Stages of Small Cell Lung Cancer

After the diagnosis, the doctors can find out the extent to which cancer has spread to other parts of the body. This process is the staging process. And so, the tumor stage explains the level of its spread to other body parts. It further helps determine the severity of the disease and recommend appropriate treatment concerning the same.

The cancer stage is generally used by doctors when discussing the survival statistics. The locations of small cell lung cancer entirely depend upon the results of the tests that have been conducted for its diagnosis. Generally, the lower number of stages of small cell lung cancer is associated with the better outcome. However, the treatment works differently for each tumor.

The Two Stage System

The doctors have used a two-stage system for treating small cell lung cancer ^​1​. Furthermore, the stages are classified as limited stages and extensive stages. In the limited stage of cancer, the efficacy increases with aggressive treatments . These treatments can also include chemotherapy, combined with radiation therapy. In the extensive stage of small cell lung cancer, chemotherapy alone has provided a better option for controlling cancer but not curing it. The stages of small cell lung cancer are :

Limited stage

It means that the cancer is located only at one portion and can be effectively treated using a single radiation field. It mainly involves cancer found only in one lung until the tumor spreads throughout the lung and may also reach the lymph nodes on the same side of the chest region. Cancer within the lymph nodes above the collarbone is the supraclavicular nodes. It is a limited stage cancer as long as they are located only at one side of the lung in the chest region. Some doctors also refer to lymph nodes at the central area of the chest known as mediastinal lymph nodes. Even though, they are located closer to the other side of the chest region.

If the cancer is confined to one particular region, which is small enough to get treated with radiation therapy is known to be the one port or one treatment area.

Extensive stage

It mainly describes the cancer spread across the lung region. And so, it can include from other portions of the lungs to the lymph nodes on the other side of the chest region or other parts of the body, involving the bone marrow. Small cell lung cancer show metastasis towards the fluid surrounding the lungs, at the extensive stage.

TNM staging system

It is a formal system for describing the growth and spread of lung cancer as per recommended by the Committee on Cancer (AJCC) TNM staging system that comprises three significant pieces of information:

Size and extent of the primary tumor (T)

It refers to how large the tumor is and whether it has grown towards the nearby organs or tissues of the lungs.

Spread to nearby (regional) lymph nodes (N)

It determines the spread of cancer to the nearby lymph nodes.

Spread (metastasis) (M) to other organs of the body

It refers to the determining the extent of cancer spread to other organs involving brain, bones, adrenal glands, liver, or the other lung.

The numbers or letters seen after T, N, and M represent more details regarding each factor. The higher numbers represent the more advanced form of cancer. As the categories T, N, and M are determined, this information is combined in stage grouping to assign an overall stage.

The earliest stage within the TNM system is stage 0, also known as carcinoma-in-situ or CIS. The other main steps range from Stage I to stage IV and are classified in letters or numbers. The lower stage number represents the less extent of cancer that has spread. A higher number means the period of spread of cancer. An earlier letter or number within a stage represents the lower stage. 

TNM staging mostly for small and non-small cell lung cancer, but it has shown significance for small cell lung cancer. Even though, the stage with the TNM system may prove to be complex, and the healthcare system is responsible for explaining the terms to the patient and their family. 

The analysis of clinical TNM staging for small cell lung cancer is studied in research studies. The survival for patients with clinical stages I and II disease has shown differences from those suffering from stage III with the involvement of N2 and N3 ^​2​. Patients suffering from pleural effusion have shown an intermediate prognosis between limited and extensive stages with hematogenous metastasis and is classified as M1 disease. The TNM system does not change the patients’ management system.

Staging evaluation

The staging procedure of small cell lung cancer has been is essential for distinguishing the patients from limited-stage to their thorax from those with distant metastasis. During the initial diagnostic phase, approximately two-thirds of the patients suffering from small cell lung cancer have been showing clinical evidence of metastasis ^​3​. In contrast, the remaining patients represented the clinical evidence of extensive nodal involvement in the hilar, mediastinal, and sometimes supraclavicular regions.

Determining Stages

The determination of the cancer stage has allowed the assessment of prognosis and a determining the treatment, mainly the chest radiation therapy or surgical excision is recommended to the patients in chemotherapy suffering from the limited stage of small cell lung cancer. If the extensive location is confirmed, the evaluation is based on the individuals’ variations of signs and symptoms among the specific patient. The standard staging procedures involve:

• Conduction of complete physical examination
• Routine blood count and serum chemistries
• Computed tomography (CT) scanning of chest and upper abdomen
• Bone scan of radionuclide
• Magnetic resonance imaging (MRI) or CT scan of the brain
• Bone marrow aspirate or biopsy used for specific patients in which treatment would change as per the outcome

The application of positron emission tomography (PET) is still under study. PET may be used in staging patients with small cell lung cancer who are considered essential for giving thoracic radiation therapy to chemotherapy, as PET may lead to upstaging or downstaging of patients and to alteration of radiation fields resulting from the identification of additional sites of nodal metastases ^​4,5​.

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