One of the first questions that a patient asks upon receiving a diagnosis of cancer is: what caused my cancer and could I have done anything to stop it? The simple answer in most cases is that we don't know. It implies that we know the cause of cancer, wherever it arises and, whilst we have identified certain risk factors for most, it's often several factors acting in unison, many of which we have yet to identify. This would explain why some patients who perceive that they've done all the right things, are still unlucky enough to be affected.
A common theme is changes to the genes that control the behaviour of the cells that make up our body, in particular programmed cell death - in essence the cell doesn't die and isn't replaced with a new one when it should do. Genes can be damaged in a number of ways: such as cigarette smoke and UV radiation, hence the risk of getting lung cancer and melanoma respectively. Others are a little more subtle such as diet and excessive alcohol intake, but there is increasing evidence that these and other lifestyle factors are playing an ever increasing role in the cause of major cancers such as breast and bowel.
Doctors certainly recognise that these cancers are more more common in high-income countries such as the USA, UK and Australia. High-income tends to go hand-in-hand with obesity, lack of exercise and excessive alcohol intake; however, whilst there is an association it doesn't necessarily explain a cause and effect. Nevertheless it suggests that cancer-causing chemicals, otherwise known as carcinogens, are to be found in higher concentrations in foods that are high in fat, for example.
Scientists are constantly striving to identify these chemicals and the precise nature of the gene damage that they cause, and it is likely to be decades rather that years before we have substantial answers. In the meantime though we would all be well advised to reduce our individual risk as best we can. So this means not only giving up smoking and staying out of the sun but also eating healthily, taking regular exercise and drinking less alcohol. Believe it or not life can still be a lot of fun having done all of this, especially if it means not getting cancer!