Cancer Staging - Types and Importance

Introduction:

Staging is a process of determining the rate of growth of cancer, that is, the size and spread of cancer in the body. When the cancer is diagnosed, three things shall be considered:

• Size of cancer.

• Regional spread (spread to surrounding tissues).

• Distant spread (spread to other parts of the body).

There will be a regular update by adding any changes in cancer during the treatment. Even though the cancer changes during treatment, staging does not. There are many staging systems, some are universal, and some are specific to cancer. While staging following things must be considered:

• Size of the tumor.

• Location of cancer.

• Type of cancer cells.

• Spread to nearby lymph nodes.

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• Spread to other parts of the body.

• Abnormality in cells and rate of growth at which cancer might grow and spread.

Staging is a common language that helps doctors to explain, and the patient understands cancer. Staging of cancer helps the doctor

• To determine the prognosis of cancer.

• Planning the treatment, which will be individual-specific.

The doctor concludes the diagnosis and provides the grading of cancer after various tests like- magnetic resonance imaging (MRI), X-rays, computed tomography (CT), positron emission tomography (PET), histopathology of cancer, and biopsy.

What Are the Different Types of Staging Systems for Cancer?

• Clinical Staging: It determines cancer by physical examination, imaging tests, and biopsy.

• Pathologic Staging: This can be done during surgical exploration of cancer or during surgical removal of the tumor mass.

• Post Neoadjuvant Therapy Staging: This helps in determining cancer after systemic therapy (chemotherapy or immunotherapy or radiotherapy) and before surgery.

• Restaging: This is done when cancer has recurred. Restaging helps to determine the treatment options for an individual.

There are other kinds of staging systems; most frequently, the systems that are in use are

1. Numbering system.

2. TNM system.

Numbering System:

Some doctors use numbers to describe the stage of cancer.

• Stage 0: In Situ- Cancer has not grown nor spread to other areas of the body.

• Stage 1: Localized- The size of the cancer is small, showing no signs of spread to other areas of the body.

• Stage 2: Size- Cancer has grown in size but without any spread to surrounding tissues.

• Stage 3: Regional- The size of the cancer is big and has spread to nearby lymph nodes, tissues, and organs.

• Stage 4: Distant- Cancer is spread to areas away from the primary tumor, that is, at least to another body organ that is away from the primary tumor. At this stage, cancer is also called secondary or metastatic cancer.

TNM Staging System:

It is the widest cancer staging system for doctors. It is used to stage malignant cancers that can spread to various parts of the body. The TNM staging system is the standard system of classification used by doctors, health centers, and hospitals that enables sharing of information and provides a better understanding of cancer to other doctors or to the patient itself.

• T- Tumor: The size of the primary tumor and its spread to surrounding tissues is analyzed. T values are assessed differently, depending on the structures involved. For example, T1 is used when there is a submucosal invasion, and T4 is used when there is an invasion of all layers of the colon.

• N- Nodal Involvement: This is used to determine the spread of cancer to the lymph nodes. Lymph nodes act as a filter when the tissue fluids enter lymphatic capillaries. N values given to a tumor are different depending on the regional lymphatic drainage and are tumor-specific.

• M- Metastasis: This is used to determine the spread of the tumor beyond regional lymph nodes.

Why Is Cancer Staging Important?

The treatment does not depend entirely on the staging of cancer. There are many other patient factors involved that play a role in treatment. Sometimes, different stages of cancer in different patients are treated with the same method. But, there is a need to know the stage of cancer to deliver the correct treatment to the patient. Cancer in its early stages may not need intense and invasive therapies like surgery, chemotherapy, radiotherapy, and targeted therapy, thereby avoiding side effects of treatment that are not necessary. Staging cancer helps to predict the course of cancer and the outcome of treatment as well.

What Are the Other Notations Used During TNM Staging?

During the TNM staging process, clinical and pathological classification is attached to the nomenclature. For clinical classification, “c” and pathological classification “p” is added in front of the capital's TNM ( ex- cT1 or pT1).

When cancer is restaged after neoadjuvant therapy, they are often classified as “y” and placed in front of TNM. For example, if the tumor is at the T1 stage after neoadjuvant therapy, it is written as “ycT1”.

When the cancer is restaged after recurrence or progression of cancer, it is written as “r” in front of TNM. For example, if the tumor is staged at the T2 stage, it is written as “rcT2”.

What Are the Different Stages of Cancer Metastasis?

‘M’ in staging is used to determine the metastasis of cancer- distant metastasis.

• Mx- Unable to measure the metastasis.

• M0- Cancer has not spread to other parts of the body.

• M1- Cancer has spread to other parts of the body.

Conclusion:

TNM staging helps doctors determine the stage of cancer and deliver appropriate treatment to the patient. It explains the anatomical extent of cancer, which allows simplification and sharing of information for research studies. The eighth AJCC (American joint committee on cancer) manual has successfully included relevant, non-anatomical factors, but only when there is strong evidence for including such factors. This inclusion has led the staging of cancer to be more specific to the individual rather than population-based.