Purpose: Following irradiation alone, secondary acute nonlymphocytic leukemia (ANLL) is uncommon; following chemotherapy alone, the risk is increased, but not as much as when combined modality treatments are used. Because ANLL seems more likely to occur in splenectomized patients, attention is focused on an unexpected association between splenectomy and the risk of secondary leukemia.
Patients and methods: The risk of ANLL was assessed in 503 patients with Hodgkin's disease (HD) homogeneously treated with combined modality therapy (mechlorethamine, vincristine, procarbazine, and prednisone [MOPP] plus radiotherapy). These patients were diagnosed from 1970 through 1984 and monitored until June 1991.
Results: ANLL was observed in one of 145 (0.69%) patients not splenectomized and in 21 of 358 (5.86%) splenectomized patients, demonstrating a significantly higher frequency of ANLL in the group of patients who underwent splenectomy. The group of patients who developed ANLL received a statistically greater number of MOPP courses than did the group not developing ANLL. ANLL was statistically more frequent in those patients who received more than four cycles of MOPP. Sex, symptoms, extent of radiotherapy, splenectomy, age, and number of MOPP courses were assessed for their impact on ANLL incidence by multivariate analysis.
Conclusion: Cox's proportional hazards regression showed that splenectomy and, as previously described by others, the number of courses of MOPP are prognostic factors that increase the risk of secondary ANLL in HD patients treated with combined modality therapy. These data raise interesting questions regarding the possible role of the spleen in leukemia development.