LEUKEMIA RISK FOLLOWING HODGKINS-DISEASE - RELATION TO CUMULATIVE DOSE OF ALKYLATING-AGENTS, TREATMENT WITH TENIPOSIDE COMBINATIONS, NUMBER OF EPISODES OF CHEMOTHERAPY, AND BONE-MARROW DAMAGE

Purpose: The development of leukemia is one of the most serious long-term complications of modern treatment for Hodgkin's disease (HD). This study was undertaken to examine the relation between risk of leukemia and various treatment factors (including cumulative dose of cytostatic drugs and interaction with radiotherapy [RT]), while also assessing the effect of treatment-induced bone marrow damage. Patients and Methods: We conducted a case-control study in a cohort of 1,939 patients treated for HD between 1966 and 1986 in the Netherlands. Detailed information from the medical records was obtained for 44 cases of leukemia and 124 matched controls, in whom leukemia had not developed. Results: The cumulative dose of mechlorethamine was the most important factor in determining leukemia risk. As compared with patients who received RT alone, patients treated with six or fewer cycles of combinations including nitrogen mustard (mechlorethamine) and procarbazine had an eightfold increased risk of developing leukemia (P = .08), while patients who received more than six of such cycles had a greater than 40- fold excess risk (P < .001). Treatment with lomustine or a combination of teniposide and cyclophosphamide also significantly increased the risk of leukemia. Patients who had received chemotherapy (CT) during two or more time periods had a nearly 40-fold increased risk of leukemia as compared with patients treated only once. The extent of RT did not further increase leukemia risk among patients who also received CT. A significantly increased risk of leukemia was found among patients with low platelet counts, both in response to initial therapy and during follow-up. Patients who experienced 2 or more half-year periods with platelet counts less than 75 x 106/mL had an approximately fivefold risk of developing leukemia, and a similar risk increase was found for patients who responded to initial treatment with a ≥70% decrease of platelet counts (as compared with patients who had a ≤ 50% decrease). Conclusion: In addition to mechlorethamine, lomustine and teniposide combinations were also linked to an elevated risk of developing leukemia. Since the number of CT episodes was found to be a strong determinant of leukemia risk, it is important that new therapies for HD continue to yield high initial cure rates. Further studies are warranted to investigate whether patients at high risk for developing leukemia may be identified from the response of their platelets to initial therapy for HD.