Secondary leukemia following treatment for Hodgkin's disease

Patients treated for Hodgkin's disease with chemotherapy or with the association of chemotherapy and radiotherapy have an increased risk of secondary leukemia. The aim of this study was to evaluate the leukemogenic risk due to these treatment modalities.

We performed a case-control study on a population of 1410 patients treated for Hodgkin's disease from 1970 to 1990 in our Institute. Among these patients, we identified 25 cases of secondary leukemia and 3 cases of myelodysplasia, all occurring more than one year after the diagnosis of Hodgkin's disease. Three cases occurred among the patients treated with radiotherapy alone. When we analyzed the risk in relation to the type of treatment (radiotherapy, chemotherapy, or both), the comparisons were relative to patients treated with radiotherapy alone.

We found that chemotherapy alone is associated with a fivefold increased risk (odds ratio = 5.4) compared with radiotherapy alone. When both treatments are used, the risk is not further increased (odds ratio = 4.4). Patients receiving more than 6 courses of chemotherapy have an excess risk (relative risk = 2.5) compared with those treated with 6 courses or less. No increased risk was observed after splenectomy.

This study confirms an increased incidence of secondary leukemia occurring in patients treated for Hodgkin's disease. The increased risk seems to be correlated with the number of courses of alkylating agent therapy, whereas it is unaffected by the addition of radiotherapy.