Radiation and Leukemia in Carcinoma of the Cervix

There is still considerable concern over radiation leukemogenesis on the part of physicians as well as laymen. For this reason we have studied the incidence of leukemia in patients with cancer of the cervix who have survived after radium treatment. Cancer of the uterine cervix was selected because it is a common tumor and there are many survivors. In those countries where statistics on the incidence of disease are kept, cervical cancer is known to have a high incidence, ranking after cancer of the digestive tract and of the breast. Survival data for this neoplasm have been studied for many years, and have been published in the Annual Report on the Treatment in Carcinoma of the Uterus (1, 2). No other form of cancer treated with radiation has such precise documentation. It is the only medical situation in which there may be enough cases to establish statistical significance (3). In general, about 40 per cent of the patients survive five years and about 75 per cent survive one year. The radium dosage has been practically uniform. It has been common practice for almost fifty years to insert a radium tube (tandem) into the uterus and an applicator (colpostat) into the vagina, exposing the patient to 5,000 to 9,000 mg. hr. In the lower stages of disease the prognosis is good, and the survival rate is high. Advanced cases (Stages III and IV) have a low survival rate. Patients with advanced carcinoma of the cervix (Stages III and IV) are less likely to have been treated with radium than the more favorable groups comprising Stages I and II. It may then be assumed that those patients treated with radium have even higher survival rates than are reported for cancer of the cervix as a whole, including all stages. The disease occurs among relatively young women, which contributes to the comparatively high survival. It may be assumed that patients who have been treated with radium have been exposed to about 8,000 mg. hr. in the pelvis in thirty days or less. In this study we have collected data both as to the number of survivors of radium treatment for cancer of the cervix and the number of cases of leukemia occurring in these survivors. Many of the patients received external irradiation with x-rays to increase the dose of radiation to the lymph node areas in the pelvis. This added radiation results in a dose of 2,000 to 3,000 rads throughout the pelvis, including a large part of the pelvic bones. The heads and necks of the femurs are also included. Some institutions omit this external irradiation in Stage I cases, but the vast majority of the survivors have received this additional therapy. The amount of bone marrow receiving radiation is probably an essential feature of both this series and the rheumatoid spondylitis series of Court-Brown (4, 5, 6). The volume of bone marrow irradiated in cancer of the cervix is greater than the volume of bone marrow irradiated in rheumatoid spondylitis, but the distribution of the dose is considerably different.