The empty pelvis syndrome: a core data set from the PelvEx collaborative

BACKGROUND

Empty pelvis syndrome (EPS) is a significant source of morbidity following pelvic exenteration (PE), but is undefined. EPS outcome reporting and descriptors of radicality of PE are inconsistent; therefore, the best approaches for prevention are unknown. To facilitate future research into EPS, the aim of this study is to define a measurable core outcome set, core descriptor set and written definition for EPS. Consensus on strategies to mitigate EPS was also explored.

METHOD

Three-stage consensus methodology was used: longlisting with systematic review, healthcare professional event, patient engagement, and Delphi-piloting; shortlisting with two rounds of modified Delphi; and a confirmatory stage using a modified nominal group technique. This included a selection of measurement instruments, and iterative generation of a written EPS definition.

RESULTS

One hundred and three and 119 participants took part in the modified Delphi and consensus meetings, respectively. This encompassed international patient and healthcare professional representation with multidisciplinary input. Seventy statements were longlisted, seven core outcomes (bowel obstruction, enteroperineal fistula, chronic perineal sinus, infected pelvic collection, bowel obstruction, morbidity from reconstruction, re-intervention, and quality of life), and four core descriptors (magnitude of surgery, radiotherapy-induced damage, methods of reconstruction, and changes in volume of pelvic dead space) reached consensus-where applicable, measurement of these outcomes and descriptors was defined. A written definition for EPS was agreed.

CONCLUSIONS

EPS is an area of unmet research and clinical need. This study provides an agreed definition and core data set for EPS to facilitate further research.

Short-term results after robot-assisted surgery for primary rectal cancers requiring beyond total mesorectal excision in multiple compartments

AIM

Rectal cancers requiring beyond total mesorectal excision (bTME) are traditionally operated using an open approach, but the use of minimally invasive robot-assisted procedures is increasing. Introduction of minimal invasive surgery for complex cancer cases could be associated with compromised surgical margins or increased complication rates. Therefore, reporting results both clinical and oncological in large series is important. Since bTME procedure reports are heterogeneous, comparing results is often difficult. In this study, a magnetic resonance imaging (MRI) classification system was used to describe the bTME surgery according to pelvic compartments.

METHODS

Consecutive patients with primary rectal cancer operated with laparoscopic robot-assisted bTME were prospectively included for 2 years. All patients had tumors that threatened the mesorectal fascia, invaded adjacent organs, and/or involved metastatic pelvic lateral lymph nodes. Short-term clinical outcomes and oncological specimen quality were registered. Surgery was classified according to pelvic compartments resected.

RESULTS

Clear resection margins (R0 resection) were achieved in 95 out of 105 patients (90.5%). About 26% had Accordion Severity Grading System of Surgical Complications grade 3-4 complications and 15% required re-operations. About 7% were converted to open surgery. The number of compartments resected ranged from one to the maximum seven, with 83% having two or three compartments resected. All 10 R1 resections occurred in the lateral and posterior compartments.

CONCLUSIONS

The short-term clinical outcomes and oncological specimen quality after robot-assisted bTME surgery were comparable to previously published open bTME surgery. The description of surgical procedures using the Royal Marsden MRI compartment classification was feasible.

A Novel Pan-RAS Inhibitor with a Unique Mechanism of Action Blocks Tumor Growth in Mouse Models of GI Cancer

Here we characterize a novel pan-RAS inhibitor, ADT-007, that potently and selectively inhibited the growth of histologically diverse cancer cell lines with mutant or activated RAS irrespective of the RAS mutation or isozyme. Growth inhibition was dependent on activated RAS and associated with reduced GTP-RAS levels and MAPK/AKT signaling. ADT-007 bound RAS in lysates from sensitive cells with sub-nanomolar EC 50 values but did not bind RAS in lysates from insensitive cells with low activated RAS. Insensitivity to ADT-007 was attributed to metabolic deactivation by UGT-mediated glucuronidation, providing a detoxification mechanism to protect normal cells from pan-RAS inhibition. Molecular modeling and experiments using recombinant RAS revealed that ADT-007 binds RAS in a nucleotide-free conformation to block GTP activation. Local injection of ADT-007 strongly inhibited tumor growth in syngeneic immune competent and xenogeneic immune deficient mouse models of colorectal and pancreatic cancer and activated innate and adaptive immunity in the tumor microenvironment.

