Stages of Small Cell Lung Cancer

Small cell lung cancer diagnosis is made among the suspected patients by integrating various methods. After the diagnosis, the doctors can find out the extent to which cancer has spread to other parts of the body. This process is known as the staging process. 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 used by doctors when discussing the survival statistics. The locations of small cell lung cancer entirely depend upon the results of the physical examination, biopsies, imaging tests, and any other related tests that have been conducted for its diagnosis. Commonly, the lower number of stages of small cell lung cancer is associated with the better outcome. None, the doctors, are capable of predicting the patient living with the signs and symptoms of small cell lung cancer, depending upon its stage due to individual differences and hence the treatment works differently for each tumor.

The doctors have used a two-stage system for treating small cell lung cancer ​1​. The stages are classified as limited stages and extensive stages. In the little stage of cancer, more efficacy is observed when more aggressive treatments are provided, such as 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 have been discussed below:

  • Limited stage means that the cancer is located only at one portion of the chest region 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 known as supraclavicular nodes. It is considered 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, although 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. Only one out of three individuals with small cell lung cancer have been diagnosed with limited-stage cancer when diagnosed initially.

  • Extensive stage: It mainly describes the cancer being spread across the lung region, even 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. Several doctors have considered small cell lung cancer to show metastasis towards the fluid surrounding the lungs, being considered at the extensive stage. Approximately two out of three individuals suffering from small cell lung cancer have reached a vast stage when their cancer is diagnosed. 

TNM staging system:

It is considered as the 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 has been mainly used for small and non-small cell lung cancer, but it has shown significance for small cell lung cancer. 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. The analysis recommended that the clinical trials in limited-stage show accurate TNM staging, and stratification is considered significant.

Staging evaluation:

The staging procedure of small cell lung cancer has been considered 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 observed to show 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.

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​.

References

  1. 1.
    Araujo LH, Horn L, Merritt RE, Shilo K, Xu-Welliver M, Carbone DP. Cancer of the Lung. Abeloff’s Clinical Oncology. Published online 2020:1108-1158.e16. doi:10.1016/b978-0-323-47674-4.00069-4
  2. 2.
    Shepherd FA, Crowley J, Van Houtte P, et al. The International Association for the Study of Lung Cancer Lung Cancer Staging Project: Proposals Regarding the Clinical Staging of Small Cell Lung Cancer in the Forthcoming (Seventh) Edition of the Tumor, Node, Metastasis Classification for Lung Cancer. Journal of Thoracic Oncology. Published online December 2007:1067-1077. doi:10.1097/jto.0b013e31815bdc0d
  3. 3.
    Amin MB, Greene FL, Edge SB, et al. The Eighth Edition AJCC Cancer Staging Manual: Continuing to build a bridge from a population-based to a more “personalized” approach to cancer staging. CA: A Cancer Journal for Clinicians. Published online January 17, 2017:93-99. doi:10.3322/caac.21388
  4. 4.
    Brink I, Schumacher T, Mix M, et al. Impact of [18F]FDG-PET on the primary staging of small-cell lung cancer. Eur J Nucl Med Mol Imaging. Published online July 17, 2004:1614-1620. doi:10.1007/s00259-004-1606-x
  5. 5.
    Bradley JD, Dehdashti F, Mintun MA, Govindan R, Trinkaus K, Siegel BA. Positron Emission Tomography in Limited-Stage Small-Cell Lung Cancer: A Prospective Study. JCO. Published online August 15, 2004:3248-3254. doi:10.1200/jco.2004.11.089