Cancer; Digestive; Prevention
Skip the colon cancer screening? Not in the U.S.
November 20, 2019
Another curve ball has been pitched in the ever-shifting world of colon cancer screening recommendations. On Oct. 2, The BMJ (British Medical Journal) published clinical practice guidelines from the U.K. suggesting that perhaps colon cancer screening is unnecessary for some adults age 50 to 79 with no history or symptoms of colorectal cancer and who have low 15-year predicted risk of developing colon cancer.
These recommendations, however, were clearly acknowledged as "weak" by the authors due to their agreement with the evidence that patients' values and preferences on whether to test and what test to varies widely.
The recommendations were based on calculating a risk-score for an individual patient using an online QCancer ® questionnaire, which includes questions about age, sex, ethnicity, lifestyle, height, weight, and medical and family history. The questionnaire was developed for individuals age 50 to 79 living in the U.K. and helps determine the risk score of developing colon cancer over next 15 years. However, it might underestimate or overestimate the risk for people from countries outside the U.K.
While the recommendations raise important points regarding shared decision-making and the benefits/risks of colon cancer screenings, I’m concerned they will generate negative effects:
- Will patients feel less motivated to be screened?
- Will fewer doctors initiate screening conversations?
- What will millennials take away from this, considering they’re at increased risk?
U.S. patients should know that these recommendations should not change current screening guidelines in the U.S. – particularly in Texas, which deviates from the national downward trend of new colon cancer diagnosis. Here, new rates of colon cancer spiked from 8,500 in 1999 to 10,000 in 2016 per the Centers for Disease Control and Prevention.
These data hit too close to home for me and my colleagues at the Harold C. Simmons Comprehensive Cancer Center. For our patients’ health, colon cancer screening has never been more important.
A closer look at the colon BMJ cancer screening guidelines
An expert panel in the U.K. sought to determine the level of cancer risk at which patients age 50 to 79 might benefit most from four variations of colon cancer screening:
- A single colonoscopy (exam of the full colon)
- A single sigmoidoscopy (exam of the lower portion of the colon)
- Fecal immunochemical test (FIT) every year
- FIT every two years
They categorized patients’ risk of developing colon cancer within 15 years based on certain known risk factors: age, sex, smoking status, personal and family history, race, and body mass index. In these guidelines, the threshold risk of participants to recommend screening was determined to be 3%.
This means that individuals with less than a 3% risk of developing colon cancer in the next 15 years might be able to forgo any form of screening. Note the “might.” Conversely, individuals with a risk greater than 3% should consider one of the four screening options.
Geography matters in colon cancer risk
Here are three more reasons why patients in the U.S. should be wary of the BMJ clinical practice guidelines findings:
The data are U.K.-specific
In many Western nations, including the U.S. and the U.K., the lifetime risk of developing colon cancer hovers around 4% to 5%. However, we cannot assume that U.K. recommendations are widely applicable to patients living in the U.S.
For starters, the U.S. is radically more ethnically diverse than the U.K. In the U.S.:
- 60.4% of the population identifies as white (not Hispanic or Latino)
- 13.4% are Black or African American
- 18.3% are Hispanic or Latino
- Nearly 6% are Asian
- 1.3% are American Indian or Alaskan Native
- 0.2% are Native Hawaiian or Pacific Islander
- 2.7% identify with two or more races
In the U.K. population, 86% identify are white; 3.3% are Black; 7.5% are Asian; and 2.2% have mixed ethnic heritage. Also, 1% identify as “other ethnic groups.”
We know that African-Americans are at increased risk for colon cancer in the U.S. More than 10% of the U.S. population identifies with that ethnicity, so the screening recommendations should not be easily transferred from the U.K. to the U.S.
Major risk factors are missing
The QCancer score fails to consider several key risk factors of colorectal cancer, including exercise and diet (i.e., consumption of processed meats and convenience foods).
Maintaining a healthy diet, reducing alcohol consumption, and getting at least 30 minutes of daily exercise has been shown to reduce the risk of several types of cancer. Colorectal cancer is among the five most commonly diagnosed cancers in Texas, and these factors must be considered in risk prediction for all patients, regardless of personal or family history.
There’s no known “safe zone” for colon cancer risk
Also, 3% is a rough estimate of the “safe zone” of risk for colorectal cancer, if such a zone exists. Using a threshold to determine who should undergo screening is dependent on the scientific reliability and robustness of the questionnaire. A low score can give patients a false sense of reassurance. We’ve seen individuals with no known risk factors develop colon cancer, and we’ve removed polyps from patients with risk scores lower than 3%.
To that end, patients at 4% are still below average risk, which could lead to lax screening and the potential for missed opportunities to prevent colon cancer.
However, if we set the study’s flaws aside, the authors raise two solid points that U.S. patients and providers should note.
Navigating the dangers of colon cancer
Dr. Syed Kazmi discusses his approach to helping patients through a colon cancer diagnosis.
Two points about colon cancer to consider
Shared decision-making is key in preventing colon cancer.
The ultimate conclusion of the study is that patient-provider communication will help save lives. Simmons Comprehensive Cancer Center and UT Southwestern providers agree.
Regardless of demographic trends, individual risk factors are the primary driver of a patient’s cancer risk. All patients should discuss personal lifestyle, family history, and genetic risk factors with their doctor to determine the best approach to colon cancer screening and prevention. These conversations are best had early, before issues arise.
Furthermore, providers must get comfortable discussing screening options beyond the gold-standard colonoscopy. Any screening tool with which a patient is comfortable should be considered.
Further data are needed to determine screening benefits among certain patient groups.
Benefits of colon cancer screening among certain patient populations is well-documented, particularly when it comes to colonoscopy. Individuals at average- to above-average risk should be screened in accordance with national guidelines and doctor recommendations.
However, the benefits are not as well known for outlying populations, such as younger adults, lower-risk patients, and individuals who don’t know their risk factors. In 2017, the recommended age for colon cancer screening was lowered from 50 to 45 by the ACS.
As such, we do not yet have long-term data for whether this change has helped save more lives in patients younger than 50, a demographic with increased colon cancer diagnoses and deaths. However, some researchers predict that more than 11,000 cancer-related deaths could be averted over five years.
A few closing thoughts
Findings from the study published in The BMJ should not change current recommendations for patients in the U.S. We know that screening prevents colon cancer deaths in the 50 to 79 age demographic, and we are learning more about the benefits of screening in younger populations.
Every adult – with or without known risk factors – should visit with their doctor about colon cancer screening options. The disease is highly curable when detected early. The American Society of Colon and Rectal Surgeons estimates a 91% five-year survival rate after early-stage diagnosis.
Partner with your doctor as a health educator. Talk with your doctor and empower yourself with the knowledge to make informed decisions about your future health.