Lung Cancer
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Lung Cancer is the third most common type of cancer in North America and is the leading cause of cancer deaths. While approximately 14% of new cancers diagnosed are lung cancers, it accounts for 25% of all cancer deaths. Lung cancer is a type of cancer that begins in the cells of the lungs as a cancerous or a malignant tumour and can spread to nearby tissues.

A tumour is a group of cells that grow and divide abnormally. There are several different types of tumours and cancers involving the lungs. Non-cancerous tumours in the lungs are called hamartoma or papilloma. A cancerous tumour, in contrast, can continue to grow into and destroy nearby tissue.  It can also spread cancer cells to other parts of the body in a process known as metastasizing.

Lung metastasis is cancer that originated elsewhere in the body and spread to the lungs. This type of cancer is treated differently to cancer that began in the lungs. Pleural mesothelioma is often mistaken for lung cancer, but this type of cancer starts in the pleura covering the lungs and not in the lungs themselves. The treatment and prognosis of pleural mesothelioma is very different from lung cancer.

Cancer that has started in the lungs is called primary lung cancer. Primary lung cancer, or bronchogenic carcinoma, is divided into two types: non-small cell lung cancer (NSCLC) or small cell lung cancer (SCLC). The type of primary lung cancer depends on the type of cell where cancer began.

Non-Small Cell Lung Cancer

Non-small-cell lung cancers (NSCLC) are the most common, comprising between 80-85% of all lung cancers. This type of cancer usually begins in the glandular tissue on the outer part of the lung, on the lung cells responsible for mucous production. There are several different types of NSCLCs, some of which are listed below. (Canadian Cancer Society)

  1. Adenocarcinomas (Most common)

These start in the glandular tissues on the outer part of the lung. They are the most common type of NSCLC. These tumours form on the lung cells responsible for mucous production. This cancer can be found in those who smoked or who never smoked, and is the most common lung cancer in women and young people.

  1. Squamous cell carcinoma (Most common in smokers)

This starts in the squamous cells that line the bronchi, or the large ducts that branch off the windpipe into the lungs. This type of cancer is most common in smokers.

  1. Large cell carcinoma (Less common)
  2. Sarcoma (Rare)
  3. Sarcomatoid carcinoma (Rare)

Small Cell Lung Cancer

Small cell lung cancers (SCLC) usually start in the cells that line the bronchi in the centre of the lung. There are two types of SCLC: small cell carcinoma and combined small cell carcinoma.

Risk Factors

Pack Years:

Although lung cancer can occur in anyone, smoking is the number one risk factor.  Those at the highest risk are individuals who have smoked over 30 pack years.  A “pack year” is defined as the number of packs smoked per day, multiplied by the number of years smoked.  An individual would have smoked 30 pack years for instance if they smoked a pack a day for 30 years, or two packs a day for 15 years.

Age:

In both smokers and non-smokers, the risk increases with age as more than half of new cases occur in those over 60 years, and the average age of diagnosis is 70 years.

Sex:

Smoking is also more common in men, and consequently, lung cancer is more common in men.

Ethnicity:

Ethnicity also plays a role in the likelihood of developing lung cancer, although the interaction is unclear.  Research has shown that black men are 20% more likely to develop lung cancer than white men. However black women are 10% less likely than white women to develop lung cancer.

Research has shown that as much as 45% of lung cancers are caused by modifiable risk factors. (Islami) These risk factors may increase the likelihood of developing lung cancer.

  • Smoking tobacco
  • Second-hand smoke
  • Radon
  • Asbestos
  • Occupational exposure to certain chemicals
  • Outdoor air pollution
  • Personal or family history of lung cancer
  • Personal history of lung disease
  • Exposure to radiation
  • Arsenic in drinking water
  • Pollutants from cooking and heating
  • Weakened immune system
  • Lupus
  • Beta-carotene supplements in smokers

Although the research has been inconclusive thus far, these factors could possibly increase the risk of developing lung cancer.

  • Occupational exposure to certain chemicals
  • Genetic mutations
  • Smoking marijuana
  • Physical inactivity
  • A diet low in vegetables and fruit

Screening

Finding lung cancer early increases the chances that treatment will be successful. Studies have shown that screening using chest x-rays and sputum tests are not effective and therefore are not recommended.

Low-Dose CT Scan

Research has shown that screening with low-dose computed tomography (low-dose CT) can find cancer in people before they have symptoms. The National Lung Screening Trial was a large clinical trial that examined the use of low-dose CT of the chest to screen for lung cancer. This trial found that participants who received the LDCT had a 20% lower chance of dying from lung cancer than those who were screened using x-rays, and also seven percent lower chance of death from any cause. (Cressman)

In adults at high risk, the Canadian Task Force on Preventive Health Care (CTFPHC) recommends screening for lung cancer with low-dose CT once per year.  High-risk individuals include those who:

  • are 50–74 years (evidence shows that screening is most effective for people in this age group)
  •  are current smokers or former smokers who quit in the last 15 years
  • have smoked 30 pack-years, which is defined as one pack per day for at least 30 years or two packs per day for 15 years

The CTFPHC also strongly recommends including support to help people quit smoking. In addition to increasing the chances of developing lung cancer, smoking also reduces the effectiveness of cancer treatments.

