Lung Cancer: Most prevalent cancer across the globe

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What is Lung Cancer?

Cancer that begins in the lungs is termed lung cancer. It is life-threatening cancer that metastasizes as soon as it forms. The most common sites for metastasis include the adrenal gland, liver, brain, and bone.

Although lung cancer can arise from any part of the lung, the region of maximum origin tends to be the epithelial cells that line the bronchi and bronchioles. This type of cancer is called bronchogenic cancer. Lungs are also the common site of metastasis for other cancers in the body, and this type of cancer has cells that resemble those found in the primary tumor site.

Lung cancer is the most common cause of death in India and across the globe. In India, lung cancer contributes to approximately 6.9 % of all new cancer cases. Around 9.3 % of the cancer-related deaths in India are associated with lung cancer. 

The incidence of lung cancer is 28.3 per 100,000 males and 28.7 per 100,000 females in India. The overall average survival rate of in developing countries like India is around 5 %.

Types of Lung Cancer:

Lung cancer is broadly divided into two types, as follows :

  • Non-small cell lung cancer is the most common type that affects both smokers and non-smokers. It is further subdivided into:
      • Adenocarcinoma – It starts in the glandular cells (cells that secrete mucus) and develops into the alveoli. It is more common in women than in men. Adenocarcinoma begins in the outer parts of the lungs initially.
      • Squamous cell carcinoma – It is also known as epidermoid carcinoma and starts in the squamous cells that line the lungs’ inner airways. These tumors are often found in the central part of the lungs near the bronchi and are mostly found in individuals with a smoking history.
      • Large cell (undifferentiated) carcinoma – It can appear in any part of the lungs. It grows and metastasizes rapidly, and this makes it harder to treat.
      • Other uncommon types – Adenosquamous carcinoma and sarcomatoid carcinoma are other types of non-small cell lung cancer that are rare.
  • Small cell lung cancer – It is also known as oat cell cancer. It grows and metastasizes faster than non-small cell lung cancer and is the leading cause of death in many countries. There are two main types of small cell lung cancer: small cell carcinoma and combined small cell carcinoma. Smoking is found to increase the risk of developing this type of cancer.

Other types – 

The other tumors that are commonly found are :

  • Lung carcinoid tumors – These start in the neuroendocrine cells of the lungs and grow slowly. It is a rare type of tumor contributing to less than 1 to 2 % of lung cancer.
  • Other lung tumors – Adenoid cystic carcinomas, lymphomas, sarcomas, and benign lung tumors like hamartomas are rare types of lung tumors treated differently from the common lung cancers.

Stages of Lung Cancer:

The different stages of lung cancer are as follows :

  • Stage 0 – Tumor is found only in the top layer of cells lining the air passages but has not spread to the lung’s deeper layers.
  • Stage I – cancer in this stage is a minimally invasive adenocarcinoma and has spread to the lung tissue’s deeper layers but not to the nearby lymph nodes and distant organs.
  • Stage II – Tumor has spread to the main bronchus, visceral pleura, or the lymph nodes on the same side. It has, however, not spread to distant organs.
  • Stage III – Tumor has spread to the lymph nodes on the opposite side or in the space between the lungs but not to the distant organs.
  • Stage IV – Cancer has spread to both lungs, nearby lymph nodes, and distant organs like the liver, bones, and brain.

Lung Cancer Symptoms

Lung cancer usually doesn’t cause any pain or symptoms in most cases. Patients with small, single masses of tumors often do not manifest any symptoms, and in these cases, the cancer is detected by a chest x-ray or CT scan. 

The symptoms that manifest when cancer has invaded the lungs, and surrounding tissues are as follows :

  • Shortness of breath
  • Wheezing
  • Chest pain
  • Hemoptysis – coughing up blood
  • Lingering cough
  • Hoarseness due to paralysis of vocal cords
  • Pancoast syndrome – shoulder pain that travels down the outside of the arm (if cancer has invaded the nerves)
  • Difficulty in swallowing 
  • Pneumonia

Once cancer begins to metastasize, the following symptoms appear :

  • Excruciating pain in the bones if lung cancer has spread to the bone
  • Neurological symptoms if cancer has spread to the brain – blurred vision, headaches, seizures, stroke symptoms, including weakness or loss of sensation in parts of the body.

What Causes Lung Cancer?

