It is now well established that the United Kingdom has poorer cancer outcomes compared with much of Western Europe (Berrino et al, 2007
). The consensus is that one of the major reasons for this is more advanced stage at diagnosis. One solution to this problem is to reduce diagnostic delays on the premise that this will lead to earlier stage diagnosis and improved outcomes. This paper will contextualise the diagnostic process and critically appraise the evidence that examines the association between delays and cancer outcomes.
Tumours typically grow progressively, with the ‘doubling time' (a recognised period of time that it takes for the tumour to double in size) being a key measure of speed of tumour growth. This varies between types of tumour but even within tumour types, there can be significant variation, leading to unpredictable differences in patterns of symptoms and symptom complexes, speed of onset and progression of symptoms (Ford and Mitchell, 1999
Around 90% of cancers will present symptomatically (Hamilton, 2008
). There is a prevailing hypothesis within primary care that most patients have symptoms that are either self-limiting or represent chronic and benign disease until proven otherwise. In cancer this may be counter-productive, and creates a dilemma for primary care. On one hand, health professionals, whether they are general practitioners (GPs) or practice nurses (who do much chronic disease management and monitoring), have to be vigilant for ‘alarm symptoms' (Jones et al, 2007
) that are rarely caused by cancer. On the other hand, they are aware that most potential cancer symptoms are almost exactly the same as those of common chronic or minor diseases. Furthermore, there may be difficulty in assessing the positive predictive value of symptoms and what they really mean, and placing these within the current National Institute for Health and Clinical Excellence (NICE) urgent suspected referral guidelines (NICE, 2005
). These have been shown to have a low predictive value in determining cancer (Allgar et al, 2006
) and may prioritise patients who stand to gain least from urgent referral in terms of survival (Neal et al, 2007
Hence, the vexed question of what can be done to reduce delays is of paramount importance. The need to determine the exact relationship between symptom duration and clinical outcomes (usually survival, but sometimes stage as a proxy for survival) is essential. Delays may occur at any stage of the diagnostic cancer journey. There may be ‘patient delays' where the patient may not recognise suspicious cancer symptoms or act on them. There may also be ‘primary care delays', where there are unnecessary delays in the recognition, onward referral of or investigation for suspicious symptoms. After this, there may be ‘system delays' where there may be a considerable wait for either non-urgent referrals (as is the case for the majority of cancer patients) or GP-initiated diagnostic investigations. Finally, ‘secondary care delays' are where there may be prolonged time spent in secondary care before diagnosis, sometimes due to patients being investigated in the ‘wrong' specialty.
While a small element of delay is inherently inevitable in all cancer diagnostic pathways, it is likely that in a significant percentage of patients there is considerable preventable delay. The important question is how much of this preventable delay leads to poorer outcomes. If people could be diagnosed earlier, what difference would this make to survival and other clinical outcomes?