Incidence and treatment of recurrent disease after cytoreductive surgery and intraperitoneal chemotherapy for peritoneally metastasized colorectal cancer: A systematic review

Repeat Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy Using Open and Closed Abdomen Techniques for Colorectal Peritoneal Metastases and Peritoneal Pseudomyxoma Recurrences: Results from Six French Expert Centers

BACKGROUND

Standard treatment for resectable peritoneal metastases (PM) combines cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC); however, the rate of recurrence remains high and repeat CRS/HIPEC may be considered in well-selected patients. We describe our postoperative and oncological outcomes.

METHODS

Between 1994 and 2024, data from 132 repeat CRS/HIPEC procedures were analyzed in this retrospective multicenter study. Morbimortality, overall survival (OS) and recurrence-free survival (RFS) were evaluated for colorectal peritoneal metastases (CRPM) and peritoneal pseudomyxoma (PMP).

RESULTS

Overall, 63 patients, including 55 patients with CRPM (87.3%) and 8 patients with PMP (12.7%), underwent CRS/HIPEC. Of these patients, 58 (92%) underwent CRS/HIPEC twice, 4 (6.3%) underwent CRS/HIPEC three times, and 1 (1.6%) underwent CRS/HIPEC four times. Peritoneal Carcinomatosis Index (PCI) score, operating room occupancy, complication and readmission rates at day 90, and length of intensive care unit and hospital stay were similar between the initial and first repeat CRS/HIPEC procedures. No 90-day postoperative mortality occurred. For CRPM, the median OS was 82.3, 53.9, and 74.5 months from the initial, first, and second repeat CRS/HIPEC procedures, respectively, with a median RFS of 22.0, 36.9, and 13.2 months, respectively. For PMP, after a median follow-up of 70.8 and 39.3 months from the initial and first repeat CRS/HIPEC procedures, respectively, all patients were alive, with a median RFS of 22.4 and 39.4 months, respectively. Multivariate analysis shown that no factor was significantly related to severe complications (Dindo-Clavien 3-4) or OS.

CONCLUSIONS

In selected patients with CRPM and PMP, CRS/HIPEC shows comparable results between the initial and repeat procedures in terms of postoperative outcomes, and appears to improve survival, especially for PMP. Repeat CRS/HIPEC is an option to be considered in patients presenting with CRPM or PMP.

Thermal ablation with and without adjuvant systemic therapy: a nationwide multicenter observational cohort study of solitary colorectal liver metastases

BACKGROUND

Thermal ablation is routinely used for solitary colorectal liver metastases (SCLM), but the added value of adjuvant systemic therapy in SCLM remains unclear. This study aimed to compare the long-term outcomes for SCLM treated by ablation alone (AB) versus ablation plus systemic therapy (AS).

METHODS

This multicenter retrospective study using nationwide data from fourteen institutions between October 2010 and May 2023, 369 patients with initial SCLM smaller than 5 cm, no extrahepatic metastases, and colorectal cancer R0 resection treated by thermal ablation were included. The crude analysis was used to analyze eligible cases between the two groups. The propensity score matching to control for potential confounders in each matched group. Subgroup analyses were performed to identify specific survival benefits.

RESULTS

61.2% (226/369) of eligible patients were treated with AS and 38.8% (143/369) with AB. During the median follow-up period of 8.8 years, 1-/3-/5-year DFS/OS rates did not differ between the two groups, when analyzed via propensity score matching ( P =0.52/0.08). Subgroup analysis revealed that AS was significantly associated with better OS than AB in patients with plasma CEA >5 ug/l ( P =0.036), T (III-IV) category of primary cancer ( P =0.034), or clinical risk score (1-2) ( P =0.041). In each matched group, the authors did find a significant difference in drug-related adverse events ( P <0.001) between AS group (24.1%, 28/116) and AB group (0.0%, 0/116).

CONCLUSIONS

For patients with plasma CEA >5 ug/l, T (III-IV) category of primary cancer, or clinical risk score (1-2), thermal ablation plus systemic therapy appeared to be associated with improved overall survival. Thermal ablation was equally effective in disease-free survival for treating SCLM, whether with or without adjuvant systemic therapy.

Repeat cytoreductive surgery with HIPEC for colorectal peritoneal metastases: a systematic review

BACKGROUND

Colorectal peritoneal metastases (CRPM) are present in 10-20% of patients at the time of their initial cancer diagnosis, and affects over 20% of those who develop colorectal cancer recurrence. Cytoreductive surgery (CRS) with HIPEC is firmly established as the optimal surgical treatment, but there is very little known about the benefit of repeat or iterative CRS. The aim of this review is to provide a systematic evaluation of the perioperative complications, survival outcomes and quality of life in patients undergoing repeat CRS with HIPEC for CRPM.

METHODS

A systematic review of PubMed, Ovid MEDLINE, EMBASE, Scopus and Cochrane databases was performed to identify all studies that reported outcomes for repeat CRS with or without HIPEC for CRPM.

RESULTS

Four hundred and ninety-three manuscripts were screened, and 15 retrospective studies were suitable for inclusion. Sample sizes ranged from 2 to 30 participants and comprised a total of 229 patients. HIPEC was used in all studies, but exact rates were not consistently stated. Perioperative morbidity was reported in four studies, between 16.7% and 37.5%. Nine studies reported mortality rate which was consistently 0%. The median overall survival after repeat CRS ranged from 20 to 62.6 months. No studies provided quality of life metrics.

CONCLUSION

Repeat CRS for CRPM has perioperative morbidity and mortality rates comparable to initial CRS, and offers a potential survival benefit in selected patients. There is however limited high-quality data in the literature.

Intraperitoneal administration of carcinoembryonic antigen-directed chimeric antigen receptor T cells is a robust delivery route for effective treatment of peritoneal carcinomatosis from colorectal cancer in pre-clinical study

BACKGROUND AIMS

Peritoneal carcinomatosis (PC) from colorectal cancer (CRC) is a highly challenging disease to treat. Systemic chimeric antigen receptor (CAR) T cells have shown impressive efficacy in hematologic malignancies but have been less effective in solid tumors. We explored whether intraperitoneal (i.p.) administration of CAR T cells could provide an effective and robust route of treatment for PC from CRC.