The main cause of lung cancer is smoking and being exposed to secondhand smoke. Smoking or inhaling cigarette smoke damages the lungs’ inner lining and is repaired by normal lung cells during the first exposure.

Subsequent exposure to the carcinogens present in cigarette smoke causes repeated damage to the lining, causing the lung cells to act abnormally and eventually turn cancerous. This type of cancer can also occur in individuals who have never been exposed to cigarette smoke and in non-smokers. 

The exact etiological factor in these cases is unknown, but certain risk factors are known to increase the chances in these cases.

Which factors increase the risk of Lung Cancer?

The risk factors are divided into modifiable risk factors and non-modifiable risk factors. 

Modifiable risk factors are those that can be changed by the individual, while non-modifiable risk factors are those that cannot be changed by the individual.

Modifiable risk factors :

  • Smoking – Tobacco smoking, cigar-smoking, pipe-smoking, low-tar or “light” cigarette smoking, and menthol cigarette smoking increase lung cancer risk by several folds.
  • Secondhand smoke – Breathing in when other person smoke is also found to increase lung cancer risk even if the individual is a non-smoker.
  • Exposure to certain substances – Exposure to radon (a radioactive gas) is the major risk factor of lung cancer in non-smokers. Occupational exposure to asbestos in mines, textile plants, and shipyards puts the person at a higher risk of developing lung cancer. Exposure to other carcinogens like uranium, arsenic, cadmium, silica, chromium products, and mustard gas also increases lung cancer chances. 
  • Dietary supplements – Consumption of beta carotene supplements by smokers is associated with a greater risk of developing lung cancer.
  • Presence of arsenic in drinking water – High levels of arsenic in drinking water increases the likelihood of developing lung cancer. This is frequently seen in Southeast Asia and South America.

Non-modifiable risk factors:

  • Exposure to radiation in the past – People who have had radiation therapy for treating Hodgkin’s lymphoma, breast cancer, and other cancers in the chest area are more prone to developing lung cancer.
  • Air pollution – Air pollution is associated with an increased risk of lung cancer, but this is a minor risk factor.
  • Family history – Patients with first- degree relatives diagnosed with lung cancer are more likely to develop lung cancer.
  • Personal history of lung cancer – Individuals who have already had lung cancer are more susceptible to getting recurrent lung cancer.
  • Lung diseases – The presence of chronic obstructive pulmonary disease increases the risk of lung cancer by four to six times, while the presence of pulmonary fibrosis is found to increase the risk by sevenfold.

How is lung cancer diagnosed? What are the screening tests?

The patient’s medical history is first gathered, and this is followed by a physical examination to look for signs of lung cancer. The following imaging tests are done to look at the suspicious areas for the presence of cancerous growth :

  • Chest x-ray It helps to identify any abnormal areas in the lungs.
  • Computed Tomography (CT) scan X-rays are used to provide clear 3- dimensional images of the body. It provides clear images of the lung tumor, its size, shape, and position, and aids in detecting enlarged lymph nodes. It also helps ascertain if cancer has spread to the adrenal glands, liver, brain, and other organs.
  • Magnetic resonance imaging (MRI) – It uses radio waves and magnetic fields to look for possible spread of lung cancer, especially to the brain and spinal cord.
  • Positron emission tomography (PET) scan – They are useful to identify the areas to which the lung cancer has spread. It can show the spread of lung cancer to the liver, bones, adrenal glands, and other organs. This scan cannot see the spread of cancer to the brain and spinal cord.
  • Bone scan A small amount of radioactive material is injected into the blood, accumulating in the bones’ cancer cells. It helps to detect the spread of lung cancer to bones. This method is not often used as PET scans help ascertain the spread of lung cancer to the bones.

The tests frequently are done to diagnose lung cancer are :

