Non-Hodgkin lymphomas in a Turkish pediatric cancer center: A developing-country model.

e22002 Background: This study aimed to evaluate the diagnostic findings and treatment outcomes of our pediatric non-Hodgkin’s lymphoma cases, gain a better understanding of the relationship between immunodeficiency and lymphoma, and contribute to the improvement of treatment processes. Methods: The clinical and demographic characteristics, subtype distributions, relapse rates and survival outcomes of 67 patients followed between 2002 and 2023 were analyzed. Results: The mean age at diagnosis was 9.16±4.70 years, ranging from 0.5 to 17.9 years, with a male-to-female ratio of 1.57. Regarding disease staging, 13.4% of patients were diagnosed at an early stage (stage I+II), while 86.6% had advanced-stage (stage III+IV) disease. Most non-Hodgkin lymphomas had a B-cell phenotype (84.9%) and 14.9% had T-cell lymphoma. The mean age of patients with B-cell lymphomas was 8.85 years, while the mean age of those with non-B-cell lymphomas was 10.97 years. The most frequent tumor localization was the abdomen (34.3%), followed by lymph node involvement (26.9%) and mediastinal involvement (11.9%). Bone marrow involvement was observed in 41.8% of patients, while central nervous system (CNS) involvement was detected in 4.5%. The most frequent presenting symptoms were pain (63.6%) and lymphadenopathy/swelling (47.0%). B symptoms were present in 25.8% of patients, with weight loss (70.6%) being the most common. Additionally, 10.6% of patients had Superior Vena Cava Syndrome, and 18.2% had Tumor Lysis Syndrome. Immunodeficiency was diagnosed in 19.7% of patients. The median time from symptom onset to diagnosis was a 1 month (range: 0-22). The duration between transplantation and lymphoma diagnosis ranged from a minimum of 5 months to a maximum of 53 months for 4 transplantation patients. The most common subtypes were Burkitt lymphoma (44.8%) and Diffuse Large B-Cell Lymphoma (14.9%). The most frequently used treatment protocol was POG9317 (39%) in B- cell lymphomas. The relapse rate was 13.6%, and the most commonly used treatment regimen for relapsed cases was the CHOP protocol. Hematopoietic stem cell transplantation was performed in 7.5% of patients, with 80% of these cases diagnosed with immunodeficiency. In terms of survival, the 2-year survival rate was 86.7% and the 5-year overall survival rate was 82.4%, while the mortality rate was calculated as 15.2%. Conclusions: The incidence, clinical presentation, and histopathologic features of pediatric NHL vary by region. Our data suggest that patients over the age of 10 years are more likely to have a T-cell lymphoma phenotype, consistent with the literature. Additionally, patients with residual tissue detected during posttreatment imaging had higher rates of relapse and mortality. We found that the frequency of immunodeficiency in our patients was much higher than in the literature (19.4%).