Underrepresentation of Small Lymphocytic Lymphoma in Clinical Trials for Chronic Lymphocytic Leukemia.

Background: Although chronic lymphocytic leukemia (CLL) and small lymphocytic lymphoma (SLL) are the same biologic disease entity and warrant identical treatment approaches, patients with SLL have frequently been excluded from clinical trials in CLL.

Methods: This study assessed the representation of patients with SLL among Phase II or III clinical trials cited in the 2024 National Comprehensive Cancer Network (NCCN) treatment guidelines.

Results: Patients with SLL were explicitly eligible for only 21 (38%) of the 56 clinical trials for CLL, comprising 222 (6%) of the 3440 enrolled patients. Notably, 380 patients with SLL were enrolled in 16 separate non-CLL clinical trials alongside patients with indolent B-cell lymphomas such as follicular lymphoma. In CLL trials, patients with SLL were included in a greater proportion of studies evaluating BTK inhibitors (67%) or BTK/BCL2 inhibitor combinations (67%) compared to BCL2 inhibitors (0%) or chemoimmunotherapy (0%).

Conclusions: Although recent and upcoming trials show a promising trend toward the inclusion of patients with SLL, further advocacy is needed to raise awareness of the biological similarities between CLL and SLL and to promote the representation of patients with SLL in CLL/SLL clinical research.