Does having diverticular disease (DD) increase the risk of colon cancer (CC)? One expert would say “yes” and another would answer “no”. Much depends on the design of studies, choice of patients, what data is fed into the computer for statistical analysis, interpretation of the results and what opinions and conclusions are made.
Research can be based on the occurrence of the two separate diseases, how many people with DD have CC and how many people with CC have DD (1). Comparison can be made with the levels of CC and DD which would be expected in the general population. Information can be expanded by including different types of cancerous lesions and their position in the colon. The diagnosis of DD is not so stable. Diverticulitis but not diverticulosis was indicated to be in a long-term causal relationship with increased risk of left-sided CC (2). However, these conditions at diagnosis can change. Diverticulitis can revert to diverticulosis with few further problems, or, diverticulosis can later progress to diverticulitis or even further to serious complications. This is a basic problem in DD research. Loffeld et al. (3) found that patients with diverticula had a significantly lower incidence of CC than controls even though they were, on average, 22 years older. On the other hand, researchers in the Netherlands considered a diagnosis of diverticulosis before the age of 60 should be a “red flag” for the initiation of a cancer prevention programme because of increased risk of polyps (4).
Women, but not men, with extensive left-sided diverticulosis were more likely to have advanced neoplasia (5). This might reflect more advanced CC at diagnosis in women (6). The symptoms suggesting CC (7) – diarrhoea, constipation, rectal bleeding, abdominal pain, abdominal mass, anaemia and positive faecal occult blood test (FOB), are similar to some which can be found with DD or even gynaecological problems. Does DD mask the symptoms of CC or does a diagnosis of DD mean different symptoms are not taken seriously because they can be so variable?
Confusion and opinions about the relationship between DD and CC abound. However a majority of reports suggest that people with diverticulosis and uncomplicated diverticulitis had no more risk of CC than that of controls or the general population (8,9). Some patients in hospital with diverticulitis had a lower life-time risk of CC on follow-up (10), while other researchers found an increased risk of CC with complicated diverticulitis (8,11). It does appear that old age and complicated diverticulitis are the most likely conditions to be associated with concomitant CC.
Research has shown that neither bacteria in the colon with DD (12) nor constipation and the use of laxatives (13) have any relevance to the incidence of CC. Low levels of dietary fibre were once considered the cause of CC but this has been disproved (14,15,16). Similarly, recent research disputes the dietary fibre theory on the cause of DD (17,18,19,20). There is interest in colon inflammation with DD increasing the risk of CC as it does with inflammatory bowel disease (IBD) ie. Ulcerative colitis and Crohn’s disease (21). At a microscopic level, pre-cancerous colon structure is different from that found with DD (22) and a study results suggested DD and CC patients were separate groups (1).
DD and CC have the same epidemiology. They are both largely found in the same age group, same countries, same era and in people having the same lifestyle. This epidemiology can be applied to other cancer sites and modern day conditions collectively called “Western diseases”. In the 1970s, these were linked to levels of dietary fibre, but this theory is now in doubt (23). There are as yet fewer cases of DD and CC in Eastern countries. The predominance of DD in the right side colon in Eastern populations produces different symptoms than DD in the sigmoid colon and cancers in different colon sites (24). Nevertheless, DD was not associated with increased risk of CC after the first year of diagnosis in Taiwan (25). A parallel increase in the prevalence of DD and CC in the 20th century in Western countries has been known for some time (12). This was noted by Tsiamoulos et al. (26) who examined preliminary data from 5 years of the English National Bowel Cancer Screening Programme. They found that patients with DD were less likely to have CC than those without DD. Overall, CC was found in 3.4% of colonoscopies and DD in 28%.
Research has been directed to the question of whether DD causes or increases the risk of CC, sometimes the opposite was found. When a decrease was found by Tsiamoulos et al. (26) they introduced the concept that DD “protects” against CC which is difficult to justify. A consideration that something else may be paramount for both conditions also makes an association between DD and CC possible. These and other diseases and cancers follow a similar pattern of increase in the last century, the common associated factor is the smoking of Western cigarettes.
Studies show that cigarette smoking is the predominant cause of CC and dose/effect relationships have been demonstrated (27,28). Women with DD were at a greater risk of perforation or abscess complications if they were smokers (29). This confirmed the results of McGarr et al. (30) who also found the risk of diverticulitis increased by smoking. Other researchers have concluded that smoking increases the risk of complications of DD (31) or that development of complications proceeds more rapidly in smokers (32). Smoking was a significant risk factor for even uncomplicated diverticulosis in a Japanese study (33). That DD might be caused by smoking Western cigarettes has been proposed (34).
Gender, liver enzyme CYP 2A6, cigarette type, East v West countries, position of lesions, are all factors found to affect the relationship between smoking and CC (27,28,35,36,37,38). These same factors were relevant to observations on DD (34). This suggests that DD and CC are two unrelated diseases with a common major cause of cigarette smoking. The risk of development of DD or CC, or neither or both, probably depends on personal genetics and lifestyle factors which might affect the risk. Until the relationship between DD and CC is clarified and confirmed, stopping smoking can only be beneficial for bowel health.
© Mary Griffiths 2014
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Tags: Cancer, Cigarettes, epidemiology, Nicotine, Statistics