Diagnostic performance of MRI for staging peritoneal metastases in patients with colorectal cancer after neoadjuvant chemotherapy.

INTRODUCTION: MRI improves the selection of patients with colorectal cancer (CRC) and peritoneal metastases (PM) for cytoreductive surgery by accurately assessing the extent of PM reflected as the peritoneal cancer index (PCI). The performance of MRI after neoadjuvant chemotherapy (NACT) for staging PM, however is unknown. The purpose of this study was to determine whether MRI could also accurately determine the PCI after NACT. MATERIALS AND METHODS: This was a single-centre, retrospective study of patients with PM from CRC or appendiceal origin who received NACT followed by diffusion-weighted (DW)-MRI and surgery from January 2016 to February 2021. Two radiologists assessed the PCI on restaging DW-MRI (mriPCI). The reference standard was the surgical PCI (sPCI). The main outcome was the diagnostic performance of restaging DW-MRI in predicting whether patients were eligible for cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC), defined as a PCI < 21 with metastases on resectable locations. If CRS-HIPEC was performed, the resected peritoneal lesions were assessed and correlated with the final pathological PCI (pPCI). RESULTS: Thirty-three patients were included. Both readers correctly detected all 23 patients with resectable disease. Eight out of ten patients with unresectable disease during staging surgery were detected by both readers with MRI. The intraclass correlation (ICC) between both readers was excellent (0⋅87 (95% CI: 0⋅75 to 0⋅93)). The ICC between pPCI and mriPCI was 0⋅74 (0⋅49-0⋅88) and 0⋅82 (0⋅66-0⋅91) for the 2 readers. Surgical PCI (sPCI) had a similar correlation as mriPCI with pPCI 0⋅82 (0⋅62- 0⋅92)) and 0⋅81 (0⋅57-0⋅92)). CONCLUSION: DW-MRI is a promising tool to reassess the peritoneal cancer index after neoadjuvant chemotherapy.

Cytoreductive surgery and hyperthermic intraperitoneal chemotherapy versus palliative systemic chemotherapy in stomach cancer patients with peritoneal dissemination, the study protocol of a multicentre randomised controlled trial (PERISCOPE II).

BACKGROUND: At present, palliative systemic chemotherapy is the standard treatment in the Netherlands for gastric cancer patients with peritoneal dissemination. In contrast to lymphatic and haematogenous dissemination, peritoneal dissemination may be regarded as locoregional spread of disease. Administering cytotoxic drugs directly into the peritoneal cavity has an advantage over systemic chemotherapy since high concentrations can be delivered directly into the peritoneal cavity with limited systemic toxicity. The combination of a radical gastrectomy with cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) has shown promising results in patients with gastric cancer in Asia. However, the results obtained in Asian patients cannot be extrapolated to Western patients. The aim of this study is to compare the overall survival between patients with gastric cancer with limited peritoneal dissemination and/or tumour positive peritoneal cytology treated with palliative systemic chemotherapy, and those treated with gastrectomy, CRS and HIPEC after neoadjuvant systemic chemotherapy. METHODS: In this multicentre randomised controlled two-armed phase III trial, 106 patients will be randomised (1:1) between palliative systemic chemotherapy only (standard treatment) and gastrectomy, CRS and HIPEC (experimental treatment) after 3-4 cycles of systemic chemotherapy.Patients with gastric cancer are eligible for inclusion if (1) the primary cT3-cT4 gastric tumour including regional lymph nodes is considered to be resectable, (2) limited peritoneal dissemination (Peritoneal Cancer Index < 7) and/or tumour positive peritoneal cytology are confirmed by laparoscopy or laparotomy, and (3) systemic chemotherapy was given (prior to inclusion) without disease progression. DISCUSSION: The PERISCOPE II study will determine whether gastric cancer patients with limited peritoneal dissemination and/or tumour positive peritoneal cytology treated with systemic chemotherapy, gastrectomy, CRS and HIPEC have a survival benefit over patients treated with palliative systemic chemotherapy only. TRIAL REGISTRATION: clinicaltrials.gov NCT03348150 ; registration date November 2017; first enrolment November 2017; expected end date December 2022; trial status: Ongoing.