SIGNIFICANCE

ADT-007 is a novel pan-RAS inhibitor with a unique mechanism of action having potential to circumvent resistance to mutant-specific KRAS inhibitors and activate antitumor immunity. The findings support further development of ADT-007 analogs and/or prodrugs with oral bioavailability as a generalizable monotherapy or combined with immunotherapy for RAS mutant cancers.

BACKGROUND

It is projected that colorectal cancer (CRC) and pancreatic ductal adenocarcinoma (PDA) will cause 52,580 and 49,830 deaths in the US in 2023, respectively (1). The 5-year survival rates for CRC and PDA are 65% and 12%, respectively (1). Over 50% of CRC and 90% of PDA patients harbor mutations in KRAS genes that are associated with poor prognosis, making the development of novel KRAS inhibitors an urgent unmet medical need (2).

Navigation-Assisted Surgery for Locally Advanced Primary and Recurrent Rectal Cancer

BACKGROUND

In some surgical disciplines, navigation-assisted surgery has become standard of care, but in rectal cancer, indications for navigation and the utility of different technologies remain undetermined.

METHODS

The NAVI-LARRC prospective study (NCT04512937; IDEAL Stage 2a) evaluated feasibility of navigation in patients with locally advanced primary (LARC) and recurrent rectal cancer (LRRC). Included patients had advanced tumours with high risk of incomplete (R1/R2) resection, and navigation was considered likely to improve the probability of complete resection (R0). Tumours were classified according to pelvic compartmental involvement, as suggested by the Royal Marsden group. The BrainlabTM navigation platform was used for preoperative segmentation of tumour and pelvic anatomy, and for intraoperative navigation with optical tracking. R0 resection rates, surgeons' experiences, and adherence to the preoperative resection plan were assessed.

RESULTS

Seventeen patients with tumours involving the posterior/lateral compartments underwent navigation-assisted procedures. Fifteen patients required abdominosacral resection, and 3 had resection of the sciatic nerve. R0 resection was obtained in 6/8 (75%) LARC and 6/9 (69%) LRRC cases. Preoperative segmentation was time-consuming (median 3.5 h), but intraoperative navigation was accurate. Surgeons reported navigation to be feasible, and adherence to the resection plan was satisfactory.

CONCLUSIONS

Navigation-assisted surgery using optical tracking was feasible. The preoperative planning was time-consuming, but intraoperative navigation was accurate and resulted in acceptable R0 resection rates. Selected patients are likely to benefit from navigation-assisted surgery.

Intraperitoneal Paclitaxel Is a Safe and Effective Therapeutic Strategy for Treating Mucinous Appendiceal Adenocarcinoma

Appendiceal adenocarcinomas (AA) are a rare and heterogeneous mix of tumors for which few preclinical models exist. The rarity of AA has made performing prospective clinical trials difficult, which has partly contributed to AA remaining an orphan disease with no chemotherapeutic agents approved by the FDA for its treatment. AA has a unique biology in which it frequently forms diffuse peritoneal metastases but almost never spreads via a hematogenous route and rarely spreads to lymphatics. Given the localization of AA to the peritoneal space, intraperitoneal delivery of chemotherapy could be an effective treatment strategy. Here, we tested the efficacy of paclitaxel given by intraperitoneal administration using three orthotopic patient-derived xenograft (PDX) models of AA established in immunodeficient NSG mice. Weekly intraperitoneal paclitaxel treatment dramatically reduced AA tumor growth in all three PDX models. Comparing the safety and efficacy of intravenous with intraperitoneal administration, intraperitoneal delivery of paclitaxel was more effective, with reduced systemic side effects in mice. Given the established safety record of intraperitoneal paclitaxel in gastric and ovarian cancers, and lack of effective chemotherapeutics for AA, these data showing the activity of intraperitoneal paclitaxel in orthotopic PDX models of mucinous AA support the evaluation of intraperitoneal paclitaxel in a prospective clinical trial.

