Outcome of Infantile Malignant Solid Tumors: A Single-Center Experience.

Background: Malignant solid tumors diagnosed during the first year of life represent a rare but clinically significant subgroup of pediatric cancers. Their biological behavior, treatment responses, and prognosis differ substantially from tumors diagnosed in older children due to developmental immaturity and age-related therapeutic limitations. Methods: We retrospectively analyzed 88 infants diagnosed with malignant solid tumors before 12 months of age at a single tertiary center between March 2011 and March 2023. Demographic, clinical, pathological, and treatment data were collected. Overall survival (OS) was estimated by Kaplan-Meier analysis, and prognostic factors were evaluated using univariate and multivariate Cox regression models. Results: Of the 98 initially screened patients, 88 were eligible for analysis. The median age at diagnosis was 7 months, with a median follow-up of 42 months. The most common tumor locations were intra-abdominal (64.7%), brain (20.5%), and bone/soft tissue (12.5%). Neuroblastoma was the leading diagnosis (30.7%), with spontaneous regression observed in 29.6% of cases. Atypical teratoid rhabdoid tumor (ATRT) was the most frequent brain tumor (9.1%). The 5-year OS for the entire cohort was 78.3%. Brain tumors were associated with significantly higher mortality (HR 4.32, p = 0.01), while intra-abdominal tumors predicted improved survival (HR 0.31, p = 0.02). Conclusions: Infantile malignant solid tumors display heterogeneous clinical behavior and outcomes. While favorable results can be achieved in neuroblastoma and soft tissue sarcomas, brain tumors, particularly ATRT, remain a therapeutic challenge. Age-specific, risk-adapted treatment strategies and earlier detection are critical to improving survival and reducing long-term sequelae in this vulnerable population.