R4 randomisation: R4 was activated in April 2014. The SIOPEN long term infusion (LTI) ch14.18/CHO trial successfully lowered the toxicity profile by prolonging the infusion time of the same total ch14.18/CHO antibody dose of 100mg/m² to 10 days of continuous infusion in relapsed /refractory patients. Hence the HRNBL1.7/SIOPEN study committee wishes to implement this more favourable immunotherapy dosing schedule for the time till the induction question R3 is answered and the HRNBL1.7/SIOPEN trial may be closed. Considering the high R2 dropout rate of patients unable to receive all immunotherapy cycles in the IL-2 s.c. combination treatment arm and not observing this effect in the current SIOPEN LTI trial, it is suggested to address the IL-2sc dose in the new R4. Therefore the potential synergistic effect of sc IL-2 will be addressed again with 50% of the original s.c. IL-2 dose. The IL-2sc dose will hence be reduced to 3 x 106 IU IL-2/m2/day s.c. in the HR-NBL1/SIOPEN R4 amendment instead of 6 x 106 IU IL-2/m2/day s.c as used in the SIOPEN LTI trial. In the second week of each IT course s.c.IL-2 will be given on days 2, 4, 6, 8, 10 in parallel to the ch14.18/CHO ctn infusion and not during the first 5 days in week 2 as scheduled in the SIOPEN LTI trial.