COMPARISON BETWEEN RADIATION-INDUCED CELL-CYCLE DELAY IN LYMPHOCYTES AND RADIOTHERAPY RESPONSE IN HEAD AND NECK-CANCER

A study was made evaluating the use of radiation-induced cell cycle de lay in lymphocytes to predict tumour response to radiotherapy. Periphe ral blood lymphocytes were isolated from whole blood from 49 patients with head and neck cancer before treatment with radiotherapy and from 25 healthy donors. The clinical response to radiotherapy was assessed at 0-2 months after treatment. The level of radiation-induced cell cyc le delay was measured using flow cytometry after mitogen stimulation o f lymphocytes, The analysis of ten normal donors gave no significant d ifference in variability between the intra-assay and the intra-donor s amples, However, the cell cycle data for lymphocytes from these health y donors showed significant inter-individual differences in G(2) phase accumulation, Patients showing no response to radiotherapy had a high level of S-phase cells compared with partial (P < 0.001) and complete responders (P = 0.016). An inverse relationship was found when analys ing the fraction of cells in G(2) (P = 0.009 and 0.034 respectively). In general, healthy donors had similar cell cycle kinetics compared wi th the non-responders. In conclusion, the result indicates that radiat ion-induced cell cycle delay in lymphocytes is inversely correlated wi th tumour response to radiotherapy in head and neck cancer patients. H owever, the value of the present test for predicting individual tumour response is limited, because of assay variability and overlap between groups.