Colorectal cancer screening for patients with a family history of colorectal cancer or adenomas

Wilkinson et al. (CFP, November 2019) are to be commended for presenting the recent Canadian/American guidelines for colorectal cancer (CRC) screening for patients with a family history of colorectal neoplasia (Leddin et al, Gastroenterology, 2018).

Unfortunately, they do not present evidence, or at least references, supporting their “conclusion” that “lifestyle advice already given to patients for weight, blood pressure and heart disease management will reduce the risk of CRC if implemented”. There is little if any evidence that treatment of blood pressure or heart disease will influence the risks for developing colorectal cancer (the authors appropriately omit discussing the complex effect of aspirin on CRC incidence and mortality). While obesity is associated with increased colorectal cancer risk, there is little if any published evidence that weight reduction will reduce that risk, (and copious evidence supporting the ineffectiveness of the medical profession in achieving longterm weight-loss).

The main concern is the recommendation for screening starting “at age 40-50 or 10 years younger than the age of the first-degree relative at diagnosis”. Previous guidelines used to say “whichever comes first” - this clause has obviously been deliberately omitted. Providing the option for the primary care practitioner to decide between ages 40 and 50, or 10 years younger than the age of the relative, makes this guideline potentially difficult to implement. The interval (5-10 years) is similarly vague.

A second concern is the recommendation to utilize FIT (fecal immunochemical testing) as an alternative. While the authors explain some of the rationale for FIT, I am concerned that they suggest that the fecal immunochemical test is generally better accepted by patients (which is true), but a positive FIT requires colonoscopy. They suggest that it may be more available in rural areas, but I am not sure that rural Canadians deserve potentially inferior CRC screening. The authors recommend that the FIT might be more feasible for patients with multiple medical comorbidities, but (because a positive FIT requires colonoscopy), I would caution primary care practitioners against organizing FIT in patients with multiple medical comorbidities and a family history of colorectal cancer, (which is the topic of this paper), especially since the authors correctly admit that FIT has not been tested in higher risk patients with a family history of CRC.

Disclosure: I am a gastroenterologist, who does colonoscopy, in a hospital setting, but not in an ambulatory clinic. I am strongly supportive of the FIT program for average risk screening.