© 1981 Oxford University Press
Re-examination of the ED01 Study
Risk Assessment Using Time
The ED
01 study undertaken by NCTR has provided extremely valuable
data which should stimulate the development of improved cancer
risk assessment procedures. A general model for carcinogenic
risk assessment including both dose level and time to response
is given herein - including several possible extensions - and
shown to be capable of fitting the ED
01 data. The need to include
time in risk assessment is clearly demonstrated. Some important
new definitions of acceptable risk which more realistically
reflect the time of the response are presented and illustrated.
The analysis of the ED
01 data indicates 1. the need to use a
relatively fine time partition if each animal's observation
time is not treated individually, 2. the considerable room-to-room
consistency in risk assessments, and 3. estimated models which
are nonlinear in both dose and time for both bladder carcinomas
and liver tumors - in contrast to the linearity of the estimated
liver tumor multistage quantal response model which ignores
time. The capability and need to do time based risk assessment
exists now.

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