Utility of LDCT in Lung Cancer Screening in a TB Endemic Region

Screening for lung cancer may reduce lung cancer mortality by diagnosing the disease at an early stage when it is treatable more effectively. There are several methods available for screening of lung cancer. These include sputum cytology, chest radiography, computed tomography (CT) of the chest, and positron emission tomography (PET). However, sputum cytology and chest radiography have been found to be ineffective as screening tests for lung cancer as there is no reduction in lung cancer mortality. The use of CT or PET for lung cancer screening may be associated with unacceptable levels of radiation exposure and enormous cost.

Low-dose computed tomography (LDCT) of the chest is a special type of CT, which uses relatively low radiation exposure to create a low-resolution image of the entire thorax. The radiation exposure associated with LDCT is 5-6 times less than that of a conventional CT scan of the thorax. LDCT screening has been to shown to result in a 20% reduction in lung cancer-specific mortality. Several national and international guidelines recommend this strategy for lung cancer screening.

Despite these guidelines and recommendations by several organizations, lung cancer screening has not been established in several developing countries, where a controversy arises due to high rates of granulomatous diseases like tuberculosis. Emerging evidence indicates that false positive results with LDCT in developing countries may not be unacceptably high as previously believed.

In this study, the investigators intend to assess the utility of lung cancer screening using low-dose computed tomography (LDCT) in India, a country with high prevalence of tuberculosis.

Inclusion criteria

• Individuals aged 55-74 years with at least 30 pack-year history of smoking (or smoking index ≥600) who are current smokers or quit within the last 15 years OR
• Individuals aged 50-74 years with at least 20 pack-year history of smoking (or smoking index ≥400) who are current or former smokers with COPD or family history of lung cancer in any first-degree relative

Exclusion criteria

• Symptomatic structural lung disease other than COPD (e.g. bronchiectasis, chronic pulmonary aspergillosis, pulmonary fibrosis)
• Severe comorbid condition which is likely to limit the survival of the patient in the opinion of the investigator (e.g. advanced lung disease, cardiovascular disease, chronic kidney disease, chronic liver disease)
• Presence of symptoms which lead to a suspicion of lung cancer (e.g. hemoptysis or unexplained weight loss [>5 kg] within the last 6 months)
• Conditions which may interfere interpretation of CT (e.g. metallic implants on chest wall, cardiac pacemakers)
• Treatment for any other cancer in the last 5 years
• Pulmonary infection (for which treatment with antimicrobials is indicated) which is active at present or was recent (within the last 3 months)
• Patients who have underwent CT chest within the last 18 months
• Negative consent