METHODS

We generated second-generation carcinoembryonic antigen (CEA)-specific CAR T cells. Various animal models of PC with i.p. and extraperitoneal metastasis were treated by i.p. or intravenous (i.v.) administration of CEA CAR T cells.

RESULTS

Intraperitoneally administered CAR T cells exhibited superior anti-tumor activity compared with systemic i.v. cell infusion in an animal model of PC. In addition, i.p. administration conferred a durable effect and protection against tumor recurrence and exerted strong anti-tumor activity in an animal model of PC with metastasis in i.p. or extraperitoneal organs. Moreover, compared with systemic delivery, i.p. transfer of CAR T cells provided increased anti-tumor activity in extraperitoneal tumors without PC. This phenomenon was further confirmed in an animal model of pancreatic carcinoma after i.p. administration of our newly constructed prostate stem cell antigen-directed CAR T cells.

CONCLUSIONS

Taken together, our data suggest that i.p. administration of CAR T cells may be a robust delivery route for effective treatment of cancer.

Utilizing Patient-Derived Organoids in the Management of Colorectal Cancer with Peritoneal Metastases: A Review of Current Literature

INTRODUCTION

Treatment of colorectal cancer-derived peritoneal carcinomatosis (CRC-PC) is challenging due to cellular heterogeneity that exhibits variable degrees of resistance to systemic as well as intraperitoneal chemotherapy. Therefore, it is not a surprise that the majority of patients undergoing cytoreductive surgery with HIPEC will experience recurrence. Patient-derived tumor organoids (PTOs) may be potentially capable of informing clinical treatment decisions at the level of the individual patient. In this study, we review the current landscape of CRC-PC PTO literature.

METHODS

PubMed was queried for peer-reviewed publications studying CRC-PC organoids. Original articles which harnessed organoids as a research platform to study CRC-PC were included for review. Xenograft organoid studies were excluded.

RESULTS

A total of 5 articles met inclusion criteria published between 2017 and 2022 and underwent complete analysis. Study topics included optimization of current therapies, identification of novel drug applications, and identification of disease mechanisms. Current therapies studied included systemic chemotherapy, targeted inhibitors, and HIPEC regimens.

CONCLUSIONS

Patient-derived tumor organoids are a valuable personalized research tool that can complement real-time clinical settings. Additional research is needed to optimize methodologies of organoid incorporation in patients with colorectal cancer with peritoneal carcinomatosis.

Immunotherapy for Peritoneal Carcinomatosis: Challenges and Prospective Outcomes

Peritoneal metastasis, also known as peritoneal carcinomatosis (PC), is a refractory cancer that is typically resistant to conventional therapies. The typical treatment for PC is a combination of cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC). Recently, research in this area has seen significant advances, particularly in immunotherapy as an alternative therapy for PC, which is very encouraging. Catumaxomab is a trifunctional antibody intraperitoneal (IP) immunotherapy authorized in Europe that can be used to diminish malignant ascites by targeting EpCAM. Intraperitoneal (IP) immunotherapy breaks immunological tolerance to treat peritoneal illness. Increasing T-cell responses and vaccination against tumor-associated antigens are two methods of treatment. CAR-T cells, vaccine-based therapeutics, dendritic cells (DCs) in combination with pro-inflammatory cytokines and NKs, adoptive cell transfer, and immune checkpoint inhibitors are promising treatments for PC. Carcinoembryonic antigen-expressing tumors are suppressed by IP administration of CAR-T cells. This reaction was strengthened by anti-PD-L1 or anti-Gr1. When paired with CD137 co-stimulatory signaling, CAR-T cells for folate receptor cancers made it easier for T-cell tumors to find their way to and stay alive in the body.

Oncological impact of intraperitoneal chemotherapy after cytoreductive surgery for patients with colorectal peritoneal metastasis: A bi-institutional retrospective analysis

BACKGROUND AND OBJECTIVES

There is a paucity of evidence on the value of intraperitoneal chemotherapy (IPC) following cytoreductive surgery (CRS) for colorectal peritoneal metastasis. This study aimed to evaluate the association between mitomycin C-IPC and survival outcomes following CRS.

METHODS

The institutional databases of two tertiary hospitals were reviewed to identify patients who underwent CRS for colorectal peritoneal metastasis. The outcomes of patients who underwent CRS without IPC were compared with those of patients who underwent CRS plus early postoperative intraperitoneal chemotherapy (EPIC) or CRS plus hyperthermic intraperitoneal chemotherapy (HIPEC). The primary endpoints were cancer-specific survival (CSS), progression-free survival (PFS), and peritoneal PFS (P-PFS).

RESULTS

In 149 patients with peritoneal metastasis alone, EPIC and HIPEC use was significantly associated with better CSS, PFS, and P-PFS in the multivariate analysis. CSS was also significantly associated with perioperative systemic chemotherapy. Among 42 patients with both peritoneal and extraperitoneal metastases, CSS was independently related to the completeness of cytoreduction score, location of extraperitoneal metastasis, and grade 3-4 complications.

CONCLUSIONS

Mitomycin C-IPC after CRS was associated with better survival outcomes than CRS alone in patients with resectable peritoneal metastasis of colorectal cancer. This study found that IPC had beneficial effects regarding P-PFS in patients with both peritoneal and extraperitoneal metastases.

Extreme cytoreductive surgery and hyperthermic intraperitoneal chemotherapy in treatment of peritoneal metastasis

Objectives

It was aimed to define the oncologic concept of "extremeness" in cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) to determine morbidity-mortality results and final oncologic outcomes.

Material and Methods

Prospectively recorded data of 666 patients with peritoneal metastases who had undergone CRS/HIPEC between 2007 and 2020 were analyzed. Patients were divided into two groups as extreme (n= 371) and non-extreme (n= 295). Extreme CRS was defined as resection of ≥5 major organs or creation of ≥2 bowel anastomoses or peritoneal carcinomatosis index (PCI)≥ 15 or re-cytoreductive surgery.

Results

More CC-1 or CC-2 cytoreduction (p <.001), increased mortality and morbidity (p <.001), prolonged operative time (p <.001), increased intraoperative erythrocyte suspension (p <.001), albumin (p <.001), fresh frozen plasma (FFP) (p <.001), and post-operative erythrocyte suspension (p <.001) usage were found in the extreme CRS/HIPEC group. Operative time, CC-1 or CC-2 cytoreduction, presence of ostomy, development of infection, and use of intra-operative albumin and FFP were found to be independent prognostic factors in Cox regression analysis. Three and five-year survival rates were significantly lower in the extreme CRS/HIPEC group (p <.001).

