Pediatric Low-Flow Vascular Malformations: Treatment Patterns and Outcomes.

Low-flow vascular malformations (LFVMs) are congenital vascular anomalies with heterogeneous clinical behavior and variable treatment response. This retrospective study described the clinical characteristics, treatment patterns, and modality-specific outcomes of children aged 0-18 years with LFVM evaluated at Hacettepe University between January 1999 and June 2020. Lesions were classified as capillary, venous, lymphatic, or combined LFVMs, and demographic, clinical, imaging, treatment, follow-up, and adverse event data were reviewed. Radiologic/clinical and symptomatic responses were assessed for sirolimus, image-guided sclerotherapy, and surgery. Among the patients, lesions were combined in 94 (40.5%), lymphatic in 80 (34.5%), and venous in 58 (25.0%). The mean age at diagnosis was 54.6 ± 55.2 months, the mean diagnostic delay was 37.6 ± 48.1 months, and the head and neck was the most frequent primary location (44.4%). Mean follow-up was 50.1 ± 42.3 months. Sirolimus was administered to 118 patients and achieved radiologic/clinical response in 55.1% and symptomatic improvement in 75.4%, with the highest symptomatic improvement observed in lymphatic malformations (84.2%). After sirolimus discontinuation, 19 patients experienced radiologic/clinical progression or symptom worsening. Sclerotherapy (n = 74) achieved radiologic/clinical and symptomatic response rates of 67.6% and 79.7%, respectively, whereas surgery (n = 54) achieved rates of 79.6% and 61.1%, respectively. Progressive disease at the last follow-up was rare (1.3%). Overall, multimodal therapy provided substantial disease control in this long-term pediatric LFVM cohort. Sirolimus primarily improved symptoms, particularly in lymphatic and combined lesions, while sclerotherapy and surgery were effective when selected according to lesion phenotype and treatment goals.