Lung cancer (Bronchogenic carcinoma) is the most common type of cancer worldwide and  a leading cause of cancer death for both men and women. Lung cancer occurs when the normal cells of lungs abnormally change their characteristics and grow uncontrollably.

Lung cancers may be primary or secondary depending upon its origin. Primary lung cancers arise from cells in the lungs whereas secondary lung cancers are the ones which have spread to the lungs from another site or organ.

Lung cancers are broadly classified into small-cell cancer and non-small-cell cancer. Non-small-cell cancers are more common and includes three subtypes: adenocarcinoma, squamous cell carcinoma and large cell carcinoma. Cancer spread outside lungs can occur to liver, bone, adrenal gland and brain. Brain metastasis can cause headache, vision loss or paralysis.

Risk factors

Lung cancer has known risk factors. Some of these include:

• Tobacco smoking:  Smoking  is the main risk factor for lung cancer.  About 8 in 10 cases of lung cancer are caused by tobacco smoking. Even passive smokers are at risk of  lung cancer.
• Radiation: Exposure from radiation therapy for other cancers (breast cancer, lymphoma) increases the risk of lung cancer.
• Exposure to environmental toxins such as asbestos, radon, arsenic is also associated with lung cancer risk.
• Family history: Although lung cancer usually  does not run in families,  a positive family history increases the risk.
• HIV infection increases risk of lung cancer.

When to visit the doctor

Lung cancer rarely causes any symptoms in its early stages. When symptoms appear, the cancer is usually in advanced stage. You should seek medical help when you develop symptoms.

Some of the symptoms of lung cancer include:

• Persistent cough;
• Difficulty breathing or wheezing;
• Coughing up blood (Hemoptysis);
• Chest pain; dull, sharp, stabbing in nature;
• Hoarseness of voice;
• Tiredness;
• Weight loss; and
• Clubbing of fingers.

When the cancer grows and compress other organs it may cause:

• Pain in shoulder, arm or neck;
• Bone pain;
• Droopy eyelids or blurred vision;
• Weakness in hand muscles; and
• Facial swelling.

Paraneoplastic syndromes:

When  lung cancer produces features not directly related to tumor mass or its metastases, it is known as Paraneoplastic syndromes. Examples of signs in this syndrome are muscle weakness, low sodium or high calcium level, blood clots.

Treatment options

As early lung cancer are mostly asymptomatic, a concern for lung cancer is raised when some abnormality (called lung nodule – lesion 3 cm or less) is seen in chest X-rays.  Based on the cancer risk factors, the physician will recommend the next best course of action such as periodic CT scan (if risk is low) or surgery (if risk is high). Tests performed to diagnose the disease include:

• Chest X-ray, blood tests.
• CT scan, positron emission tomography (PET) scan;
• Biopsy: a sample of the abnormal cell is taken out to assess through microscope. It could be obtained through needle through the chest wall, bronchoscopy or surgery;
• MRI,  Bone scan: To detect the spread of cancer.

Depending upon the site, type, stage of cancer and your general health, treatment options of lung cancer include:

• Surgery: In early stages of cancer surgery is done to remove  the cancer.
• Radiotherapy: If cancer has not spread to other organs, radiation is used to kill cancer cells.
• Chemotherapy: It is used in combination with surgery before or after depending upon the type of cancer. It may also be used to treat cancers that have spread to other organs.

Prevention

Avoiding smoking is the best preventive measure for lung cancer. Even quitting smoking if you smoke also reduces the risk. Screening certain high risk individuals (age 55-80 years, 30 pack year history, who currently smoke or have quit within 15 years) with a low-dose CT scan has shown to improve mortality from lung cancer.