Conclusion

High-volume peritoneal metastatic disease can be completely resected with extreme cytoreduction in carefully selected patients responsive to chemotherapy. Since the significant morbi-mortality related to the treatment of peritoneal metastasis is a real concern, it should be considered in experienced complex cancer centers that provides relatively better oncological outcomes compared to conventional treatments.

Conditional Survival Following Cytoreductive Surgery with Hyperthermic Intraperitoneal Chemotherapy for Peritoneal Surface Malignancies: An Analysis from the US HIPEC Collaborative

INTRODUCTION

The long-term prognosis of patients who undergo cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) for peritoneal surface malignancies (PSM) varies considerably on the basis of histological and operative factors. While overall survival (OS) estimates are used to inform adjuvant therapy and surveillance strategies, conditional survival may provide more clinically relevant estimates of prognosis by accounting for disease-free time elapsed.

PATIENTS AND METHODS

All patients from 12 academic institutions who underwent CRS ± HIPEC for PSM from 2000 to 2017 were retrospectively analyzed. OS and disease-free survival (DFS) rates were calculated using the Kaplan-Meier method while conditional overall (COS) and conditional disease-free survival (CDFS) rates were calculated at 1, 2, or 3 years from surgery for different tumor histologies.

RESULTS

Overall, 1610 patients underwent CRS ± HIPEC. Among patients with benign appendiceal mucinous tumors (N = 460), 5-year OS and COS at 3 years were 92.1% and 96.3% (Δ4.2%), respectively. For patients with well-differentiated appendiceal cancers (N = 400), 5-year OS and COS at 3 years were 76.3% and 88.3% (Δ12.0%), respectively. For patients with high-grade appendiceal cancers (N = 258), 5-year OS and COS at 3 years were 43.8% and 75.4% (Δ31.6%), respectively. For patients with colorectal cancers (N = 362), 5-year OS and COS at 3 years were 31.8% and 67.3% (Δ35.5%), respectively. For patients with peritoneal mesothelioma (N = 130), 5-year OS and COS at 3 years were 67.6% and 89.7% (Δ22.1%), respectively. Similar trends were observed for DFS/CDFS.

CONCLUSION

The conditional survival of patients undergoing CRS ± HIPEC for PSM is associated with tumor histology. COS and CDFS provide a more accurate, dynamic estimate of survival than OS and DFS, especially for patients with more aggressive histologies.

Age alone is not a barrier to efficacy of cytoreductive surgery and hyperthermic intraperitoneal chemotherapy for colorectal peritoneal metastases: analysis of 1138 patients from the UK and Ireland Colorectal Peritoneal Metastases Registry

BACKGROUND

The management of colorectal peritoneal metastases continues to be a challenge but recent evidence suggests cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC) can improve survival. Uncertainty about the relationship between age and tumour biology makes patient selection challenging particularly when reported procedure related morbidity is high and impact on survival outcomes unknown. The UK and Ireland Colorectal Peritoneal Metastases Registry was reviewed to assess the influence of age on efficacy of CRS and HIPEC.

METHODS

A review of outcomes from the UK and Ireland Colorectal Peritoneal Metastases Registry was performed. Data from 2000 to 2021 were included from five centres in the UK and Ireland, and the cohort were sub-divided into three age groups; <45 years, 45-65 years and >65 years old. Primarily, we examined post-operative morbidity and survival outcomes across the three age groups. In addition, we examined the impact that the completeness of cytoreduction, nodal status, or adverse pathological features had on long-term survival.

RESULTS

During the study period, 1138 CPM patients underwent CRS HIPEC. 202 patients(17.8%) were <45 years, 549 patients(48.2%) aged 45-65 years and 387 patients(34%) >65 years. Overall, median length of surgery (CRS and HIPEC), median PCI score and rate of HIPEC administration was similar in all three groups, as was overall rates of major morbidity and/or mortality. Complete cytoreduction rates (CC0) were similar across the three cohorts; 77%, 80.6% and 81%, respectively. Median overall survival for all patients was 38 months following complete cytoreduction.

CONCLUSION

Age did not appear to influence morbidity or long-term survival following CRS and HIPEC. When complete cytoreduction is achieved survival outcomes are good. The addition of HIPEC can be performed safely and may reduce local recurrence within the peritoneum.

Adjuvant chemotherapy for high-grade appendiceal cancer after cytoreductive surgery with hyperthermic intraperitoneal chemotherapy

INTRODUCTION

There are no available data on the efficacy of adjuvant chemotherapy (ACT) in stage IVA/B high-grade mucinous appendiceal cancer treated with CRS/HIPEC. We evaluated the association between ACT and survival in this cohort.

MATERIALS AND METHODS

A single-institution retrospective cohort study using a prospective database was conducted. Stage IVA/B high-grade mucinous appendiceal cancer patients who underwent CRS/HIPEC with CC-0/1 were included. Survival was compared between ACT and no chemotherapy (NoCT) patients. Subgroup analysis was performed with adjustment for confounding variables.

RESULTS

We identified 180 patients: 77 ACT and 103 NoCT. ACT regimens included 5-FU/capecitabine (13%), oxaliplatin-based (63%), and irinotecan-based (21%), combined with bevacizumab in 27% of cases. Median number of cycles was 9 (IQR: 6-12). Median overall survival (OS) did not significantly differ between ACT and NoCT (53 vs 75 months, p = 0.566). Multivariable Cox regression showed no OS benefit for ACT vs NoCT in patients with neoadjuvant chemotherapy (HR 1.14; 95%CI: 0.38-3.39) or without it (HR 1.33; 95%CI: 0.69-2.57), with signet ring cell (HR 0.89; 95%CI: 0.38-2.06) or other histologies (HR 1.11; 95%CI: 0.50-2.46), positive lymph nodes (HR 1.60; 95%CI: 0.74-3.49), or peritoneal cancer index ≥20 (HR 1.08; 95%CI: 0.55-2.11) after adjusting for other factors.

