Since radiotherapy or chemotherapy alone may be ineffective, they are
more and more often combined. In this in vitro studies the effects of
the chronology of the treatments and of the time interval between them
are evaluated. In murine leukaemia L1210 cells and in murine mammary
adenocarcinoma Ca755 cells the highest efficacy, i.e. the lowest survi
val fraction, was observed when radiotherapy was administered 6 h befo
re Fluorouracil (FU). To mimic treatment in man, a daily combined trea
tment was also tested. Under these circumstances, the chronology of th
e treatments and the time interval between them had different conseque
nces, the highest efficacy being noticed when both treatments were giv
en at the same time.