Risk of second cancer in patients with hairy cell leukemia: long-term follow-up.
PURPOSE: The purpose of the present study was to assess the risk of second cancers in patients with hairy cell leukemia (HCL). PATIENTS AND METHODS: We investigated the incidence of additional cancers in those patients registered in the nationwide registry of the Italian Cooperative Group for the Study of HCL, asking the cooperating centers for additional information on initial and subsequent therapies and on time and type of second malignancies, if they developed. Here we report the final results of this survey, consisting of 54 cases of second malignancies (excluding nine cases of epithelial skin cancer) which developed in 54 patients of 1,022 with adequate follow-up. RESULTS: The cumulative risk of development of a second cancer was 5%, 10%, and 14% at 5, 10, and 15 years, respectively. The incidence of second malignancies was not significantly higher than the expected rate (standardized incidence ratio [SIR], 1.01; 95% confidence interval [CI], 0.74 to 1.33; P = 1.0). However, the SIR of non-Hodgkin's lymphoma in the entire cohort was 5.3 (95% CI, 1.9 to 11.5). Second malignancies occurred in eight (4.7%) of 386 patients who never received interferon (IFN), nine (5.9%) of 495 patients treated with IFN at the time of diagnosis, and seven (6.9%) of 102 patients who received IFN as second-line therapy. These differences were not statistically significant. Analysis of the separate calendar periods did not reveal any particular trends with respect to variations in SIR. CONCLUSION: The present study does not support the suspicion that patients with HCL are at increased risk of additional second malignancies, although the incidence of lymphoid neoplasms was significantly higher than expected. In addition, our data indicate that IFN therapy did not exert an oncogenic effect in such patients.