon cancer, both indicating a need for colonoscopy."
He and colleagues developed two tools. One is applicable to patients who have had limited endoscopy screening of a portion of the colon with sigmoidoscopy and the other can be used for patients without any test involving visualisation of the colon.
Among 3,025 subjects in the derivation set (mean age 57.3 ± 6.5 years; 52% women), advanced proximal colorectal neoplasia (APN) prevalence was 4.5%; 2,859 (94.5%) had complete data on risk factors. Independently associated with APN were age, sex, cigarette smoking, cohabitation status, metabolic syndrome, non-steroidal anti-inflammatory drug use and physical activity. This model (without distal findings) was well-calibrated (p=0.62) and had good discrimination (c-statistic = 0.73).
In low-, intermediate- and high-risk groups that comprised 21, 58 and 21% of the sample, respectively, APN risks were 1.47% (95% CI, 0.67–2.77%), 3.09% (CI, 2.31–4.04%) and 11.6% (CI, 9.10–14.4%), respectively (p<0.0001), with no proximal CRCs in the low-risk group and two in the intermediate-risk group. When tested in the validation set of 1455, the model retained good metrics (calibration p=0.85; c-statistic=0.83), with APN risks in low- (22%), intermediate- (56%) and high-risk (22%) subgroups of 0.62% (CI, 0.08–2.23%) 2.20% (CI, 1.31–3.46%) and 13.0% (CI, 9.50–17.2%), respectively (P < 0.0001).
There were no proximal CRCs in the low-risk group, and two in the intermediate-risk group. The model with distal findings performed comparably, with validation set metrics of 0.18 for calibration, 0.76 for discrimination and APN risk (% sample) in low-, intermediate-, and high-risk groups of 1.1 (69%), 8.3 (22%) and 22.3% (9%).
For various reasons, especially expense, and the need for patient preparation and anaesthesia, many countries other than the United States, Germany and Poland do not embrace routine screening colonoscopy, preferring to use sigmoidoscopy, stool-based tests for hidden bleeding, or both.
Sigmoidoscopy is a simpler procedure which only examines the lower portion of the colon (referred to medically as the distal colon) and is performed every five-to-ten years. Stool samples are inexpensive, easy to use and should be repeated annually or biennially. Predictive, data-based, tools for identifying average-risk patients at highest risk are invaluable for determining who to recommend for colonoscopy and who may be well-screened without colonoscopy, according to Imperiale.
“These models stratify large proportions of average-risk persons into clinically meaningful risk groups, and could improve screening efficiency, particularly for noncolonoscopy-based programme,” the authors concluded.