SIGNIFICANCE

The activity and safety of intraperitoneal paclitaxel in orthotopic PDX models of mucinous appendiceal adenocarcinoma supports the evaluation of intraperitoneal paclitaxel in a prospective clinical trial of this rare tumor type.

External multicentre validation of pseudomyxoma peritonei PSOGI-Ki67 classification

BACKGROUND

Pseudomyxoma peritonei (PMP) is a rare malignant disease. Adding of the Ki67 proliferation index to the PSOGI PMP classification provided two different subcategories of the extensive HG-PMP group (HG-PMP ≤15% and HG-PMP >15%) with different survival in a previous unicentric study. This study aims to carry out an external and multicentre validation of this new proposed classification.

METHOD

It was a prospective analysis of samples from a historical and international cohort of patients. A representative area with higher cellular density was used to determine the Ki67%. The Ki67 proliferation index (%) was determined in all the HG-PMP patients. A Cox proportional hazard models and multivariable COX models were used. The Kaplan-Meier method and the two-tailed log-rank test were used to analyse the effect of different PSOGI-Ki67 categories on OS and DFS. Its predictive accuracy was analysed using Harrel's C-index and the ROC curve. The calibration was performed using the calibration plots matching.

RESULTS

After exclusions, 349 patients were available for analysis. The 5-years OS were 86% for LG-PMP, 59% for HG-PMP≤15, 38% for HG-PMP>15 and 42% for SRC-PMP (p = 0.0001). The 5-years DFS were 49% for LG-PMP, 35% for HG-PMP≤15, 16% for HG-PMP>15 and 18% SRC-PMP (p = 0.0001). The discrimination capability of PSOGI-Ki67 was validated.

CONCLUSION

the PSOGI-Ki67 classification discriminates and predicts the OS and DFS in patients with PMP dividing the HG-PMP category into two well-defined sub-categories. The Ki67 proliferation index should be incorporated routinely in the pathology report for these patients.

Determining a minimum data set for reporting clinical and radiologic data for pseudomyxoma peritonei

Objectives

Pseudomyxoma peritonei (PMP) is a rare cancer currently affecting over 11,736 patients across Europe. Since PMP is so uncommon, collaboration between scientific centers is key to discovering the mechanisms behind the disease, efficient treatments, and targets pointing to a cure. To date, no consensus has been reached on the minimum data that should be collected during PMP research studies. This issue has become more important as biobanking becomes the norm. This paper begins the discussion around a minimum data set that should be collected by researchers through a review of available clinical trial reports in order to facilitate collaborative efforts within the PMP research community.

Content

A review of articles from PubMed, CenterWatch, ClinicalTrials.gov and MedRxiv was undertaken, and clinical trials reporting PMP results selected.

Summary

There is a core set of data that researchers report, including age and sex, overall survival, peritoneal cancer index (PCI) score, and completeness of cytoreduction, but after this, reports become variable.

Outlook

Since PMP is a rare disease, it is important that reports include as large of a number of standardised data points as possible. Our research indicates that there is still much ground to cover before this becomes a reality.

Antitumor activity of intraperitoneal paclitaxel in orthotopic patient-derived xenograft models of mucinous appendiceal adenocarcinoma

