Therapeutic radiation for lymphoma: risk of malignant mesothelioma

Ionizing radiation has been used since the 1950s to treat a variety of cancers. Cancer patients who are treated with radiotherapy have shown increased risks for a variety of second malignancies, including mesothelioma, in several recent reports. The only existing study of Hodgkin lymphoma (HL) and subsequent mesothelioma had a short observation period.

The authors used Surveillance, Epidemiology, and End Results data over a 30-year period to identify patients with HL and non-Hodgkin lymphoma (NHL) who also were diagnosed with mesothelioma. Standardized incidence ratios (SIR) and absolute excess risks were calculated by sex and treatment modality for both types of lymphoma.

Twenty-six patients were identified who had mesothelioma as second primaries based on 21,881 diagnoses of HL and 101,001 diagnoses of NHL. There was a statistically significant increase in mesothelioma (4 diagnoses; SIR, 6.59; 95% confidence interval [95% CI], 1.79-16.87) among men with HL who received radiation, but no women survivors were identified who had a diagnosis of mesothelioma. For NHL survivors, there was a nonsignificant excess of mesothelioma among men (SIR, 1.91; 95% CI, 0.77-3.93) and women (SIR, 3.75; 95% CI, 0.77-10.95) who had received radiation treatment. There were no increases among patients who were unirradiated.

Mesothelioma rates for patients who had received radiotherapy were increased for survivors of HL and NHL. No increases were observed among the unirradiated. These findings and the existing body of supporting studies confirmed that radiotherapy is a cause of mesothelioma.