The benefits of screening include early diagnosis, which is a very important factor in the likelihood of treatment success.  There are some potential risks associated with screening as well. The risks of lung cancer screening include exposure to radiation, false-positive results, and any potential complications from follow up tests that result from false positive results. (Hoffman)

Symptoms

There may be no signs or symptoms in the early stages of lung cancer. For many, the symptoms don’t begin until cancer has already advanced to the later stages. The first signs are usually coughing or shortness of breath. The signs and symptoms are the same for all of the different types of lung cancer and can include: (Canadian Cancer Society )

  • a cough that gets worse or doesn’t go away
  • shortness of breath
  • wheezing
  • chest pain that is always felt and gets worse with deep breathing or coughing
  • blood in mucus coughed up from the lungs
  • chest infections like bronchitis or pneumonia that don’t get better or keep coming back
  • weight loss
  • fatigue
  • hoarseness or other voice changes
  • difficulty swallowing
  • collapsed lung
  • larger than normal lymph nodes in the neck or above the collarbone
  • a buildup of fluid around the lungs (pleural effusion)
  • bone pain
  • a headache
  • weakness

Paraneoplastic syndrome describes a phenomenon in which substances produced by cancer cells affect the normal function of other organs or tissues. For example, squamous cell carcinoma is likely to cause hypercalcemia or too much calcium in the blood. Other examples of paraneoplastic syndromes include syndrome of inappropriate antidiuretic hormone (SIADH), Cushing syndrome, Lambert-Eaton syndrome, or paraneoplastic cerebellar degeneration.

Diagnosis

Doctors diagnose lung cancer using a combination of health history, physical exam, imaging, and lab tests. Further tests may include a complete blood count (CBC). A CBC measures the number and quality of white blood cells, and blood chemistry tests give an idea of overall health. (NIH National Cancer Institute)

Some of the tests that doctors use to diagnose and stage lung cancer are:

  • Chest x-rays: these are often the first tests done to indicate that there may be cancer in the lungs by showing a spot, tumour, or change.
  • CT scans (computed tomography): uses specialized x-ray equipment to create a 3D image of the lungs. These can be used to show the size, location, and shape of a tumour. They can also find any abnormally large lymph nodes and can be used to guide a biopsy.
  • PET Scan (positron emission tomography): produces an image of the whole body to indicate whether, and how far cancer has spread.
  • MRI (magnetic resonance imaging): uses powerful magnetic forces to create cross-sectional images of organs.
  • Ultrasound: used to look for a buildup of fluid around the lungs, and to guide a biopsy during an endoscopy.
  • Biopsy: a doctor removes cells or tissues so that they can be tested in a lab. A pathologist will test the cells to confirm if they are cancer or not.
  • Fine needle aspiration: uses a very thin needle and syringe to remove a sample of cells, tissue, or fluid. These cells can be used to diagnose lung cancer.
  • Core biopsy: like a fine needle aspiration, but uses a larger needle to remove tissues. Larger amounts of tissue help with diagnosis and identifying type of cancer.
  • Endoscopy: is performed to remove tissue and see how far lung cancer has spread. Doctors use a flexible or rigid tube with a light and lens to look inside the body. A bronchoscopy looks at the large airways of the lungs, the trachea and bronchi. A mediastinoscopy looks at the area between the lungs called the mediastinum. A thoracoscopy looks inside the chest cavity, including the chest wall, lining of lungs, lymph nodes in the chest.
  • Sputum tests: mucus coughed up from the lungs may be examined for cancer cells. Tumours of the large bronchi, or squamous cell tumours, shed cancer cells into sputum.
  • Immunohistochemistry: looks for certain proteins called antigens that are found on the surface of cells. These proteins can help identify the type of cancer.
  • Molecular tests: look for changes or mutations in genes of lung cancer cells. These changes affect the type of treatment given because some chemo drugs are more powerful against cells with these changes. Molecular tests will often examine for changes in epidermal growth factor receptor (EGFR). This is a protein found on the surface of cells that help cells to grow.
  • Pulmonary Function Tests: check how well the lungs are functioning. These tests measure how much air a patient can hold in their lungs and how well the patient can expel air. Accurate results are very important if surgery is an option because they tell the doctors how much lung capacity will remain after a part of the lung is removed.

Staging

Once lung cancer is diagnosed, oncologists determine the size of a tumour and how far it has spread.  This is called staging.  Staging is based on symptoms and the results of diagnostic tests. NSCLC is staged as 0 to IV, and SCLC is considered either “limited” or “extensive”. Staging depends mainly on the size of the tumour, how deeply the tumour has invaded nearby tissue, and whether or not the cancer has spread to the lymph nodes or other parts of the body.

In stage 0, cancer cells are found only in the lining of the airway, or the air sacs.  With each stage, the tumour is slightly larger, and the likelihood that it has metastasized has increased. In stage IV cancer has spread to the other lung, and to other areas of the body.

