Lung Cancer: Most Common Cancer of Modern Time

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Lung Cancer, the most common cancer in the world in modern time and the most common cause of cancer death, both in male and female.

Although the rates are decreasing in men, still increasing overall, which indicates the incidence is increasing among women. The ratio of men to women is nearly 1.2:1. 

Lung cancer commonly develops between 40 to 70 years of age with a peak incidence in the age of 50 to 60 years. Only a very few cases, it may appear before the age of 40 years. However, about 80% of the patients die within 1 year of diagnosis.

Causes of Lung Cancer:

87-90% of lung cancer is related to cigarette smoking, including both active and passive smokers. although the chance of being affected with lung cancer depends on the amount of daily smoking, the tendency to inhale and the duration of smoking.
Cessation of smoking for 10 years can reduce the risk but never to the control level. 

Other important causes are-
  • High dose ionizing radiation.
  • Exposure to Randon (Rn), Asbestos, Polycyclic aromatic hydrocarbons.
  • Occupational exposure to Arsenic(As), Chromium (Cr), Nickel (Ni), Uranium (Ur), Petroleum products and oils.
The incidence is slightly higher in urban areas, which may reflect the difference in atmospheric pollution i.e. air pollution.

Genetic predisposition and some pre-existing lung diseases like lung fibrosis can increase the risk of lung cancer. 

Types of Lung Cancer:

Lung cancers are largely classified into-

      • Non-Small Cell Lung Cancer (NSCLC)
      • Small Cell Lung Cancer (SCLC)

Non-small Cell Lung Cancers are further subdivided into-

          1. Adenocarcinoma
          2. Squamous Cell Carcinoma
          3. Large Cell Carcinoma
Among all types of lung cancer, Adenocarcinoma is more common in women. Smoking is thought to be the possible cause, although the basis of this is unclear. But Squamous cell cancer is more common in men and closely related to smoking. 

Staging of Lung Cancer:

To diagnose the severity of the disease and for treatment purpose, staging of lung cancer is done. The staging is as follows:

Stages of NSCLC:

Stage I: Cancer localized to the lung or part of the lung, without any lymph node involvement.
Stage II:  Cancer involves the lung and draining lymph node.
Stage III: It is called locally advanced disease, because of it's severity and prognosis. It is subdivided into-
  • Stage IIIA: Cancer spread to the lymph nodes on the same side of the affected lung.
  • Stage IIIB: Cancer involves the lymph nodes of the opposite side of the chest also.
Stage IV: It is the end stage of the lung cancer and prognosis is not good. It indicates the distance metastasis as well i.e. when it involves other systems of the body.

Stages of SCLC:

SCLC tends to grow more rapidly than NSCLC, but SCLC is more responsive to chemotherapy.

Limited or Early Stage:  Cancer localized to the affected part or whole lung.
Extensive or Advance Stage: Cancer spread to both lungs or chest.

Symptoms of Lung Cancer:

Symptoms may vary depending on the extent & site of the disease. Usually, when a tumor occurs in a large bronchus, it produces symptoms early but if it originates in a peripheral bronchus, it can extend without producing symptoms.
However, the site and extent of the disease, the presenting features are more or less as follows:

  • A chronic cough or gradual worsening of a cough.
  • Passage of blood with sputum i.e. hemoptysis.
  • Shortness of breathing.
  • Chest pain.
  • Repeated lung problems like pneumonia, bronchitis, pleural effusion.
  • Changes in the voice or hoarseness of voice.
These all are the symptoms related to the lung but extrapulmonary features i.e. symptoms not related to lungs may be present, they are-
  • Fatigue.
  • Loss of appetite.
  • Difficulty in swallowing.
  • Progressive weight loss.
  • Swelling of arm and face.
  • Clubbing (drumstick appearance of fingers and toes).
  • Bone fractures not related to accidental injury or trauma.
  • Joint problems.
Early stage lung cancer is difficult to diagnose because the tumours can grow for a long time without producing symptoms or even if the patient develops the symptoms like a cough and fatigability, they think it is due to other cause. As a result, the disease remains undiagnosed for most of the time.

Diagnosis of Lung Cancer:

  1. Chest X-ray: A single chest X-ray can help to diagnose the disease although it can mislead pulmonary tuberculosis, fungal infection, organising pneumonia or metastatic lung cancer.
  2. CT scan: it may reveal mediastinal or metastatic spread.
  3. Bronchoscopy.
  4. CT scan-guided biopsy and histopathology.
  5. Positron Emission Tomography (PET): Not routinely performed. It is usually done to determine whether it will surgically cure or not.

Treatment Options for Lung Cancer:

  • Surgical Treatment: 5 years survival rate for Stage I disease is about 75% and for Stage II disease is about 55% after proper surgical and post-operative care. But in case of Stage III, IV and SCLC, surgery has poor or no roll.
  • Chemotherapy: Small cell lung cancer (SCLC) is more responsive to chemotherapy than NSCLC.
  • Radiotherapy: It can increase the survival rate in selected patients who have localised disease.
  • Immunotherapy: In a few cases, immunotherapy may be effective. Immunotherapy includes-
            1. Monoclonal antibody therapy.
            2. Checkpoint inhibitors.
            3. Therapeutic vaccine.
            4. Adoptive T-cell transfer.
  • Combined therapy:  It includes two or more treatment options to get a better outcome.

Side Effects of Treatment:

  • Emotional Breakdown.
  • Loss of memory and concentration.
  • Hair loss.
  • Oral ulcer and tooth decay.
  • Nausea and vomiting.
  • Diarrhoea.
  • Generalized weakness.
  • Numbness or tingling sensation in the hands and feet.
  • Weight loss or gain.

Prognosis:

The overall prognosis of lung cancer is very poor. About 80% of the patients die within one year of diagnosis of the disease and 5 years survival rate is only 5-8%.


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