Association between CD79B expression and polatuzumab vedotin efficacy, and therapy-induced changes in CD79B expression in diffuse large B-cell lymphoma.

Polatuzumab vedotin (PV), a CD79B-directed antibody-drug conjugate, is approved for treating diffuse large B-cell lymphoma (DLBCL). However, the clinical relevance of CD79B expression and the frequency of loss or decrease after PV-containing therapy remain unclear. We evaluated immunohistochemical CD79B expression using H-score (0-300) in 91 patients with DLBCL before PV-containing therapy and assessed post-treatment changes. Low CD79B expression was observed in 15 (16%) patients, including one case with no expression. Relapsed/refractory (R/R) DLBCL occurred more frequently in cases transformed from low-grade B-cell lymphoma than in de novo DLBCL (23% vs. 2%, P = 0.009), as well as in CD10-positive (25% vs. 49%, P = 0.033) and MUM1-negative (71% vs. 46%, P = 0.028) cases. R/R DLBCL also tended to occur more frequently in CD20-negative DLBCL than CD20-positive DLBCL (2% vs. 13%, P = 0.099). CD79B expression level was not associated with R/R DLBCL incidence. Among 15 patients with DLBCL with low CD79B expression, 60% achieved and maintained complete response after PV-containing therapy. Among 24 patients with recurrent tumor biopsies, 13% showed loss of/decreased CD79B expression. In conclusion, immunohistochemical CD79B expression was not significantly associated with PV-containing therapy efficacy, which remained effective even in DLBCL with low CD79B expression.