Appendiceal adenocarcinomas (AAs) are a rare and heterogeneous mix of tumors for which few preclinical models exist. The rarity of AA has made performing prospective clinical trials difficult, and in part because of this AA remains an orphan disease with no chemotherapeutic agents approved by the FDA for its treatment. AA has a unique biology in which it frequently forms diffuse peritoneal metastases, but almost never spreads via a hematogenous route and rarely spreads to lymphatics. Given its localization to the peritoneal space we hypothesized that intraperitoneal (IP) delivery of chemotherapy could be an effective treatment strategy. Here we tested the efficacy paclitaxel given by IP administration using three orthotopic PDX models of AA established in NSG mice. Weekly treatment of 25.0 mg/kg of IP paclitaxel dramatically reduced AA tumor growth in TM00351 (81.9% reduction vs. control), PMP-2 (98.3% reduction vs. control), and PMCA-3 (71.4% reduction vs. control) PDX models. Comparing the safety and efficacy of intravenous (IV) to IP administration in PMCA-3, neither 6.25 nor 12.5 mg/kg of IV paclitaxel significantly reduced tumor growth. These results suggest that IP administration of paclitaxel is favorable to IV administration. Given the established safety record of IP paclitaxel in gastric and ovarian cancers, and lack of effective chemotherapeutics for AA, these data showing the activity of IP paclitaxel in orthotopic PDX models of mucinous AA support the evaluation of IP paclitaxel in a prospective clinical trial.

A PRRX1 signature identifies TIM-3 and VISTA as potential immune checkpoint targets in a subgroup of microsatellite-stable colorectal cancer liver metastases

Disease recurrence and drug resistance are major challenges in the clinical management of patients with colorectal cancer liver metastases (CLM), and because tumors are generally microsatellite stable (MSS), responses to immune therapies are poor. The mesenchymal phenotype is overrepresented in treatment resistant cancers and is associated with an immunosuppressed microenvironment. The aim of this work was to molecularly identify and characterize a mesenchymal subgroup of MSS CLM to identify novel therapeutic approaches. We here generated a mesenchymal gene expression signature by analysis of resection specimens from 38 CLM patients using ranked expression level of the epithelial-to-mesenchymal transition related transcription factor PRRX1. Downstream pathway analysis based on the resulting gene signature was performed and independent, publicly available datasets were used to validate the findings. A subgroup comprising 16% of the analyzed CLM samples were classified as mesenchymal, or belonging to the PRRX1high group. Analysis of the PRRX1 signature genes revealed a distinct immunosuppressive phenotype with high expression of immune checkpoints HAVCR2/TIM-3 and VISTA, in addition to the M2 macrophage marker CD163. The findings were convincingly validated in datasets from three external CLM cohorts. Up-regulation of immune checkpoints HAVCR2/TIM-3 and VISTA in the PRRX1high subgroup is a novel finding, and suggests immune evasion beyond the PD-1/PD-L1 axis, which may contribute to poor response to PD-1/PD-L1 directed immune therapy in MSS colorectal cancer. Importantly, these checkpoints represent potential novel opportunities for immune-based therapy approaches in a subset of MSS CLM.

Intraperitoneal administration of cabazitaxel-loaded nanoparticles in peritoneal metastasis models

Colorectal and ovarian cancers frequently develop peritoneal metastases with few treatment options. Intraperitoneal chemotherapy has shown promising therapeutic effects, but is limited by rapid drug clearance and systemic toxicity. We therefore encapsulated the cabazitaxel taxane in poly(alkyl cyanoacrylate) (PACA) nanoparticles (NPs), designed to improve intraperitoneal delivery. Toxicity of free and encapsulated cabazitaxel was investigated in rats by monitoring clinical signs, organ weight and blood hematological and biochemical parameters. Pharmacokinetics, biodistribution and treatment response were evaluated in mice. Biodistribution was investigated by measuring both cabazitaxel and the 2-ethylbutanol NP degradation product. Drug encapsulation was shown to increase intraperitoneal drug retention, leading to prolonged intraperitoneal drug residence time and higher drug concentrations in peritoneal tumors. As a result, encapsulation of cabazitaxel improved the treatment response in two in vivo models bearing intraperitoneal tumors. Together, these observations indicate a strong therapeutic potential of NP-based cabazitaxel encapsulation as a novel treatment for peritoneal metastases.

