Radiation sensitivity in vitro of cells isolated from human tumor surgical specimens

The radiation sensitivity of cells isolated directly from human tumor surgical specimens was studied using the Courtenay soft agar colony assay. Aerobic cell survival curves covering 2-3 decades were achieved for eight melanomas, seven ovarian, six cervix, five breast, four bladder, and four squamous cell carcinomas of the head and neck and two seminomas. Cell survival following exposure to 2.0 Gy was measured also for several other tumors of these histological types. Experiments repeated with cells stored in liquid nitrogen showed that the survival assay gave highly reproducible results. The D0 (0.61-1.65 Gy) as well as the surviving fraction at 2.0 Gy (0.12-0.66) differed considerably among individual tumors of the same histological type. Neither of these parameters was therefore significantly different for the seven tumor categories. However, about one-third of the melanomas showed a higher surviving fraction at 2.0 Gy than the highest value measured for the other tumors. Two of three seminomas showed surviving fractions at 2.0 Gy in the absolute lower range, i.e., below 0.20. Altogether the data were consistent with the suggestion recently put forward that the clinical radiocurability of tumors may be correlated to the cell surviving fraction in vitro at 2.0 Gy. However, it was not possible on the basis of individual tumors to investigate whether the surviving fraction at 2.0 Gy was correlated to the clinical radiocurability, since adequate clinical data were not available for the parent tumors. It is suggested that melanomas may be especially suitable for prospective studies aimed at establishing whether such a correlation really does exist. If a significant correlation can be verified, then a very important conclusion may be drawn from our data: the radiocurability of human tumors may differ almost just as much among individual tumors of the same histological type as among individual tumors of different histology.