Lung cancer

What it is

Lung cancer is cancer that starts in the lungs, and it is the leading cause of cancer death worldwide. It begins when cells in the lung or airways develop DNA changes that let them grow out of control, form a tumour, and sometimes spread to lymph nodes, brain, bone, liver, or other organs. The two main categories are non-small cell lung cancer, which accounts for about 85% of cases, and small cell lung cancer, which is less common but usually grows and spreads faster.

Lung cancer is also called lung carcinoma or bronchogenic carcinoma. Smoking is the biggest risk factor, but lung cancer can also occur in people who have never smoked. Other risks include secondhand smoke, radon, asbestos and other occupational exposures, air pollution, prior chest radiation, and family history. In India, tobacco exposure remains a major driver, including smoked forms such as cigarettes and bidis, and many patients are diagnosed at a later stage because early disease may cause no symptoms.

A simple way to classify lung cancer is:

Main type	Common subtypes	Typical behavior
Non-small cell lung cancer (NSCLC)	Adenocarcinoma, squamous cell carcinoma, large cell carcinoma	Usually grows more slowly than small cell lung cancer
Small cell lung cancer (SCLC)	Small cell carcinoma	Often linked to smoking; tends to spread early

How it works

Lung cancer develops through a series of genetic and molecular changes. In healthy tissue, lung cells divide in a controlled way and die when they are damaged or old. In cancer, mutations and other DNA changes switch on growth signals or switch off tumour-suppressor pathways. This allows abnormal cells to survive, multiply, invade nearby tissue, and eventually metastasise.

Different lung cancers often have different biology. NSCLC may carry targetable alterations such as EGFR, ALK, ROS1, BRAF, MET, RET, NTRK, KRAS, or others, depending on the subtype and the person. These biomarkers matter because they can guide treatment. SCLC is usually driven by a different pattern of molecular changes and is less often treated with targeted drugs.

The location of the tumour also affects symptoms. A cancer near a large airway may cause cough, wheeze, or coughing up blood. A tumour near the outer lung may cause chest pain. If the cancer spreads, symptoms may come from the involved organ, such as headache or seizures with brain metastases, or bone pain with bone metastases.

Diagnosis / how it's measured

Lung cancer is diagnosed with a combination of imaging, tissue sampling, and staging tests. A chest X-ray may first suggest a problem, but CT scan is more informative. If cancer is suspected, doctors usually need a biopsy to confirm the diagnosis and determine the exact type.

Common diagnostic steps include:

1. Imaging: Chest CT is standard. PET-CT may help assess spread. Brain MRI is often used in selected patients, especially when advanced disease is suspected.
2. Biopsy: Tissue may be obtained by bronchoscopy, CT-guided needle biopsy, endobronchial ultrasound-guided sampling, or surgery.
3. Pathology: The lab identifies whether the tumour is NSCLC or SCLC and may define the subtype.
4. Biomarker testing: For many patients with NSCLC, especially advanced non-squamous disease, tumour tissue or blood may be tested for actionable mutations and for PD-L1 expression.
5. Staging: Staging describes how far the cancer has spread and helps guide treatment.

Symptoms that can lead to evaluation include a new cough that does not go away, coughing up blood, chest pain, shortness of breath, hoarseness, unexplained weight loss, recurrent chest infections, bone pain, or new neurologic symptoms. Early lung cancer may cause no symptoms at all.

For people at high risk, screening can detect some lung cancers earlier. International guidelines support low-dose CT screening for selected adults with a heavy smoking history. Screening is not the same as diagnosis, and it is meant for people without symptoms. In India, access and implementation vary, so screening decisions should be individualised with a clinician.

Evidence and uses

Treatment depends on the cancer type, stage, molecular profile, symptoms, and the person's overall health. The main treatment options are surgery, radiation therapy, chemotherapy, targeted therapy, immunotherapy, and palliative care. Many patients receive a combination.

For early-stage NSCLC, surgery offers the best chance of cure when the tumour can be removed safely. Depending on the case, this may be a lobectomy or a smaller resection. Radiation may be used when surgery is not possible. Some patients also need chemotherapy, immunotherapy, or targeted therapy before or after surgery.

For locally advanced NSCLC, treatment often includes chemotherapy and radiation, sometimes followed by immunotherapy in selected patients. For metastatic NSCLC, treatment is guided by biomarkers. If a targetable mutation is present, an oral targeted drug may work better than standard chemotherapy. If no targetable driver is found, immunotherapy alone or with chemotherapy may be used depending on PD-L1 and other factors.

For SCLC, chemotherapy and immunotherapy are commonly used, often with radiation depending on stage. SCLC can respond well at first, but relapse is common.

Supportive and palliative care are important at every stage, not only at the end of life. Good symptom control can improve quality of life and may help patients tolerate cancer treatment better. This can include treatment for breathlessness, pain, cough, fatigue, anxiety, nutrition problems, and complications such as pleural effusion.

When to see a clinician

See a clinician promptly if you have a cough lasting more than a few weeks, cough up blood even once, develop unexplained shortness of breath, chest pain, hoarseness, repeated chest infections, or lose weight without trying. Urgent assessment is especially important if symptoms are new or worsening in a current or former smoker.

Seek urgent care for severe breathlessness, large-volume bleeding with cough, confusion, seizures, or sudden weakness. These can signal complications that need immediate treatment.

If you smoke or used to smoke heavily, ask whether you might qualify for low-dose CT screening. Quitting smoking still helps, even after many years, because it lowers future lung cancer risk and improves outcomes after diagnosis.

Limitations and open questions

Lung cancer is not one disease. Outcomes vary widely by stage, subtype, and molecular profile, so broad statements about prognosis can be misleading. Some patients with early-stage disease are cured, while advanced disease is often treatable for longer periods than in the past but may not be curable.

Research is moving quickly in biomarker testing, targeted drugs, immunotherapy combinations, and earlier detection. Even so, not every patient benefits from newer treatments, resistance can develop, and access may differ across hospitals and regions, including in India. Evidence for screening and treatment is strongest when care is guided by pathology, stage, and molecular testing rather than symptoms alone.

There is no proven Ayurvedic or herbal treatment that can replace standard lung cancer care. Some traditional remedies may help with general wellbeing or symptom relief for some people, but evidence in humans is limited, mixed, or not specific to lung cancer. Patients should discuss any herb, supplement, or alternative therapy with their oncology team because interactions and delays in effective treatment can cause harm.