Study design: This is a prospective, multicentre, randomised, parallel group, phase II-III study with randomisation between CRS + HIPEC with perioperative systemic therapy (experimental arm) and upfront CRS + HIPEC alone (control arm). The study starts as a randomised phase II study to investigate the feasibility of accrual and the safety of neoadjuvant systemic therapy prior to CRS + HIPEC. If criteria of feasibility and safety are met, the study continues as a phase III study with 3-year overall survival as primary endpoint.