The glossary explains some of the words used across this website and covers some key cancer and research terms, which primarily focus on lung cancer.

Early detection

The identification of cancerous or precancerous cells or areas of tissue (lesions) in an otherwise healthy (asymptomatic) population. Lung cancer screening is a form of early detection.1 See also ‘Asymptomatic’, ‘Lesion’ and ‘Organised screening’

Early diagnosis

The identification of lung cancer in people who first present to a healthcare professional with symptoms, enabling the disease to be diagnosed at an early stage of its progression. This does not refer to cancerous or precancerous cells or lesions found during screening of an  asymptomatic individual.1 See also ‘Asymptomatic’, ‘Early detection’, ‘Late presentation’ and ‘Symptoms’

Early stage lung cancer

Early stage lung cancer usually refers to stages I, II and IIIA of non-small-cell lung cancer, as well as limited-stage small-cell lung cancer.2 See also ‘Advanced lung cancer’, ‘Stage’ and ‘Surgical resection’

Efficacy and effectiveness

Efficacy is how well an intervention works in a controlled environment, such as a clinical trial, whereas effectiveness refers to how well an intervention works when implemented in the real world. Efficacy may be reported to be quite high in a trial, but during the roll-out of a screening programme in the general population, other factors may undermine its success.3

Eligibility criteria

A set of requirements that must be met for a person to be included in a study, prevention or treatment programme. These criteria ensure that selected participants are most likely to benefit from the intervention (i.e. they share similar risk factors for a disease that the intervention seeks to improve). In a lung cancer screening programme, for example, the target population may be similar in terms of age, smoking history and medical history. See also ‘Risk factor’

Emergency presentation

Emergency presentation is when lung cancer is identified in a person being admitted to an emergency health service, such as accident and emergency (A&E).4


A lung condition that damages the air sacs in the lungs and causes shortness of breath. It is mostly caused by long-term exposure to airborne irritants.5

Empiric therapy

Treatment that is given based on experience, rather than a precise diagnosis or cause of a disorder. This can be required in emergency situations due to a lack of relevant information.6


The study of the determinants, occurrence and distribution of health and disease in a given population.7 See also ‘determinant’

Epidermal growth factor receptor (EGFR)

A biomarker that, when mutated, can cause increased division in cancer cells. It can be treated with medication that blocks the biomarker action, thus slowing cancer growth. 8 See also ‘biomarker’.


  1. World Health Organization. 2017. Guide to cancer early diagnosis. Geneva: WHO

  2. Kauczor HU. 2019. Best practice and feasibility of lung cancer screening to improve lives. Diagnostic and Interventional Radiology

  3. Onder G. EMA Workshop: Ensuring safe and effective medicines for an ageing population.  Available from: [Accessed 27/04/22]

  4. British Lung Foundation. 2015. Tackling emergency presentation of lung cancer: An expert working group report and recommendations. London, UK: British Lung Foundation

  5. Centers for Disease Control and Prevention. 2022. Epidermal growth factor receptor. Available from: [Accessed 03/08/2023]

  6. Brachman PS. 1996. Chapter 9: Epidemiology. In: Baron S, ed. Medical Microbiology. 4th edn. Galveston, TX: University of Texas Medical Branch at Galveston

  7. Mayo Clinic. 2017. Emphysema. Available from: [Accessed 04/08/2023]

  8. 2020. HIV/AIDS Glossary: Empiric Therapy. Available from: [Accessed 10/08/2023]