The cytostatic efficiency of gamma-rays on organotypic cultures of malignant cells is greater with irradiation at 23 degrees C compared to 37 degrees C.

The cytostatic efficiency of gamma-rays was determined following irradiation at 23 degrees C or 37 degrees C on A549 human lung carcinoma cells, irradiated either in monolayers or in three-dimensional organotypic cultures (nodules) with a dose-rate of 0.5 Gy/min. For the monolayers, the residual colony forming ability of single cells, and for the nodules, the growth rate, the proportion of regenerating or disaggregating nodules and the growth rate of regenerated nodules were measured. The efficiency of radiation was slightly improved by irradiating the monolayers at 23 degrees C compared to 37 degrees C. The difference was much more pronounced in the nodules, as deduced from (i) length of the time interval between irradiation and appearance of regeneration buds; (ii) growth rate of the regenerated nodules and (iii) growth rate of their progeny analysed over one year of subcultivation. Since organotypic cultures have a structure close to that of tumoral tissue, this result may present some useful applications for tumor radiotherapy.