In the initial trial design, the immune modulating treatment was based on CTLA-4 blockade by ipilimumab; however, the advent of PD-1/PD-L1 blockade in the palliative treatment of MCC (presented at AACR, ASCO and ESMO) dramatically changed the treatment environment to an extent that applying treatments other than by PD-1/PD-L1 blockade had become very difficult. Moreover, the side effects of PD-1/PD-L1 blocking are far less frequent than side effects of ipilimumab. Consequently, randomization into the previous Ipilimumab treatment arm A will be stopped. New patients will be randomized to nivolumab treatment instead. Patients randomized already into the Ipilimumab-arm will be evaluated descriptively. Patients randomized into the observation arm (arm B) will be evaluated together with the newly randomized arm B-patients.