Comparison of cellular radiosensitivity between different localizations of head and neck squamous-cell carcinoma

The prognosis of carcinomas arising from various sites in the head and neck varies even when the stage of the disease is taken into consideration, e.g. laryngeal carcinoma has a more favourable prognosis compared to oral-cavity malignancies. The purpose of this study was to evaluate intrinsic cellular radiosensitivity as one possible explanation for the observed differences in the survival rates of different anatomical groups. The radiation survival curves were determined for well characterized cell lines derived from laryngeal carcinoma (n = 14), pharyngeal carcinoma (n = 6), carcinoma of the oral cavity (n = 14) and the skin of the face (n = 3). The intrinsic radiosensitivity was expressed as area under the survival curve (AUC) values, and this cellular parameter was compared with clinical data and survival of the patients. The intrinsic radiosensitivity in the whole group varied between 1.0 Gy and 2.8 Gy with an average of 1.9 Gy. The mean AUC values for the laryngeal cell lines were 2.0 Gy +/- 0.2, for the oral cavity 1.8 +/- 0.3 Gy, for the pharynx 1.8 +/- 0.2 Gy and for cutaneous carcinoma 2.1 +/- 0.1 Gy. There was a slight difference between the groups of glottic and supraglottic cell lines (mean 1.8 +/- 0.2 Gy and 2.1 +/- 0.3 Gy, respectively), which is consistent with the differences in clinical curability of these cancers. Otherwise, the differences in cellular radiosensitivity of the carcinoma groups studied did not reach statistical significance. These results indicate that the intrinsic radiosensitivity of squamous-cell carcinoma (SCC) of the larynx does not significantly differ from that of SCC of other sites of the head and neck. Variations in the intrinsic radiosensitivity do not as such seem to explain the observed differences in radiocurability of SCC variously localized in the head and neck.