• Surgery
• Lung Cancer

Lung Cancer

Lung cancer as seen on a chest x-ray- Rollover mouse to view lung tumour

The Cause of Lung Cancer

Lung cancer develops when healthy lung cells become damaged and transform into malignant cells. Malignant cells rapidly multiply and grow abnormally into surrounding tissue and can travel to other parts of the body (metastasize).

About 85% of lung cancers are attributed to ongoing or previous cigarette smoke exposure. Cigarette smoke exposure is the single largest contributor to the development of lung cancer. However, it is possible for lifetime non-smokers to develop lung cancer due to other risk factors. A risk factor can be thought of as any toxic exposure, underlying medical condition or genetic predisposition that contributes to the development of cancer. Toxins such as asbestos, radon (a radioactive gas that can be found in the basements of some homes) and dust/fumes from certain metals are examples of other contributory exposures. Anyone with a parent, brother or sister who has lung cancer is also at a higher risk of developing the disease. Thus, an individual develops lung cancer as a result of the amount of lifetime cigarette smoke exposure, other toxin exposures in the work place or home, and the person’s genetic predisposition for developing cancer.

There are a variety of other risk factors that may be specific to an individual which can be discussed with your physician.

Types and Severity of Lung Cancer
(Classification and Staging)

Overtime, a malignant cell will grow into an abnormal mass of cells called a tumour. When a tumour is identified or suspected, a physician orders tests to assess the disease. There are two goals of these investigations:

1. Classification of the type of lung tumour
2. Staging of the tumour to assess the degree of spread in the lung and body

Lung Tumour Classification

A lung tumour is an abnormal mass of cells within the lung and does not always represent lung cancer. Some abnormal lung masses (tumours) are not malignant because they do not have the ability to spread or metastasize to other parts of the body. These tumours are called Benign and are not cancer. When invasive malignant cells are found within the lung this is cancer. The cancer can be primary (from the lung) or a metastases (cancer from elsewhere in the body). Primary lung cancer indicates that the malignant transformations originated within the lung.

Primary lung cancers are divided into two groups based on how the malignant cells appear under the microscope. They can be either Non-Small Cell Lung Cancer (NSCLC) or Small Cell Lung Cancer (SCLC). There are a variety of subtypes of Non-Small Cell Lung Cancer depending on the type of lung tissue that the tumour arises from. Figure 1 below shows the classification.

 

Staging Lung Cancer

The stage of lung cancer describes how the disease has spread within the body. Staging is different for Small Cell and Non-Small Cell Lung Cancer.

Three factors are considered in staging of Non-Small Cell Lung Cancer (NSCLC). This is referred to as “TNM” Staging which stands for “Tumour, Nodes, Metastases”.

1. T = Tumour: The size of the mass
2. N = Nodes: The number and location of lymph nodes that the cancer has spread to
3. M = Metastases: Whether or not the cancer has traveled to locations outside of the lung

There are four different stages of Non-Small Cell Lung Cancer with subsets at each stage. Table 1 below is a simplification of the different stages of lung cancer.

Table 1: Staging of Non-small Cell Lung Cancer*

Stage I	A cancer that can be completely removed with no spread outside of the tumour
Stage II	A cancer that has spread to the lymph glands within the lung
Stage III	A cancer that has spread to the lymph glands in the centre of the chest
Stage IV	The tumour has spread to distant sites (eg. liver, bone, brain)
*Details of each stage and subdivisions of stages can be found in TNM Staging (7th Edition) referenced below

Small Cell Lung Cancer (SCLC) is a less common and more aggressive form of lung cancer. The Staging process for SCLC is shown in Table 2 below.

Table 2: Staging of Small Cell Lung Cancer

Limited Stage	Cancer is in one side of the thorax (chest) with local lymph nodes involvement only.
Extensive Stage	Cancer spread is more extensive.

Imaging and Investigations in Lung Cancer

Once you have been diagnosed with lung cancer, your physician may order a variety of imaging and investigative tests to properly stage it. In general, all patients with suspected lung cancer receive a Chest Radiograph (Xray) and a Computed Tomography (CT) scan at a minimum. Some of the common tests are outlined below.

