Wise or wide (WoW) study protocol: a national, multicentre, prospective, randomised and controlled, parallel group, non-inferiority study to compare single-staged versus two-staged excisions of thin invasive (≤1.0 mm) melanoma

Background Sweden has one of the highest incidence rates of cutaneous melanoma globally, and the incidence is rapidly increasing. Melanoma mortality is linked to the thickness of the primary tumour, with thicker melanomas having a poorer prognosis. Thin invasive melanomas (<= 1.0 mm Breslow thickness) have excellent prognosis. Traditionally, the surgical approach for melanoma involves a two-step procedure of a diagnostic excision followed by a wide local excision (WLE) with 10 mm clinical margins. The WLE aims to remove potential microsatellites and residual melanoma, which in theory would prevent loco-regional recurrence and could improve survival. However, recent research questions the necessity of WLE for thin invasive melanomas, given their favourable prognosis, minimal risk of microsatellitosis and low rates of residual melanoma found in WLE tissue specimens.Methods and analysis This multicentre, non-inferiority, randomised controlled trial seeks to enrol 2486 patients with thin invasive melanomas that are completely excised with >= 1.5 mm histopathological margins following the diagnostic excision. Patients will be randomly assigned to either a control group that will undergo a WLE with 10 mm clinical margins according to current clinical routine or an experimental group without a WLE. The primary and secondary endpoints are recurrence-free survival at 5 and 10 years, respectively, with tertiary aims including postoperative complications, scar quality, patient satisfaction and quality of life, healthcare resource utilisation as well as differences in biomarkers of recurrent and non-recurrent melanomas. Patients will be assessed at clinical follow-up visits at 3 months as well as at 1, 2, 3, 5 and 10 years.Ethics and dissemination Approval of this study was obtained from the Swedish Ethical Review Authority (2024-03274-01). The findings of the study will be presented at international scientific meetings and published in peer-reviewed academic journals.Trial registration number NCT06363591.