The study, coordinated by Volkan Hazar of Memorial Health Care in Antalya together with dozens of colleagues across the country, enrolled 132 children under 21 years of age who experienced their first relapse of acute lymphoblastic leukemia between February 2017 and June 2022. Patients were treated at 27 different centers nationwide, and their data were collected through a shared registry, giving researchers an unusually complete view of real-world practice outside the controlled environment of a single specialized hospital.

Each child was assigned to either a standard-risk or high-risk group based on well-established criteria, including how quickly the leukemia returned and where it reappeared. Of the total, 67 patients fell into the standard-risk category and 65 into the high-risk group. This risk stratification, a cornerstone of modern relapse therapy, is designed to intensify treatment for those least likely to respond while sparing others from unnecessary toxicity.

All patients were managed according to the ALL-IC REL 2016 guideline, a protocol developed through international collaboration that prescribes multi-agent chemotherapy induction followed by risk-adapted consolidation, often including hematopoietic stem cell transplantation. The researchers tracked several key endpoints: whether children achieved a second complete remission, how long they survived without new events, and how many died from complications of treatment itself.

The headline result is that 81.8 percent of patients achieved a second complete remission after induction, although 17.4 percent failed to reach remission at all. Achieving remission is the essential gateway to potentially curative consolidation, typically transplantation, so a success rate above 80 percent confirms that the protocol remains feasible and effective at re-establishing disease control for the majority of relapsed patients, even in a middle-income setting.

The estimated five-year overall survival for the entire cohort was 51.4 percent, with event-free survival of 43.2 percent. That means roughly half of the children treated under this protocol were alive five years after relapse, a figure that reflects both genuine therapeutic progress and the persistent lethality of relapsed disease. During follow-up, 37.1 percent of patients suffered a second relapse, and 64 of the 132 children died over the study period.

The risk-group divide proved stark. Standard-risk patients enjoyed a five-year overall survival of 65.4 percent and event-free survival of 57.3 percent, while their high-risk counterparts fared far worse, with corresponding rates of just 37.5 percent and 29.0 percent. Both differences were highly statistically significant. The authors conclude that the ALL-IC REL 2016 guideline delivered encouraging outcomes for standard-risk children but left a substantial gap for the high-risk group.

Two factors emerged as powerful predictors of poor outcome: very early relapse, meaning the leukemia returned shortly after initial treatment, and age of 10 years or older at the time of relapse. Additionally, measurable residual disease detected by flow cytometry at the end of induction, at a threshold of 0.1 percent or higher, showed an adverse trend for both overall and event-free survival. Minimal residual disease, the microscopic trace of leukemia cells that survives therapy, is increasingly recognized as one of the most informative prognostic markers in relapsed ALL, capable of revealing treatment failure long before overt relapse.

The study also sounded an alarm about treatment-related mortality and deaths occurring while patients were officially in remission. These deaths, often driven by infections and organ toxicity during intensive chemotherapy or following transplantation, remained substantial in the Turkish cohort. Such losses underscore that survival in relapsed leukemia depends not only on eradicating the cancer but also on the quality of supportive care, including infection prevention, transfusion support, and intensive care availability.

Perhaps the most consequential implication of the study concerns access to modern immunotherapies. Agents such as blinatumomab, inotuzumab ozogamicin, and chimeric antigen receptor T-cell therapy have transformed outcomes for high-risk relapsed ALL in high-income countries, but they remain difficult to access in many parts of the world. The authors argue that the survival gap they documented for high-risk patients highlights the urgent need for standardized minimal residual disease monitoring, improved supportive care, refined transplantation strategies, and broader access to immunotherapy. As real-world evidence accumulates from diverse health systems, studies like this one provide an essential benchmark for measuring progress toward closing the survival gap between children treated in wealthy nations and those treated elsewhere.

Subject of Research: Real-world outcomes of pediatric first-relapsed acute lymphoblastic leukemia treated under the ALL-IC REL 2016 guideline in Türkiye

Article Title: Real-world outcomes of children with first relapsed acute lymphoblastic leukemia treated according to the ALL-IC REL 2016 guideline in Türkiye

Article References: Hazar, V., Güneş, A. M., Yaralı, H. N., Yalçın, K., Küpesiz, F. T., Karapınar, T. H., Ayçiçek, A., Zengin, E., Evim, M. S., Özbek, N. Y., Yılmaz, B., Özdemir, Z. C., Karasu, G. T., Küpesiz, O. A., Yıldırım, Z. K., Bıçakçı, Z., Kebudi, R., Özek, G., Tokgöz, H., … Gülen, H. (2026). Real-world outcomes of children with first relapsed acute lymphoblastic leukemia treated according to the ALL-IC REL 2016 guideline in Türkiye. Annals of Hematology. https://doi.org/10.1007/s00277-026-07281-w

Image Credits: AI Generated

DOI: 10.1007/s00277-026-07281-w

Keywords: relapsed acute lymphoblastic leukemia, pediatric oncology, ALL-IC REL 2016, minimal residual disease, hematopoietic stem cell transplantation, treatment-related mortality, overall survival, event-free survival, risk stratification, immunotherapy access, multicenter study, Türkiye