• Survival rate - the percentage of people who will be alive at a certain time after diagnosis. The 'overall survival rate' is when it includes all people with a specific cancer type.
  
  Survival rates can describe any given length of time. However, researchers usually give cancer statistics as a 5-year relative survival rate.

• 5-year relative survival rate - the percentage of people who will be alive 5 years after diagnosis. It does not include those who die from other diseases.
  
  Example: The 5-year relative survival rate for people with bowel cancer is 70.6% (2014-2018). This means that around 70 out of every 100 people with bowel cancer will be alive five years after diagnosis.
  
  Researchers also calculate survival statistics for specific cancer stages. The stage helps describe where a cancer is located, if or where it has spread, and whether it is affecting other parts of the body. Survival statistics can vary by stage.
  
  Example: The 5-year relative survival rate for people diagnosed with stage 1 bowel cancer is 98.6% (2011). This means that nearly 99 out of every 100 people with stage 1 bowel cancer will be alive in 5 years after diagnosis.
  
  Researchers base 5-year survival statistics on people whose cancer was treated at least five years ago. The statistics may not reflect the latest treatment advances.

• Disease-free survival rate - the percentage of people in complete remission after finishing treatment.

• Progression-free survival rate - the percentage of people who did not have new tumor growth or cancer spread during or after treatment. The disease may have responded to treatment completely or partially, or the disease may be stable. This means the cancer is still there but not growing or spreading.

Using survival statistics to determine prognosis

Prognosis depends on the stage of cancer at diagnosis. For example, the 5-year relative survival rate for early-stage bowel cancer is as high as 98.6%. For metastatic bowel cancer, the rate is around 13.4%.

Using survival statistics to evaluate treatment options

Specialists often use 5-year relative survival rates to evaluate and compare treatment options. They consider the survival rate a good indication of the following:

• Whether the cancer will respond to treatment

• Whether the treatment will successfully extend the person’s life

Survival statistics help specialists decide which treatments provide the most benefit. They also help specialists weigh the benefits against the risks. For example, a specific treatment may be very effective in treating the cancer, but a person might experience unpleasant side effects from it.

Statistics can provide helpful information, but they are not the only factor used for treatment planning.

The concept of 'cure'

The word 'cure' does not apply perfectly to cancer. Sometimes undetected cancer cells are still in the body after treatment. These cells can cause the cancer to come back later. Specialists call this a recurrence or relapse.

The medical community considers many cancers 'cured' when specialists cannot detect cancer five years after diagnosis. But recurrence after five years is still possible.

Source: Adapted from Cancer Facts & Figures 2020, American Cancer Society (January 2020)