What are the Stages of Cancer?

Cancer staging is the process of determining the amount of cancer present in a patient at the time of diagnosis, as well as its location and spread. This measurement helps a doctor determine individual treatment plans.

Treatment plans may include radiation therapy, chemotherapy, and surgery among other treatment types. These may be used on their own or in conjunction with each other. The location and spread of a cancer will determine which treatments will be given. For example, a local cancer has not spread to other parts of the body, so a localized treatment such as radiation therapy or surgery may be sufficient. A cancer that has metastasized may need a combination of treatments. Some cancers that have spread may require systemic therapy, which is a type of treatment that circulates throughout the body such as chemotherapy or hormone therapy.

Cancer staging also helps determine the following:

• The projected treatment effectiveness
• The intention of the treatment – whether curative or palliative
• Can help predict the chance of recovery
• Can help predict the chance of recurrence

Cancer staging provides doctors an effective, standardized method of communication for the entire cancer care team as well as other hospitals or clinics. This common language ensures that everyone knows what to expect when cancer size or spread are described.

Types of Cancer Staging

There are two main types of cancer staging.

• Clinical staging: The estimate of spread of cancer based on imaging scans, physical exams, and biopsies.
• Pathologic staging: A type of staging that may be determined if surgery is being performed. The pathologic stage number may be different than the clinical stage. Pathologic staging gives the cancer care team more precise information that can help fine tune individual treatment plans.

There are two main staging systems: number and TNM systems.

The Number System

The number system classifies the stages of cancer as described below.

• Stage 0: A group of abnormal cells in situ. This precancer has not spread, and may or may not turn into a cancer at a later date.
• Stage I: A small and localized tumor that has not spread.
• Stages II & III: The cancer has grown and has spread to nearby tissues or lymph nodes, but not other parts of the body.
• Stage IV: The cancer has grown and spread to at least one other organ within the body, which is known as a secondary or metastatic cancer.

The TNM System

The TNM (Tumor, Node, Metastasis) system is another type of cancer staging. This system describes the size of tumor at the time of diagnosis, whether it is present in lymph nodes, and whether a cancer has metastasized.

• T: Indicates the size of the cancer and how far it has spread. Measured on a scale of 1 – 4, 1 being the smallest.
• N: Indicates whether a cancer has spread to the lymph nodes. Measured on a scale of 0 – 3. 0 indicates that no lymph nodes are affected while 3 indicates the presence of many lymph nodes with cancerous cells.
• M: Indicates if a cancer has metastasized. Measured as 0 or 1: 0 indicates that the cancer has not spread while 1 marks that a cancer has spread.

A TNM diagnosis may look like T1 N1 M0 for a small cancer that has not spread far. A large cancer that has metastasized may look like T4, N3, M1. There are many more combinations that are unique to describe every individual case.

Other letters may be used to further divide and refine the categories as appropriate.

It is important to note that an individual’s cancer stage does not change over time even if the tumor shrinks or grows. The stage is always the same as the first diagnosis even if it recurs or spreads to another part of the body. As the cancer changes, additional information is added to the diagnosis and treatments are adjusted.

The reason for this is that survival statistics and information about treatment by stage refers to the cancer stage at diagnosis. For instance, statistics are not the same for stage II lung cancer as stage IV lung cancer, and vice versa.

Cancer Restaging

It is uncommon for doctors to restage a cancer. Cancer restaging occurs most often in clinical trials. A cancer may be a candidate for restaging if additional tests must be performed to determine the spread and extent of a cancer, or the response of a cancer to treatment.

During cancer restaging, the tests run are usually the same that were performed in the original diagnosis. After these new tests, a new stage may be assigned as appropriate. A lowercase “r” is added before the new stage to indicate that the cancer has been restaged.

Cancer Grading

In addition to the stages listed above, there are three grades of cancer. The grades are indicators as to how quickly the cancer will grow or spread.

• Grade I: Cells resemble normal cells and do not grow or spread quickly.
• Grade II: Cells do not look normal and are growing faster than normal cells.
• Grade III: Cells look abnormal and are growing at a fast, aggressive rate.

Differentiation

Differentiation is another way to describe the observed changes of cells. The term ‘differentiation’ refers to the organization and level of development of tumor cells within the tumor itself.

• Well Differentiated: The cells and structures are similar to the tumor. These tumors tend to grow and spread at a slower rate.
• Undifferentiated or Poorly Differentiated: The cells and structures are not similar to the tumor. These tend to grow and spread at a faster rate.