Lung cancer: when lung's cells grow out of control

Lung cancer is a cancer type that originates in the lungs (two spongy organs that are found inside of the thoracic cavity that absorb oxygen when inhaling and release carbon dioxide when exhaling).

When you breathe, air enters through your mouth (or nose) and passes into the lungs via the trachea. The trachea divides into two tubes called bronchi, which enter the lungs and branch into smaller bronchi. These further divide into even smaller branches called bronchioles. At the end of the bronchioles are tiny air sacs known as alveoli.

The alveoli absorb oxygen from the inhaled air into the bloodstream and remove carbon dioxide from the blood, which is expelled from the body when you exhale. The primary functions of the lungs are to take in oxygen and expel carbon dioxide.

Lung cancer typically begins in the cells lining the bronchi or in other parts of the lungs, such as the bronchioles or alveoli.

Lung cancer is classified into two main types based on the appearance of cancer cells under a microscope:

• Non-small cell lung cancer (NSCLC): this type includes several subtypes of lung cancer that behave similarly, such as:
  • Squamous cell carcinoma
  • Adenocarcinoma
  • Large cell carcinoma
• Small cell lung cancer (SCLC): this type occurs almost exclusively in smokers and is less common than NSCLC

Several factors can increase the risk of lung cancer. Some of these risk factors, such as smoking, can be controlled, while others, such as family history, cannot.

Risk factors for lung cancer include:

• Smoking
• Secondhand smoke exposure
• Exposure to radon gas
• Exposure to asbestos or other carcinogens
• Family history of lung cancer
• Exposure to radioactive minerals like uranium
• Inhalation of chemicals or minerals such as arsenic, beryllium, cadmium, silica, vinyl chloride, nickel compounds, chromium compounds, coal products, mustard gas, and chloromethyl ethers
• Environmental pollution
• Radiation therapy to the lungs
• Arsenic in drinking water

Most cases of lung cancer do not show symptoms until the disease has already spread. (lung cancer is known as one of the “silent cancers”). However, individuals with advanced-stage lung cancer may experience the following symptoms:

• A persistent or worsening cough
• Chest pain that intensifies with deep breaths, coughing, or laughter
• Hoarseness
• Loss of appetite or weight
• Coughing up blood or rust-colored sputum (mucus)
• Shortness of breath
• Fatigue or weakness
• Recurring or persistent infections, such as bronchitis or pneumonia
• Wheezing
• Horner syndrome
• Superior vena cava syndrome
• Paraneoplastic syndromes

Lung cancer usually appears mainly in elderly people. About 2 in 3 people diagnosed with lung cancer are over 65 years old, while less than 2% are under 45 years old. The average age at diagnosis is approximately 70 years. People who are diagnosed with stage I lung cancer have the highest survival rate (35%). Survival is lower for those diagnosed in stage III (6%). Survival at stage IV could not be calculated at five years because of the small number of people who survived more than two years. Survival for those with unknown stage is similar to those with stage III disease (6%).

Source: SEER Program – Surveillance, Epidemiology, and End Results – U.S. National Cancer Institute

IMPORTANT: THE EARLY DIAGNOSIS OF CANCER IS OF VITAL IMPORTANCE BECAUSE A CANCER DIAGNOSED AT AN EARLY STAGE —BEFORE IT HAS GROWN TOO MUCH OR HAS SPREAD TO OTHER AREAS OF THE BODY–- HAS A GREATER LIKELY OF BEING SUCCESSFULLY TREATED. ON THE CONTRARY, IF THE CANCER HAS SPREAD TO OTHER ORGANS, TREATMENT BECOMES MORE DIFFICULT, AND GENERALLY THE CHANCE OF SURVIVAL IS MUCH LOWER.

As shown in the graph below, lung cancer mortality rates are substantially higher for patients diagnosed at advanced stages or after metastasis.

Doctors currently consider age and smoking history as the primary factors for assessing lung cancer risk in symptomatic patients.

For high-risk individuals, a computed tomography (CT) scan is recommended. While CT scans are effective in identifying lung nodules, they have limitations: only 28% of high-risk patients screened with CT scans test positive for cancer, as most nodules detected are benign.

In fact, 97% of lung nodules are not cancerous, as they can result from various conditions, such as fungal infections, tuberculosis, lung abscesses, pneumonia, rheumatoid arthritis, Wegener's granulomatosis, or sarcoidosis. Moreover, 25% of suspected nodules turn out to be benign, meaning that 1 in 4 patients with suspicious nodules does not have a tumor.

So, because these procedures are inherently limited to findings of masses or nodules, without providing critical molecular information to discriminate between malignant and benign, a biopsy is needed to confirm, with certain added problems that this entails: first, the risk The added stress associated with the biopsy can be difficult for patients to bear; Second, for those patients with advanced or inaccessible cancers, biopsy may not be an option; and finally, all of these procedures add significant costs throughout treatment.

A cost-effectiveness analysis published on November 6, 2014, in the New England Journal of Medicine (based on data from the National Lung Screening Trial) estimated that the cost of a CT scan is $1,631 per person, with $81,000 spent per quality-adjusted life year gained.