Your Risk for Colon Cancer

50,630:
this is the projected number of colorectal cancer (CRC) -related deaths for 2018 in the U.S. Only lung cancer-related deaths exceed this number.

How does CRC start? It begins as a benign growth – polyp / adenoma. The most frequent initiating mutation is in the APC gene, and less frequently - in the proteins beta-Catenin, Axin, and KRAS. Given sufficient time - approximately 10 years - and the right mutations (i.e., mutations that allow self-sufficiency in growth signaling, resistance to apoptosis, potential for unlimited growth, etc), malignancy develops.

Once the malignancy has established itself, cure is unlikely. Therefore, the best approach is this of prevention; the words of Ben Franklin are still valid:

… an ounce of prevention is worth a pound of cure…

The power of prevention is best understood when we look at the leading causes of death for the past 100 years. NEJM has published a great review that summarizes the ten leading causes of death in the U.S. since 1900. If we compare 1900 to 2010, we will find that the three biggest killers in 1900 were the gastrointestinal infections, pneumonia, and TB.  However, these were no longer the biggest killers in 2010 (the last year in the NEJM review).

How did we achieve that? Sanitation, better nutrition, vaccination, and antibiotics. Except for the antibiotics, the rest of the measures/changes were preventive.

Since the 1960s we have also seen reduction in heart disease-associated deaths due to prevention with medications that control blood pressure and cholesterol.

The lesson is that any significant victory against a disease is achieved through preventive strategies. There is no doubt in my mind that we will claim a significant victory against cancer, when we dedicate more financial resources to prevention. Cervical cancer is the perfect example how prevention through screening and vaccines reduces cancer deaths.

However, can we prevent colorectal cancer (CRC)? Obviously, screening is one answer; although quite invasive, colonoscopy detects early lesions. What else can we do? The American Institute for Cancer Research (AICR) has estimated that approximately 45% of all CRC cases can be prevented mostly through lifestyle changes. The institute has come up with five simple recommendations … that may slash the number of CRC cases by half! The problem with all these recommendations is that they require self-discipline.

The increased intake of fiber is one of the recommendations. Although the topic has been controversial for the past few decades, in 2003, two massive prospective epidemiological studies (one from Europe and one from the U.S.) concluded that fiber does protect against colon cancer: increasing the intake of fiber from 15 g to 35 g results in 40% decrease in risk.

Here is the summary of one of the studies:

Lancet 2003 May 3;361(9368):1496-501.Bingham SA:  
We prospectively examined the association between dietary fibre intake and incidence of colorectal cancer in 519978 individuals aged 25-70 years in ten European countries. Participants completed a dietary questionnaire in 1992-98 and were followed up for cancer incidence. …data for 1065 reported cases of colorectal cancer were included in the analysis. Dietary fibre in foods was inversely related to incidence of large bowel cancer (adjusted relative risk 0.75 [95% CI 0.59-0.95] for the highest versus lowest quintile of intake), the protective effect being greatest for the left side of the colon, and least for the rectum. After calibration with more detailed dietary data, the adjusted relative risk for the highest versus lowest quintile of fibre from food intake was 0.58 (0.41-0.85). No food source of fibre was significantly more protective than others, and non-food supplement sources of fibre were not investigated. In populations with low average intake of dietary fibre, an approximate doubling of total fibre intake from foods could reduce the risk of colorectal cancer by 40%.

In 2011, AICR and the continuous update project announced that the protective effect of fiber against colon cancer is upgraded from probable to convincing.