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Knowing a disease’s natural history helps make decisions

It is vital to be aware of a disease’s natural outcome in order to make pertinent treatment decisions, in particular to define the aim of treatment.

Both patients and healthcare professionals need to be aware of a disease’s natural history, i.e. its outcome without medical intervention.

Prostate cancer, for example, is one of the most common cancers in men aged over 50. When patients with a localised prostate cancer which was untreated from the start were monitored over a period of 20 years, the findings showed that in around 60% of them the cancer did not get worse and had little impact on their life expectancy. Only a minority of deaths were linked to prostate cancer, and these were in the small number of patients with an undifferentiated-type cancer (around 5% of localised cancers). Similarly, mammography screening for breast cancer has not been shown to reduce mortality, whereas it can cause physical and psychological adverse effects.

The same applies to a benign infection such as uncomplicated urinary infection in young women, which eventually clears up spontaneously and only rarely leads to complications.

Knowing the natural outcome of illnesses means that patients and healthcare professionals can make a free, informed choice as to the best treatment option and the appropriate behaviour, based on the awareness that systematic treatment does not necessarily improve life expectancy or quality, especially when medical intervention has adverse effects.

©Prescrire 2008

Source: "Histoire naturelle" Rev Prescrire 2008 ; 28 (296): 401.