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Hearing is Believing?

"What I tell you three times is true," proclaimed the Bellman in the Hunting of the Snark, and many people seem to believe that if something is repeated often, then it must be right.

One statement, asserted confidently and repeatedly recently, has been that cancers are on the increase, and that no-one survives chemotherapy. Whatever your stance in the debate on alternative treatment which engendered these remarks, basic facts demonstrate that neither statement is correct. Yet they continue to be repeated and treated as true.

It's a relatively simple matter to find solid figures to refute these claims, as this sort of information is tracked by a variety of organisations around the world. In the US, for example, there's been a 16% decline in deaths from cancer (excluding lung cancer) since the 1950s, and even lung cancer has shown a small but significant drop recently. Part of the reason for the decline is that we are getting better at detecting and treating many forms of cancer, particularly in their early stages.

Cancer specialists typically talk about a five-year survival rate, monitoring those living five years after diagnosis whether they are disease-free, in remission or under treatment. This rate is adjusted to provide a relative rate, so that it can be compared to normal life expectancy which has its own risks, such as death from accidents, old age or heart disease. One alternative treatment proponent stated that chemotherapy doesn't cure cancer, but merely delays the death beyond the five-year margin in some sort of conspiracy by the "cancer industry" to hide those deaths.

While the five-year rate has its uses in providing cross-cancer comparisons, there are numerous long-term studies with readily available figures. One, which tracked people undergoing intensive treatment for Hodgkin's disease, found a one-year survival rate of 92%, a five-year rate of 81%, a 72% survival rate at 10 years and a 62% at 15 years post-chemotherapy. Those aren't bad odds, given the alternative, so to speak.

It can be hard to challenge someone who asserts that what they are saying is correct, but that's the essence of good citizenship as well as of good science....

Vicki Hyde is the editor of New Zealand Science Monthly.