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Colorectal Cancer

Ideas about causes of bowel (colorectal) cancer

The causes of bowel (colorectal) cancer in most people are still unknown but,

“The biggest single risk factor is age. 95 in 100 bowel cancers (95%) are diagnosed in people aged 50 or over. So the risk increases as you get older.’ Cancer Research UK January 2016 

Some families have a strong history of the disease and there are a number of inherited conditions such as FAP (familial adenomatous polyposis) and HNPCC (hereditary non polyposis colorectal cancer) which increase the risk of developing the disease. There is also evidence to suggest that it may be related to the diet of those who eat a lot of red and processed meat. Other risk factors include; a personal history of polyps, ulcerative colitis and Crohn’s disease (other chronic bowel diseases causing inflammation of the bowel), smoking, alcohol, being overweight and a lack of exercise. None of these risk factors necessarily mean you will develop the disease and some people who do develop it do not have any risk factors at all.

 

There is a strong family history of bowel cancer in Stephens family due to HNPCC (Lynch syndrome).

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Age at interview: 19
Sex: Male
Age at diagnosis: 15
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We’ve a strong family history of bowel cancer. An extremely strong family history of it, something called HNPCC, hereditary nonpolyposis colorectal cancer otherwise known as Lynch syndrome but that’s down my Dad’s side.

Yeah so yeah, in my family there’s something called Lynch syndrome, which it means we’ve got a gene,

How do you spell that? L

L Y N C H  which means there’s a, a gene that runs in the family which means a certain protein isn’t made like so it’s basically a faulty mis-match repair gene which means we’re more likely to get cancer. There’s a 50:50 chance that this gene is passed on or a 50:50 chance that this gene shows in each person so unfortunately I’m showing positive for the gene, so I’m more likely to get cancer, so throughout my Dad’s side there has been people who have been more likely to get cancer statistically and they have got cancer more often. Bowel cancer is the most common… and there’s other types as well.
People interviewed in this study were often aware of the some of the risk factors currently supported by medical evidence but many could not link these to themselves. In these cases people often had their own ideas about why they had developed the disease. These ideas are summarised below and represent individual beliefs not proven facts. Nonetheless, people's own ideas about the possible causes of bowel (colorectal) cancer are important because they help us understand popular assumptions about who gets cancer and what kinds of behaviour might be linked to getting the disease. They also suggest possible avenues for future research.

Poor diet, heredity and stress were the factors most people named as likely causes of bowel cancer. Some people felt that they had become vulnerable to the disease because of their lifestyle or a combination of factors which, when added together, had triggered their illness. Others mentioned poor bowel habits and other bowel conditions as an issue while two people named environmental contamination as a possible cause of their disease. 

Most people were aware of a link between a diet high in red meat and processed meat and bowel (colorectal) cancer. One man recalled his liking for red meat, which he saw as the direct cause of his illness. But while many people shared this view of diet as a likely cause of the disease they felt that it did not apply in their case since their eating habits were fundamentally healthy. One man expressed anger at having developed cancer despite having always eaten well. Another woman strongly rejected the assumption that people who got bowel (colorectal) cancer necessarily had poor diets.

 

Recalls his former eating habits and how they may have caused him to develop cancer.

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Age at interview: 87
Sex: Male
Age at diagnosis: 62
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I have a theory, I'm not a medical person, but I have this theory that my colostomy was entirely due to my eating habits and my eating habit was that when I ate meat the meat I preferred above all others was lamb, I loved lamb, I could eat plenty of it.

And in the days of yore a lamb used to have a collar of fat around it about an inch or more of fat all the way round it and I used to eat all of that, I loved the fat of meat.

Now I think that that's the most unhealthy thing that one could eat but I couldn't stop myself till I stopped eating meat altogether, that's an actual fact.

And I believe that that contributed much towards it because that's polysaturated fat and it's one of the things that all the medical world tells you is bad for you.

I used to love salt beef sandwiches, that's another thing and I used to go to the shop and have these salt beef sandwiches. They put salt beef on about that thick and then that much of fat on for me at my request and dollops of mustard on the top as well.

Now you see I did eat more than my portion of fat, that I know and therefore I probably or may well have myself to blame for it.

 

Expresses anger at having developed bowel cancer despite having followed a healthy diet.

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Age at interview: 60
Sex: Male
Age at diagnosis: 60
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I looked at my parents they were 80, 81, why should I worry about it? Everyone keeps telling you about your parents and keep eating 5 pieces of fruit and vegetables, I live on fruit and vegetables. I don't need red meat.

If I did eat red meat it was very lean, very small amounts. I'd go for the chicken or the fish, fish preferably always, fish preferably. I'd eat the oily fish. I'd have the E tablets every morning with the 400 IUs, the antioxidants, I'd eat grapefruits till they come out of my ears, every breakfast as much as possible even now. I love grapefruits.

All the things that I've picked up on that these would keep you on the good road to a healthy lifestyle, I've done. I really, I was angry about that because I thought well I've done everything I should do, I couldn't do any more.
 

