Lymphocyte telomere length correlates with in vitro radiosensitivity in breast cancer cases but is not predictive of acute normal tissue reactions to radiotherapy.

PURPOSE: To examine the hypothesis that lymphocyte telomere length may be predictive of both breast cancer susceptibility and severity of acute reactions to radiotherapy. MATERIALS AND METHODS: Peripheral blood lymphocyte cultures from breast cancer patients (with normal or severe skin reactions to radiotherapy) and normal individuals were assessed for in vitro radiosensitivity as measured by apoptosis, cell cycle delay and cytotoxicity. Telomere lengths were determined by a flow cytometric fluorescence in situ hybridization assay (FLOW-FISH). RESULTS: Female breast cancer cases (n = 24) had reduced lymphocyte telomere lengths by comparison with healthy controls (n = 20, p < 0.04). However, the average age of healthy controls was less (45.4) than cases (53). When the control group was modified to give a better age match (51.5, n = 13) the reduced telomere length in cases was not significantly different from controls. Lymphocytes from breast cancer cases also showed reduced cell cycle delay (p < 0.001) and increased apoptosis (p < 0.01) following irradiation in vitro at 3 and 5 Gy respectively, compared to healthy controls. Statistical significance was maintained with the improved age matching of groups. Comparison of lymphocytes from breast cancer patients with normal (n = 11) and severe (n = 13) skin reactions to radiotherapy failed to identify differences in telomere length or cellular radiosensitivity in this limited sample. CONCLUSIONS: This study adds to the evidence suggesting a correlation between altered cellular radiosensitivity and breast cancer. However, in the cases investigated, telomere length does not appear to be predictive of acute skin reactions to radiotherapy.