From the ECONOMIST
The causes of cancer
Chancing your arm
A recent paper does not show that two-thirds of cancer cases are due to bad luck
Not written by, but rather, merely posted by Louis Sheehan
WHAT could be more welcome in a season that demands fresh starts, abstinence and “detoxing” than to discover that you do not have to lift a finger to avoid cancer? A paper published last week in Science seemed to offer seasonal bingers every reason for ripping up their New Year’s resolutions. According to many reports of the research, it suggested two-thirds of human cancers are caused by nothing more than bad luck.
Clean-living folk will be pleased to hear that the scientists concerned are saying nothing of the sort. One of the paper’s authors, Cristian Tomasetti of Johns Hopkins University, was happy to clarify: “We have not showed that two-thirds of cancer cases are about bad luck. Cancer is in general a combination of bad luck, bad environment and bad inherited genes.”
Organs renew themselves from special cells called stem cells that, when they divide, produce one daughter cell which is another stem cell, and a second which goes on to generate descendants that are cells needed by the tissue in question. Dr Tomasetti and Dr Vogelstein plotted the average number of times a stem cell divides during the course of a lifetime in 31 types of tissue against the lifetime risks of cancer developing in those tissues. They found a strong correlation.
The results indicate that two-thirds of the variation in cancer risk between different tissues is caused by chance mutations associated with cell division. This is not the same as saying that two-thirds of cancer cases are caused by chance, because the results do not offer any information about the relative rates of occurrence of the cancers in question. Moreover, Dr Tomasetti and Dr Vogelstein were unable to include two of the most common cancers (breast and prostate) in their analysis, because the relevant stem-cell data are not available for these. What their study does explain is the long-known but curious phenomenon that apparently similar parts of the body suffer different rates of cancer. Stem-cell turnover means, for example, that tumours of the large intestine are commoner than those of the small one, while basal-cell carcinomas in the skin are commoner than melanomas.
None of this, though, is reason for fatalism. Copying errors during cell division are by no means the only source of cancer-causing mutations. Chemicals that damage DNA, ultraviolet light, ionising radiation and viral infections are all culprits too—and culprits that can often be avoided by thoughtful behaviour.
Overall, according to research done in Britain by Cancer Research UK, a charity, 42% of cancer cases are tied to factors within an individual’s control. These include smoking (which, through the carcinogenic chemicals it creates, causes 86% of lung cancer, 65% of oesophageal cancer, 37% of bladder cancer and 29% of pancreatic cancer), poor diet (51% of stomach cancer and 56% of head and neck cancer), overexposure to sunlight (86% of malignant melanomas) and infection with papilloma virus (almost 100% of cervical cancer). Obesity, alcohol and lack of exercise are also in the frame. The best advice, then, remains: keep slathering on the sun cream, avoid tobacco smoke, eat and drink well, exercise regularly and, if you are a young woman, have an anti-papilloma vaccination.
Not written by, but rather, merely posted by Lou Sheehan
Posted but not written by: Lou Sheehan
[ One of my intentions with this blog is to simply collect articles of interest to me for purposes of future reference. I do my best to indicate who has actually composed the articles. NONE of the articles have been written by me. Further, this ‘blog’ will contain various drafts of unknown writings just to be saved in the event they are needed by me, etc.– Louis Sheehan ]
Feel free to ignore this blog! I am intending to use it as a repository of various writings: drafts, doodles, etc. If there ARE any articles here, they are posted but not written by: Lou Sheehan