CHROMOSOME-ABERRATIONS IN LYMPHOCYTES FROM WOMEN IRRADIATED FOR BENIGN AND MALIGNANT GYNECOLOGICAL DISEASE

Excess leukemias have occurred after partial-body radiotherapy for cer vical cancer and benign gynecological disease (BGD). However, the leve l of risk is nearly the same in both groups, about twofold, despite a tenfold difference in average dose to active bone marrow (8 Gy vs 0.7 Gy, respectively). High-dose cell killing has been postulated as one e xplanation for this apparent inconsistency. To examine whether chromos ome aberration rates observed in lymphocytes many years after exposure might serve as population markers of cancer risk, blood samples were taken from 60 women treated for BGD (34 with radiation) and cytogeneti c data compared with previous results from 96 women irradiated for cer vical cancer. Remarkably, the rate of stable aberrations, which reflec ts nonlethal damage in surviving stem cells, was only slightly higher among the cancer patients. Thus the lower-dose regimens to treat benig n disorders resulted in much higher aberration yields per unit dose th an those for cervical cancer. Assuming that the fraction of cytogeneti cally aberrant stem cells that survive radiotherapy contributes to the leukemogenic process, these data are then consistent with the epidemi ological observations of comparable overall leukemia risks seen in the se two irradiated populations. Accordingly, for patient populations gi ven partial-body radiotherapy, stable aberrations at a long time after exposure appear to serve as biomarkers of effective risk rather than as biomarkers of radiation dose received.