We observed bidirectional increased risks between B- and T-cell lymphomas, with estimated risks >5-fold higher than the general population.
The magnitude of these associations varied substantially by lymphoma subtype, supporting etiologic heterogeneity among different subtypes.
Lymphoma survivors have a significantly higher risk of developing second primary lymphoma than the general population; however, bidirectional risks of developing B- and T-cell lymphomas (BCL; TCL) specifically are less well understood. We used population-based cancer registry data to estimate the subtype-specific risks of second primary lymphoma among patients with first BCL (n=288,478) or TCL (n=23,747). We observed nearly five-fold increased bidirectional risk between BCL and TCL overall (TCL following BCL: standardized incidence ratio [SIR]=4.7, 95% confidence interval [CI]=4.2-5.2; BCL following TCL: SIR=4.7, 95%CI=4.1-5.2), but the risk varied substantially by lymphoma subtype. The highest SIRs were observed between Hodgkin lymphoma (HL) and peripheral T-cell lymphoma-not otherwise specified (PTCL-NOS) (PTCL-NOS following HL: SIR=27.5, 95%CI=18.4-39.4; HL following PTCL-NOS: SIR=31.6, 95%CI=17.3-53.0). Strikingly elevated risks also were notable for angioimmunoblastic T-cell lymphoma (AITL) and diffuse large B-cell lymphoma (DLBCL) (AITL following DLBCL: SIR=9.7, 95%CI=5.7-15.5; DLBCL following AITL: SIR=15.3, 95%CI=9.1-24.2). These increased risks were strongest within the first year following diagnosis but remained persistently elevated even at ≥5 years. In contrast, SIRs were <5 for all associations of TCL with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) and follicular lymphoma (FL). These patterns support etiologic heterogeneity among lymphoma subtypes and provide further insights into lymphomagenesis.