Real-World Evaluation of T-Prolymphocytic Leukemia Outcomes Using the 2019 T-PLL International Study Group Criteria

Introduction: T-Cell Prolymphocytic Leukemia (T-PLL) is a rare, aggressive T-cell malignancy with very poor prognosis. CLL criteria have historically been used for diagnostic and response criteria for T-PLL, but due to the T-PLL's distinct biology and clinical features in 2019 the International Study Group (TPLL-ISG) developed the first consensus criteria for diagnosis and response assessment to harmonize clinical research in T-PLL (Staber et al, Blood, 2019). Diagnostic criteria included both major and minor criteria, while standardized criteria were developed for complete response (CR), complete response with incomplete marrow recovery (CRi), partial response (PR), and stable disease (SD). While the TPLL-ISG consensus criteria are an important step towards uniformity in diagnosis and response assessment, the applicability of these criteria has not been assessed in a real-world population. We evaluated the diagnosis and clinical responses of the OSU T-PLL population using the TPLL-ISG criteria to evaluate the concordance of historical outcomes with previous diagnostic/response criteria. Methods: We retrospectively evaluated all patients diagnosed with T-PLL at The Ohio State University between 2009-2022. Diagnosis and response were evaluated utilizing the TPLL-ISG criteria. Overall survival (OS), progression-free survival (PFS), and duration of response (DOR) were assessed using Kaplan-Meier methods and log-rank test. Results: A total of 32 patients, with an average follow-up time of 23 months were evaluated. All patients met the TPLL-ISG criteria for the diagnosis of T-PLL with 29 (91%) meeting major criteria and 22 (69%) meeting both major and minor criteria; concordant with prior studies. 23 patients (72%) were TCL1A positive (by cytogenetics or FISH) and 18 patients (56%) had nodal involvement via PET or CT scan. For all patients, median OS and PFS were 20 months (95% CI 6-45) and 4 months (95% CI 2-17), respectively. Using TPLL-ISG criteria, the overall response rate (ORR) (CR/CRi/PR) to first line treatment was 63% with a median OS of 45 months (95% CI 8-88) and PFS of 26 months (95% CI 4-46). Median DOR was 16 months (range 1-36). The median OS and PFS for patients who achieved a CR were 45 months and 37 months, respectively. For those with a Cri, the OS/PFS was not reached and for those with PR, OS was 7 months and PFS 3 months. The median OS and PFS for patients treated with frontline alemtuzumab (n=26) was 20 months and 4 months and 8 months and