Varying Latency Impact on Incidence of Second Primary Malignancy Among Patients with B-Cell Malignancy

OBJECTIVES: The objective was to investigate the incidence rate (IR) of second primary malignancy (SPM) following B-cell malignancy diagnosis (chronic lymphocytic leukemia [CLL], mantle cell [MCL], marginal zone [MZL], Waldenström macroglobulinemia [WM], diffuse large B-cell, follicular, hairy cell leukemia).

METHODS: National Cancer Institute’s Surveillance, Epidemiology, and End Results database from 2000 to 2019 was analyzed. The SPM IR per 100 person-months and the multiple primary standardized incidence ratio (MP-SIR) of observed versus expected were calculated for patients with B-cell malignancy. Patients with a previous malignancy were excluded from both calculations. Patients with an SPM within 3 months following B-cell malignancy were excluded from the IR calculation. Additional analyses examined IR under two other scenarios to understand the impact on IR: 1) limiting the prior malignancy exclusion to past 3 years only, and 2) including patients with SPM within 3 months.

RESULTS: The IR of any SPM was 0.19 (95% CI: 0.187, 0.195), ranging from 0.19 (MCL) to 0.23 (WM). The MP-SIR for any SPM was 1.58 (95% CI: 1.55, 1.61), ranging from 1.50 (CLL/MCL) to 1.73 (MZL). The MP-SIR for any hematological SPM was 4.46 (95% CI: 4.30, 4.63), ranging from 2.09 (MCL) to 5.92 (MZL). Excluding patients with a prior malignancy within 3 years had little impact on IR (0.20, 95% CI: 0.198, 0.206). Including patients with SPM within 3 months increased IR slightly (0.22, 95% CI: 0.216, 0.224).

CONCLUSIONS: Patients with a B-cell malignancy had a 58% greater occurrence of any SPM and 446% greater occurrence of any hematological SPM than expected in the general population. Varying latency and prior malignancy exclusions, to further understand how IR of SPMs may be impacted by the methodology imposed, had only a slight influence.