Mesoglycan for the secondary prevention of superficial vein thrombosis: a randomized, controlled, double-blind study (METRO Study)-rationale and protocol.

No data is available about pharmacological secondary prevention of superficial vein thrombosis (SVT) despite 10-15% of patients develop venous thromboembolic complications at 3-6 months after an adequate treatment of the acute phase. To verify efficacy and safety of mesoglycan in secondary prevention of SVT recurrence and venous thromboembolic complications. Phase III multicenter, double-blind, randomized, superiority trial comparing mesoglycan 50 mg bid vs placebo in consecutive patients with a SVT extended at least 5 cm, after the initial 45-day treatment course with fondaparinux 2.5 mg once-daily. Primary efficacy outcome: SVT recurrence/extension, symptomatic venous thromboembolism (VTE), asymptomatic proximal deep-vein thrombosis, death. Primary safety outcome: major bleeding. We hypothesized a 12-month 15% incidence of the primary efficacy outcome in placebo group and a 50% risk reduction in mesoglycan group. A bilateral log-rank test with a sample of 650 patients (randomization 1:1) reach a 90% power, with an α-error of 0.025, of detecting a 7.0% difference (HR = 0.51) after 12 months of treatment, considering a 10% patients drop-out. At deadline (December 31, 2022) 570 patients have been randomized (10% drop rate). Mean age was 63.9 years, 58.8% were women. SVT involved great saphenous vein in 69.3%, small saphenous vein in 13.1%, and collaterals in 17.6% of patients. SVT was the first event in 61.7%, a recurrence in 38.3%, provoked in 50.2% and unprovoked in 49.8%. Patients not experiencing a primary outcome, or not retiring their consent will be followed up to December 31, 2024 when the final data analysis will be performedClinicalTrials.gov: NCT03428711.