What is Disease Free Survival (DFS) and Event Free Survival (EFS) in clinical trials?

Definition

Disease-Free Survival (DFS) refers to the time from randomization (or initiation of treatment in single-arm trials) to the recurrence of the disease or death due to any cause (whichever occurs first).

Event-Free Survival (EFS) refers to the time from randomization (or initiation of treatment in single-arm trials) to the first occurrence of any of the following events: progression of disease preventing surgical treatment, local or distant relapse, or death from any cause, etc.

Position/Pro-Con

equivalent to Progression-Free Survival (PFS). Progression-Free Survival (PFS), Disease-Free Survival (DFS), Event-Free Survival (EFS) are similar in meaning as endpoints.

Disease-Free Survival (DFS) primarily assesses disease recurrence and is frequently used to evaluate adjuvant therapy post-surgery or radiotherapy.

Event-Free Survival (EFS), compared to Disease-Free Survival (DFS), adds a surgical intervention criterion and is often used to evaluate neoadjuvant therapy pre-surgery, or radiotherapy.

When survival duration makes Overall Survival (OS) difficult to maintain as the primary endpoint, DFS, EFS can serve as important endpoint indicators. Such as in breast cancer, colorectal cancer adjuvant therapy where DFS can be the main endpoint, and EFS as the main endpoint in neoadjuvant therapy before radical mastectomy for breast cancer, etc.

Both DFS and EFS include non-tumor deaths, with non-progression deaths in early or locally advanced tumors potentially creating more bias compared to late-stage tumors. If deaths occurring after long-term loss to follow-up are all defined as disease recurrence, it might overestimate the treatment effect. But distinguishing between tumor/non-tumor deaths, and omitting non-tumor deaths, could result in bias when determining the cause of death.