(59) Incidence of Second Primary Malignancies (SPMs) in Relapsed/Refractory (R/R) B-Cell Non-Hodgkin's Lymphoma (NHL) and Multiple Myeloma (MM) Patients in England

Publication Number: 1104

Background: There are growing concerns that treatments for r/r B-cell NHL and r/r MM may be associated with increased risk of SPMs in these patient populations. While preliminary data from ongoing clinical trials suggest that SPM incidence is within the expected range, current available SPM incidence benchmarks are unreliable due to small sample sizes.

Objectives: To estimate incidence rates (IRs) of first SPMs in r/r B-cell NHL and r/r MM patients overall and in select subgroups of interest using the Cancer Analysis System (CAS), a population-level database that collects data on cancer registrations for nearly all cancer patients in England.

Methods: Patients were included in the study if they were diagnosed with incident B-cell NHL or MM during 2013-2018; and had evidence of r/r disease, defined as the initiation of a second line of therapy (LoT), identified using a LoT algorithm, during 2013-2019. IRs of first SPMs in r/r B-cell NHL and r/r MM patients were calculated per 1000 person-years at risk (PYAR), starting at date of r/r disease, and stratified by age at r/r disease, sex, ethnicity, year of initial B-cell NHL or MM diagnosis, and type of SPM (e.g., solid, haematological). Preliminary results are rounded per masking requirements.

Results: Of the eligible incident patients identified, there were 9440 B-cell NHL patients and 4780 MM patients identified as having r/r disease by the LoT algorithm. Median age at r/r disease was 68 (NHL) and 69 (MM) years; patients were primarily white (~90%) and male (~60%), with a median (IQR) follow-up time of 18 (6-31) months for r/r NHL patients and 16 (8-30) months for r/r MM patients. Approximately 5% of r/r NHL and r/r MM patients developed at least one SPM on or after the r/r disease date. The overall IR of first SPM was approximately 40 (95% CI: 30-40) and 20 (95% CI: 20-30) per 1000 PYAR in r/r NHL and r/r MM patients, respectively . The rate of SPMs increased with age at r/r disease in both cohorts. Patients who had their initial NHL or MM diagnosis in earlier years had a higher rate of SPMs than those diagnosed more recently. Approximately 32% of r/r NHL and 42% of r/r MM patients who had an SPM after developing r/r disease were diagnosed with a solid tumour.

Conclusions: These results suggest that the incidence of SPM among patients with r/r B-cell NHL or r/r MM is low and increases with age at r/r disease, and that most SPMs are not solid tumours. To our knowledge, this is one of the first studies that uses real-world data to estimate a population-level background incidence for SPMs in r/r B-cell NHL and r/r MM patients, regardless of therapy received.