ALBERT

Description: Background: Vascular anomalies are diverse entities and can range in severity from self-limiting to life-threatening. Diagnosis and care of these patients is challenging due to overlapping clinical and histologic features. Recently, it has been established that many vascular anomalies arise from somatic mutations in cancer genes (PIK3CA, AKT, NRAS). Use of cancer genomics in patients with vascular anomalies may establish a genetic diagnosis and expand use of targeted medical therapies. We evaluated the utility of targeted next generation sequencing for vascular anomalies patients at a single pediatric center. Methods: Using OncoPanel, a hybrid-capture and massively parallel sequencing assay that surveys DNA sequences of 447 genes implicated in cancer, we analyzed genetic variants in lesional tissue from vascular anomalies patients evaluated at Boston Children's Hospital between 5/2/2017 and 3/23/2020. Results: A total of 276 patients were consented and sequenced under the Dana Farber Cancer Institute Profile protocols DFCI 11-104 (n= 68) and DFCI 17-000 (n= 208). Clinical diagnoses prior to testing were varied and 11 patients (7%) had an unknown diagnosis. Tissue was analyzed for 138 patients. Targeted sequencing resulted in diagnostically significant alterations in 80 of 138 (57%) of patients and therapeutically significant alterations in 58 of 138 (42%) patients. To date, 18 patients in our cohort have been treated with medical therapy informed by their genetic diagnosis. Several more await enrollment on clinical trials. For patients with diagnoses previously categorized as unknown (n=11), sequencing led to identification of a genetic variant in 6 patients (54%). Additionally, 8/138 patients had variants requiring further evaluation for potential germline involvement. Discussion: Next generation sequencing in vascular anomalies patients identified actionable variants in a large proportion of the patients in our cohort. The mTOR inhibitor sirolimus has been used to treat a variety of vascular anomalies, but not all patients respond to this treatment. Targeted therapies based on specific genotypes hold promise as clinical trials in vascular anomalies are emerging. Additionally, sequencing in this cohort identified several variants suggesting a germline cancer predisposition requiring follow-up. Use of next generation sequencing has clinical utility and increased use of this testing may improve diagnosis, prognosis, and treatment for patients with vascular anomalies. Disclosures Adams: Novartis: Consultancy; Venthura: Consultancy. OffLabel Disclosure: Sirolimus is used off-label for the treatment of vascular anomalies.