The primary objective of the study aims to compare the immune profiles (circulating cytokines and lymphocytes) before and after (6 to 8 weeks) the first infusion of immune checkpoint inhibitors in patients with melanoma treated in the adjuvant setting(cohort A) or in metastatic setting(cohort B); and to study the association of these immune profiles with relapse- or progression-free survival.

This study will analyse the association of biomarkers with relapse- or progression-free survival of stage III or IV melanoma patients, divided in 3 sub-cohorts:

• Patients treated in the adjuvant setting (cohort A): new user of immune checkpoint blockers.
• Patients treated in the metastatic setting (cohort B): - B1: new users of immune checkpoint blockers; - B2: prevalent users of immune checkpoint blockers treated with complementary radiotherapy.

For patients of cohort A and B1, immune profiles characteristics will be evaluated before initiation of treatment (=baseline), and at each radiological evaluation of the tumour response, up to maximum 12 months as duration.

The maximal duration of treatment will be 12 months for patients treated in the adjuvant setting. For metastatic patients, the duration of treatment will be decided by physician according to different factors (responses, progression, toxicities, ...).

For patients in cohort B2, the characteristics of the immune profiles will be evaluated before radiotherapy initiation,, within 6 weeks after the end of radiotherapy, then at the 2 following radiological evaluations of the tumour response

Inclusion Criteria:

• Patient aged ≥ 18 years;
• Totally resected stage III or IV melanoma totally resected, treated with a immune therapy (pembrolizumab or nivolumab ou other immune checkpoint inhibitors) as adjuvant treatment;
• Unresectable stage IIIC/D or IV metastatic melanoma, treated with immune therapy (pembrolizumab or nivolumab or immune checkpoint inhibitors) which should be associated by a radiotherapy ;
• Patient has been informed about the study and signed the consent;
• Affiliated to the French social security scheme.

Exclusion Criteria:

• Pregnant or breastfeeding woman;
• Patient refusal;
• Patient receiving a immunosuppressor;
• Undergo a general corticotherapy of > 10 mg/kg/day since more than 7 days;
• Patient who participate to another blind interventional study receiving blinded treatment;
• Patient without any social protection by organization.