CONCLUSIONS

In our cohort, colon-type ACT was not associated with better OS in stage IVA/B mucinous appendiceal cancer after CRS/HIPEC, even after adjusting for confounders. This may be due to different tumor biology than colon cancer or small sample size. Prospective collaborative studies are needed.

Comprehensive Treatment Algorithms of the Swiss Peritoneal Cancer Group for Peritoneal Cancer of Gastrointestinal Origin

Peritoneal cancer (PC) is a dire finding, yet in selected patients, long-term survival is possible. Complete cytoreductive surgery (CRS) together with combination immunochemotherapy is essential to achieve cure. Hyperthermic intraperitoneal chemotherapy (HIPEC) and pressurized intraperitoneal aerosol chemotherapy (PIPAC) are increasingly added to the multimodal treatment. The Swiss Peritoneal Cancer Group (SPCG) is an interdisciplinary group of expert clinicians. It has developed comprehensive treatment algorithms for patients with PC from pseudomyxoma peritonei, peritoneal mesothelioma, gastric, and colorectal origin. They include multimodal neoadjuvant treatment, surgical resection, and palliative care. The indication for and results of CRS HIPEC and PIPAC are discussed in light of the current literature. Institutional volume and clinical expertise required to achieve best outcomes are underlined, while inclusion of patients considered for CRS HIPEC and PIPAC in a clinical registry is strongly advised. The present recommendations are in line with current international guidelines and provide the first comprehensive treatment proposal for patients with PC including intraperitoneal chemotherapy. The SPCG comprehensive treatment algorithms provide evidence-based guidance for the multimodal care of patients with PC of gastrointestinal origin that were endorsed by all Swiss clinicians routinely involved in the multimodal care of these challenging patients.

GECOP-MMC: phase IV randomized clinical trial to evaluate the efficacy of hyperthermic intraperitoneal chemotherapy (HIPEC) with mytomicin-C after complete surgical cytoreduction in patients with colon cancer peritoneal metastases

BACKGROUND

The French PRODIGE 7 trial, published on January 2021, has raised doubts about the specific survival benefit provided by HIPEC with oxaliplatin 460 mg/m² (30 minutes) for the treatment of peritoneal metastases from colorectal cancer. However, several methodological flaws have been identified in PRODIGE 7, specially the HIPEC protocol or the choice of overall survival as the main endpoint, so its results have not been assumed as definitive, emphasizing the need for further research on HIPEC. It seems that the HIPEC protocol with high-dose mytomicin-C (35 mg/m²) is the preferred regime to evaluate in future clinical studies.

METHODS

GECOP-MMC is a prospective, open-label, randomized, multicenter phase IV clinical trial that aims to evaluate the effectiveness of HIPEC with high-dose mytomicin-C in preventing the development of peritoneal recurrence in patients with limited peritoneal metastasis from colon cancer (not rectal), after complete surgical cytoreduction. This study will be performed in 31 Spanish HIPEC centres, starting in March 2022. Additional international recruiting centres are under consideration. Two hundred sixteen patients with PCI ≤ 20, in which complete cytoreduction (CCS 0) has been obtained, will be randomized intraoperatively to arm 1 (with HIPEC) or arm 2 (without HIPEC). We will stratified randomization by surgical PCI (1-10; 11-15; 16-20). Patients in both arms will be treated with personalized systemic chemotherapy. Primary endpoint is peritoneal recurrence-free survival at 3 years. An ancillary study will evaluate the correlation between surgical and pathological PCI, comparing their respective prognostic values.

DISCUSSION

HIPEC with high-dose mytomicin-C, in patients with limited (PCI ≤ 20) and completely resected (CCS 0) peritoneal metastases, is assumed to reduce the expected risk of peritoneal recurrence from 50 to 30% at 3 years.

TRIAL REGISTRATION

EudraCT number: 2019-004679-37; Clinicaltrials.gov: NCT05250648 (registration date 02/22/2022, ).

Lymph Node Metastases from Visceral Peritoneal Colorectal Metastases are Associated with Systemic Recurrence

BACKGROUND

Visceral peritoneal colorectal metastases (VPCMs) may further metastasize to lymph nodes that drain those organs. The rate of lymph node metastases (LNMs) from VPCMs and their clinical and prognostic significance are unknown.

METHODS

This study retrospectively analyzed the authors' institutional databases of 160 patients with peritoneal colorectal metastases who underwent cytoreductive surgery and hyperthermic intraperitoneal chemotherapy. Patients with LNM-VPCM (n = 12) were identified by pathologic reports, and both their short- and long-term outcomes were compared with those of patients without LNM-VPCM.

RESULTS

The clinical presentation and primary tumor pathologic characteristics did not differ between the two groups. The patients with LNM-VPCM had a higher tumor burden (measured by the peritoneal carcinomatosis index [PCI]) and visible remnant disease compared with those who had no LNM-VPI (10 vs 5.5 [p = 0.03] vs 33.3% vs 6.8% [p = 0.007], respectively). The postoperative outcomes also were comparable. The patients with LNM-VPCM had a shorter overall survival (OS) than those without LNM-VPCM (median OS, 22.5 months; 95% confidence interval [CI], 15.1-29.9 months vs 40.1 months; 95% CI, 38.1-42 months; p = 0.02). However, only tumor grade and PCI were predictors of OS in the multivariate analysis (hazard ratio [HR], 2.33 [p = 0.001]; 1.77 [p = 0.03], respectively). The study showed that LNM-VPCM was associated with systemic but not peritoneal recurrence compared with non-LNM-VPCM (81.8% vs 51.6% for systemic recurrence, respectively; p = 0.05).

CONCLUSION

The small distinct group of patients defined by LNM-VPCM were prone to systemic recurrence. Given its correlation with systemic recurrence, LNM-VPCM may indicate the need for adjuvant treatment.

Repeat Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy Is Not Associated with Prohibitive Complications: Results of a Multiinstitutional Retrospective Study

BACKGROUND

Cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) is offered to select patients with peritoneal metastases. In instances of recurrence/progression, a repeat CRS/HIPEC may be considered. The perioperative morbidity and the potential oncologic benefits are not well described.

PATIENTS AND METHODS

We performed a retrospective analysis of a multiinstitutional database to assess the perioperative outcomes following repeat CRS/HIPEC (repeat). Kaplan-Meier and Cox estimates were used to assess survival.

