(P 270) ORAL VINORELBINE ACTIVITY FOR PROGRESSIVE DESMOID FIBROMATOSIS TUMOURS IN YOUNG PATIENTS

Objective: Desmoid-type fibromatosis (DTF) are rare tumours in children and adolescents. Their ability to be locally invasive and relapsing justifies a systemic treatment for symptomatic advanced/progressive forms to avoid complications due to extensive local therapy (surgery/radiotherapy). Oral vinorelbine showed promising activities in adults’ tumours series.

Methods: Retrospective review of all medical files in young patients (< 25 years) treated with oral vinorelbine (alone or in combination) for an advanced or progressive DTF in 8 large centres from “Société Française des Cancers de l’Enfant” (SFCE) network. All MRI at progression and during therapy were reviewed considering contours of the lesion, diameters (2D), and volume (3D) of the tumor according to RECIST 1.1, and percentage of hypoT2-signal intensity changes (normalized to muscle). Descriptive statistics were employed.

Results: From 2005 to 2020, 24 patients with DTF received oral vinorelbine: median age of 13.9 years [1-23], with limbs primary for 16 cases. Twenty-one patients had large tumour (size ≥ 5 cm). Median number of prior systemic lines of treatment was 1 (range, 1-2), most often based on intravenous low dose methotrexate and vinblastine (16 cases). Before oral vinorelbine initiation, all patients had progressive disease (PD): clinical (3 cases) and radiological (21 cases). Oral vinorelbine was delivered exclusively in 18 patients (80%) for a median duration of 12 months (range, 1-42) with various schedules. Toxicity profile was favourable, without any grade 3-4 toxicity. Overall response was three partial response (PR) (13%), 18 stable disease (78%) and two PD (9%). Three patients considered stable disease using standard RECIST 1.1, had > 65% tumor volume reduction, thus classified as partial response according to volumetric RECIST threshold. T2-signal intensity decreased for 16 patients and was associated with partial response or stable disease with symptomatic improvement.

Conclusion: Oral vinorelbine appears to be an effective treatment option to stabilize progressive or advanced DTF in young patients, with a well-tolerated and outpatient administration. This result support testing this therapy in first line and in combination to improve response rate and quality of life in this chronic disease.

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