Lung cancer is a major public health concern worldwide, accounting for a significant proportion of cancer-related deaths. In India, lung cancer is the 4th most common cancer in terms of incidence and number of deaths. Approximately 80,000 new cases of lung cancer are diagnosed, with a similar number of lung cancer-related deaths occurring every year.

Cigarette smoking is the most common cause of lung cancer. Other risk factors include exposure to secondhand tobacco smoke, exposure to radiation or toxic materials such as asbestos and arsenic, having close family members who have had cancer, older age, and having other types of lung problems such as chronic obstructive pulmonary disease (COPD) or pulmonary fibrosis.

Clinical Presentation

When lung cancers are small in size and in the early stages, a person is usually asymptomatic. However, as the tumor increases in size and the disease advances, one or more symptoms may develop. Some common symptoms of lung cancer include:

• Persistent cough: A new, persistent, or worsening cough that may sometimes be blood-tinged.
• Chest pain.
• Shortness of breath: This may occur with exertion and, in advanced stages, even at rest.
• Wheezing: A whistling sound during breathing.
• Hoarseness of voice.
• Headache with swelling: Swelling of the face, arms, and neck may occur in some cases.
• Symptoms associated with tumors in the upper part of the lungs: These may include arm, shoulder, and neck pain, weakening of the hand muscles, droopy eyelid, and blurred vision.
• Unexplained weight loss.
• Tiredness or fatigue.
• Bone pain: Pain may be more severe at night.

Diagnosis of Lung Cancer

When an oncologist suspects lung cancer based on the patient's medical history and physical examination, several investigations may be advised. These may include a contrast-enhanced CT (CECT) scan or PET-CT scan to assess the size and spread of the tumor, along with a biopsy to confirm the diagnosis and determine the subtype of cancer.

A biopsy may be performed through bronchoscopy, which involves inserting a flexible tube with a camera and small instruments through the mouth or nose and into the windpipe. Other approaches include a CT-guided fine-needle biopsy or removal of fluid collected in the chest, if present.

In some cases, surgical procedures may be required when biopsies obtained through conventional methods are inconclusive. These procedures may include:

• Mediastinoscopy: Used to obtain a biopsy from lymph nodes in the center of the chest.
• Video-assisted thoracoscopic surgery (VATS): A less invasive approach used to obtain lung tissue for diagnosis.
• Thoracotomy: A larger surgical procedure that may be used to remove larger portions of lung tissue or tumors.

The tissue obtained during biopsy is sent to an experienced oncopathologist for confirmation of the cancer, identification of its subtype, such as non-small cell lung cancer or small cell lung cancer, and molecular characterization.

With the advancement of next-generation sequencing (NGS) methods, important biomarkers may be tested to help determine which targeted therapy or immunotherapy may be appropriate for the patient. These biomarkers can include programmed cell death ligand 1 (PD-L1) expression, epidermal growth factor receptor (EGFR) mutations, anaplastic lymphoma kinase (ALK) translocations, and c-ROS oncogene 1 (ROS1) translocations, among others.

Management of Lung Cancer

The management of lung cancer depends on several factors, including the stage, histology, and molecular profile of the tumor. Treatment options may include:

1. Surgery

Surgery is generally considered for early-stage, localized cancers and may involve removal of the tumor along with nearby lymph nodes.

2. Radiation Therapy

Radiation therapy uses high-energy X-rays or other forms of radiation, such as proton therapy, to destroy cancer cells. It may be used after surgery or for symptom relief in stage 4 cancers, including cases involving painful bone metastases.

3. Chemotherapy

Chemotherapy uses medicines that kill or control cancer cells. It may be given before surgery to shrink the cancer and make it easier to remove. Depending on the stage, chemotherapy may also be given after surgery to reduce the risk of cancer growth or spread. In stage 4 cancers where surgery and radiation are not considered appropriate, chemotherapy may be used as part of systemic treatment.

4. Targeted Therapy

Targeted medicines are designed to act on specific molecular changes in cancer cells. For example, patients with certain EGFR-positive cancers may receive targeted medicines such as afatinib or osimertinib. Patients with certain ALK translocations may be treated with medicines such as crizotinib, ceritinib, or alectinib. Crizotinib may also be used for certain ROS1-positive cancers.

5. Immunotherapy

Immunotherapy helps the immune system recognize and attack cancer cells. Its use depends on the type and stage of lung cancer and relevant molecular or biomarker findings.

Choosing the Right Treatment

Choosing the appropriate therapy is an important part of lung cancer management. However, there is no single treatment that is suitable for every patient. Treatment decisions depend on factors such as the stage of disease, histological subtype, molecular characteristics, overall health, and other individual considerations.

Precision medicine is an important approach in modern lung cancer care, allowing evidence-based and personalized treatment strategies to be considered for individual patients.

Follow-Up Care

After completion of therapy for early-stage lung cancer, long-term follow-up is required. Follow-up care helps monitor for recurrence, identify second primary cancers, and assess for late toxicities associated with chemotherapy and radiation therapy.

Patients should remain alert to symptoms that could indicate recurrence or progression of cancer. These may include:

• Headaches
• Convulsions or seizures
• Shortness of breath
• Chronic or persistent cough
• Bone pain
• Abdominal pain or distension
• Jaundice
• Unexplained weight loss despite adequate food intake

Any new, persistent, or unexplained symptoms should be discussed with the treating healthcare team.

Lung Cancer Screening and Prevention

Cigarette smoking is responsible for a large proportion of lung cancer cases. Therefore, one of the most effective ways to reduce the risk of lung cancer is to avoid smoking. People who do not smoke should not start, while those who smoke should consider quitting.

Smoking cessation can substantially reduce the risk of developing lung cancer over time. The risk continues to decrease after quitting, although it may take many years to approach the risk level of someone who has never smoked.

Yearly screening with a low-dose CT (LDCT) scan is recommended for certain people at higher risk of lung cancer based on their age and smoking history. Screening eligibility should be determined according to current clinical guidelines and an individual's risk factors.

The National Lung Screening Trial (NLST) in the United States found that screening with low-dose CT reduced lung cancer mortality compared with chest X-ray screening among people at high risk. Early detection can provide an opportunity for potentially curative treatment in appropriate patients, particularly when lung cancer is diagnosed at an early stage.