RESULTS

In the entire cohort, 2157 patients were analyzed, with 158 (7.3%) in the repeat cohort. The rate of complete cytoreduction was 89.8% versus 83.0% in initial versus repeat groups. The overall incidence of major complications was similar (26.3% vs. 30.7%); however, reoperation was more common in the repeat group. Perioperative outcomes such as length of stay and nonhome discharge were not significantly different. For the entire cohort, 5-year overall survival (OS) was 56.0% in the initial group and 59.5% in the repeat group. In patients with only appendiceal cancer, we observed a 5-year OS of 64.0% in the initial group compared with 67.3% in the repeat cohort. For patients with appendiceal cancer who developed a recurrence/progression, median OS was 36 months in the no repeat operation group compared with 73 months for those that did. Multivariable regression demonstrated that completeness of cytoreduction and tumor grade were associated with OS, but repeat operation was not.

CONCLUSIONS

Repeat CRS/HIPEC is not associated with prohibitive risk. Survival is possibly improved, and therefore, repeat operation should be considered in selected patients with recurrent or progressive disease.

Adjuvant Systemic Chemotherapy vs Active Surveillance Following Up-front Resection of Isolated Synchronous Colorectal Peritoneal Metastases

Importance

To date, there are no data on the value of adjuvant systemic chemotherapy following up-front resection of isolated synchronous colorectal peritoneal metastases.

Objective

To assess the association between adjuvant systemic chemotherapy and overall survival following up-front resection of isolated synchronous colorectal peritoneal metastases.

Design, Setting, and Participants

In this population-based, observational cohort study using nationwide data from the Netherlands Cancer Registry (diagnoses between January 1, 2005, and December 31, 2017; follow-up until January 31, 2019), 393 patients with isolated synchronous colorectal peritoneal metastases who were alive 3 months after up-front complete cytoreductive surgery with hyperthermic intraperitoneal chemotherapy were included. Patients allocated to the adjuvant systemic chemotherapy group were matched (1:1) with those allocated to the active surveillance group by propensity scores based on patient-, tumor-, and treatment-level covariates.

Exposures

Adjuvant systemic chemotherapy, defined as systemic chemotherapy without targeted therapy, starting within 3 months postoperatively.

Main Outcomes and Measures

Overall survival was compared between matched groups using Cox proportional hazards regression analysis adjusted for residual imbalance. A landmark analysis was performed by excluding patients who died within 6 months postoperatively. A sensitivity analysis was performed to adjust for unmeasured confounding by major postoperative morbidity.

Results

Of 393 patients (mean [SD] age, 61 [10] years; 181 [46%] men), 172 patients (44%) were allocated to the adjuvant systemic chemotherapy group. After propensity score matching of 142 patients in the adjuvant systemic chemotherapy group with 142 patients in the active surveillance group, adjuvant systemic chemotherapy was associated with improved overall survival compared with active surveillance (median, 39.2 [interquartile range, 21.1-111.1] months vs 24.8 [interquartile range, 15.0-58.4] months; adjusted hazard ratio [aHR], 0.66; 95% CI, 0.49-0.88; P = .006), which remained consistent after excluding patients who died within 6 months postoperatively (aHR, 0.68; 95% CI, 0.50-0.93; P = .02) and after adjustment for major postoperative morbidity (aHR, 0.71; 95% CI, 0.53-0.95).

Conclusions and Relevance

Findings of this study suggest that in patients undergoing up-front resection of isolated synchronous colorectal peritoneal metastases, adjuvant systemic chemotherapy appeared to be associated with improved overall survival. Although randomized trials are needed to address the influence of potential residual confounding and allocation bias on this association, results of this study may be used for clinical decision-making in this patient group for whom no data are available.

Preventive intraperitoneal hyperthermic perfusion chemotherapy for patients with T4 stage colon adenocarcinoma

BACKGROUND

Hyperthermic intraperitoneal chemotherapy (HIPEC) has been shown to be an effective treatment for peritoneal tumors; whether preventive HIPEC after radical resection for T4 stage colon adenocarcinoma could decrease peritoneal recurrence remains unknown. The aim of the present study was to compare peritoneal recurrence and short-term survival in patients with T4 stage colon adenocarcinoma undergoing HIPEC plus adjuvant chemotherapy or adjuvant chemotherapy alone following surgery.

METHODS

We retrospectively reviewed T4 stage colon adenocarcinoma patients who had radical tumor resection at our institution between January 2014 and January 2019. Clinical data were extracted from the database at our institution, and patient survival and long-term complications were assessed through repeated outpatient examinations and telephone interviews.

RESULTS

A total of 352 patients were included in this study; 157 patients received postoperative HIPEC plus adjuvant chemotherapy (HIPEC group), 195 patients received adjuvant chemotherapy alone (conventional chemotherapy group). Forty-one (26.1%) patients in the HIPEC group had a peritoneal recurrence and the peritoneum was the first site of tumor recurrence in 6 (14.6%) of them. However, 73 (37.4%) patients experienced peritoneal recurrence in the conventional group, and the peritoneum was the first site of tumor recurrence in 25 (34.2%) (p = 0.019). Disease-free survival in the HIPEC group at 1 and 3 years was 93.3% and 61.1%, respectively, versus 89.3% and 51.7% in the conventional chemotherapy group (p = 0.038). Overall survival in the HIPEC group at 1 and 3 years was 100.0% and 82.7%, respectively, versus 100.0% and 76.9% in the conventional chemotherapy group (p = 0.420). The two groups did not differ with respect to severe complications.

CONCLUSIONS

Preventive HIPEC after radical surgery may decrease peritoneal recurrence and promote disease-free survival for T4 stage colon adenocarcinoma. Large-scale randomized controlled studies are needed to confirm the results of our study.

Comprehensive tumor profiling reveals unique molecular differences between peritoneal metastases and primary colorectal adenocarcinoma

BACKGROUND AND OBJECTIVES

Peritoneal metastases (PM) from primary colorectal cancer (pCRC) are associated with poor outcomes; however, molecular differences are not well defined.

METHODS

We compared unpaired tumor profiles of patients with pCRC and PM from Caris Life Sciences. Testing included next-generation sequencing of 592 genes, microsatellite instability (MSI) and tumor mutational burden (TMB). Mutations were test-defined as pathogenic (PATH).

