Lung cancer as seen on a chest x-ray- Rollover mouse to view lung tumour
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.
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:
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.
Figure 1: Classification of types of lung tumours
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”.
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.|
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.
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.
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).|
|5 yr survival rates
Recurrence of lung cancer
Operative mortality (death)
Ability to sample lymph nodes
|*Equivalent outcomes are based on clinical trials (reference below).|
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.
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Chapter 85: Neoplasms of the Lung. Minna J, Schiller J.
Cancer Canada Website
Toronto Notes 2013
VATS vs. Lobectomy
1) Yan T, Black D, Bannon P, McCaughan B. Systematic review and meta-analysis of randomized and nonrandomized trials on safety and efficacy of video-assisted thoracic surgery lobectomy for early stage non-small cell lung cancer.
Journal of Clinical Oncology 2009; 27:2553-2562.
2) Linden D, Linden K, Oparka J. In patients with resectable non-small cell lung cancer, is video-assisted thoracoscopic segmentectomy a suitable alternative to thoracotomy and segmentectomy in terms of morbidity and equivalence of resection?
Interactive Cardiovascular and Thoracic Surgery 2014; 19:107-110.