Colorectal Cancer _ ___________________________________________________________________________
Evidence supports screening for colorectal cancer as part of routine care for all adults 45 to 50 years of age or older, especially those with first-degree relatives with colorectal cancer, for the following reasons [120; 121]: • Increased incidence in those 50 years and older
Unfortunately, despite sophisticated nationwide efforts to elevate screening awareness, routine screening of eligible individuals remains low [126]. Currently, only about half of Americans 50 years of age or older, for whom screening is recommended, report having had colorectal cancer testing consistent with current guidelines [127]. To better understand potential provider and systemic obstacles to achieving higher utilization rates of colorectal cancer screening, a national survey of colorectal cancer screening education, prioritization, and self-perceived preparedness was performed of 835 primary care residents. In regards to advising patients about colorectal cancer screening, current colorectal cancer screening guidelines, and criteria for familial colorectal cancer syndromes, a significant proportion of respondents felt they lacked sufficient knowledge in these areas. These data suggest opportunities to improve the colorectal cancer screening curriculum in primary care residency programs [128]. As colonoscopy has increasingly become widespread and preferred as a colorectal cancer screening approach, questions concerning its optimal use have emerged. Research has now established that the ability of colonoscopy to detect precancerous polyps and malignant tissue critically depends on examination quality. Patient adherence to pre-colonoscopy preparation is also essential. Practice guidelines addressing these important issues have been published to bridge the knowledge gaps between the latest research, primary care, and specialist providers. Practice guidelines for colorectal cancer screening are updated as new information becomes available. For example, in 2014 the National Comprehensive Cancer Network (NCCN) expanded its recommendation for screening for Lynch syndrome to all patients diagnosed with colorectal cancer [129; 130]. The National Comprehensive Cancer Network recommends universal screening for Lynch syndrome in all patients with colorectal cancer, in order to maximize sensitivity for Lynch syndrome detection and simplify care processes. (https://www.nccn.org/professionals/physician_gls/pdf/ genetics_colon.pdf. Last accessed March 14, 2022.) Level of Evidence : 2a (Based upon lower-level evidence, there is uniform NCCN consensus that the intervention is appropriate.)
• Ability to identify high-risk groups • Slow growth of primary lesions
• Better survival of patients with early-stage lesions • Relative simplicity and accuracy of screening tests Consistent evidence supports population-level colorectal cancer screening, which has become the foundation for primary colorectal cancer prevention. In a 2012 study involving 2,602 patients initially referred to colonoscopy for adenomas and nonadenomatous polyps from 1980 to 1990, participants were followed up to 23 years (median: 15.8 years). Their mortality from colorectal cancer was compared against the expected colorectal cancer mortality in the general population. Colonoscopy was associated with a 53% reduction in mortality (12 colorectal cancer deaths versus 25.4 expected). During the first 10 years post-polypectomy, colorectal cancer mortality was comparable between patients with adenomas or nonadenomatous polyps [122]. In another study, 46,551 healthy subjects between 50 and 80 years of age were randomized to annual or biennial fecal occult blood testing (FOBT) or no screening from 1976 to 1992. Those with positive FOBT screens received colonoscopy and treatment for malignant findings. At 30-year follow-up, 33,020 had died, 732 from colorectal cancer, including 200/11,072 (1.8%) with annual, 237/11,004 (2.2%) with biennial, and 295/10,944 (2.7%) with no screening. At 30 years, colorectal cancer mortality was reduced by 32% with annual screening and 22% with biennial screening compared with no colorectal cancer screening [123]. Researchers compared 3,148 patients with first diagnosis of colorectal cancer with 3,274 non-colorectal cancer subjects to assess associations between colonoscopy for specific indications and the risk of colorectal cancer over a 10-year period. History of screening colonoscopy was associated with a reduction of colorectal cancer risk of 89% and of malignancy in the right colon of 78%. History of diagnostic colonoscopy (and indication) was associated with colorectal cancer risk reduction of 67% with assessment of positive FOBT; 67% with surveillance after a preceding colonoscopy; 72% with assessment of rectal bleeding; and 85% with assessment of abdominal symptoms [124]. Another large study followed 40,826 patients for a median 7.7 years to study the impact of adenoma removal during screening colonoscopy on colorectal cancer mortality. Using data from the Norway national cancer and cause-of-death registries, researchers found that, relative to expected colorectal cancer mortality (the general Norwegian population), adenoma removal during screening was associated with a 25% reduction in mortality rate [125].
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