Statistics are thrown around a lot in Cancer World, and it can be difficult to understand them and to evaluate their personal relevance for our own situations. A good general reminder is that all statistics refer to a group of people, not to any one person. For any one of us, the real number is going to be 100% or 0%. We aren't going to have a 42% recurrence.
This is a very helpful and clear explanation from Cancer Net about understanding statistics used to predict recurrence and survival. Here is the start and a link to read more:
Understanding Statistics Used to Guide Prognosis and Evaluate
One of the first questions people diagnosed with cancer may ask is, “what’s the chance of survival?” Understanding survival statistics becomes very important. A doctor can use them to estimate a patient’s prognosis, or chance of recovery, and determine treatment options. Read below to learn how.
Estimating how long people live after a cancer diagnosis
Researchers usually give survival statistics as rates. The rates describe the percentage of people with a specific cancer type who will be alive a certain time after diagnosis. Survival rates can describe any given length of time. However, researchers usually give cancer statistics as a 5-year relative survival rate. The rate describes the percentage of people with cancer who will be alive 5 years after diagnosis. It does not count those who die from other diseases. (NOTE FROM HESTER: THE 5 YEAR MARK IS CHOSEN BECAUSE THEY HAVE TO CHOOSE SOMETHING, AND THIS IS A GOOD NUMBER TO WORK WITH. IT IS NOT BECAUSE THERE IS SOMETHING MAGIC ABOUT SURVIVING FOR 5 YEARS AND THEN BEING ABLE TO THINK YOU ARE CURED.)
Sometimes, researchers calculate survival statistics to include all people with a specific cancer type. The stage of cancer doesn’t matter. Researchers call this an overall rate.
Example: The 5-year relative survival rate for women with cervical cancer is about 68%. This means that about 68 out of every 100 women with cervical cancer will be alive 5 years after diagnosis.
Researchers calculate other survival statistics for specific cancer stages. The stage indicates the tumor’s size. It also describes whether and how far the cancer has spread. Survival statistics can vary by stage.
Example: The 5-year relative survival rate for early-stage cervical cancer is 92%. This means that 92 out of every 100 women with early-stage cervical cancer will be alive 5 years after diagnosis.
Read more: http://www.cancer.net/navigating-cancer-care/cancer-basics/understanding-statistics-used-guide-prognosis-and-evaluate-treatment