RESULTS

Six hundred seventeen pCRC and 348 PM patients had similar gender (55% male) and age (median 59). PATHs were similar between PM and pCRC in KRAS, BRAF, SMAD2, SMAD4, and PTEN. pCRC PATHs were increased in APC (76% vs 48%, P < .01), ARID1A (29% vs 12%, P < .05), TP53 (72% vs 53%, P < .01), PIK3CA (22% vs 15%, P < .05), and FBXW7 (13% vs 7%, P < .01) compared with PM. Mucinous PM had more PATHs in GNAS (19% vs 8%, P = .032) while nonmucinous PM had more PATHs in BRAF (13% vs 8%, P = .027). Right-sided PM had decreased PATHs in APC (39% vs 68%, P < .0001), ARID1A (7% vs 38%, P < .004), and TP53 (48% vs 65%, P = .033) while there were no difference for left-sided PM. Nine percent of pCRC and 6% of PM were MSI-high (P = NS). There was no difference in TMB-high, TMB-intermediate, or TMB-low between PM and pCRC.

CONCLUSIONS

PM have similar rates of KRAS mutation with increased PATHs in GNAS (mucinous) and BRAF (nonmucinous) compared to pCRC. No differences in MSI or TMB were identified between PM and pCRC tumors. These findings inform future study into the molecular profile of PM.

Evaluation of repeat cytoreductive surgery and heated intraperitoneal chemotherapy for patients with recurrent peritoneal carcinomatosis from appendiceal and colorectal cancers: a multicentre Canadian study

Background

Peritoneal recurrences after cytoreductive surgery (CRS) and heated intraperitoneal chemotherapy (HIPEC) for appendiceal and colorectal cancers are frequent. This study aimed to evaluate the safety, technical feasibility and perioperative and long-term outcomes of repeat CRS/HIPEC in patients with recurrent peritoneal carcinomatosis of colorectal and appendiceal origin.

Methods

Data were collected from patients treated from 2000 to 2016 for recurrent peritoneal carcinomatosis from appendiceal or colorectal cancer with CRS/HIPEC at 2 specialist centres. Data on demographics, procedure details, morbidity and survival were recorded. Analyses compared the iterations of CRS/HIPEC to assess the safety and effectiveness of repeat surgery.

Results

Of all patients who underwent CRS/HIPEC in the 2 centres, 37 patients underwent a repeat procedure. Operative time was similar for the first and second surgeries (412.1 v. 412.5 min, p = 0.74) but patients had a significantly lower peritoneal carcinoma index score with the second surgery (21.8 in the first iteration v. 9.53 in the second iteration, p < 0.001) and significantly less blood loss (1762 mL in the first iteration v. 790 mL in the second iteration, p = 0.001). There was a nonsignificant decrease in grade III–IV complications and there was no 30-day mortality associated with repeat procedures. For patients with colorectal cancer, median disease-free survival was 9.6 months and median overall survival was 40 months. For patients with appendiceal cancer, median disease-free survival was 15 months and overall survival was 64.4 months.

Conclusion

Repeat CRS/HIPEC procedures for recurrent appendiceal and colorectal peritoneal carcinomatosis are safe in well-selected patients, without increased morbidity or mortality, and they are associated with significant long-term survival, particularly for patients with appendiceal cancers. These results support the use of repeat CRS/HIPEC in these patients.

Optimal Surveillance Frequency After CRS/HIPEC for Appendiceal and Colorectal Neoplasms: A Multi-institutional Analysis of the US HIPEC Collaborative

BACKGROUND

No guidelines exist for surveillance following cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) for appendiceal and colorectal cancer. The primary objective was to define the optimal surveillance frequency after CRS/HIPEC.

METHODS

The U.S. HIPEC Collaborative database (2000-2017) was reviewed for patients who underwent a CCR0/1 CRS/HIPEC for appendiceal or colorectal cancer. Radiologic surveillance frequency was divided into two categories: low-frequency surveillance (LFS) at q6-12mos or high-frequency surveillance (HFS) at q2-4mos. Primary outcome was overall survival (OS).

RESULTS

Among 975 patients, the median age was 55 year, 41% were male: 31% had non-invasive appendiceal (n = 301), 45% invasive appendiceal (n = 435), and 24% colorectal cancer (CRC; n = 239). With a median follow-up time of 25 mos, the median time to recurrence was 12 mos. Despite less surveillance, LFS patients had no decrease in median OS (non-invasive appendiceal: 106 vs. 65 mos, p < 0.01; invasive appendiceal: 120 vs. 73 mos, p = 0.02; colorectal cancer [CRC]: 35 vs. 30 mos, p = 0.8). LFS patients had lower median PCI scores compared with HFS (non-invasive appendiceal: 10 vs. 19; invasive appendiceal: 10 vs. 14; CRC: 8 vs. 11; all p < 0.01). However, on multivariable analysis, accounting for PCI score, LFS was still not associated with decreased OS for any histologic type (non-invasive appendiceal: hazard ratio [HR]: 0.28, p = 0.1; invasive appendiceal: HR: 0.73, p = 0.42; CRC: HR: 1.14, p = 0.59). When estimating annual incident cases of CRS/HIPEC at 375 for non-invasive appendiceal, 375 invasive appendiceal and 4410 colorectal, LFS compared with HFS for the initial two post-operative years would potentially save $13-19 M/year to the U.S. healthcare system.

CONCLUSIONS

Low-frequency surveillance after CRS/HIPEC for appendiceal or colorectal cancer is not associated with decreased survival, and when considering decreased costs, may optimize resource utilization.

Impact of Synchronous Versus Metachronous Onset of Colorectal Peritoneal Metastases on Survival Outcomes After Cytoreductive Surgery (CRS) with Hyperthermic Intraperitoneal Chemotherapy (HIPEC): A Multicenter, Retrospective, Observational Study

Background

Careful selection of patients with colorectal peritoneal metastases (PM) for cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC) is crucial. It remains unknown whether the time of onset of colorectal PM (synchronous vs metachronous) influences surgical morbidity and survival outcomes after CRS with HIPEC.

