To generate meaningful data regarding ctDNA that would infer risk of recurrence in stage III melanoma patients.

Cancer cells harbor and can acquire potentially hundreds of mutations, many of whom are found in the ctDNA. Circulating tumor DNA (ctDNA) holds the promise for the 50% of participants who do not need adjuvant therapies - participants could be monitored to ensure no increase in ctDNA. Participants treated could then be followed for the earliest possible blood level signs of recurrence (incr. ctDNA) and more quickly be switched to more effective therapies. Further, the treating physician could hold therapy until the first signs of ctDNA based recurrence for those participants that would benefit.

Blood sample from a biobank will be used to identify to monitor ctDNA. These blood samples were drawn at baseline, 3 months, 6 months and 18 months.

Inclusion Criteria:

• Age ≥18
• Confirmed fully resected Stage IIIb-IV cutaneous melanoma; including patients treated neoadjuvantly within three months prior to resection.

Exclusion Criteria:

• Treatment plan inconsistent with the standard of care systemic adjuvant therapies 4.0 Study Design

Retrospective biobanking samples collected at baseline, 3 months, 6 months and 18 months.