Radiosensitivity of human head and neck squamous cell carcinomas in primary culture and its potential as a predictive assay of tumor radiocurability.

The intrinsic radiosensitivity of human tumor cell cultures correlates with the clinical radiosensitivity of several different tumor histologies, as evidenced by analyses of low dose parameters of radiation survival curves generated from a large number of cell lines. Such radiosensitivity has therefore served as a basis of attempts to develop predictive assays of tumor radiocurability. In this study, the tumors from 72 patients with head and neck squamous carcinoma have been grown in an adhesive tumor-cell assay system and radiosensitivity (S2: survival at 2.0 Gy) values have been measured. The characteristics of these cultures, such as growth rate, clonogenicity and growth enhancement by epidermal growth factor, do not correlate with S2. The average S2 value of the 72 cultures is 0.33, which is lower than for cultures derived from melanomas and lung adenocarcinomas. Twenty-six patients followed up for at least 15 months have been evaluated for local tumor control. The average S2 value of the seven patients with recurrences in this group is slightly higher (0.43) than that from the other patients (0.30). There is considerable overlap of S2 values in the two groups, and more patients must be evaluated before the groups can be compared statistically.