Abstract
Introduction Diffuse large B-cell lymphoma (DLBCL) is a heterogenous disease with varied expressions of CD30. Brentuximab vedotin (BV) is a CD30-directed antibody-drug conjugate approved for treatment of patients with relapsed or refractory DLBCL in combination with lenalidomide (Len) and rituximab (R). In the phase 3 ECHELON-3 study (NCT04404283), BV + Len + R showed significant overall survival (OS) benefit compared with placebo + Len + R in patients with relapsed or refractory DLBCL. Subgroup analysis from this study showed that BV + Len + R provided clinical benefit regardless of CD30 expression level. We hypothesized that even sub-threshold levels of CD30 expression, below the detection limits of immunohistochemistry (IHC), may be sufficient to elicit the antitumor activity of BV. Here, we further investigated whether trace amounts of CD30 staining are required for patients to benefit from BV + Len + R.
Methods In the ECHELON-3 study, patients with relapsed or refractory DLBCL were randomized 1:1 to receive BV + Len + R or placebo + Len + R. The primary endpoint was OS, with progression-free survival (PFS) and objective response rate (ORR), per Lugano 2014, as key secondary endpoints. CD30 expression was assessed by IHC by central and/or local testing. CD30 positivity was scored as the percentage of CD30 positive cells out of neoplastic cells or out of total lymphocytes, when neoplastic cells could not be distinguished. In this updated analysis, patients with CD30 <1% staining by central laboratory IHC were further grouped into CD30 <1% with trace staining and CD30 <1% with no staining.
Results Overall, 60 patients in the BV + Len + R group had CD30 <1% expression; of these, 34 had CD30 <1% with trace staining and 26 had CD30 <1% with no staining. In the placebo + Len + R group, 63 patients had CD30 <1% expression; of these, 36 had CD30 <1% with trace staining and 27 had CD30 <1% with no staining. In the overall CD30 <1% groups, numerically greater OS and PFS benefits were observed with BV + Len + R vs placebo + Len + R (HR for OS, 0.57; 95% CI, 0.36-0.89 and HR for PFS, 0.53; 95% CI, 0.34-0.82). In patients with CD30 <1% with trace staining, BV + Len + R showed a numerically higher OS compared with placebo + Len + R, with HR of 0.48 (95% CI, 0.26-0.90); median OS was 15.6 vs 5.2 months. In patients with CD30 <1% with no staining, there was a trend toward higher OS with BV + Len + R vs placebo + Len + R, with HR of 0.66 (95% CI, 0.34-1.28); median OS was 14.8 vs 11.8 months. Similarly, in patients with CD30 <1% with trace staining, BV + Len + R showed a trend toward longer PFS compared with placebo + Len + R, with HR of 0.60 (95% CI, 0.33-1.11); median PFS was 2.8 vs 1.5 months. In patients with CD30 <1% with no staining, a numerically longer PFS benefit was observed with BV + Len + R vs placebo + Len + R, with HR of 0.41 (95% CI, 0.21-0.79); median PFS was 4.2 vs 2.7 months. In the overall groups, ORR was 60.0% with BV + Len + R and 34.9% with placebo + Len + R. Higher ORR was observed with BV + Len + R compared with placebo + Len + R in both CD30 <1% with trace staining (55.9% vs 25.0%) and CD30 <1% with no staining (65.4% vs 48.1%) groups.
Conclusions Results from this updated analysis indicate that visible CD30 detection by IHC is not required for response to BV + Len + R in patients with relapsed or refractory DLBCL. Treatment with BV + Len + R showed efficacy benefit compared with placebo + Len + R regardless of CD30 expression level, including in patients with no visible CD30 IHC staining. These results are consistent with those from the overall ECHELON-3 study population, in which significant improvement in OS was demonstrated with BV + Len + R compared with placebo + Len + R.
