In vitro radiosensitivity of tumour cells and fibroblasts derived from head and neck carcinomas: mutual relationship and correlation with clinical data

The aim was to characterize the Variation in the cellular in vitro radiosen sitivities in squamous cell carcinomas of the head and neck, and to test fo r a possible correlation between different measures of radiosensitivity and the clinical and histopathological data. Cellular in vitro radiosensitivit ies were assessed in tumour biopsies from 71 patients using the modified Co urtenay-Mills soft agar clonogenic assay combined with an immunocytochemica l analysis. Radiosensitivity was quantified as the surviving fraction after a radiation dose of 2 Gy irrespective of cell type (overall SF2), or based on identification of cell type (tumour cell SF2, fibroblast SF2). Sixty-th ree biopsies were from primary tumours, and eight were from recurrences. Ov erall plating efficiency ranged from 0.005 to 1.60% with a median of 0.052% . The majority of the colonies obtained from the biopsies were fibroblast m arker-positive; the proportion of tumour marker-positive colonies ranged fr om 1 to 88% with a median of 15%. The median overall SF2 was 0.47 (range 0. 84-0.96), the median tumour cell SF2 was 0.50 (range 0.11-1.0) and the medi an fibroblast SF2 was 0.49 (range 0.24-1.0). Comparing data from independen t experiments, the overall SF2 was significantly correlated with the SF2 of fibroblasts (2P = 0.006) but not with the tumour cell SF2. The tumour cell and fibroblast radiosensitivities measured in the same individuals were no t correlated (r = 0.06, 95% CI [-0.19, 0.30]). This finding seems to preclu de a strong correlation between the radiosensitivity of tumour cells and fi broblasts. Concerning the clinical characteristics, neither of the measures of tumour radiosensitivity was correlated with T- and N-category, stage, t umour size, sex and age. However, the tumour cell radiosensitivity decrease d with increasing grade of histopathological differentiation (2P = 0.012). The same tendency was found in two independent analyses of the same patient material. This correlation was not significant in case of the overall SF2 or the fibroblast SF2.