What is the clinical difference between a disease and a sickness?

What is the difference between overall survival and disease-free survival?

• for example:I don't understand the exact difference between these sentence: The overall agreement between 2-year disease-free survival and 5-year overall survival was 79%, and between 3-year disease-free survival and 5-year overall survival was 81%. or No significant difference in 5-year overall survival was identified, but patients in the chemotherapy arm had a prolonged disease-free survival rate of 51%

• Answer:

  The word "survival" can be confusing in this context. 5 year overall survival refers to the fraction of patients who are still alive after 5 years. 2 year disease free survival refers to the fraction of patients who don't have evidence of cancer after 2 years. In your examples this translates into: 1) The later the cancer recurred (longer disease free survival) the more were alive after 5 years. 2) The fraction of patients who were alive after 5 years were the same, but those who had chemotherapy had their recurrence later that those who did not.