Lung Cancer

Overview

 

Lung cancer is the deadliest type of cancer in both, men and women. Each year, many people die of lung cancer than breast, colon and prostate cancers combined. Cigarette smoking is the leading cause of lung cancer. However, lung cancer has occurred in people who have never smoked. Initially, lung cancer is asymptomatic. Lung cancer can be detected with the help of an X-ray.

 

Symptoms

  • Chronic cough for more than a month
  • Coughing up blood (Haemoptysis)
  • Shortness of breath
  • Wheezing
  • Chest pain
  • Fatigue
  • Difficulty in swallowing
  • Progressive weight loss
  • Loss of appetite
  • Joint problems
  • Swelling of the arms and face

Causes

SMOKING AND LUNG CANCER:

Smoking, particularly cigarettes, is by far the main contributor to lung cancer. Cigarette smoke contains over 60 known carcinogens, including radioisotopes from the radon decay sequence, nitrosamine, and benzopyrene. Additionally, nicotine appears to depress the immune response to cancerous growths in exposed tissue. Smoking accounts for 80–90% of lung cancer cases.

Passive smoking - the inhalation of smoke from another's smoking - is a known cause of lung cancer in nonsmokers. A passive smoker can be classified as someone living or working with a smoker. Those who live with someone who smokes have a 20–30% increase in risk while those who work in an environment with second hand smoke have a 16–19% increase in risk.

RADON GAS AND LUNG CANCER:

Radon is a colourless and odourless gas generated by the breakdown of radioactive radium, which in turn is the decay product of uranium, found in the Earth's crust. The radiation decay products ionise genetic material, causing mutations that sometimes turn cancerous. The risk increases 8–16% for every 100 Bq/m increase in the radon concentration.

ASBESTOS AND LUNG CANCER:

Asbestos can cause a variety of lung diseases, including lung cancer. Tobacco smoking and asbestos have a synergistic effect on the formation of lung cancer. Asbestos can also cause cancer of the pleura, called mesothelioma (which is different from lung cancer).

AIR POLLUTION AND LUNG CANCER:

Outdoor air pollution has a small effect on increasing the risk of lung cancer. Fine particulates (PM2.5) and sulfate aerosols, which may be released in traffic exhaust fumes, are associated with slightly increased risk. For nitrogen dioxide, an incremental increase of 10 parts per billion increases the risk of lung cancer by 14%. Outdoor air pollution is estimated to account for 1–2% of lung cancers.

Tentative evidence supports an increased risk of lung cancer from indoor air pollution related to the burning of wood, charcoal, dung or crop residue for cooking and heating. Women who are exposed to indoor coal smoke have about twice the risk. Also, a number of by-products of burning biomass are known for suspected carcinogens.

GENETICS AND LUNG CANCER:

It is estimated that 8-14% of lung cancer is due to inherited factors. In relatives of people with lung cancer, the risk is increased 2.4 times. This is likely due to a combination of genes.

OTHER CAUSES:

Numerous other substances, occupations and environmental exposures have been linked to lung cancer.

  • Production and mining of some metals and arsenic compounds
  • Some products of combustion
  • Ionising Radiation
  • Toxic gases 
  • Rubber production and crystalline silica dust

Diagnosis

Performing a chest radiograph is one of the first investigative steps when a person reports symptoms that may suggest lung cancer. This may reveal an obvious mass, widening of the mediastinum (suggestive of spread to lymph nodes there), atelectasis (collapse), consolidation (pneumonia), or pleural effusion. CT imaging is, typically, used to provide more information about the type and extent of disease. Bronchoscopy or CT-guided biopsy is often used to sample the tumour for histopathology.

