Lung Cancer

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Definition/Description

Lung cancer is the uncontrolled growth of abnormal cells that start off in one or both lungs and arises from the cells of the respiratory epithelium. Cancer that is formed initially in the lungs is known as primary lung cancer and cancer that begins in another area of the body but then spreads to the lungs is called secondary lung cancer. Primary lung cancer is divided into two types which are classified as small cell lung cancer and non-small cell lung cancer. The classification of these two types of primary lung cancer is established by the type of cells in which the cancer starts.

Non-small-cell lung cancer is the most common type of primary lung cancer, as it accounts for more than 80% of cases. It is further divided into 3 subtypes: squamous cell carcinoma, adenocarcinoma and large-cell carcinoma

Squamous cell carcinoma

• Located 2/3 central and 1/3 periphery of the lung
• Arises from large airway epithelial cells
• Strong association with cigarette smoking
• Tends to create obstruction and cause distal atelectasis
• Best prognosis

Adenocarcinoma

• Located in the periphery of the lung
• Arises from small airway epithelial cells and type II alveolar cells
• Most common type of lung cancer in non-smokers and more prevalent in women

Large-cell carcinoma

• Located in the periphery of the lung
• Similar to adenocarcinoma but the lesions tend to be larger

Small-cell lung cancer is a highly malignant tumor derived from cells exhibiting neuroendocrine characteristics. It is a less common type that accounts for about 15-20% of cases and usually spreads faster than non-small-cell lung cancer. It is often at a more advanced stage when it is diagnosed (British Lung Foundation, 2015). This type of lung cancer, which has the strongest association with cigarette smoking, leads to the worst prognosis due to it’s rapid growth.

Epidemiology

Lung cancer is one of the most common and serious types of cancer. It is the second highest cancer incidence in both males and females, following prostate cancer in men and breast cancer in women. It is diagnosed in over 41,000 people every year in the UK and is the leading cause of cancer death around the world. In 2008, lung cancer contributed to 13% or 1.6 million of total cancer cases and 18% or 1.4 million cancer-related deaths worldwide. Lung cancer incidence and mortality rates are highest in the United States and developed countries and almost 9 in 10 lung cancer cases occur in people aged 60 years or older.

Aetiology

Smoking
Cigarette smoking is the leading cause of lung cancer and accounts for about 85% of diagnosed lung cancer patients. Smoking is also most strongly associated with small cell lung cancer and squamous-cell carcinoma. Risk for lung cancer increases with the duration, intensity and depth of smoke inhalation. Second-hand smoking also causes lung cancer, but is less strongly associated compared to active smoking. Cigarettes contain more than 60 carcinogens that have been shown to induce cancers. Nicotine causes addiction to cigarette smoking and has been shown to inhibit apoptosis, proliferate cells, and cause angiogenesis in lung tumours.
Cigar and pipe tobacco smoking produces relatively large particles that only reach the upper airways, where cigarette smoking reaches the distal airways because it produces fine particles. Therefore, the risk of lung cancer is lower with cigar and pipe smoking. Smokers of all ages will benefit from the cessation of smoking, but the risk of developing lung cancer will still be increased compared to never smokers. Never smokers are individuals who smoked fewer than 100 cigarettes in their lifetime but this still accounts for 25% of lung cancers worldwide.

Occupational and Environmental exposure
A number of environmental risk factors have been identified, most of which often relates to occupational exposures such as asbestos, tar, soot, and a number of metals such as arsenic, chromium, and nickel. Air pollution has also been linked to increased risk of lung cancer.
Radon gas, a radioactive gas that percolates up soil and becomes concentrated inside buildings, have been posed as a significant risk factor for lung cancer.

Genetics
There is a genetic susceptibility which increases the risk of lung cancer among first-degree relatives.

Other factors
There are several other factors that increase the risk of developing lung cancer, and they include:

• Gender (men more predisposed than women)
• Dietary factors
• Individuals with chronic obstructive pulmonary disease
• Ethnicity
  

Investigations

Chest X-ray
A chest X-ray is usually the first step in diagnosing lung cancer. Tumours usually appear as white/grey masses. Chest X-rays do not always give a clear enough diagnosis, due to the fact that they can’t distinguish between multiple conditions (ex. consolidation and lung abscess)

CT scan
A CT scan or Computerised (axial) tomography scan, usually carried out after a chest X-ray, takes a series of x-rays at different angles and through the use of computer processors produces a series of cross-sectional images of specific areas of a scanned object, allowing the user to see inside the object. This scan gives a very accurate picture of where a tumour is and its size.
Before having a CT scan, you will be given an injection of a contrast medium. This is a liquid containing a dye that makes the lungs show up more clearly on the scan. The scan is painless and takes 10-30 minutes to complete.

PET-CT scan
A PET-CT or Positron Emission Tomography computerised tomography,is usually conducted if the results of a CT scan show an early stage cancer. the PET-CT is able to identify where there are active cancer cancer cells. These results are quite useful in helping with diagnosis and treatment.
Before undergoing a PET-CT the individual is injected with a slightly radioactive material. The scanner then works by detecting the radiation given off by the injected radiotracer.

Bronchoscopy and biopsy
A bronchoscopy is a procedure that allows a physician to remove a small sample of cells from the inside of the lung using a bronchoscope. The bronchoscope is a small tube like device which is passed through the mouth or nose and down through the throat into the airways. this procedure is slightly uncomfortable however it is relatively quick and only takes a few minutes.

Other types of biopsies include:

• Percutaneous needle biopsy
• Thoracoscopy
• Mediastinoscopy
• Screening

According to the NHS there is currently no national screening program for lung cancer in the UK. The lack of a National screening program is due to the complexity of the tests required to identify lung cancer. No simple, and quick test sensitive enough to outweigh possible risks associated with screening is yet available (ex. radiation exposure during x-rays).

Clinical Manifestations

Cough

• Presence of mass irritates the cough receptors in the airway
• More common in squamous cell carcinoma and small cell lung cancer (more commonly found in the central airways)
• Obstruction from central airway could also lead to post-obstructive pneumonia and distal atelectasis

Weight loss

• Cancer induced proteolysis and lipolysis leads to loss of muscle and adipose tissue.

Hemoptysis

• Tumor in the central airway
• Tumor-induced angiogenesis result in blood vessels that are leaky and twisted, leading to easy ruptures and causing hemoptysis

Dyspnea

• Obstruction of Airway leading to shortness of breath
• Mechanoreceptors and chemoreceptors are activated in the lungs due to cachexia or hypoxemia/acidosis

Chest pain

• Tumor involving pleural surface causing pleuritic chest pain

Pleural Effusion (chest pain, dyspnea)

• Benign pleural effusion may be due to lymphatic obstruction, post-obstructive pneumonitis, or atelectasis
• Malignant pleural effusion occurs when malignant cells and present in pleural fluid
  
  

Physiotherapy and Other Management

Physiotherapy and other management. Other health professionals will be treating your patient. What is their input?

Prevention

Brief consideration of how this pathology could be prevented and the physiotherapy role in health promotion in relation to prevention of disease or disease progression.

Resources

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Recent Related Research (from Pubmed)

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References

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