RecruitingDrug trialStudy in Children and Adolescents of 177Lu-DOTATATE (Lutathera®) Combined With the PARP Inhibitor Olaparib for the Treatment of Recurrent or Relapsed Solid Tumours Expressing Somatostatin Receptor (SSTR) (LuPARPed).Study in children and adolescents of 177Lu DOTATATE (Lutathera®) combined with the PARP inhibitor olaparib for treatment of recurrent or relapsed solid tumours expressing somatostatin receptors (SSTR) (LuPARPed)