  • Sputum cytology – It helps to detect cancers that start in the major airways of the lungs. To perform this test, sputum samples are collected early in the morning for three days, and these are analyzed in the lab for the presence of cancer cells. This test cannot be used for diagnosing other types of lung cancer.
  • Thoracentesis – This test involves collecting the fluid around the lung (pleural effusion) and examining it for the presence of cancer cells. For this test, the skin is numbed, and a needle is inserted between the ribs for collecting the fluid.
  • Biopsy – The different biopsy methods used for collecting a sample of the lung tumor tissue for examination to detect the presence of cancer cells are as follows :
      • Fine needle aspiration biopsy – It is done to detect cancer in the lymph nodes between the lungs. A very fine and hollow needle is used to collect the cells and tissue from the suspicious site.
      • Transtracheal fine-needle aspiration biopsy – A needle is passed through the trachea or bronchi during bronchoscopy or endobronchial ultrasound for collecting the tissue sample.
      • Core biopsy – A larger needle is used to remove larger samples of the tissue. This is preferred over fine-needle aspiration biopsy as the core sample tissue collected is large in this method.
      • Transthoracic needle biopsy – A needle is used to collect the tissue sample from the outer part of the lungs by using a CT scan or fluoroscopy.
  • Bronchoscopy – A tube attached with a camera and light is used to view the lungs and other structures to detect tumors and other blockages in the lungs’ larger airways.

Treatment :

The different treatment options for lung cancer are :

  • Surgery – Surgery is usually done to remove lung cancer and a portion of the healthy tissue. The surgical procedures that are commonly recommended are :
        • Lobectomy – The entire lobe of one lung is removed.
        • Pneumonectomy – The entire lung is removed.
        • Segmental resection – In this surgery, a large portion of the lung is removed but not the entire lobe.
        • Wedge resection or segmentectomy – A part of the lobe is removed. This surgery is done when the person’s lung functioning is not enough to withstand the removal of the entire lobe.
        • Video-assisted thoracic surgery or thoracoscopy – It is a procedure used to treat early-stage cancers. Smaller incisions are used, and fewer complications are developed due to this surgery.
  • Radiofrequency ablation – High energy radio waves are used to heat the tumors and destroy the cancer cells. This is done by using a needle-like probe that is guided to the tumors by CT scan. On reaching the tumors, the needle-like probe passes an electrical current, and this heats the tumor. This procedure is done using local anesthesia. 
  • Radiation therapy – External beam or internal beam radiation therapy is used to treat lung cancer and control its spread. It utilizes high energy x-rays and is often used in combination with chemotherapy. For metastasized lung cancer, this therapy helps to relieve the symptoms and pain.
  • Chemotherapy – The commonly used chemotherapy drugs include cisplatin, carboplatin, paclitaxel, gemcitabine, etoposide, and vincristine. A combination of two chemotherapeutic drugs is often used to treat early-stage lung cancer. In contrast, advanced stages are treated using a single drug, especially if the patient is elderly or in poor overall health.
  • Targeted therapy – Anti-angiogenesis inhibitors like bevacizumab and ramucirumab target the vascular endothelial growth factors and stop the formation of new blood vessels needed for the growth and survival of the cancer cells. Epidermal growth factor receptor (EGFR) inhibitors like afatinib, dacomitinib, and gefitinib target the EGFR to inhibit tumor cells’ growth. Other drugs commonly used in this therapy target the ALK gene, ROS1 gene, and BRAF gene to stop the multiplication and facilitate the destruction of the cancer cells.
  • Immunotherapy – Immune checkpoint inhibitors like nivolumab, atezolizumab, and pembrolizumab are used to target PD-1 for boosting the immune response against the cancer cells. Other drugs used under this therapy include ipilimumab, a CTLA-4 inhibitor that blocks the protein CTLA-4 located on the T-cells to boost the immune response.

Ways to prevent Lung Cancer

Cancer of Lungs cannot be prevented, but certain lifestyle modifications reduce the risk of developing it. These are :

  • Staying away from tobacco. Stop smoking and avoid breathing secondhand smoke.
  • Avoid or reduce exposure to radon and other carcinogenic agents in the workplace.
  • Include more vegetables and fruits in the diet.
  • Exercise regularly.
  • Consult with the doctor if any symptoms manifest and go for screening tests if needed.

Frequently Asked Questions 

1. Is lung cancer curable?

  • Lung cancer is curable if detected early, but the rate of recovery falls once cancer starts metastasizing. Advanced stage can be treated using palliative chemotherapy, which is found to increase the patient’s lifespan.

2. What is the survival rate of lung cancer?

  • The average 5-year survival rate of stage I lung cancer is 92 %, while stage II is 60 %. The survival rate of stage III lung cancer is reduced and is estimated to be in the range of 13 to 26 %, while that of stage IV is less than 10 %.

