Prognostic Impact of ALK on Anaplastic Large Cell Lymphoma of CNS

Abstract Introduction and background Anaplastic large cell lymphoma (ALCL) is an atypical clinicopathological entity and its central nervous system (CNS) involvement is rarer still, presenting a diagnostic challenge to physicians. Based on the absence or presence of anaplastic lymphoma kinase (ALK) fusion, it presents as either ALK-negative or ALK-positive subtype, the latter predominantly having a favourable prognosis and presenting in younger patients. The definitive impact of the said ALK protein on the course of the illness is the main area of interest of this study. Methodology The study question was designed using the PICO (participants, interventions, comparisons and outcomes) strategy. We conducted a systematic review in accordance with the PRISMA guidelines and a literature search using PubMed, Google Scholar and Cochrane library using keywords like ‘anaplastic large cell lymphoma’, ‘ALCL’, ‘ALK’ and ‘CNS’. Results We included 30 cases of ALCL in our study, of which 24 cases were ALK positive and the remaining were negative. Eighty-six percent of the former showed 2-year survival when receiving interventions such as methotrexate-based chemotherapy, radiation, non-methotrexate-based chemotherapy and surgery, while none of the ALK-negative patients passed an 8-month survival period. In this study, we assessed the histology, immunochemistry, prognostic factors and treatment methods of disease based on previous records and came to the conclusion that ALCL involving CNS had a better prognosis with a positive ALK protein status and also certain other prognostic factors such as meningeal involvement, T cell as a marker and age less than 18 years.