(SLB-020) Risk of Secondary Primary Malignancies among Patients with Selected Hematologic Cancers: US population-based analysis of SEER

Background: With improvements in management of hematologic cancers, survivors may be at higher risk of secondary primary malignancy (SPM).

Objectives: Utilizing data from the Surveillance, Epidemiology and End Results (SEER) database, this study analyzed risks of SPM in patients with several hematologic cancers of interest (HCI) and then compared these risks to the general US population.

Methods: Patients’ first primary malignancy (FPM) diagnosed from 2000 to 2016 from SEER 17 registry with an HCI (CLL, AML, MCL, MM, FL and DLBCL) were included. Patients with SPM diagnosed within one month of FPM were excluded. Follow-up for incidence of SPM diagnosis began one month after FPM diagnosis until the earliest censoring event (death, loss to follow-up, attained age > 89 or study end [12/31/ 2021]). Risks of SPM were reported as frequencies, percentages, incidence rates and standardized incidence ratios (SIR), which were calculated by dividing the observed incidence of SPM by expected incidence of SPM in the general population.

Results: A total of 241,719 patients with newly diagnosed HCI were reported from 2000 to 2016. Mean age was 62.5 years and majority were Non-Hispanic White (71.2%) and male (56.1%). Median survival was 6.4 years after FPM diagnosis. Overall, 30,833 patients (12.8%) developed at least one SPM with 34,273 SPMs observed during follow-up. Among patients with FPM of CLL, AML, MCL, MM, DLBCL, and FL, SPMs occurred in 8,902 (18.5%), 1146 (4.5%), 1,015 (13.8%), 4,833 (8.4%), 7,740 (12.0%), and 7,197 (18.5%), respectively. Overall, mean person years at risk was 7.1 for all HCI combined (range 4.7-9.5). Patients diagnosed at an early stage, not receiving chemotherapy as first-line treatment, and FPM diagnosis in earliest years of SEER registry were more prone to SPM. SIRs of SPM among the 6 FPM cancers combined were 1.3 [95% CI: 1.30-1.33] for any SPM malignancy type, 3.1 [3.01-3.15] for hematologic and 1.1 [1.09-1.12] for any solid tumor malignancy. Within each HCI type, risk of hematologic SPM was higher than risk of solid tumor SPM. Hodgkin lymphoma (HL), myeloid and monocytic leukemia and Non-HL were the most common SPM.

Conclusions: In this nationwide, population-based registry, we observed that risks of SPM were significantly elevated among all HCIs, compared to the general population. In general, incidence of SPM among the different HCIs increased as a function of increased median survival time following FPM diagnosis. Prolonged survival of patients with hematologic cancer highlights the importance of continuing efforts and strategies to appropriately screen individuals with an FPM for risk of SPM.