The PIPAC-OPC7 Study: The Use of PET/CT Scans as a Method of Evaluation in Patients Treated With PIPAC, a Pilot Study.

Inclusion Criteria: * Patients with synchronous or metachronous histology or cytology proven GC, PC, CRC, or OC with clinical evidence of PM. * Patients who are eligible for and offered PIPAC at the discretion of the dedicated multidisciplinary tumor conference and subsequent out-patient evaluation at Odense PIPAC Center * Patients with a maximum of one extra-peritoneal metastasis at CT dated within one month of inclusion. * Patients in Eastern Cooperative Oncology Group performance status 0-1. * Patients \>18 years of age. * Patients must be able to give mandatory oral and written consent in Danish. Exclusion Criteria: * Concomitant systemic chemotherapy (bidirectional treatment). * Known allergies to contrast dye. * Any other significant disease or disorder which, in the opinion of the investigator, may either put the patient at risk because of participation in the trial, or may influence the results.