Impact on second malignancy risk of the combined use of radiation and chemotherapy for lymphomas

The risk of a second malignancy was determined for 999 patients given primary treatment using chemotherapy only, radiation therapy only, or both for Hodgkin's Disease or a non-Hodgkin's lymphoma at Duke University Medical Center between 1970 and 1981. The incidence, 10-year actuarial risk, and relative risk of developing an acute leukemia, solid tumor, or second lymphoma were determined by treatment modality and initial lymphoma type. Among the 313 Hodgkin's disease patients, the acute leukemia actuarial risk was 2.0% after chemotherapy, 1.4% after radiation therapy, and 0.9% after combined treatment with chemotherapy and radiation therapy. Their relative risk for acute leukemia was 51.3 overall (95% confidence interval [CI] 13.8 to 131.8) and was elevated in each treatment group. Among the 686 non-Hodgkin's lymphoma patients, the acute leukemia actuarial risk was zero after radiation therapy, 4.6% after chemotherapy, and 4.5% after the combined treatment, again not significantly different between treatment groups. The leukemia relative risk was 10.6 (95% CI 3.4 to 24.8) in the chemotherapy and 11.9 (95% CI 3.2 to 30.6) in the combined treatment group. Among both the Hodgkin's disease and non-Hodgkin's lymphoma populations, the combined treatment group had a lower actuarial risk for solid tumors than either the chemotherapy or radiation therapy group (P less than 0.02). Solid tumor actuarial risk did not differ significantly between the chemotherapy and radiation therapy groups. Hodgkin's disease patients had a solid tumor relative risk that was elevated significantly after radiation therapy (6.5; 95% CI 2.4 to 14.0) and to a lesser extent after chemotherapy (2.6; 95% CI 0.8 to 6.1) or combined treatment (1.7; 95% CI 0.2 to 6.0). Solid tumor relative risk among non-Hodgkin's lymphoma patients was 0.3 for the combined treatment, 0.8 for the chemotherapy, and 1.0 for the radiation therapy group. None of the Hodgkin's disease patients developed a non-Hodgkin's lymphoma. This study found no significant difference in leukemia risk among lymphoma patients treated with chemotherapy and the combined treatment. It also found that the overall risk of a second malignancy is no higher after treatment with the combined therapy than with chemotherapy or radiation therapy alone.