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Background The development of peritoneal metastases (PM) in patients with colorectal cancer (CRC) connotates a poor prognosis. Circulating tumour (ctDNA) is a promising tumour biomarker in the management CRC. This systematic review aimed to summarize the role of ctDNA in patients with CRC and PM. Methods Following the Preferred Reporting Items for Systematic Reviews and Meta‐analyses (PRISMA) guidelines, a systematic review of the literature until June 2022 was performed. Studies reporting on the utility of ctDNA in colorectal PM were included. A total of eight eligible studies were identified including a total of 167 patients. Results The findings from this review suggest an evolving role for ctDNA in CRC with PM. ctDNA can be isolated from both plasma and peritoneal fluid, with peritoneal fluid preferred as the liquid biopsy of choice with higher mutation detection rates. Concordance rates between tissue and plasma/peritoneal ctDNA mutation detection can vary, but is generally high. ctDNA has a potential role in monitoring anti‐EGFR treatment response and resistance, as well as in predicting future prognosis and recurrence. The detection of ctDNA in plasma of patients with isolated PM is also possibly suggestive of occult systemic disease, and patients exhibiting such ctDNA positivity may benefit from systemic treatment. Limitations to ctDNA mutation detection may include the size of peritoneal lesions, as well as the fact that PM poorly shed ctDNA. Conclusion While these findings are promising, further large‐scale studies are needed to better evaluate the utility of ctDNA in this subset of patients.

Background The association between the imaging response (structural or metabolic) to neoadjuvant chemotherapy (neoCT) before colorectal liver metastasis (CRLM) and survival is unclear. Method A total of 201 patients underwent their first CRLM resection. A total of 94 (47%) patients were treated with neoCT. A multivariable, Cox proportional hazard regression analysis was performed to compare overall survival (OS) and progression‐free survival (PFS) between response groups. Results Multivariable regression analysis of the CT/MRI (n = 94) group showed no difference in survival (OS and PFS) in patients who had stable disease/partial response (SD/PR) or complete response (CR) versus patients who had progressive disease (PD) (OS: HR, 0.36 (95% CI: 0.11–1.19) p = .094, HR, 0.78 (95% CI: 0.13–4.50) p = .780, respectively), (PFS: HR, 0.70 (95% CI: 0.36–1.35) p = .284, HR, 0.51 (0.18–1.45) p = .203, respectively). In the FDG‐PET group (n = 60) there was no difference in the hazard of death for patients with SD/PR or CR versus patients with PD for OS or PFS except for the PFS in the small CR subgroup (OS: HR, 0.75 (95% CI: 0.11–4.88) p = .759, HR, 1.21 (95% CI: 0.15–9.43) p = .857), (PFS: HR, 0.34% (95% CI: 0.09–1.22), p = .097, HR, 0.17 (95% CI: 0.04–0.62) p = .008, respectively). Conclusion There was no convincing evidence of association between imaging response to neoCT and survival following CRLM resection.

There is continued debate about the survival benefit of neoadjuvant chemotherapy in patients with resectable colorectal liver metastases (CRLM). In this retrospective cohort study, we compared the overall survival and progression‐free survival between patients who received neoadjuvant chemotherapy prior to CRLM resection with those who underwent CRLM upfront. A multivariable Cox proportional hazard regression analysis was performed to adjust for potential confounders.

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