Increased frequency of sister chromatid exchanges in lymphocytes of breast cancer patients

Spontaneous and mitomycin‐C (MMC)‐induced rates of sister chromatid exchanges (SCEs) were studied in peripheral blood lymphocytes (PBLs) of 40 patients with cancer of the breast and 40 healthy female volunteers as controls. Spontaneous SCE per cell value in PBL cultures was 7.72 for the breast cancer patients, which was significantly higher (p < 0.001) than the 6.28 SCEs per cell scored for the controls. Eight of the patients were studied a second time, 3 to 6 months following surgical removal of the tumour. A significant (p < 0.05) reduction in SCE per cell value was observed following mastectomy. MMC‐induced frequencies of SCE remained comparable in patients and controls. Cellular kinetics, calculated as average generation time (AGT) from the frequency of cells in Ml, M2 and M3 cycles, were comparable in patients and controls.