Comparison of the radiosensitivity of normal-tissue cells with normal-tissue reactions after radiotherapy

To investigate whether the in vitro radiosensitivity of normal lymphocytes and fibroblasts evaluated by the micronucleus (MN) assay predicts acute and late reactions after radio-therapy in cancer patients.

Studies were performed on blood samples from 31 cervical and head and neck cancer patients and on skin fibroblasts from eight of the cancer patients. The radiosensitivity of lymphocytes and of fibroblasts was also assessed in 24 and five healthy donors, respectively. Radiosensitivity was measured after in vitro irradiation with doses ranging from 2 to 5 Gy using micronucleus frequency (the number of micronuclei per single binucleated (BN) cell) and the percentage of BN cells with micronuclei. The in vitro results were compared with the maximum grade of acute and late reactions.

There was no significant difference in cellular radiosensitivity between cancer patients and healthy donors. Although cancer patients differed considerably in normal-cell radiosensitivity, no correlation was found between radiosensitivity, either of lymphocytes or fibroblasts, and acute and late clinically observed side effects. In addition, no relationship was observed between the radiosensitivity of lymphocytes and fibroblasts derived from the same donors.

The data do not support the usefulness of the MN assay in predicting normal-tissue response to radiotherapy in cancer patients.