By definition, cancer is a disease characterized by excessive proliferation of cells and their unregulated growth. Consequently, the cells invade other neighboring tissues. Lung cancer biologically occurs in the two porous structures called lungs found in the chest that are responsible for respiration. The risk of developing lung cancer is 30 times more in smokers than non-smokers.
What Are The Symptoms Of Lung Cancer?
Lung cancer is asymptomatic, especially in the early stages. However, as it progresses, it may present with:
- Chest pain
- Dyspnea
- Wheezing and a prolonged worsening cough
- Weight Loss
- Anorexia
- Hoarseness of voice
- Swelling of the face and neck due to nodular involvement
- Back pain
- Fatigue and malaise
- Blood in the sputum
- Increased frequency of respiratory infections and pneumonia
Etiology Of Lung Cancer
The exact cause of lung cancer is not known. However, a recent study correlates lung cancer with certain carcinogens found in tobacco, asbestos, and radon. When an individual smokes, the immune cells work to remove the particles from the lung. However, over time, the cells become damaged; therefore, they cannot eliminate the particulate matter. The accumulated particulate matter induces the production of chemokines, growth factors, multiple neuropeptides, and other inflammatory mediators that interrupts the normal cell cycle regulation.
Other Risk Factors That Predispose An Individual To Lung Cancer are:
Tobacco Smoke
Tobacco smoke increases the chances of developing lung cancer by 300% in smokers. Also, recently there have been cases where passive or secondhand smokers develop lung cancer. The American Lung Association has reported over 7,000 lung cancer cases due to passive smoking, especially among family members of chronic smokers.
Occupational Exposure
Radon is a chemical found in the majority of the building materials found in homes and offices. The World Health Organization attributes about 30% of lung cancer-related deaths to radon exposure. Additionally, research has linked asbestos as one of the leading cause of mesothelioma, a type of lung cancer.
Other chemical substances linked to lung cancer are arsenic, chromium, nickel, cadmium, uranium, and some petroleum products like coal.
Familial And Genetic Predisposition
If one of your family members had a history of lung cancer, you are more predisposed to developing lung cancer. The percentage of predisposition increases when the family member was a 1st or 2nd-degree relative.
Vitamins supplements
Previously, it was thought that taking beta carotene supplements lowered the propensity to develop lung cancer. However, recent studies revealed that beta carotene increases the risk of developing lung cancer in smokers and alcoholics.
Race, Ethnicity, And Gender
Generally, women are more likely to develop lung cancer compared to men at an early age. However, as they grow old, the population dynamics changes, where older males are more likely to develop lung cancer than older females. Also, blacks and Hispanics are more predisposed to getting lung cancer due to their genetic makeup.
Diseases
A prolonged period of some viral or bacterial infection without treatment may propagate the development of lung cancer.
Classification of lung cancer
Lung cancer is broadly classified into small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). These two types of cancer differ in their etiology, distribution, pathogenesis, and treatment.
Non-small Cell Lung Carcinoma
It is the most common type of lung cancer, responsible for 80-85% of lung cancer cases. NSCLC is common among smokers. Other causative agents are asbestos, radon, metal dust, arsenic, and petroleum products. The pathogenesis of NSCLC originates from the lung's epithelium and progresses to other regions in the lung. NSCLC is further sub-classified into:
Adenocarcinoma
Adenocarcinoma accounts for about 30% of all non-small cell carcinoma. This type of cancer begins at the alveolar and ascends the bronchial tree. Adenocarcinomas develop slowly, and it takes a long time before the signs and symptoms present. Additionally, this type of lung cancer is common in both smokers and non-smokers.
The Squamous Cell or Epitheloid Carcinoma
This type of lung cancer starts from the epithelial lining of the lung, particularly in the airways.
Large Cell or Undifferentiated Carcinoma
This type of lung cancer involves the undifferentiated cells of the lung. Also, it is tough to treat because it is very aggressive.
Small Cell Lung Cancer
This type of cancer occurs in 15% of individuals diagnosed with lung cancer. It grows more rapidly; therefore, it is more aggressive. However, the SCLC responds well to chemotherapy and radiation therapy.
