The effect on XXXX @entity521 spheroids of fractionated radiation regimes calculated to be equivalent for damage to late responding normal tissues.

@entity1 @entity5 @entity16 @entity521 @entity15392
@entity5 ( @entity5 ) are a useful in vitro model of @entity1 @entity5 . An experiment was designed to assess the likely therapeutic advantage of hyperfractionation--a proposed strategy in radiotherapy. A cell line ( @entity15392 -G) derived from @entity1 @entity521 was grown as @entity5 . This @entity5 line is radiosensitive with low capacity for repair of sublethal radiation damage. These properties make @entity15392 -G a suitable line to test the theoretical advantage of hyperfractionation. @entity5 were irradiated using alternative fractionated regimens, with fraction sizes varying from 0.5 to 4 Gy. In each experiment, the total dose was chosen to make the regimens theoretically isoeffective for damage to late-responding normal tissues (calculated using the linear-quadratic mathematical model with alpha/beta = 3 Gy). The radiation responses of @entity5 were evaluated using the end-points of regrowth delay and "proportion cured". Regimens using smaller doses per fraction were found to be markedly more effective in causing @entity16 @entity5 , as assessed by either end-point. These experimental findings support the proposal that hyperfractionation should be a therapeutically advantageous strategy in the treatment of @entity5 whose radiobiological properties are similar to those of the @entity5 line @entity15392 -G.
