Researchers reviewed eight studies involving more than 1,500 patients over 30 years to assess the accuracy of doctors' survival predictions.
They found that doctors' survival predictions are frequently inaccurate and usually over-optimistic, being out by more than a month a quarter of the time. However, their predictions become more accurate closer to death.
Despite their tendency to be over-optimistic, predictions of up to six months are nevertheless reliable, being closely correlated with actual survival. This suggests that doctors are able to sense when things are starting to go wrong, say the authors.
Doctors need to be aware of their tendency to over-estimate survival as it may affect the patients' prospects for achieving a good death, they conclude.