Lung cancer is the most commonly diagnosed cancer and the leading cause of cancer-related deaths globally. File
| Photo Credit: The Hindu
The insidious nature of lung cancer has made it one of the most formidable public health challenges of our time. Lung cancer was first discovered in the early 1900s in autopsies. Later advances in imaging technologies, bronchosopy, and molecular diagnostics helped diagnose it more frequently and reliably in the 20th century. As we confront this growing epidemic on August 1, observed as World Lung Cancer Day, understanding the multifaceted aspects of lung cancer — from its risk factors to the critical importance of early detection — becomes paramount.
A silently growing concern
Lung cancer is the most commonly diagnosed cancer and the leading cause of cancer-related deaths globally. As per the Indian Council of Medical Research (ICMR), the incidence of lung cancer is rising rapidly every year in India, and contributes to 10% of cancer deaths. India ranks fourth globally in terms of the absolute number of lung cancer cases, with 81,000 cases and 75,000 deaths reported in 2022. This is expected to double by 2025.
Currently, lung cancer is most often detected in Indians only at Stage 3 or 4, by which time it is no longer curable, leading to poor survival rates. Over half of the patients present with distant metastasis at diagnosis. This delay is often due to inadequate screening, resource constraints, lack of a structured referral system, and a high burden of tuberculosis (TB). Primary care physicians may not recognise lung cancer due to these factors. So, an augmented intelligence system to suggest diagnoses based on imaging or history may help.
While India has developed frameworks for different cancer screening programmes, lung cancer is yet to be included. The recent ICMR call to researchers for a rigorous evaluation of population health to set the appropriate guidelines for screening is an encouraging sign.
The increasing prevalence of lung cancer is attributed not only to smoking but also to rising levels of air pollution. Alarmingly, the number of lung cancer deaths attributed to air pollution has surged by nearly 30% since 2007. When a large number of harmful substances accumulate in the air, such as particulate matter (PM10, PM2.5, toxic metals) and gases (sulphur dioxide, nitrogen dioxide), they can cause detrimental effects on lung health, resulting in lung cancer.
Smoking tobacco (including cigarettes, beedis, cigars, and pipes) is the primary risk factor for lung cancer. Factors affecting non-smokers include exposure to second-hand smoke, occupational hazards (such as asbestos, radon and certain chemicals), air pollution, hereditary cancer syndromes, and previous chronic lung diseases. Notably, about 40% of lung cancer patients in north India are non-smokers. This underlines the need for broader awareness and preventive measures. Often, a combination of factors contributes to lung cancer among non-smokers. One of the strongest predictors can be genetic mutation. Lung cancers associated with non-smokers often affect younger individuals and show distinct genetic changes compared to smoker-related cancers.
Importance of early detection
The high rate of disability-adjusted life years due to lung cancer in India underscores the critical need for early detection, which is vital to improving lung cancer outcomes. Despite having a considerable burden of lung cancer, India does not have a systematic lung cancer screening programme because of cost and logistical constraints, and concerns regarding high false-positive rates owing to the TB burden. Although newer medications may extend life in advanced stage lung cancer, these are often expensive. It is better to prevent and detect it early.
When detected early enough, lung cancer is curable. Lung cancer can be diagnosed by imaging methods such as Chest X-ray and CT scan. Chest X-rays typically only pick up nodules or masses which are either greater than 2 cm in size or closer to the chest wall (<2.5 cm), and so may not detect early-stage lung cancer effectively. There are no blood biomarkers for lung cancer yet, although active investigation into various techniques including exhaled breath analysis is ongoing.
In recent times, the Low-Dose Computed Tomography (LDCT) has emerged as a game-changer. This scan uses five times less radiation than a conventional CT scan and has become the first choice for early lung cancer screening. It is currently being recommended in the United States and Europe for routine lung cancer screening. Since LDCT uses a much lower dose of radiation, the test can be done periodically and sometimes even annually in certain groups.
Studies have shown that LDCT can lower the mortality rate from lung cancer by 20% compared to detection with Chest X-rays and by 24% compared to no screening at all. Although LDCT uses lower radiation, the sensitivity allows detection of potentially cancerous nodules or lesions within the lungs years before the onset of symptoms, improving both the range of possible therapies and treatment.
Lung cancer is a serious problem that demands a concerted effort from individuals, healthcare providers, and policymakers to raise awareness, implement smoking cessation programmes as well as safety measures for occupational exposures. In addition, research into better diagnostic technologies and treatment modalities for the Indian population, alongside a national lung cancer screening programme, will be required to combat this silent epidemic and ensure better survival rates.
Dr. Madhu Sasidhar, Pulmonologist and Critical Care Specialist, and President and CEO, Hospitals Division, Apollo Hospitals; Dr. Sai Praveen Haranath, American Board Certified in Internal Medicine, Pulmonologist and Critical Care Specialist, Apollo Hospitals, Jubilee Hills
