Population-based prognostic instrument (SweMR 2.0) for melanoma-specific survival - An ideal tool for individualised treatment decisions for Swedish patients.

Introduction: The prognosis for patients with melanoma has improved due to better treatments in recent years and updated tools to accurately predict an individual's risk are warranted. This study aims to describe a prognostic instrument for patients with cutaneous melanoma and its potential as a clinical device for treatment decisions.

Methods: Patients with localised invasive cutaneous melanoma diagnosed in 1990-2021 with data on tumour thickness were identified from the population-based Swedish Melanoma Registry. The parametric Royston-Parmar (RP) method was used to estimate melanoma-specific survival (MSS) probabilities. Separate models were constructed for patients (≤1 mm) and (>1 mm) and prognostic groups were created based on all combinations of age, sex, tumour site, tumour thickness, absence/presence of ulceration, histopathologic type, Clark's level of invasion, mitoses and sentinel lymph node (SLN) status.

Results: In total, 72 616 patients were identified, 41 764 with melanoma ≤1 mm and 30 852 with melanoma >1 mm. The most important variable was tumour thickness for both (≤1 mm) and (>1 mm), that explained more than 50% of the survival. The second most important variables were mitoses (≤1 mm) and SLN status (>1 mm). The prognostic instrument successfully created probabilities for >30 000 prognostic groups.

Conclusions: The Swedish updated population-based prognostic instrument, predicts MSS survival up to 10 years after diagnosis. The prognostic instrument gives more representative and up-to-date prognostic information for Swedish patients with primary melanoma than the present AJCC staging. Additional to clinical use and the adjuvant setting, the information retrieved could be used to plan future studies.