Leukemia in patients following radiotherapy for malignant neoplasms in the pelvic region.

A prospective study of 1572 women treated with radiotherapy for cervical (1478 women) and ovarian cancer (94 women) was done. Patients had been followed clinically and especially by blood tests between 1961 and 1981, comprising 8990 woman-years (WY). Following radiotherapy, 5 patients developed non-lymphocytic leukemia [2 acute myeloblastic leukemia (AML), 1 acute monocytic leukemia (AMoL), and 2 chronic myeloid leukemia (CML)]. Based on rates for the general population, 0.45 case would be expected and, therefore, the relative risk was 11.2. The average mean marrow dose for all our subjects was calculated to be 1177 rad, the risk of radiation-induced leukemia was 0.43 excess case per year per one million women exposed to 1 rad of radiation to the bone marrow. Four patients with cervical cancer who developed leukemia were in a high-dose-rate group treated with both a linear accelerator (Linac) and remote afterloading system (RALS), and 1 patient with ovarian cancer who developed leukemia was treated with a Linac alone. This is the first report of a statistically significant increased risk of leukemia for patients treated with large doses of radiation for malignant neoplasms in the pelvic region.