Despite its incident being on a decline over the past 20 years, colorectal cancer (CRC) remains the second leading cause of cancer death in the United States. The US Preventive Services Taskforce (USPSTF) has recently updated their 2008 recommendations for CRC screening and reiterated that all asymptomatic adults aged 50-75 years undergo screening with any of the available screening methods, including flexible sigmoidoscopy, colonoscopy, fecal occult blood test, stool DNA (sDNA) testing, fecal immuno-chemical testing and CT colonography.
The expert panel in USPSTF reviewing the evidence on effectiveness of screening proposes, “screening for colorectal cancer should start at age 50 years and continue until age 75 years. There is evidence that screening for colorectal cancer in average-risk, asymptomatic adults aged 50 to 75 years is of substantial net benefit.”
According to a careful estimate by the American Cancer Society, one in 20 people in the US is likely to develop colon cancer in their lifetime. It is the forth most diagnosed cancer and second most common reason for death in Americans. CRC is most frequently diagnosed in adults aged 65 to 74 year. The risk is higher in men and the Black population. In 2016, 134,000 people will be diagnosed with CRC; and the disease will claim about 49,000 lives. The majority of these deaths can be prevented by applying existing medical knowledge, putting the screening tools to correct use and advising the target population to undergo screening at regular intervals.
Published recently in JAMA, the USPSTF current review comprises a series of recommendation statement, updated systematic evidence review and report of the microsimulation modeling study. In their review, the USPSTF has weighed the benefits and harms of each service and re-investigated the clinical significance and effectiveness of the screening tools for colorectal cancer, and found all to be equally effective and yielding comparable life-years gained in susceptible individuals. These screening strategies include a) stool based tests; guaiac-based fecal occult blood test (gFOBT) or fecal immunochemical test (FIT) and stool DNA (sDNA) testing, b) direct visualization tests; colonoscopy, flexible sigmoidoscopy, and computed tomography (CT) colonography, and c) direct visualization and stool-based tests; flexible sigmoidoscopy with FIT.
The USPSTF stands firm on its earlier recommendations on the frequency of these exams; FOBT or FIT (every one year), stool DNA testing (every one to three years), colonoscopy (every 10 years), flexible sigmoidoscopy and CT colonography (every five years), and flexible sigmoidoscopy + FIT (every 10 years; FIT every one year).
What’s new in USPSTF’s current recommendations is that this time around the panel expands its approach to include observational evidence about the benefits of screening tests. For this purpose, the USPSTF commissioned a systematic evidence review to address the various screening tools, their effectiveness and the harms they carry. The panel also reviewed the performance characteristics of all these screening tests for detecting polyps and cancer. In addition, the USPSTF also commissioned a report from the CISNET Colorectal Cancer Working Group to suggest optimal age for starting and stopping screening for CRC as well as the screening intervals.
The current recommendations, therefore, have been proposed after a thorough research and clinical investigation. The new points included are:
– 2016 recommendation has increased variety of new screening tests including the older ones.
– People beyond 76 years to 85 years should have screening tests depending on their previous screening history. If they have been screened in the past and their health is good then should prefer getting screened over skipping it; as screening side effects can be by passed because of their good health. If vice versa then skip screening option.
-People beyond 86 years should bypass the screening because in this age side effects of screening can become overwhelmingly prominent.
In 2008, the USPSTF lacked sufficient evidence to assess and ascertain the benefits and harms of CTC and sDNA testing. For this purpose, the panel decided to conduct a systematic review to update relevant evidence.
Developing in the colon or the rectum, colorectal cancer accounts for substantial morbidity and mortality worldwide. It most commonly affects men aged 68-69 and women aged 73, although risk is markedly lower in the latter, i.e., about 30-40%. There is convincing evidence that screening for colorectal cancer reduces disease and economic burden. However, despite the availability and abundance of several screening tools, as many as about one-third of adults evade screening. Based on their pros and cons, different screening methods hold different appeal (or aversion) for the consumers. For instance, colonoscopy is time-consuming, invasive and demands bowel preparation and sedation. Stool-based screening, although quick and noninvasive, requires handling of stool by the person which is nauseating and repelling to many.
Another endoscopic technique, i.e., flexible sigmoidoscopy along with an annual FIT, may be an attractive option for eligible candidates who are willing to go for an endoscopy but want to avoid colonoscopy (the most direct and thorough review of the inside of the digestive tract).
The USPSTF, however, does not specifically prefer one test over another given the lack of evidence from head-to-head comparative trials. The panel advises clinicians to involve patients in informed decision-making about the screening strategy that would benefit them most, provide feasibility and prompt adherence.
Experts at USPSTF believe that for successful execution of colorectal cancer screening programs, multiple implementation strategies should be devised, such as using healthcare provider and patient reminder systems including brochures, letters and videos, providing clinician assessment and feedback about screening rates, and ensuring availability and an easy access to screening.
The benefit and relevance of screening for CRC reduce after 75. Among older adults, the most important consideration for clinicians and patients is whether the patient has previously been screened. Those who have never been screened before can benefit “moderately” (B recommendation) from the screening. However, USPSTF recommends against screening in older adults who have previously been screened for and were reported negative for CRC. In older age, colonoscopy renders more harm and adverse events than benefit. It can lead to anxiety, discomfort, dehydration and can induce death. Likewise, USPSTF has found adequate evidence that screening for CRC earlier than 50 is more harmful than beneficial.
For reasons not clearly understood, men and the black race are at the highest risk for colorectal cancer. Studies reveal inequalities in screening as well as a delay in diagnosis, follow-up, and treatment accounting for the higher incidence. The USPSTF current recommendations apply to all racial/ethnic groups.
While a very influential guideline organization, the USPST is not the only panel to release health and screening recommendations. The National Comprehensive Cancer Network, American College of Physicians and the Canadian Task Force release recommendations for various medical conditions including colon cancer. What’s interesting is that recommendations from all advisory bodies complement each other and there is no dire contrast or contradiction.
Colorectal screening, in return, can prevent cancer since it detects polyps and precancerous lesions in the colon and the rectum. While most polyps are non-cancerous, excising them in time mitigates the future risk of cancer in susceptible individuals.
Despite its frequent availability, screening for colorectal cancer remains underused in the United States. Since there are no empirical data to suggest that any of the strategies provides a greater net benefit, the panel concludes the best screening test is the one that gets done. Screening in eligible population will result in the greatest reduction in colorectal cancer deaths.