Effect of single dose ionizing radiation on the cellular proliferation and apparent radiosensitivity of melanoma.

An important variable in determining in vitro cell survival is the time interval between treatment and assay. One manifestation of radiation damage is the introduction of a division delay in which the post-radiation division rate is less than the pre-radiation division rate. We have examined the influence of length of incubation on radiosensitivity of murine and human melanoma cells in a soft-agar assay. In general, the longer the incubation period the larger was the median colony diameter within control or experimental groups. Hence apparent radiosensitivity decreased with increased length of incubation.