Limited SCLC lung cancer is confined to one side of the chest, and extensive SCLC means that the lung cancer has spread to another side, or to other organs.

Staging helps doctors to decide which therapy to use. Accurate staging is extremely important because treatments that are effective at one stage could actually be harmful at another stage.  (Christopher Slatore MD and Suzanne C Lareau RN)

Treatment

Doctors diagnose lung cancer using a physical exam, imaging, and lab tests. Treatment depends on the type, stage, and how advanced the cancer is. Treatments include surgery, chemotherapy, radiation therapy, and targeted therapy. (Cella) Targeted therapy uses substances that attack cancer cells without harming normal cells.

  • Surgery:

Surgery is a treatment option for early-stage NSCLC and provides the best chance for a cure. Lung surgery is a complex operation however, with serious risks. A thoracotomy is any surgery that creates an incision into the lungs, and is the most commonly used type of surgery. With increasing frequency however, doctors are using a technique called Video-assisted thoracic surgery (VATS), which require smaller incisions than a traditional thoracotomy. A rigid tube with a tiny video camera is placed through a small hole in the chest to allow the surgeon to see inside the chest.  Two other small holes allow the surgical instruments into the chest to perform the surgery.  Surgeons commonly use this technique to remove early-stage tumours near the outside of the lungs. (National Cancer Institute)

There are several different surgical options including:

  • Pneumonectomy: removes the entire lung.
  • Lobectomy: removes an entire lobe (often preferred).
  • Segmentectomy or wedge resection:only part of the lobe is removed. This may be done if the patient does not have enough lung function to remove the whole lobe.
  • Sleeve resection:used to treat some cancers in the large airways of the lungs, such as the trachea. This option may preserve more lung function.
  • Radiofrequency ablation (RFA): this is an option for those who have a small tumour near the outer edge, and can’t tolerate surgery. This type of operation uses high-energy radio waves to heat and destroy the tumour. (Casal)
  • Radiation therapy: A machine aims high-energy radiation at your body to kill the cancer cells.  This procedure is painless, but may cause side effects such as sore throat or shortness of breath. It is used more commonly with early lung cancer, instead of surgery.  After surgery, this therapy can be used to destroy any cancer cells that may be left.  It may also be used in conjunction with chemotherapy for more advanced cancers. Radiation therapy can help shrink a tumour that is blocking the airway.
  • Chemotherapy: This type of therapy uses drugs administered intravenously to kill cancer cells and can be used alone or with radiation therapy. Chemotherapy is responsible for many side effects depending on which drugs are used. Chemotherapy patients may suffer from infections, bruise easily, or feel weak or tired.  Other side effects include hair loss, poor appetite, nausea, vomiting, and weight loss.
  • Targeted therapies are very specific therapies that are used for NSLC that has spread. For example, one type of therapy is used only if there is a very specific gene change. When used correctly, these therapies can block the growth and spread of lung cancer. Medications may be administered orally or intravenously depending on type of therapy. The list of potential side effects is quite long and varied.
  • Immunotherapy is the use of a patient’s own immune system to identify and destroy cancer cells. This type of therapy is sometimes effective against NSCLC in patients whose cancer has returned after chemotherapy or other treatments. The list of potential side effects is quite long and varied. (Hollen)

Lung cancer is the leading cause of cancer deaths, and is by far the most preventable.  Symptoms frequently don’t appear until late stages and treatments are often unsuccessful. Avoiding cigarette smoke exposure is the best way to reduce the chances of developing lung cancer, and lung cancer screening for those who smoke is the most effective way to detect cancer early.

It is important for those diagnosed with lung cancer to take advantage of available supports.  (Canadian Cancer Society) (Canadian Cancer Society) There are many support groups, networks, and sources of information that may be useful for those with cancer. Much information and support are available through the Canadian Cancer Society or the American Cancer Society, as well as through local cancer clinics and family doctors’ offices.

Written by Lisa Borsellino, BSc

References:

(1) Canadian Cancer Society. 09 12 2017 <http://www.cancer.ca/en/cancer-information/cancer-type/lung/risks/?region=on>.
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(3) Canadian Cancer Society. “Advanced Cancer.” 2017.
(4) Canadian Cancer Society. “Lung Cancer: Understanding your Diagnosis.” 2017.
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(9) Hoffman, Richard and Rolando Sanchez. “Lung Cancer Screening.” Medical Clinics 101.4 (2017): 769-785.
(10) Hollen, Patricia J., et al. “Measurement of quality of life in patients with lung cancer in multicenter trials of new therapies. Psychometric assessment of the Lung Cancer Symptom Scale.” Cancer 73.8 (1994): 2087-2098.
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(12) National Cancer Institute. “What You Need to Know About Lung Cancer.” NIH Publication No. 12-1553. 2012.
(13) NIH National Cancer Institute. <https://www.cancer.gov/types/lung/patient/non-small-cell-lung-treatment-pdq#section/_164>.

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