Lung cancer often appears as a solitary pulmonary nodule on a chest radiograph. However, the differential diagnosis is wide. Many other diseases can also give this appearance, including tuberculosis, fungal infections, metastatic cancer, or organising pneumonia. Less common causes of a solitary pulmonary nodule include hamartomas, bronchogenic cysts, adenomas, arteriovenous malformation, pulmonary sequestration, rheumatoid nodules, Wegener's, or lymphoma. Lung cancer can also be an incidental finding, as a solitary pulmonary nodule on a chest radiograph or CT scan done for an unrelated reason. The definitive diagnosis of lung cancer is based on histological examination of the suspicious tissue in the context of the clinical and radiological features.

Treatment

Treatment for lung cancer depends on cancer's specific cell type, how far it has spread, and the person's performance status. Common treatments include palliative care, surgery, chemotherapy, and radiation therapy.

SURGERY FOR LUNG CANCER:

If investigations confirm NSCLC (non-small-cell lung carcinoma), the stage is assessed to determine whether the disease is localised and amenable to surgery or if it has spread to the point where it cannot be cured surgically. CT scan and Positron Emission Tomography are used for this determination. If mediastinal lymph node involvement is suspected, mediastinoscopy may be used to sample the nodes and assist staging. Blood tests and pulmonary function testing are used to assess whether a person is well enough for surgery. If pulmonary function tests reveal poor respiratory reserve, surgery may not be a possibility. 

In most cases of early-stage NSCLC, removal of a lobe of the lung (lobectomy) is the surgical treatment of choice. In people who are unfit for a full lobectomy, a smaller sublobar excision may be performed. However, wedge resection has a higher risk of recurrence than lobectomy. Rarely, removal of a whole lung (pneumonectomy) is performed. Video-assisted thoracoscopic surgery and VATS lobectomy use a minimally invasive approach to lung cancer surgery. VATS lobectomy is equally effective, as compared to conventional open lobectomy, with less postoperative illness. 

In SCLC (small-cell lung carcinoma), chemotherapy and/or radiotherapy is used. However, the role of surgery in SCLC is being reconsidered. Surgery might improve outcomes when added to chemotherapy and radiation in early stage SCLC.

RADIOTHERAPY FOR LUNG CANCER:

Radiotherapy is often given together with chemotherapy and may be used with curative intent in people with NSCLC who are not eligible for surgery. This form of high-intensity radiotherapy is called radical radiotherapy. A refinement of this technique is Continuous Hyperfractionated Accelerated Radiotherapy (CHART), in which a high dose of radiotherapy is given in a short time period.

For potentially curable SCLC cases, chest radiotherapy is often recommended in addition to chemotherapy.

If cancer growth blocks a small section of bronchus, brachytherapy (localised radiotherapy) may be given directly inside the airway to open the passage. Compared to external beam radiotherapy, brachytherapy allows a reduction in treatment time and reduced radiation exposure to healthcare staff.

Recent improvements in targeting and imaging have led to the development of stereotactic radiation in the treatment of early-stage lung cancer. In this form of radiotherapy, high doses are delivered in a small number of sessions using stereotactic targeting techniques. Its use is primarily in patients who are not surgical candidates due to medical comorbidities.

For both NSCLC and SCLC patients, smaller doses of radiation to the chest may be used for symptom control (palliative radiotherapy).

CHEMOTHERAPY FOR LUNG CANCER:

The chemotherapy regimen depends on the tumour type. Small-cell lung carcinoma (SCLC), even relatively early stage disease, is treated primarily with chemotherapy and radiation. In advanced non-small cell lung carcinoma (NSCLC), chemotherapy improves survival and is used as first-line treatment, provided the person is well enough for the treatment.

Adjuvant chemotherapy refers to the use of chemotherapy, after the curative surgery, to improve the outcome. In NSCLC, samples are taken from nearby lymph nodes, during surgery, to assist staging. If stage II or III disease is confirmed, adjuvant chemotherapy improves survival by 5% at five years. Adjuvant chemotherapy for people with stage IB cancer is controversial, as clinical trials have not clearly demonstrated a survival benefit. Trials of preoperative chemotherapy (neoadjuvant chemotherapy) in resectable NSCLC have been inconclusive.


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