In vitro radiation survival parameters of human colon tumor cells.

As part of an ongoing research program in the biology of human colon cancer cells, a database is being generated on the radiation responses of established lines in vitro. In this report, data are summarized on the graded single dose clonogenic survival responses to graded single doses of 250 kVp X rays of 16 exponentially growing lines. These data were analyzed using the linear quadratic (LQ) formalism for X ray inactivation; the 95% confidence limits on the colony forming efficiencies (CFEs), the alpha and beta parameters from the LQ equation, the surviving percentage at 2 Gy, and the mean inactivation dose (D, Gy) are listed herein. The average D from these 16 colon tumor lines was 2.35 Gy (95% confidence limits 2.10-2.60 Gy), which indicates that these tumor cells are of equal radioresistance to melanoma or head and neck cells, with only glioblastoma cells being of greater radioresistance.