Clinical Characteristics and Prognostic Analysis of Non-NPM1-ALK Fusions in Pediatric Patients With ALK-Positive Anaplastic Large-Cell Lymphoma: A Single-Center Retrospective Study in China.

[PURPOSE] Non-NPM1-ALK fusions in pediatric anaplastic lymphoma kinase (ALK)-positive anaplastic large-cell lymphoma (ALK+ ALCL) are rare and insufficiently characterized in Chinese populations. This study analyzed the clinical features, treatment responses, and potential prognostic implications of these variants.

[METHODS] In this retrospective study, eight pediatric patients with ALK+ ALCL and non-NPM1-ALK fusions were diagnosed between April 2017 and April 2025. For prognostic comparison, a cohort of 107 newly diagnosed patients with NPM1-ALK fusions was used. Clinical data, treatment courses, and outcomes were reviewed. Event-free survival (EFS) was estimated using the Kaplan-Meier method.

[RESULTS] Among 128 ALK+ ALCL patients, 8 (6.3%) had non-NPM1-ALK fusions (TPM3, n = 3; ATIC, n = 2; CLTC, MYH9, TRAF1, n = 1 each). At a median follow-up of 17.5 months (range, 1.2-97.9), all patients were alive. Analysis of patients with non-NPM1-ALK fusions (n = 7, newly diagnosed) indicated a trend toward inferior 5-year EFS compared with the NPM1-ALK group. Within the non-NPM1-ALK cohort, no events were observed in the three patients TPM3-ALK fusions, while four patients with other fusion types experienced relapse or disease progression. ALK inhibitors (crizotinib/alectinib) were associated with sustained remission in three patients with relapsed/refractory disease.

[CONCLUSION] Pediatric ALK+ ALCL with non-NPM1-ALK fusions exhibits diverse clinical features and outcomes. TPM3-ALK fusions might correlate with a more favorable course, while other variants may face a potentially higher relapse risk. ALK inhibitors showed promising efficacy in the salvage setting. These preliminary findings highlight the need for larger prospective studies to validate mutation-specific risk stratification and therapeutic strategies.