The small cell lung carcinoma is further sub-classified into two, namely the small cell carcinoma, also known as the oat cell carcinoma, and the combined small cell carcinoma. SCLC is associated with paraneoplastic syndrome.
Another type of lung cancer is bronchial carcinoids. They are rare and occur in about 5% of individuals diagnosed with lung carcinoma. This type of cancer is aggressive, and it is predominant among the younger population under 40 years. It is not linked to smoking. Additionally, this type of cancer secretes hormonal-like substances and can be surgically treated.
Lung cancer can metastasize to other organs through the lymphatic system or the bloodstream. Metastasis occurs when the cancer is categorized as stage IV lung cancer. Also, lung cancer can result from metastasis from another site.
How Do Specialists Categorize Lung Cancer?
When a loved one is diagnosed with lung cancer, the doctor says that they have Stage II, stage III, or stage IV lung cancer. In most scenarios, the patient or family member does not understand what these terms mean. Here is a list that will clarify.
Cancers are categorized according to the TNM system, where T stands for tumor size, N stands for nodular involvement, and M stands for metastasis.
For NSCLC:
- In the Occult stage: fluid aspirated from the lung shows signs of cancer; however, the doctors cannot locate the tumor in the lung.
- In stage 0: The cancerous cells are superficial and affect a tiny portion of the lung.
- In stage I: biopsy or imaging has identified the cancerous mass that is confined to one side of the lung.
- In stage II: The cancer is located in one lung and the neighboring lymph nodes.
- In stage III: It is sub-classified into two stages, namely 3A and 3B. In 3A, the cancer has affected one lung and lymph nodes on the same side that the cancer had originated. Whereas, in stage 3B, the cancer has affected one lung and the lymph nodes on the opposite side of the chest. Sometimes the extent of nodular involvement extends to the collar bone.
- In stage IV: The cancer has spread to both lungs, surrounding area, and distant organs.
For SCLC, it is classified into a limited stage and an extensive stage. In the limited-stage, the cancer is confined to the lung where it started and the surrounding lymph nodes. In the extensive stage, the cancer has spread from origin to other distant lymph nodes and organs.
Diagnosing Lung Cancer
Diagnosis involves extensive history taking, imaging techniques, tissue and fluid biopsy, and bronchoscopy.
Extensive history taking will highlight if an individual was a smoker or their occupation exposed them to the possible carcinogens. It will also outline the familial and genetic predisposition of the individual to lung cancer.
The doctor may recommend diagnostic imaging techniques like X-rays, ultrasound, and magnetic resonance imaging. A CT scan gives a more detailed image of the extent of the spread of the cancer. Pet scans involve the use of radioactive components to identify the location of the cancerous mass.
Sputum cytology and fluid extracted from needle aspiration may reveal cancerous cells. Tissue biopsy is the gold standard technique in identifying cancerous cells. It involves the surgical extraction of the suspected cancerous mass and extensive laboratory investigation. Other techniques are bronchoscopy, mediastinoscopy, and thoracoscopy.
Treatment
Depending on the lung cancer stage, a specialist may recommend treatment using one or a combination of the therapy listed below.
Surgical Removal
It is the most appropriate treatment approach for a consolidated cancerous mass in the early stages. It involves partial or total surgical removal of a lung.
Radiation Therapy
This involves illuminating the chest region with a high-intensity laser beam or a radioactive compound to kill the cancerous cells. It is recommended after surgical removal to kill the remaining cancer cells.
Chemotherapy
Whether it is through intravenous or oral agents, chemotherapy has proven a useful technique in reducing the tumor's size. In recent drug development, the chemotherapeutic agents are developed to target the cancerous cell while sparing the normal healthy cells. This is known as targeted therapy.
Immunotherapy
Immunotherapy entails techniques that will boost your immunity.
Symptomatic Therapy
It is for cancer patients who are in stage IV lung cancer unresponsive to all types of therapy. Symptomatic management aims at making the patient more comfortable and lessens the pain. Patients are given analgesics and oxygen therapy as they are having difficulties in breathing.
