The intrinsic radiosensitivity of normal and tumour cells

Purpose: To examine whether in vitro measurements of normal and tumour cell radiosensitivity can be used as prognostic factors in clinical oncology. Materials and methods: Stage I-III cervix carcinoma patients were treated with radical radiotherapy with a minimum of 3 years' follow-up. Lymphocyte and tumour radiosensitivities were assayed using, respectively, a limiting dilution and soft agar clonogenic assay to obtain surviving fraction at 2 Gy (SF2). The results were related, in an actuarial analysis, to late morbidity assessed using the Franco-Italian glossary. Results: Patients with radiosensitive lymphocytes had a significantly increased risk of developing late complications (n = 93, p = 0.002). Increasing tumour radiosensitivity was associated with an increased risk of morbidity (n = 113, p = 0.032). A significant correlation was found between fibroblast and tumour cell radiosensitivity (r = 0.57, p = 0.03), but a weak inverse association was found between lymphocyte and tumour cell radiosensitivity (r = - 0.32, p = 0.03). Patients with radiosensitive lymphocytes and tumour cells had higher levels of late complications than those whose cells were radioresistant. Conclusion: The work described highlights the importance of cellular radiosensitivity as a parameter determining the clinical response to radiotherapy.