3. What is the cost of lung cancer treatment in India?

  • The average cost of lung cancer surgery is estimated to be around 4 to 7 lakhs, while radiofrequency ablation is approximately 2 lakhs. The cost of chemotherapy is around Rs.30,000 per cycle.

4. Does age and gender play a role?

  • Lung adenocarcinoma is more common in females and people of the elderly age group. Most cases of lung cancer are diagnosed in individuals above 65 years of age.

Cancer Hospitals in India

  1. Asian Institute of Oncology, S.L.Raheja Hospital, Raheja Hospital Road, Mahim, Mumbai 
  2. Cancer Institute (WIA),  Adyar, ChennaiJaslok hospital research Centre, Mumbai
  3. Dharamshila Cancer Hospital & Research Centre, Vasundhara Enclave, New Delhi 
  4. Dr. B. Borooah Cancer Institute, Gopinath Nagar, Guwahati
  5. Dr. Rai Memorial Cancer Institute 562, Anna Salai, Chennai, Tamil Nadu
  6. Rajkot Cancer Society, Mr. N.P. Cancer Institute, Raiya Road, Rajkot, Gujarat
  7. Regional Cancer Centre, Medical College Campus, P.B.2417, Thiruvanthapuram , Kerala.
  8. Tata Memorial Centre, Dr. Ernest Borges Marg, Parel, Mumbai 
  9. The Gujarat Cancer & Research Insitute, M.P. Shah Cancer Hospital, New Civil Hospital Compound Asarwa, Ahmedabad 
  10. Rajiv Gandhi Cancer Hospital & Research Institute, Sector 5, Rohini, Delhi
  11. Bhagwan Mahaveer Cancer Hospital & Research Centre, Jawaharlal Nehru Marg, Jaipur 

Other reputed Cancer Hospitals and Institutes in India:

  1. Regional Centre for Cancer Research, Adyar, Chennai.
  2. Regional Centre for Cancer Research and Treatment, Mangalabag, Cuttack – 753 007.
  3. Rotary Cancer Centre, 117/K/11, Gutaiya, G.T.Road, Kanpur  – 208 002, India
  4. Advanced Centre for Treatment, Research and Education in Cancer (ACTREC), Sector 22, Kharghar, Navi Mumbai – 410 210
  5. Amala Cancer Research Centre, Amalangar, Trichur.
  6. Bose Institute
  7. Cancer Treatment & Research Centre, Lion District 324 C-1, Seethammadhara North Extn., Visakhapatnam – 530 013 (AP).
  8. Chittaranjan Cancer Institute, 37, S.P. Mukherjee Road, Kolkata 700026
  9. Christian Cancer Centre, Kakinada Pithapuram Road, Kakinada – 533 003, Andhra Pradesh
  10. All India Institute of Medical Sciences, Ansari Nagar, New Delhi – 110016.
  11. Dr. Bhubaneshwar Barooah Cancer Institute, Gopinath Nagar, Guwahati – 781 016, Assam.
  12. G.V.N. Cancer Centre, No.16, Kiledar Street, Tiruchirapalli – 620 002, Tamil Nadu.
  13. Goa Cancer Society, GM Cancer Hospital & Research Institute, Dr. E. Borges Road, Dona Paula – 403 004, Goa.
  14. Indian Rly. Cancer Institute & Research Centre, N.E. Railway, Lahartara, Varanasi – 221 002, Uttar Pradesh.
  15. Institute of Cytology & Preventive Oncology, I-7, Sector 39, P.O.Box No. 544, Near Degree College, Opposite City Centre, Noida – 201 301, Uttar Pradesh.
  16.  International Cancer Centre,  Neyyoor,  Tamilnadu  – 629 802.
  17. International Network for Cancer, Treatment, & Research Room No. 127A, Sir Gangaram Hospital, Rajinder  Nagar, New  Delhi -110 060.
  18. J.K. Cancer Institute (C.S.V.M. Medical College), Kanpur  – 208 002, Uttar Pradesh.
  19. Jagdish Cancer & Research Centre, 3-6-20, Tirumala Apts. Skyline Lane, Basheer Bagh, Hyderabad.
  20. Jawaharlal Nehru Cancer Hospital, & Research Centre, Idgah Hills, PB No. 32 Bhopal – 462 001.
  21. Mohan Das Oswal Cancer Treatment & Research Centre, G.T. Road, Sherpur, Ludhiana – 141 009, Punjab.
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