© 1981 Oxford University Press
Re-examination of the ED01 Study
Adjusting for Time on Study
Gaylor (1980) describes conclusions drawn from the initial analysis
of the ED
01 study. These conclusions failed to take adequate
account of differences in time on study for animals at different
doses. Several consequences of this are discussed. Two conclusions
of Gaylor's are identified that are open to question. The ED
01 liver and bladder tumor data, adjusted for time-on-study, are
used to firmly reject several mathematical models that have
been proposed for low-dose extrapolation. The complexities that
arise from differences in time-on-study are shown to cast serious
doubt on the general concept of low-dose extrapolation, when
it is attempted independent of time to tumor. It is pointed
out that the problems of statistical analysis that arise when
dosed animals live longer than controls (as occurred in the
ED
01 study) raise questions about the design of lifetime feeding
studies in general.

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