Venous Malformation, Low Flow

Superficial venous malformations (SVMs) are rare congenital anomalies that present as bluish masses. These masses may be focal, with limited skin involvement, or segmental, with more extensive involvement. They may be associated with syndromic conditions such as blue rubber nevus syndrome. SVMs are characterised by a progressive worsening course, with repeated episodes of superficial venous thrombosis occurring. These episodes become more frequent over time, causing acute, intense and often highly debilitating pain. To limit progression and in cases of functional impairment, long-term treatments may be offered. These include venous compression, targeted therapies such as mTOR inhibitors, and, where possible, surgical treatment or sclerotherapy. However, the management of intra-SVM superficial venous thrombosis is not currently standardised, especially in the pediatric population. This study aims to evaluate the benefits of Acetylsalicylic acid (ASA) as an add-on treatment to local non-steroidal anti-inflammatory drug for the management of thrombotic episodes in superficial venous malformations in children aged 6 to 17 years.

Recent studies have demonstrated that growth of vascular malformations can be driven by genetic variants in one of 2 signalling pathways. Targeted drugs specific to these pathways have been developed and shown to be effective in treating cancer. This study will describe the effectiveness of (i) 48 weeks of alpelisib therapy for participants with slow-flow vascular malformations and a gene mutation in one of these signalling pathways (module 1) and (ii) 48 weeks of mirdametinib therapy for participants with fast-flow vascular malformations and a gene mutations in the other signalling pathway (module 2).

There are two parts of the study. In Part 1, the invesitgaotrs want to investigate whether treatment with apixaban improves pain and quality of life in patients with painful venous malformations The participants are randomized to different treatment orders of the two treatment periods with apixaban and placebo. Arm 1 starts apixaban followed by placebo and arm 2 starts with placebo followed by apixaban. Between the treatment sequences there will be a washout period of minimum one week. The participants will register pain and use og pain medication in a diary every day for one week before start of treatment and before evaluation of effect. Also, a quality of life form will be filled out before each consultation. In Part 2, the investigators will investigate long-term effect and safety of apixaban and reduce dose after 3 months to find the minimal effective dose. Part 2 includes participants from Part 1 study who experienced effect of treatment or who agree to continue apixaban treatment. Study start of Part 2 is at the end of Part 1. All participants receive the same dose of apixaban as in part 1 (5 mg twice daily), and after 3 months (visit 2) the dose is reduced to 2.5 mg twice daily.