The bidirectional increased risk of B-cell lymphoma and T-cell lymphoma.

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 (BCLs and TCLs) 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 fivefold 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; HL following PTCL-NOS: SIR = 31.6). 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; DLBCL following AITL: SIR = 15.3). 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 and follicular lymphoma. These patterns support etiologic heterogeneity among lymphoma subtypes and provide further insights into lymphomagenesis.