Archive for the ‘Cancer’ Category

OTHER CAUSES OF LUNG CANCER: OCCUPATION

Monday, July 18th, 2011
Ideas about the cause of lung cancer have been so dominated by recognition of the effect of smoking for the last forty years that it is sometimes easy to forget that there may be other important causal factors and that lung cancer still occurs in non-smokers. The effect of smoking is so strong that it can be quite difficult to unravel other causes, because the presence of a few smokers in any group will so alter the statistics. However, there are undoubtedly other factors at work in the development of lung cancer and many of them can now be judged.
Once suspicion has been cast on an occupation it is a relatively straightforward, although laborious, task to examine the risk by comparing the incidence of lung cancer in workers in that occupation with that of the general population, and then doing more detailed work to look at the effect of the number of years spent in the occupation or the dose of the suspected agent to which the workers are exposed. Occupational hazard of lung cancer has been shown to be present for workers with asbestos, chrome, hydrocarbon chemicals in the old-style coke and gas industries, some chemicals used in the paint industry and for those who mine uranium (who are probably affected by radon gas from the rocks). New and effective regulations have been brought in to control these industries and the risks have been substantially reduced or eliminated. Careful monitoring remains necessary. Less certain risks have been suggested for workers with cadmium, nickel and vinyl chloride, and some fibres used in the textile industries, and precautions are now taken in industries based on these substances. Butchers appear to have a very small excess of lung cancer over the level which might be predicted. This is entirely unexplained and appears to be independent of smoking habits.
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THE IDENTIFIABLE CAUSES OF CANCER: DRUGS

Tuesday, May 24th, 2011
The question the reader will ask at this point is ‘Given all this epidemiological study, do we know the causes of cancer?’ Broadly the answer is ‘yes’ in many circumstances and for many cancers, and the opportunities for prevention that this understanding generates are there to be taken. We do not always know how the factors that have been identified by the epidemiological studies discussed in this chapter link up to what is being learned in the laboratories of the molecular biologists. This connection is being made rapidly and will be increasingly clear by the end of the century. Epidemiology has been very successful in discovering or confirming which features of our lives in the Western world can be now identified as causes of cancer.
Very few medicines have been implicated as causing cancers but there are three groups of drugs where cancer is probably an important and often unavoidable side effect. Hormones have already been mentioned. The very drugs that are used for treating cancers by chemotherapy include some (particularly those known as alkylating agents) which interfere with DNA and, hence, with some genes. Cases of leukaemia and other cancers are being discovered as a delayed after-effect of such drugs in patients who have been cured of their first cancer by such chemotherapy. Not all the drugs used in chemotherapy have this effect and modem treatments appear to have reduced the risks considerably. The third group which may put people at risk are those drugs which are used to suppress the body’s immune function. These are used for patients who have had transplants and in such patients, particularly those with kidney transplants, certain rare kinds of cancer, including those known as lymphoma, have been found. As a result of the risks, these patients have to be monitored very carefully.
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DIET AND CANCER

Friday, March 25th, 2011
The link between diet and cancer is one of the most challenging areas of current research. Some things are known with reasonable certainty, some things will be known for certain quite soon and others remain rather speculative. We believe that the link between fibre (and perhaps starch) and cancer of the large bowel is reasonably well established. The link between fat and breast cancer may not be direct and causal. Similarly, the link between fat or meat and bowel cancer may not be a direct causative one. The link between vitamin A and carotene and prevention of lung cancer and probably other cancers is still unproven, although a lot of supportive evidence exists which may be confirmed by the results of important trials in the next five years or so. Obesity is strongly associated with a number of relatively uncommon cancers. The evidence incriminating food additives and substances produced in cooking and then eaten is relatively slender except for that relating to anatoxins from fungi, which may be important in liver cancer in the developing world. Certain nitrogen compounds in rood, especially when it is smoked or preserved, are possibly implicated in stomach cancer. So what does a practical person do about diet in order to
minimize cancer risk?
These are among the most difficult recommendations we have to make because the area is so important but so uncertain. It is sensible to think about food rather than the nutrients of which it consists since this is the choice facing the individual. It seems also sensible to think about enjoyable food because only this advice is likely to be accepted. Any changes have to be moderate, easy and cheap. Any supplement to diet must be simple, cheap and accessible.
We have been impressed by some evidence and confounded by some. The science of nutrition can be rather inexact. The International Agency for Research on Cancer in Lyon has a programme to collect the dietary facts from 350,000 Europeans in the next few years. We await their results with interest and wish them good luck – they may need it.
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DIET AND CANCERThe link between diet and cancer is one of the most challenging areas of current research. Some things are known with reasonable certainty, some things will be known for certain quite soon and others remain rather speculative. We believe that the link between fibre (and perhaps starch) and cancer of the large bowel is reasonably well established. The link between fat and breast cancer may not be direct and causal. Similarly, the link between fat or meat and bowel cancer may not be a direct causative one. The link between vitamin A and carotene and prevention of lung cancer and probably other cancers is still unproven, although a lot of supportive evidence exists which may be confirmed by the results of important trials in the next five years or so. Obesity is strongly associated with a number of relatively uncommon cancers. The evidence incriminating food additives and substances produced in cooking and then eaten is relatively slender except for that relating to anatoxins from fungi, which may be important in liver cancer in the developing world. Certain nitrogen compounds in rood, especially when it is smoked or preserved, are possibly implicated in stomach cancer. So what does a practical person do about diet in order tominimize cancer risk?These are among the most difficult recommendations we have to make because the area is so important but so uncertain. It is sensible to think about food rather than the nutrients of which it consists since this is the choice facing the individual. It seems also sensible to think about enjoyable food because only this advice is likely to be accepted. Any changes have to be moderate, easy and cheap. Any supplement to diet must be simple, cheap and accessible.We have been impressed by some evidence and confounded by some. The science of nutrition can be rather inexact. The International Agency for Research on Cancer in Lyon has a programme to collect the dietary facts from 350,000 Europeans in the next few years. We await their results with interest and wish them good luck – they may need it.*65\194\4*