Site-specific relative risks of second primary malignancies among patients with Waldenstrom macroglobulinemia.

Abstract

e18566 Background: Waldenstrom Macroglobulinemia (WM) is a rare and indolent B-cell malignancy characterized by overproduction of monoclonal immunoglobulin M protein. The long duration of survival for most patients with WM and the use of potentially carcinogenic agents during therapy raise concerns about the development of second primary malignancies. However, the relative risks of second primary malignancies among patients with WM are not well-documented. Therefore, we investigated site-specific relative risks of second primary malignancies among patients with primary WM. Methods: Data from 9 population-based registries of the Surveillance, Epidemiology, and End Results program were used to identify patients diagnosed with primary WM between 1973 and 2007 for whom follow-up data were available. Standardized incidence ratios (SIRs) with corresponding 95% confidence intervals (CIs) of site-specific second primary malignancies were estimated by dividing the number of observed cases of second primary malignancies for the specific site within the WM cohort by the number of expected cases (standardized by age, sex, race/ethnicity, and calendar-year) of secondary primary malignancies for the specific site in the general United States population. Results: The WM cohort (n=1,521) yielded 226 second primary malignancies during 6,958 person-years of follow-up (incidence density = 3,248 cases/100,000 person-years of follow-up). Potentially durable estimates of higher site-specific relative risks were observed for colon (SIR=2.3, 95% CI: 1.6, 3.3), lung (SIR=1.7, 95% CI: 1.2, 2.4), non-Hodgkin lymphoma (SIR=4.9, 95% CI: 3.2, 7.1), myeloma (SIR=4.9, 95% CI: 2.2, 9.2), and acute myeloid leukemia (SIR=5.9, 95% CI: 2.2, 12.8) compared to the general US population. Conclusions: Our results indicate that patients with WM have a higher relative risk of second primary malignancies for several sites. Although the higher relative risks of second primary hematologic malignancies may be treatment- or immunologically-related, the modestly higher relative risks of second primary solid tumors may be the result of detection bias or risk factors shared between WM and the specific solid tumors.