The effect of anticancer therapy on the incidence of sister chromatid exchanges (SCE's) of the peripheral lymphocytes was studied in 13 patients with oral cancer. For comparison, the influence of three anticancer agents to SCE's of cultured lymphocytes from healthy adults was also examined. SCE's were detected by Hoechst-Giemsa technique, following incubation of the cells in the presence of 5-bromodeoxyuridine.
The baseline SCE frequency in normal subjects was 7.68±3.70 per metaphase. SCE level was elevated moderately when the cells were treated in vitro with peplomycin (PEP), but was not affected by bleomycin (BLM) nor 5-fluorouracil (5-FU). Mitotic activity was suppressed markedly by 5-FU, and in lesser degree by PEP.
The mean SCE score in the untreated oral cancer patients was slightly higher (9.08±2.98) than the control level. Chemotherapy with BLM elevated SCE score a slight degree (11.28±2.28). During the course of chemoradiotherapy, SCE frequency was markedly increased (21.35±6.27), when the patients had been exposed to 10 to 12 Gy of radiation doses. Inhibition of mitoses progressed in parallel with the incidence of the SCE level in a few patients under chemo- or chemoradiotherapy.
As increased SCE's of the peripheral lymphocytes are considered to reflect damages to DNA of non-tumorous cells, it is suggested thet SCE analysis could be a useful tool for monitoring unfavorable side effects caused by anticancer agents.