Medical Imaging

1. Chest Xray – Usually two views are taken of the chest. This is a preliminary study with very mild radiation exposure.
2. Computed Tomography (CT) – This imaging modality uses elliptical Xrays to construct a two dimensional image of the chest that can be viewed from different angles.
3. Magnetic Resonance Imaging (MRI) – This imaging method uses magnetic resonance and in the setting of lung cancer is used to image the brain for metastases (spread of cancer). If you are claustrophobic, or have metallic implants, you may need a CT scan of the brain instead.
4. Positron Emission Tomography (PET) Scan – In this study the patient is injected with sugar molecules with a tracer attached to them. Cells that are growing or multiplying rapidly (for example cancer cells) take up the sugar the most and appear bright on imaging. This will tell your surgeon if the cancer has spread outside of the chest cavity, to the bones, liver and adrenal glands.
5. Endobronchial Ultrasound (EBUS) – This method utilizes a camera to travel down the airway and obtain images of the lung tissue from within the lung airspace using sound waves.

Other Investigations

1. Fiberoptic Bronchoscopy – This study involves the use of a camera to travel down the airway and into the patient’s lung. Samples can be taken from within the lung during the study.
2. Mediastinoscopy – This study involves a small incision in the chest with a camera placed into the area between the lungs. The patient is asleep for the study and samples of tumour or lymph nodes can be taken.
3. Transthoracic fine needle aspiration biopsy – A needle is guided into the patient’s chest to sample a tumour so that a pathologist can determine the type of tumour cells.
4. Thoracentesis – This study involves drainage of fluid from within the chest. This may be a diagnostic test to determine the type of cancer cells in the fluid or a treatment for symptoms related to fluid around the lungs.
5. Pulmonary Function Tests (PFTs) – These tests assess the patient’s ability to breath and help guide surgical options.
6. Bone Marrow Biopsy – This study is indicated if there is suspected spread of cancer to the bone.

 

 

Surgical Options for Lung Cancer

The role of a Thoracic Surgeon in the treatment of lung cancer is to surgically remove tumours. The following are some of the types of surgical procedures used to treat lung cancer.

• Wedge or Segmental removal of a tumour with a margin of healthy tissue around it.
• Lobectomy which removes a single lung lobe. Lobes are a section of lung and there are 3 lobes in the right lung and two lobes in the left lung.
• Pneumonectomy which is the removal of an entire lung.
• Lymph node dissection which removes lymph nodes that may have cancer cells in them.

The surgeon must determine which cancer tumours can be removed and this depends on the tumour staging and health status of the patient. In general, Small Cell Lung Cancer is not operable. For Non-Small Cell Lung Cancer Stages I and II are usually operable and sometimes Stage III as well. Some patients cannot tolerate surgery regardless of tumour stage because removal of all or part of the lung would make it impossible for them to breathe adequately. These patients are not considered operable candidates.

Two surgical methods exist for removal of a lung cancer including: Video Assistant Thoracoscopic Surgery (VATS) and Open Lobectomy. A description of these procedures and list of benefits of each operation are provided below.

Information below is provided as a guide only since each patient situation is unique . You should discuss which option is best for you with your surgeon.

Table 5: VATS vs Open Lobectomy

	Video Assisted Thoracoscopic Surgery (VATS)	Open Lobectomy
Description	A type of minimally invasive surgery that uses a 2-4 cm incision between the ribs to access the inside of the chest (thorax) with fiber optic cameras and surgical tools.	A classic surgical approach that opens the chest and spreads two ribs to allow the surgeon to operate with a clear field of vision in the inside of the chest (thorax).
Equivalent Results*	5 yr survival rates Recurrence of lung cancer Operative mortality (death) Operative complications Ability to sample lymph nodes
Benefits	Decreased post-operative pain Shorter hospital stay Shorter time with chest tube (drain)	May be used for more advanced disease or larger tumours
Limitations	Cannot be used if significant internal scarring, May not be possible for larger tumours Occasionally the operation must be converted to an open operation to address unexpected findings or complications	Increased trauma to the thorax (rib cage) and skin/soft tissues Longer healing time and increased postoperative pain
*Equivalent outcomes are based on clinical trials (reference below).

Additional Therapy:

Some patients will require additional treatment based on the tumour stage. In general, patients with stage I lung cancer do not need any additional therapy except for operation. Patients with stage II lung cancer are generally candidates for chemotherapy, although this is highly dependent upon risk factors for chemotherapy. Stage III lung cancers are advanced and usually require a more complex treatment course.