Intervention: Neoadjuvant combination chemotherapy plus bevacizumab for three 3-weekly (CAPOX + BEV) or four 2-weekly (FOLFOX + BEV) cycles, followed by restaging with thoraco-abdominal CT-scan. In case of progressive systemic disease (e.g. liver or lung metastases), the best possible palliative treatment is offered. In case of progressive peritoneal disease without progressive systemic disease, patients undergo explorative laparotomy, followed by CRS in case of resectable disease, and HIPEC in case of a CC0/1 cytoreduction. In case of responsive or stable disease, one 3-weekly (CAPOX) or two 2-weekly (FOLFOX) neoadjuvant cycles of combination chemotherapy without bevacizumab are administered. Subsequently, not earlier than 3 weeks after the last day of the last cycle of combination chemotherapy, patients undergo explorative laparotomy, followed by CRS in case of resectable disease, and HIPEC in case of a CC0/1 cytoreduction. Only in patients with stable disease/response upon neoadjuvant treatment, and a sufficiently good clinical condition, adjuvant combination chemotherapy is administered according to the neoadjuvant regimen, but without bevacizumab, for four 3-weekly cycles (CAPOX) or six 2-weekly cycles (FOLFOX).