Leukemia and other cancers following radiation treatment of pelvic disease.

Follow-up studies of patients treated for cancer of the cervix with radiotherapy have shown such women to be at little or no increased risk of leukemia subsequent to the radiation exposure. However, women exposed to lower doses of radiation in the pelvic area, in the induction of an artificial menopause, appear to show increased risks of both leukemia and cancers of those sites directly in the radiation field. The studies of these two types of radiation exposure are reviewed. The findings may possibly be reconciled with each other on the basis of the distribution of radiation dose to the bone marrow. Irradiation for cancer of the cervix delivers radiation doses to a small portion of the marrow which are probably lethal for most marrow cells. The mean dose to cells distant from the cervix may be too small to produce a detectable increase in leukaemia incidence. The lower and more uniformly distributed radiation dose used to induce an artificial menopause will be less lethal for marrow cells and may consequently deliver a higher "effective" marrow dose to surviving--cells, resulting in an increased leukemia risk.