
140 Exposure-Response Modeling: Methods and Practical Implementation
5.8 Interval censored data
Although right censoring is the most common type of censoring, interval cen-
soring (IC) is also common (Sun, 200 6). An interval censored TTE refers to the
fact that we only know subject i had an event within a time interval (L
i
, R
i
),
but not the exact time of occurrence. IC includes rig ht censoring as a special
case with R
i
= ∞, observed event time with L
i
= R
i
= T
i
. One example of
IC is the time to disease progression (DP) in many types of diseases. For solid
tumors, DP is defined according to tumor siz e changes, which can only be
measured infrequently.