Introduction
These days, the main cause of sickness and death worldwide is cancer. Cancer is a major health concern .75% of all fatalities worldwide are noncommunicable diseases(NCDs). In India, NCDs account for 63% of deaths, with cancer being the topmost cause(9%).
Lung cancer, or Bronchogenic carcinoma, refers to a tumour originating in the lung parenchyma or within the bronchi. At the beginning of the 20th century, lung cancer was sporadic, but now there is a rise in the number of cases due to an increase in smoking among the population. It is a significant public health concern, especially in low and middle-income countries like India. Here we are going to discuss the causes, symptoms, risk factors, types and many more things about lung cancer.
What is lung cancer?
Lung cancer, a disease caused due to the uncontrolled cell division of the lungs. Eventually, these uncontrollably created mass or tumor cells disrupt the normal functioning of the organ.
In 2020, lung cancer contributed to 11.4% of all the new cancer cases and 18% of all the cancer-related deaths. The highest lung cancer rates have been reported among males in Turkey and among females in Hungary. In 2022, researchers identified approximately 2.48 million new lung cancer cases globally, with the highest incidence observed in men (approx. 1.57 million) compared to women ( approx. 0.91 million). The most common histological subtype is adenocarcinoma, followed by squamous cell carcinoma. Its incidence and mortality vary geographically, with the highest rate in East Asia, North America, and some parts of Europe. It predominantly affects the elderly above 65 years of age.
In India, expert projects the number of cases to rise to approximately 81,219 in males and 30,109 in females by 2025. The highest incidence is found to be in Mizoram, specifically in the Aizawl district.
Types of Lung Cancer
There are two main types of lung cancer- Small cell lung cancer and Non-small cell lung cancer.
The most common type of lung cancer is non-small cell carcinoma. Around 85% of all the lung cancer are non small cell carcinoma. These are of 3 types adenocarcinoma, squamous cell carcinoma, large cell carcinoma. Out of these three adenocarcinoma is most common. It starts in the mucus forming glands in the airway lining. Squamous cell carcinoma arises from the flat ( epithelial) cells of the airway lining. It tends to grow near the center of the lung. In Large cell carcinoma, cancer cells appear larger than the typical cell under the microscope.
Small cell lung cancer accounts for 15-20% of all the cases of lung cancer. Usually caused by smoking. It is also classified as neuroendocrine tumors because it arises from neuroendocrine cells of the lung.
STAGES OF LUNG CANCER
Stage 0: Cancer is within the top-lining of the lung or bronchus. Not spread to other parts of lung or body.
Stage 1: Cancer hasn’t spread outside lung
Stage 2: Larger than stage 1. Spread to LN inside the lungs. More than 1 tumor within the lobe of the lung
Stage 3: Larger than stage 2. Spread to nearby lymph node, structures, more than 1 tumor in different lobes of ipsilateral lung
Stage 4: Cancer have spread to contralateral lung, fluid around the lung or hear or to distant organs
Metastatic lung cancer: When tumor spread to the other lung or the other organ from the site of origin, or we can say 4th stage of lung cancer. Its harder to treat.
Causes and Risk Factors
Smoking is the biggest risk factor for lung cancer, responsible for the majority of the cases. It is responsible for more than 7 out of 10 cases. Tobacco smoke contains many carcinogenic substances. Secondhand smoke, also known as passive smoking, increases a non-smoker’s risk of lung cancer by about 20-30%. Smoking also causes cancer such as esophageal cancer and oral cancer. Products included in smoking are cigars, pipe-tobacco, snuff, chewing tobacco, smoking cannabis.
Radon, a natural radioactive gas, cause approximately 10-20% of lung cancer cases worldwide. Expert consider it the second leading cause of lung cancer after smoking, with estimates varying depending on the geographical and exposure differences.
Workers exposed to carcinogens like asbestos, silicone, arsenic, cadmium, coal, nickel, chromium, diesel fumes, polycyclic aromatic hydrocarbons(PAH), have significantly increased risk of devloping lung cancer. Occupational exposure accounts for 10% of the cases overall. Workers in mining, constructions, manufacturing, welding, aluminium production, rubber manufacturing , truck drivers and mechanics are at increased risk of developing lung cancer.
Genetic mutations—both acquired and inherited—play a significant role in lung cancer development, with TP53, KRAS, EGFR, and ALK being among the most frequently altered genes. Most mutations are acquired, but inherited variants can also increase risk, especially in combination with environmental exposures.
Signs and Symptoms
Most people with lung cancer do not develop any symptoms unless the cancer is advanced. Symptoms usually appears in advance stage of cancer. They include:
- New onset of cough, not resolving with medication
- Hemoptysis- blood during coughing
- Difficulty in breathing
- Hoarseness of voice
- Wheezing
- Chest pain
- Finger clubbing( bulbar enlargement of fingertips)
- Bone pain
- Headache
- Seizures
- Ataxia
- weight loss
- loss of appetite
- lymph node enlargement
- Swelling in body
Diagnosis of lung cancer
In addition to clinical assesment, diagnosis may involve a range of imaging studies, laboratory investigations and diagnostic procedures
Imaging: The first investigation done is chest x-ray. Findings include white grey mass or opacity in the lung field. It can also present as consolidation not resolving by antibiotics. A tumor blocking the airway can make part of the lung collapse, which doctors can see as a shadow or dark area on a chest X-ray. Pleural effusion, mediastinal widening, cavitation are other findings. But these findings do not give a definitive diagnosis. The other imaging, includes CT-SCAN, MRI, PET-SCAN, used to know the size, extent and spread of the tumor.
Laboratory investigations: Blood investigations play a less important role in diagnosis of lung cancer. The sputum cytology is a non-invasive method to detect lung cancer by identifying the cancer cells in the sputum under the microscope. It is useful in detecting centrally located tumors like squamous cell carcinoma as compared to peripheral located carcinoma. It is valuable when invasive procedures are contraindicated.
Procedures: Diagnostic procedures are the confirmatory investigations for lung cancer. It includes bronchoscopy guided biopsy or endobronchial guided ultrasound guided biopsy of lymph nodes. In biopsy a small part of the tissue is excised to evaluate it under the microscope. It is the gold standard investigation for the diagnosis.
Treatment and Prevention
Treatment: Treatment depends on the type, stage, age and patient’s clinical condition. The main treatment options include surgery, chemotherapy, radiation therapy, immunotherapy. Doctors combine these methods for treatment depending on the type , stage, and other factors.
Stage 1 and 2 : Surgery is the primary treatment at this stage. The Surgeon remove the tumor and affected part of the lung , followed by chemotherapy or radiotherapy to kill the residual cancer cells.
Stage 3: The treatment includes combination of chemotherapy, radiotherapy and surgery depending on the lymph node involvement, tumor size and clinical status of the patient.
Stage 4: This is the advance stage of cancer. Only palliative care is given using chemotherapy or immunotherapy or targeted therapy. At this stage main goal of the treatment is just to control spread of cancer and relieve symptoms.
Prevention:
- The most effective way to prevent lung cancer is to avoid lung tobacco in all forms.
- Avoid secondhand smoke.
- Promoting smoke-free environment.
- Reduce the exposure to environmental and occupational carcinogens.
- Reducing air pollution
- Implementing tobacco control policies
- Screening min high risk individuals via low dose computed tomography(LDCT)
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