Abstract 2181: Treatment-free remission after discontinuation of ALK tyrosine kinase inhibitors (TKIs) in patients with ALK-positive anaplastic large cell lymphoma (ALCL)
Authors: Kim Jinyong , Kim Soyeon , Kim Tae Min , Youk Jeonghwan , Kim Miso , Keam Bhumsuk , Kim Dong-Wan , Heo Dae Seog 
Published: April 2023

Introduction: ALK-positive ALCL accounts for 0.8% of Korean lymphoma patients. ALK TKIs are effective and durable, but clinical outcomes after treatment discontinuation are unknown. We analyzed outcomes and minimal residual disease (MRD) in adult ALK-positive ALCL patients who discontinued ALK TKIs after achieving treatment-free remission.

Methods: Six patients who achieved responses to crizotinib (N=5) and ceritinib (N=1) were analyzed. RNA extracted from the blood or tissues before TKI treatment were subjected to multiplex PCR-based next generation sequencing (NGS) using ARCHER® RNA Fusionplex® to detect NPM-ALK fusion. MRD was assessed by droplet digital PCR (ddPCR) of peripheral blood mononuclear cells (PBMCs) after the treatment discontinuation. Undetectable MRD was defined as less than one lymphocytic cell per 10,000 leukocytes (10-4) in peripheral blood.

Results: Patients received ALK TKIs as second line (N=3) or third line and beyond (N=3). All achieved complete metabolic responses after median 28.5 months (range, 1.7-93.9) of treatments (Table 1). Before TKI, LY1 patient had no morphologic evidence of bone marrow involvement, but NPM1-ALK fusions were detected by NGS and ddPCR in blood, bone marrow, and tissue. LY1 patient remained in remission at 27.8 months after crizotinib discontinuation. In all patients, NPM1-ALK fusion were not detected in the PBMCs after discontinuing ALK TKIs for median 38.2 months (range, 0-61.9). No patient re-initiated anti-lymphoma therapies.

Conclusion: Out data demonstrated that treatment-free remission was durable for more than two years in ALK-positive ALCL patients following the cessation of ALK TKIs. MRD-guided

discontinuation decision may be considered for ALK-positive ALCL patients treated with ALK inhibitors who had undetectable MRD.

Table 1. Summary of patient characteristics and outcomes of ALK TKI discontinuation No. Sex Age at diagnosis Ann Arbor stage ALK TKI Lines of prior therapy Treatment duration of ALK TKI (months) Reason for cessation Duration of ALK TKI cessation (months) Best response to ALK TKI Time of MRD assessment after TKI cessation MRD after TKI cessation 1 M 22 IIB Crizotinib 3 93.9 Fertility 27.8 CR 5.6 Negative 2 F 20 IVB Crizotinib 1 90.9 Fertility 25.9 CR 0.0 Negative 3 M 23 IV Ceritinib 1 42.7 Adverse event 61.9 CR 61.9 Negative 4 F 58 IV Crizotinib 3 1.7 Cost 86.6 CR 72.1 Negative 5 F 64 IVB Crizotinib 1 13.6 Cost 31.0 CR 14.4 Negative 6 M 75 IV Crizotinib 2 11.7 Cost 80.2 CR 62.0 Negative

Citation Format: Jinyong Kim, Soyeon Kim, Tae Min Kim, Jeonghwan Youk, Miso Kim, Bhumsuk Keam, Dong-Wan Kim, Dae Seog Heo. Treatment-free remission after discontinuation of ALK tyrosine kinase inhibitors (TKIs) in patients with ALK-positive anaplastic large cell lymphoma (ALCL) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2181.