Abstract
Cultured fibroblast cells from 19 patients with non‐Hodgkin's lymphoma (NHL), 3 patients with ataxia telangiectasia (AT), 3 AT heterozygotes and 11 (presumed) normal subjects were studied for impaired colony‐forming ability after chronic gamma irradiation. Five cell lines from the NHL patients were also examined for the sensitivity to acute gamma irradiation, as compared with those of normal subjects. To ascertain the degree of radiosensitivity of different cell lines, a comparison was made of the D~l0~ values (radiation dose resulting in 10% survival) for each cell line, estimated “by eye” from the actual survival curves, and also from the calculated curves fitted to a log‐linear model. It was observed that the acute gamma irradiation failed to show any appreciable difference in the radiation response of the cell lines from NHL patients as compared with those of normal subjects. However, chronic irradiation demonstrated significantly increased radiosensitivity in at least 10‐12 NHL patients with a p value of < 0.05, when the D,~10~ values of each patient's cell line were compared with the calculated composite values for the normals. When the D~l0~ values of the NHL patients and the normal subjects were compared as 2 groups, the former appeared to be significantly more sensitive to chronic gamma irradiation (p < 0.0001). The same level of significant difference in radiosensitivity was found between the 2 groups when their D~37~ values (radiation dose resulting in 37% survival) were compared. In general, the radiation response of the NHL patients was similar to that of the AT homozygotes and heterozygotes used as a positive control group. Our data thus show that increased radiosensitivity is associated with the NHL patients studied, indicating an underlying abnormality of their DNA repair.