SummaryThe aim was to characterize the variation in the cellular in vitro radiosensitivities in squamous cell carcinomas of the head and neck, and to test for a possible correlation between different measures of radiosensitivity and the clinical and histopathological data. Cellular in vitro radiosensitivities were assessed in tumour biopsies from 71 patients using the modified Courtenay-Mills soft agar clonogenic assay combined with an immunocytochemical analysis. Radiosensitivity was quantified as the surviving fraction after a radiation dose of 2 Gy irrespective of cell type (overall SF 2 ), or based on identification of cell type (tumour cell SF 2 , fibroblast SF 2 ). Sixty-three biopsies were from primary tumours, and eight were from recurrences. Overall 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 marker-positive; the proportion of tumour marker-positive colonies ranged from 1 to 88% with a median of 15%. The median overall SF 2 was 0.47 (range 0.24-0.96), the median tumour cell SF 2 was 0.50 (range 0.11-1.0) and the median fibroblast SF 2 was 0.49 (range 0.24-1.0). Comparing data from independent experiments, the overall SF 2 was significantly correlated with the SF 2 of fibroblasts (2P = 0.006) but not with the tumour cell SF 2 . The tumour cell and fibroblast radiosensitivities measured in the same individuals were not correlated (r = 0.06, 95% CI [-0.19, 0.30]). This finding seems to preclude a strong correlation between the radiosensitivity of tumour cells and fibroblasts. Concerning the clinical characteristics, neither of the measures of tumour radiosensitivity was correlated with T-and N-category, stage, tumour size, sex and age. However, the tumour cell radiosensitivity decreased 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 SF 2 or the fibroblast SF 2 .Keywords: predictive assays; in vitro radiosensitivity; squamous cell carcinoma of the head and neck; differentiation; fibroblasts; tumour cells
1074British Journal of Cancer (1999) 79(7/8), 1074-1084 © 1999 Cancer Research Campaign Article no. bjoc.1998 Received 11 al, 1991;West et al, 1997), tumour diameter, disease stage and patient age (West et al, 1997).The current report is an extension of a study using the modified CourtenayÐMills soft agar clonogenic assay, to measure in vitro radiosensitivity in squamous cell carcinomas of the head and neck (SCCHN) (Stausb¿l-Gr¿n et al, 1995). This previous study drew attention to the fact that stromal fibroblasts in addition to tumour cells were colony-forming in soft agar. An immunocytochemical analysis was developed to identify the origin of the colonies, and this provided estimates of the radiosensitivity of tumour cells (tumour cell SF 2 ), stromal fibroblasts (fibroblast SF 2 ), and an overall estimate (overall SF 2 ) in the same pat...