We study the growth rate of a cell population that follows anage-structured PDE with time-periodic coefficients. Our motivationcomes from the comparison between experimental tumor growth curvesin mice endowed with intact or disrupted circadian clocks,known to exert their influence on the cell division cycle.We compare the growth rate of the model controlled by a time-periodiccontrol on its coefficients with the growth rate of stationarymodels of the same nature, but with averaged coefficients. We firstly derive a delay differential equation which allows us to proveseveral inequalities and equalities on the growth rates. We alsodiscuss about the necessity to take into account the structure ofthe cell division cycle for chronotherapy modeling. Numerical simulationsillustrate the results.
