Definition and Overview

Squamous cell carcinoma (SQC) of the lung is a type of lung cancer.

Lung cancer has two main types. They are called small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). SQC is a subtype of NSCLC. Other types of NSCLC are adenocarcinoma and large cell carcinoma.

NSCLC is more common than SCLC. It accounts for about 80-85% of all lung cancers. SQC is the second most common type of NSCLC. It accounts for about 25-30% of all cases. It commonly starts in early cells found in the centre of the lungs. The condition does not cause symptoms in the early stages. Thus, it is often found when it has already spread to other parts of the body. This is a cause for concern because early detection is key to achieve better treatment outcomes. If the condition is found at an advanced stage, the patient’s chances of survival within five years are less than 20%.

Causes of Condition

The cause of SQC of the lung is unknown. But most cases are attributed to smoking. Other risk factors are exposure to certain chemicals and genetics.

Up to 90% of lung cancer cases are associated with cigarette smoking and exposure to cigarette smoke. Cigarette smoke contains many carcinogenic compounds and toxins. These include tar, nicotine, and carbon monoxide. These harmful substances can cause permanent damage to the lungs.

Lung cancer can also occur due to exposure to cancer-causing agents in the workplace. These include uranium, diesel exhaust, coal products, and nickel compounds.

Other risk factors are the following:

  • Genetics - Studies found that having close relatives with lung cancer increases one’s risk of the disease. This risk can further increase if they are smoking. These people can benefit from regular lung cancer screening tests. These tests are used to catch the disease early. This is important because early-stage lung cancers are responsive to treatment.

  • Radiation therapy - Radiation therapy for the treatment of cancer in or around the chest area increases the risk of lung cancer.

  • Lung diseases - Certain lung conditions are thought to increase the risk of lung cancer. These include pulmonary fibrosis (PF) and chronic obstructive pulmonary disease (COPD). PF causes scarring in the lungs. This interferes with a person’s ability to breathe normally. COPD, on the other hand, is a term that refers to a number of progressive lung diseases. These include chronic bronchitis and emphysema.

  • Prolonged exposure to air pollution.

Key Symptoms

Most lung cancer patients do not have symptoms in the early stages. Symptoms begin to develop when cancer advances and lung tissues become damaged. The first sign is a cough (with or without blood) that does not go away even with standard treatment. Other symptoms include chest pain, wheezing, and shortness of breath. There may also be other signs depending on the extent of damage. These include difficulty swallowing (if cancer cells spread to the oesophagus) and chronic lung infections (if the large airway becomes obstructed).

Other signs are fatigue, weight loss, and loss of appetite. Depression and mood changes are also common.

Who to See and Types of Treatments Available

Lung cancer patients are treated by a team of doctors. These include cancer and pulmonary (lung) specialists. The team also includes doctors specialising in pain management.

The condition is diagnosed with laboratory and biomarker tests and biopsies. Imaging tests are also used. These include chest x-rays, CT and PET scans, and magnetic resonance imaging (MRI). The results of these tests help doctors to:

  • Identify the type of lung cancer the patient has.

  • Determine the stage of cancer.

  • Identify the best possible treatment for the patient.

The stages of SQC of the lung range from I to IV. The higher the stage, the more difficult it becomes to cure the disease.

In stage I, the tumour is very small and confined to the lung. In stages II and III, the tumour is bigger but still confined to the lung. Stage IV lung cancer is the most serious. It means that cancer has spread to other parts of the body. Lung cancer can spread to the bone and brain. When this happens, removing cancer cells can become very challenging.

Lung cancer treatment depends on many factors. These include:

  • The patient’s preference and overall health condition.

  • The size and position of the tumour.

  • The stage of cancer (whether or not it has spread to the bones and brain).

Early-stage lung cancer can be cured in some cases. This is possible if all cancer cells are removed during surgery. The prognosis is also good if cancer cells are contained in just one area of the lung. In patients with advanced lung cancer, treatment focuses on relieving their symptoms. Doctors focus on ensuring that they are not in pain. They also work on improving the patient’s quality of life.

In general, treatment of all types of lung cancers involves the surgical removal of the abnormal growth. Surgeons may also need to remove a small part of the lung or the entire lung. This depends on the stage of cancer. Surgery is often followed by chemotherapy and radiotherapy.

Newer therapies can also be used to improve treatment outcomes. These include targeted therapy and immunotherapy. Each treatment has risks and benefits. Chemotherapy, for example, can cause nausea, vomiting, and hair loss. It is also often associated with weight loss due to poor appetite. The risks and benefits of all therapies are discussed by the patient’s medical team before any treatment is initiated. Each therapy is only considered if its benefits outweigh its risks.

The prognosis of lung cancer patients is generally poor. This is because the disease is often caught when it has already spread to other parts of the body. The five-year survival rate for stage 1 NSCLC is only 45-49%. This number goes down to just 1% for patients with stage 4 lung cancer.

Lung cancer kills about 1.5 million people every year. Because it can be very difficult to treat, the preferred approach is to prevent it from occurring. Steps that can be taken to lower a person’s risk of lung cancer are the following:

  • Do not smoke or stop smoking as soon as possible.

  • Avoid secondhand smoke and air pollution.

  • Eat a healthy diet that is high in fruits and vegetables.

  • Be more active. A sedentary lifestyle can increase many health risks.

References:

  • American Cancer Society. Cancer Facts & Figures 2017. Atlanta, Ga: American Cancer Society; 2017.

  • Amos CI, Pinney SM, Li Y, et al. A susceptibility locus on chromosome 6q greatly increases lung cancer risk among light and never smokers. Cancer Res. 2010;70:2359–2367.

  • Caporaso N, Dodd KW, Tucker MA. New Malignancies Following Cancer of the Respiratory Tract. In: Curtis RE, Freedman DM, Ron E, Ries LAG, Hacker DG, Edwards BK, Tucker MA, Fraumeni JF Jr. (eds). New Malignancies Among Cancer Survivors: SEER Cancer Registries, 1973-2000. National Cancer Institute. NIH Publ. No. 05-5302. Bethesda, MD, 2006.

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