Heredity was seen as a likely cause by people who had colorectal cancer in the family. For some who were the first to have it, the link had been confirmed since pre-cancerous polyps had been found in family members who are now regularly checked for early signs of the disease. Others cited cancer in the family as a possible cause even if it was another kind of cancer or had affected distant relatives. One woman was undergoing investigation for a rare genetic syndrome associated with bowel (colorectal) cancer.

High levels of stress were identified by a number of people as the possible trigger of their illness whether the stress was related to work, relationships, or emotional trauma.

 
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Relates a discussion amongst cancer patients who all felt that their illness had been triggered...

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Age at interview: 53
Sex: Male
Age at diagnosis: 51
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And it was interesting talking to other cancer sufferers there and in the course of the two or three days, when I was chatting to people, it was evident that every single person I spoke to - and that was the majority of the people there had had some serious traumatic experience in their lives in the eighteen months to two years leading up to their cancer.

Was that true for you as well?

And it was true for me as well. In the, in the year or two leading up to my diagnosis, because I'm freelance I, I've, because work was getting less and less, I was concerned about that and earning, and concerned about maintaining my income and therefore I was taking work which is slightly outside my, my normal area and, and overcompensating and taking on too much work.

And that meant that I was working you know late evenings and weekends and it also then put a lot of pressure on me domestically. At the time my partner was putting a lot of, correctly or incorrectly, was putting a lot of emotional pressure on me because I wasn't available to be part of the family. And I'm fairly convinced that that sparked the whole thing off.

 
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She wonders whether a traumatic experience earlier in life could have played a part in her...

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Age at interview: 33
Sex: Female
Age at diagnosis: 28
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You know I don't, I've kind of thought about sort of traumatic things as well that have happened, a traumatic thing that happened in my childhood when my parents separated and somehow that might have somehow got kind of translated into bodily symptoms as well and I think that sort of plays a part maybe in when it happens.

I think it was going to happen you know but when it happens I think can be kind of emotionally affected. But I don't wanna go too far down that road because I feel like that very easily gets into like self-blame actually and, and doesn't feel particularly helpful really.

A lifestyle involving poor diet, lack of exercise, smoking and excessive drinking was generally felt to be one that could lead to a serious illness like bowel (colorectal) cancer. However many people could not understand why they had developed the disease since they had never lived in that way. People who thought their lifestyle might have contributed to their developing colorectal cancer often felt it was some combination of factors like overwork, diet, environment, and heredity. One woman who had always put other people's needs before her own felt that this could have contributed to her illness.

 

Explains his view of cancer as caused by a combination of factors.

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Age at interview: 52
Sex: Male
Age at diagnosis: 45
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Well I now find out it's hereditary and I had an uncle and auntie die of bowel cancer but that was at the age of 75 and 80. But because there is a link now between the hereditary aspect of the family I think that's one reason.

Second could be my lifestyle in terms of the type of food and the stresses of life in travelling, having to be in a different country almost on a weekly basis and the stresses of coping with airline delays, trains and whatnot had some bearing in terms of my illness. It certainly must have speeded it up in some format so I think stresses do have an effect on the cancer spreading.

What was your diet like before you became ill?

I certainly did not eat fruits as a norm, or have high fibre sort of cereals and diet so that perhaps had contributed.

But I don't think that's the only reason. I think food is an aspect but I think maybe microwave food, also ingredients in preservatives and stuff like that probably has some kind of effect. But I don't think it's just one aspect which causes cancer, it's probably a mixture of five or six aspects of lifestyle.
 

Poor or irregular bowel habits were linked to the development of cancer by some people. One woman felt that delaying bowel movements and straining had caused an injury which later became cancerous. Another related her cancer to a history of constipation since childhood as well as another bowel disease (ulcerative colitis) in the family. 

 

Believes that poor bowel habits and straining led to her developing cancer.

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Age at interview: 37
Sex: Female
Age at diagnosis: 34
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But I, I think it was a case of, looking back I used to, if I was at work, now you might find this strange, if I was at work and I needed to go to the toilet I tended not to. I tended to want to wait until I'd come home! And whether that had any, any sort of contributing facts to it I don't know. You know if its lying in your guts rotting basically, because that's what its doing isn't it? And I've done that quite a lot you know so.

And then, you know, if you're constipated and you go to the toilet and it's quite difficult to do you obviously, I hurt myself, I remember doing it, I went to the toilet and I come down and I said to my husband "Oh God I've really hurt myself" because I was badly constipated at the time and I remember thinking oh that's really sore, and for two days it was really sore.

And surprise, surprise that's where my tumour was found, so, that is probably initially what started mine off, started the ball rolling, started the repairing going on and then it just not stopping. Because that was exactly the same place where the tumour was found. I suppose when I went to the toilet and hurt, ruptured myself and I knew I'd done it. I would say that's what started mine, what's caused mine, definitely. Definitely.
 

Environmental contamination was considered by two people to be a possible cause of their disease although they acknowledged that no link had so far been proven. One man had been exposed to radiation while in the RAF while another, whose wife has also had cancer, lives beside National Grid electricity wires.

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Last reviewed August 2016.

Last updated August 2016.

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