Table 7.

Definitions of time to event end points³⁰

End point	Definition	Comment
Time to progression (TTP)	Duration from start of treatment to disease progression, with deaths due to causes other than progression censored	TTP is useful in assessing the activity of a drug and the durability of treatment benefit, but does not take into account the fact that a treatment may be associated with increased treatment-related deaths and hence should be assessed in conjunction with progression-free survival
Progression-free survival (PFS)	Duration from start of the treatment to disease progression or death (regardless of cause of death), whichever comes first	Should be reported in conjunction with TTP
Event-free survival (EFS)	The definition for EFS depends on how ‘event’ is defined. In many studies, the definition of EFS used is the same as PFS. EFS may include additional ‘events’ that are considered to be of importance besides death and progression, including serious drug toxicity	In general in myeloma, most studies reporting EFS are in fact referring to PFS. PFS is a more specific term and is the preferred term to be used, unless the definition of EFS includes additional ‘events’ besides progression or death that are considered important to take into account
Disease-free survival (DFS)	Duration from the start of CR to the time of relapse from CR. DFS applies only to patients in complete response	Unlike TTP and PFS, the end point of DFS applies only to the subset of patients in complete response, and as such has limited value in myeloma at present
Duration of response (DOR)	Duration from first observation of partial response to the time of disease progression, with deaths due to causes other than progression censored. Duration of CR and PR should each be reported	Unlike TTP and PFS, the end point of DOR applies only to a subset of patients in the study who achieve at least partial response. It expresses the durability of response

Reproduced with permission from Anderson et al.³⁰