Survival in mantle cell lymphoma patients burdened by a second primary malignancy

Second primary malignancies (SPMs) increasingly affect mantle cell lymphoma (MCL) survivors. In nationwide Danish and Swedish cohorts (2000–2020), we evaluated overall survival among MCL patients with SPMs versus matched non-lymphoma individuals with comparable malignancies and MCL patients without SPMs, respectively. Of 3094 MCL survivors, 19% in Denmark and 15% in Sweden developed an SPM, with a median of three years from MCL diagnosis to first SPM. MCL patients with SPMs had about double the mortality risk compared with non-lymphoma counterparts (pooled HR 2.1, 95% confidence interval (CI) 1.3–3.5), and worse survival than MCL patients without SPMs (pooled HR 1.6, 95% CI 1.4–1.9). In Swedish MCL patients with SPMs, deaths were attributed to subsequent hematologic malignancies (9%), solid cancers (14%), primary MCL (23%), non-cancer causes (11%), with 40% still alive. Development of SPMs in MCL is associated with substantially higher mortality, supporting long-term surveillance and proactive management of late complications.