Methods

Patients with histologically proven colorectal PM who underwent CRS with HIPEC between February 2006 and December 2017 in two Dutch tertiary referral hospitals were retrospectively included from a prospectively maintained database. The onset of colorectal PM was classified as synchronous (PM diagnosed at the initiational presentation with colorectal cancer) or metachronous (PM diagnosed after initial curative colorectal resection). Major postoperative complications (Clavien–Dindo grade ≥ 3), overall survival (OS), and disease-free survival (DFS) were compared between patients with synchronous colorectal PM and those with metachronous colorectal PM using Kaplan–Meier analyses, proportional hazard analyses, and a multivariate Cox regression analysis.

Results

The study enrolled 433 patients, of whom 231 (53%) had synchronous colorectal PM and 202 (47%) had metachronous colorectal PM. The major postoperative complication rate and median OS were similar between the patients with synchronous colorectal PM and those with metachronous colorectal PM (26.8% vs 29.7%; p = 0.693 and 34 vs 33 months, respectively; p = 0.819). The median DFS was significantly decreased for the patients with metachronous colorectal PM and those with synchronous colorectal PM (11 vs 15 months; adjusted hazard ratio, 1.63; 95% confidence interval, 1.18–2.26).

Conclusions

Metachronous onset of colorectal PM is associated with early recurrence after CRS with HIPEC compared with synchronous colorectal PM, without a difference in OS or major postoperative complications. Time to onset of colorectal PM should be taken into consideration to optimize patient selection for this major procedure.

Electronic supplementary material

The online version of this article (10.1245/s10434-019-07294-y) contains supplementary material, which is available to authorized users.

Iterative cytoreductive surgery with or without hyperthermic intraperitoneal chemotherapy for colorectal peritoneal metastases: A multi-institutional experience

BACKGROUND AND OBJECTIVES

The aims of this multi-institutional study were to assess the feasibility of iterative cytoreductive surgery (iCRS)/hyperthermic intraperitoneal chemotherapy, iCRS in colorectal peritoneal carcinomatosis (CRPC), evaluate survival, recurrence, morbidity and mortality outcomes, and identify prognostic factors for overall survival.

METHODS

Patients with CRPC that underwent an iCRS, with or without intraperitoneal chemotherapy, from June 1993 to July 2016 at 13 institutions were retrospectively analyzed from prospectively maintained databases.

RESULTS

The study comprised of 231 patients, including 126 females (54.5%) with a mean age at iCRS of 51.3 years. The iterative high-grade (3/4) morbidity and mortality rates were 23.4% and 1.7%, respectively. The median recurrence-free survival was 15.0 and 10.1 months after initial and iCRS, respectively. The median and 5-year survivals were 49.1 months and 43% and 26.4 months and 26% from the initial and iCRS, respectively. Independent negative predictors of survival from the initial CRS included peritoneal carcinomatosis index (PCI) > 20 ( P = 0.02) and lymph node positivity ( P = 0.04), and from iCRS, PCI > 10 ( P = 0.03 for PCI 11-20; P < 0.001 for PCI > 20), high-grade complications ( P = 0.012), and incomplete cytoreduction ( P < 0.001).

CONCLUSION

iCRS can provide long-term survival benefits to highly selected colorectal peritoneal carcinomatosis patients with comparable mortality and morbidity rates to the initial CRS procedure. Careful patient selection is necessary to improve overall outcomes.

Short-term outcomes after laparoscopic cytoreductive surgery in patients with limited peritoneal metastases from colorectal cancer

BACKGROUND

The purpose of this study was to investigate the safety of laparoscopic cytoreductive surgery versus open surgery for patients with limited peritoneal metastases from colorectal cancer.

METHODS

Laparoscopic surgery for patients with colorectal cancer with peritoneal metastases has been performed at our institution since December 2004. We retrospectively evaluated data from patients with colorectal cancer metastatic to the peritoneum, with a peritoneal cancer index ≤10. We compared short-term operative and survival outcomes in the laparoscopic cytoreductive surgery group and open cytoreductive surgery group.

RESULTS

A total of 21 patients underwent open cytoreductive surgery and 42 underwent laparoscopic cytoreductive surgery, of whom 6 (14%) required open conversion. Clinicopathologic characteristics and operative outcomes were comparable between the groups. Complete cytoreduction was achieved in all patients in the laparoscopic cytoreductive surgery group and in 19 patients (91%) in the open cytoreductive surgery group (P = .042). Both the mean hospital stay and use of postoperative narcotics were significantly less in the laparoscopic cytoreductive surgery group than in the open cytoreductive surgery group. The type of operation (open cytoreductive surgery versus laparoscopic cytoreductive surgery) was not related to survival outcomes.

CONCLUSION

With careful selection by experienced laparoscopic surgeons, laparoscopic cytoreductive surgery was technically feasible and safe to treat colorectal cancer patients with limited peritoneal metastases.

Early Investigations and Recent Advances in Intraperitoneal Immunotherapy for Peritoneal Metastasis

Peritoneal metastasis (PM) is an advanced stage malignancy largely refractory to modern therapy. Intraperitoneal (IP) immunotherapy offers a novel approach for the control of regional disease of the peritoneal cavity by breaking immune tolerance. These strategies include heightening T-cell response and vaccine induction of anti-cancer memory against tumor-associated antigens. Early investigations with chimeric antigen receptor T cells (CAR-T cells), vaccine-based therapies, dendritic cells (DCs) in combination with pro-inflammatory cytokines and natural killer cells (NKs), adoptive cell transfer, and immune checkpoint inhibitors represent significant advances in the treatment of PM. IP delivery of CAR-T cells has shown demonstrable suppression of tumors expressing carcinoembryonic antigen. This response was enhanced when IP injected CAR-T cells were combined with anti-PD-L1 or anti-Gr1. Similarly, CAR-T cells against folate receptor α expressing tumors improved T-cell tumor localization and survival when combined with CD137 co-stimulatory signaling. Moreover, IP immunotherapy with catumaxomab, a trifunctional antibody approved in Europe, targets epithelial cell adhesion molecule (EpCAM) and has shown considerable promise with control of malignant ascites. Herein, we discuss immunologic approaches under investigation for treatment of PM.

