Skip the colon cancer screening? Not in the U.S.

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.