Incidence of solid malignancies (SM) among patients with Waldenström macroglobulinemia (WM): Analysis of the SEER database (2000-2019).

e18902 Background: WM is an indolent disease with a median survival of ~ 16 years following diagnosis. We aimed to study the incidence of various SM among patients with WM, which can help in their targeted surveillance. Methods: We used SEER 17 registry to identify adult [ > 20 years(y)] patients(pts) with an index diagnosis (dx) of WM between 2000- 2019. We included ICD-O-3 codes 9671/3 (Lymphoplasmacytic lymphoma) and 9761/ (Waldenstrom macroglobulinemia) to identify index dx. Only first of the two codes was used if both were mentioned for same pt. Pts were grouped based on age at WM dx ≤60y (young) and > 60y (old) for analysis. We used ICD-O-3/WHO 2008 codes assigned to site of SM to identify subsequent diagnosis ( > 2months after index diagnosis) of SM. We included the first SM site, for pts with > 1 subsequent SM. We analyzed SM sites with > 15 patients. We excluded patients with diagnosis made from death certificate or autopsy. Follow up period was till December 2019. Demographics and treatment details were extracted using SEER Stat v 8.4.0.1 software. Statistical analyses were performed using R 4.2.2. Chi-squared test was used to calculate difference between categorical variables. Kaplan Meier method and log rank test were used to estimate overall survival (OS). Results: We identified 8099 patients with a dx of WM, of which 794 (9.8%) had subsequent SM. WM and SM were diagnosed at median (IQR) ages of 70 (62-76)y and 74 (67-81)y, with a median gap of 41 (20-79) months. Majority of WM survivors with SM were males (517/794, 65.1%), white (91.4%) and old ( > 60y) (79.2%) at WM diagnosis. Ten SM sites, each with > 15 pts were identified (Table). Most common site of SM in young WM females was breast, while it was lung and bronchus(LB) in the older group. In males, prostate, and LB were two most common sites in each age-groups. 1% of older male patients developed breast cancer. (Table1) Of note, thyroid was a common site, 9.3% of SM, in young WM female cohort. Cecum and most of brain cancers were noted among pts with old age at WM dx. Overall survival was poorest for LB. Conclusions: There was a 10% incidence of SM in WM survivors during 2000-2019. LB cancer carried worst OS among WM survivors and was the most prevalent, second to gender specific cancer, among patients with relatively younger onset WM. [Table: see text]