Not possible to recruit patients during COVID, and not possible to start enrolling after the pandemic.

To evaluate if surgical removal of residual disease adds benefit in stage IV melanoma patients with partial response or stable disease after a minimum 9 months of first-line PD-1 inhibition. Primary endpoint: Disease-free survival (DFS) at 12 months.

A Phase II Randomized Controlled Open-Label Parallel Group Interventional Multicenter Trial. Patients with metastatic melanoma, stratified for stage M1a or M1b/M1c, that have received first-line treatment with PD-1 inhibitors for a minimum of 9 months resulting in either partial response or stable disease according to RECIST 1.1 will be eligible. Patients will be screened for operability based on CT-scans examined by a multidisciplinary team, with the criteria that complete (R0) resection of all metastases should be possible. If the multidisciplinary team find that this would be possible, patients will be included and randomized 1:1 to either surgery with continued PD1-inhibition or current standard of care with continued PD1-inhibition only. At progression, treatment will be according to the treating medical oncologist. Active follow-up will be performed for 12 months.

Inclusion Criteria:

• Age above 18 years
• Signed and dated written informed consent before the start of specific protocol procedures
• Biopsy or cytology proven metastatic melanoma stage M1a, M1b or M1c
• Have received a minimum of 9 months of immunotherapy (PD1-inhibitor alone or in combination) resulting in stable disease or partial response according to RECIST 1.1
• Metastases judged to be radically resectable by surgery at a multidisciplinary conference
• ECOG performance status 0-2

Exclusion Criteria:

• Brain metastasis (M1d)
• Previous treatment with BRAF/MEK inhibitors
• Inability to understand given information or undergo study procedures according to protocol