Common sense for a common problem: the question of screening the average-risk population for colorectal neoplasia.
Bibliographic record
Abstract
here is a discrepancy between the advice given in Canada regarding screening of the average-risk population for colorectal cancer and knowledge regarding the natural history of this cancer. The benign phase of colorectal cancer development is sufficiently long and predictable to allow for its prevention. Colorectal cancer differs from breast and prostate cancer in this respect. Screening for colorectal neoplasia allows not only for the early detection of cancer during the asymptomatic stage but also for its elimination during its benign phase. The loss to the patient of a failure to screen for colorectal neoplasia is, therefore, greater than with cancers for which individuals are commonly screened. The cost of the initial care of colon cancer is several times more than for cancers of the cervix, breast or prostate. This magnifies the cost to the health care system of failure to screen for colorectal neoplasia. To justify screening an averagerisk population, the prevalence of the disease and the benefit of intervention must be sufficient. Colorectal cancer is common in Canada, affecting about 50 people per 100 000 population per year. The annual incidence increases predictably with age so that 1%, 2% and 3% of people are affected in their 50s, 60s and 70s, respectively. Without a prevention policy, 6000 in every 100 000 Canadians will develop colorectal cancer over their lifetime. The screening tool should be reliable, sensitive and capable of intervention. In the case of colorectal neoplasia, only colonoscopy fulfills these criteria. The Canadian Task Force on Preventive Health Care did not include colonoscopy in its 2001 update of guidelines regarding colon cancer, but suggested that fecal occult blood testing (FOBT) and flexible sigmoidoscopy be included in the periodic health examination of asymptomatic people over 50 years of age. 1 Even these recommendations are not as widely advocated as screening for other cancers, so their application has been limited. In effect, Canada has no policy for the prevention of colon cancer. Heightening public awareness of colon cancer requires the ready availability of a test to reassure the individual. FOBT misses most of the benign precursors of colon cancer and many of the malignant lesions. Attempts to improve the sensitivity and specificity of the test by examining feces for DNA (a panel of 21 mutations), instead of blood, have not been successful. Although the missed lesion rate dropped from 89.2% with FOBT to 81.8% with DNA, the test is, as yet, insufficiently sensitive to provide the patient or the patient’s physician with reassurance. 2 Flexible sigmoidoscopy misses between 65% and 35% of patients with advanced colonic neoplasia, and it has been suggested that the higher proportion of missed lesions occurs in women. 3
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.057 | 0.193 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.003 | 0.002 |
| Bibliometrics | 0.004 | 0.003 |
| Science and technology studies | 0.011 | 0.059 |
| Scholarly communication | 0.011 | 0.041 |
| Open science | 0.007 | 0.014 |
| Research integrity | 0.027 | 0.047 |
| Insufficient payload (model declined to judge) | 0.007 | 0.002 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".