Do you mean implementation-wise?

Because mathematically, you just have a "treatment term" with, say, the chemotherapy parameter "Ct" in your ODE system, where

"Ct" = 0 whenever outside of the treatment cycle and

"Ct" = value 7 days in a row, then one month break, then again etc.

on the time domain T, which you'd need of course to discretise according to your needs.