G359(P) Characterising the disease presentations of lch over 10 yr at a uk ptc

Background Langerhans Cell Histiocytosis (LCH) describes a clinical spectrum of disease caused by accumulation of pathologicallangerhan’scells infiltrating tissues. Further understanding regarding the patho-physiology and natural history of langerhans cell histiocytosis has emerged with the understanding of its status as a clonal BRAF stimulated malignancy. Objectives To characterise the disease presentations of Langerhans Cell Histiocytosis in a UK Principal treatment centre (PTC) over the past 10 years. Methods Our PTC serves a population of 3.6 million sharing care with 11 regional shared care centres. A retrospective case review was performed for all patients treated for LCH over the last 10 years. Data were collected on demographics, disease location, treatment modality, intervals of remission free outcome and latest evaluation at follow up. Results 1041 children have been treated for cancerover the past 10 years (1/1/2006–31/12/2016). We identified 45 cases of LCH from children aged 2 mths to 16 years (median age of 2 years 6 mths) in our database accounting for 4% of our patients. There were 44% females and 58% males. 64% of cases presented with single-system disease at diagnosis and 36% with multi-system disease. 4 children were identified as having diabetes insipidus at diagnosis 2.5%. 33/45 (73%) had a biopsy performed consistent with LCH, 10 had no biopsy performed and 2 had a biopsy which was negative but were treated as per LCH due to typical clinic-radiological correlation. 2 cases of neurodegenerative LCH were identified in this case series. Multi-system patients have a more challenging course and in our series 10/18 (56%) went on to have a recurrence and of these 2 patients have had 4 relapses and are still undergoing further therapy. Conclusions Our centres experience over the past 10 years which shows the full spectrum of presentation from the benign self-limiting single system bony disease to that of extensive multi-system disease leading to secondary HLH. Novel strategies to evaluate and monitor BRAF in blood and urine such as those being employed in the latest international LCH IV trial offer the opportunity to better understand the risk factors for disease severity.