[Treatment Landscape of Mature NK/T-cell Lymphomas: Treatment Outcomes in Japan and Future Prospects].

Mature NK/T-cell lymphomas are a rare group of lymphoma subtypes, represented by extranodal NK/T-cell lymphoma (ENKL) and aggressive NK-cell leukemia (ANKL). Both subtypes are strongly associated with Epstein-Barr virus and show a high prevalence, particularly in East Asia and Central and South America. In Japan, ENKL currently accounts for approximately 1% of all malignant lymphomas, whereas ANKL is even rarer, accounting for approximately 0.1%. ENKL and ANKL share many clinical and pathological features. However, as evidence regarding differences in molecular biological characteristics, including genetic and chromosomal abnormalities, has gradually accumulated, they have been recognized as distinct disease entities since the 2001 WHO classification (3rd edition). Since the 2000s, the treatment of ENKL has markedly advanced with the development of non-anthracycline-based regimens. In Japan, RT-2/3DeVIC for localized-stage ENKL and SMILE for stage IV and relapsed/refractory ENKL were developed and remain the current standard of care. In contrast, because ANKL is a rare disease and reports on its treatment are limited, it is usually treated using strategies for advanced-stage ENKL. This review focuses on ENKL and ANKL, providing an overview of their disease characteristics, evolving treatment and prognosis, and future challenges and perspectives.