Perioperative Systemic Chemotherapy, Cytoreductive Surgery, and Hyperthermic Intraperitoneal Chemotherapy in Patients With Colorectal Peritoneal Metastasis: Results of the Prospective Multicenter Phase 2 COMBATAC Trial

BACKGROUND

Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) as parts of an interdisciplinary treatment concept including systemic chemotherapy can improve survival of selected patients with peritoneal metastatic colorectal cancer (pmCRC). Nevertheless, the sequence of the therapeutic options is still a matter of debate. Thus, the COMBATAC (COMBined Anticancer Treatment of Advanced Colorectal cancer) trial was conducted to evaluate a combined treatment regimen consisting of preoperative systemic polychemotherapy + cetuximab followed by CRS + HIPEC and postoperative systemic polychemotherapy + cetuximab.

PATIENTS AND METHODS

The COMBATAC trial is a prospective, multicenter, open-label, single-arm, single-stage phase 2 trial. Twenty-six patients with synchronous or metachronous colorectal or appendiceal peritoneal carcinomatosis were included. Enrollment was terminated prematurely by the sponsor because of slow recruitment. Progression-free survival as primary end point and overall survival were estimated by the Kaplan-Meier method. Also evaluated were morbidity according to Common Terminology Criteria for Adverse Events v4.0 and feasibility of the combined treatment concept.

RESULTS

Median progression-free survival for the intention-to-treat population (n = 25) was 14.9 months. Median overall survival was not reached during the study duration. Ninety-two adverse events were documented in 16 patients, including 14 serious adverse events in 9 patients. The overall morbidity rate was 64%, and the grade 3/4 morbidity rate was 44%. Of all grade 3/4 morbidity events, 36.4% were related to systemic chemotherapy and 22.7% to surgery, whereas 40.9% were not directly related. There was no treatment-related mortality.

CONCLUSION

The results of the COMBATAC trial show that the multimodal treatment concept consisting of perioperative systemic chemotherapy and CRS + HIPEC is safe and feasible. Progression-free survival in selected patients with colorectal or appendiceal peritoneal metastasis might be improved.

[Surgical treatment of peritoneal metastases of colorectal cancer]

Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) may significantly improve overall survival in selected patients with peritoneal metastases of colorectal cancer. For good oncological results complete macroscopic cytoreduction is crucial; furthermore, a linear correlation between peritoneal tumor load, as determined by the peritoneal cancer index (PCI) and overall survival has been demonstrated; therefore, surgical treatment should be initiated as early as possible. Synchronous resection of up to three liver metastases may be performed safely and with good results and no influence on the morbidity. With respect to intraperitoneal chemotherapy, mitomycin C and oxaliplatin are most commonly used and may be regarded as equal; however, for perioperative chemotherapy study results are so far inconclusive with some trials hinting at decreased overall survival following neoadjuvant chemotherapy. Adjuvant therapy is likely to improve overall survival if at least 6 cycles are applied. Early detection of peritoneal metastases is difficult at present but might be facilitated in the future by the use of liquid biopsies, which may detect circulating free tumor-specific DNA or RNA. In the meantime, planned second-look laparotomy should be considered for patients at high risk of peritoneal recurrence. In addition, several international studies are currently evaluating the concept of adjuvant or prophylactic HIPEC. The CRS and HIPEC may be repeated in cases of recurrence and should be considered in suitable patients, applying the same criteria as for primary CRS and HIPEC. A recurrence-free interval of >2 years is associated with a significantly better prognosis.

Treatment of peritoneal carcinomatosis with hyperthermic intraperitoneal chemotherapy in colorectal cancer

The peritoneum is the second most common site of metastasis after the liver and the only site of metastatic disease in approximately 25% of patients with colorectal cancer (CRC). In the past, peritoneal carcinomatosis in CRC was thought to be equivalent to distant metastasis; however, the transcoelomic spread of malignant cells is an acknowledged alternative pathway. Metastasectomy with curative intent is well accepted in patients with liver metastasis in CRC despite the paucity of randomized trials. Therefore, there is rationale for local treatment with peritonectomy to eliminate macroscopic disease, followed by hyperthermic intraperitoneal chemotherapy to destroy any residual free tumour cells within the peritoneal cavity. The aim of this paper is to summarize the current evidence for cytoreduction and hyperthermic intraperitoneal chemotherapy in the treatment of peritoneal carcinomatosis in CRC.

Intraperitoneal immunotherapy: historical perspectives and modern therapy

Intraperitoneal immunotherapy represents a novel strategy for the management of peritoneal metastases (PM). Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) has remained the gold standard of treatment for patients with PM, yet despite optimal treatment, recurrence rates remain high and long-term survival poor. From Coley's toxins to immune checkpoint inhibitors, the wide variety of anticancer immunotherapeutic strategies are now garnering attention for control of regional disease of the peritoneal cavity. Early studies with vaccine-based therapies, adoptive cell transfer, immune checkpoint inhibitors, and chimeric T cells with tumor-specific antigen receptors (CAR-T cells) are being performed, showing promise for control of peritoneal spread and induction of lasting anticancer immunity. In addition, catumaxomab, a trifunctional antibody, has been approved for intraperitoneal immunotherapy in Europe for the control of malignant ascites in patients with epithelial cell adhesion molecule positive cancers. We review a brief history of immunotherapy and current modalities under investigation for intraperitoneal use in the treatment of PM.

Therapeutic options for peritoneal metastasis arising from colorectal cancer

Peritoneal metastasis is a common sign of advanced tumor stage, tumor progression or tumor recurrence in patients with colorectal cancer. Due to the improvement of systemic chemotherapy, the development of targeted therapy and the introduction of additive treatment options such as cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC), the therapeutic approach to peritoneal metastatic colorectal cancer (pmCRC) has changed over recent decades, and patient survival has improved. Moreover, in contrast to palliative systemic chemotherapy or best supportive care, the inclusion of CRS and HIPEC as inherent components of a multidisciplinary treatment regimen provides a therapeutic approach with curative intent. Although CRS and HIPEC are increasingly accepted as the standard of care for selected patients and have become part of numerous national and international guidelines, the individual role, optimal timing and ideal sequence of the different systemic, local and surgical treatment options remains a matter of debate. Ongoing and future randomized controlled clinical trials may help clarify the impact of the different components, allow for further improvement of patient selection and support the standardization of oncologic treatment regimens for pmCRC. The addition of further therapeutic options such as neoadjuvant intraperitoneal chemotherapy or pressurized intraperitoneal aerosol chemotherapy, should be investigated to optimize therapeutic regimens and further improve the oncological outcome.