Table 1

Developing an intervention: defining and understanding the problem

Key TasksCommentary
1. Define and quantify the problemLung cancer is usually advanced and incurable at diagnosis. If more patients had earlier stage disease at diagnosis, more could be treated curatively and survival times from palliative treatment could be lengthened. A systematic review of factors that increase patient delay in lung cancer found non-recognition of symptom seriousness, older age, and lower education and social class were associated with later presentation, which is the essential underlying problem. A previous study found that the median time between onset of symptoms and consultation was 99 days (14 weeks) (IQR 31–381).
2. Identify and quantify the population most affected, most at risk, or most likely to benefit from the interventionThe most important risk factors for lung cancer are pack years of smoking and increasing age. Trials of lung cancer screening have generally defined ‘low risk’ as a history of less than 20 pack years and ‘high risk’ as a history of 20 pack years or more. Among ex-smokers, increased risk persists after smoking cessation for at least 10 years. Between 1999 and 2003 in Scotland, 92% of males and females diagnosed with lung cancer were aged ≥55 years. Therefore, a Scottish population aged ≥55 years, with a history of 20 pack years or more, who are current smokers or gave up within the past 10 years, can be regarded as at high risk of developing lung cancer and as an appropriate target group for this intervention. It is estimate that approximately 5% of the population of Northeast Scotland fall into this high risk group.
3. Understand the pathways by which the problem is caused and sustainedIn another study by the same authors independently predictive factors of delayed presentation were:

  • Symptoms — those whose first symptoms were cough, shortness of breath, change in longstanding cough, haemoptysis, or loss of appetite, consulted sooner than those without. Those with a change in a longstanding cough waited longer than the median total delay.

  • Past medical history — those with COPD waited longer, but those with renal failure or a previous chest infection went sooner. Those with known cardiovascular disease went sooner, but those with previous gastrointestinal disease waited longer.

  • Social — increasing time between first symptom and consultation was associated with living alone. There was a non-significant trend for those without paid work to take longer (P = 0.09).

  • Behavioural — Increasing pack years of smoking was associated with longer delay

  • Health service factors — frequent consulters consulted sooner. There was a non-significant trend for those who knew their GP well socially to take longer (P = 0.08).

  • Knowledge — those reporting more knowledge of lung cancer took longer to consult.


Several psychological and social models can be used to conceptualise the pathways that lead from symptom onset to consultation in lung cancer. These include the Zola’s Triggers; Social Cognitive Theory; Common Sense Self-Regulation Model; Illness Prototypes; Illness Action Model; Network Episode Model. Consequently the finding is interpreted in light of these. These models are about observation rather than action so the study moved towards the Theory of Planned Behaviour and Implementation Intentions. This helped the study to clarify the pathways by which the problem was caused and sustained, and hence the targets for action.
4. Explore whether these pathways may be amenable to change and, if so, at which pointsSymptom appraisal: could be impacted by raising salience of lung cancer as a possible cause for symptoms
Attitudes to consultation: could be enhanced by emphasising the potential benefits of early consultation and the acceptability of doing so
Subjective norm: involving others in the intervention, for example spouses, friends, may heighten subjective norm (social pressure to perform an action), influencing intention to act. Involving others may also influence symptom appraisal and attitudes to consultation.
Perceived behavioural control or self-efficacy: could be impacted by establishing that getting an appointment in primary care is ‘easy’ partly by training in phrases to use to get a consultation.
Implementation intentions: could be enhanced by clear action plans supported by the knowledge that their own practice was participating in and supportive of the study and consultation was sanctioned. Additionally, reception staff were asked to provide access to these patients reporting appropriate symptoms.
5. Quantify the potential for improvementThe study’s previous research suggests that 75% of people with lung cancer have the potential to consult sooner. They thus estimate that the intervention has the potential to cause this proportion of people with lung cancer to initially consult sooner