T cell receptor repertoire sequencing reveals chemotherapy-driven clonal expansion in colorectal liver metastases

BACKGROUND

Colorectal liver metastasis (CLM) is a leading cause of colorectal cancer mortality, and the response to immune checkpoint inhibition (ICI) in microsatellite-stable CRC has been disappointing. Administration of cytotoxic chemotherapy may cause increased density of tumor-infiltrating T cells, which has been associated with improved response to ICI. This study aimed to quantify and characterize T-cell infiltration in CLM using T-cell receptor (TCR) repertoire sequencing. Eighty-five resected CLMs from patients included in the Oslo CoMet study were subjected to TCR repertoire sequencing. Thirty-five and 15 patients had received neoadjuvant chemotherapy (NACT) within a short or long interval, respectively, prior to resection, while 35 patients had not been exposed to NACT. T-cell fractions were calculated, repertoire clonality was analyzed based on Hill evenness curves, and TCR sequence convergence was assessed using network analysis.

RESULTS

Increased T-cell fractions (10.6% vs. 6.3%) were detected in CLMs exposed to NACT within a short interval prior to resection, while modestly increased clonality was observed in NACT-exposed tumors independently of the timing of NACT administration and surgery. While private clones made up >90% of detected clones, network connectivity analysis revealed that public clones contributed the majority of TCR sequence convergence.

CONCLUSIONS

TCR repertoire sequencing can be used to quantify T-cell infiltration and clonality in clinical samples. This study provides evidence to support chemotherapy-driven T-cell clonal expansion in CLM in a clinical context.

Minimum standards of pelvic exenterative practice: PelvEx Collaborative guideline

This document outlines the important aspects of caring for patients who have been diagnosed with advanced pelvic cancer. It is primarily aimed at those who are establishing a service that adequately caters to this patient group. The relevant literature has been summarized and an attempt made to simplify the approach to management of these complex cases.

Cost-effectiveness of molecularly matched off-label therapies for end-stage cancer - the MetAction precision medicine study

BACKGROUND

Precision cancer medicine (PCM), frequently used for the expensive and often modestly efficacious off-label treatment with medications matched to the tumour genome of end-stage cancer, challenges healthcare resources. We compared the health effects, costs and cost-effectiveness of our MetAction PCM study with corresponding data from comparator populations given best supportive care (BSC) in two external randomised controlled trials.

METHODS

We designed three partitioned survival models to evaluate the healthcare costs and quality-adjusted life years (QALYs) as the main outcomes. Cost-effectiveness was calculated as the incremental cost-effectiveness ratio (ICER) of PCM relative to BSC with an annual willingness-to-pay (WTP) threshold of EUR 56,384 (NOK 605,000). One-way and probabilistic sensitivity analyses addressed uncertainty.

RESULTS

We estimated total healthcare costs (relating to next-generation sequencing (NGS) equipment and personnel wages, molecularly matched medications to the patients with an actionable tumour target and follow-up of the responding patients) and the health outcomes for the MetAction patients versus costs (relating to estimated hospital admission) and outcomes for the BSC cases. The ICERs for incremental QALYs were twice or more as high as the WTP threshold and relatively insensitive to cost decrease of the NGS procedures, while reduction of medication prices would contribute significantly towards a cost-effective PCM strategy.

CONCLUSIONS

The models suggested that the high ICERs of PCM were driven by costs of the NGS diagnostics and molecularly matched medications, with a likelihood for the strategy to be cost-effective defying WTP constraints. Reducing drug expenses to half the list price would likely result in an ICER at the WTP threshold. This can be an incentive for a public-private partnership for sharing drug costs in PCM, exemplified by ongoing European initiatives.

CLINICALTRIALS.GOV, IDENTIFIER

NCT02142036.

Abstract 2467: SPECT-imaging guided development and evaluation of targeted alpha therapy (TAT) for colorectal liver metastasis

BACKGROUND: Only a small fraction of patients with colorectal liver metastases (CLM) is eligible for curative resection, and novel treatment options are highly needed. The high linear-energy transfer of short-ranged alpha particles can induce complex double-stranded DNA breaks, leading to cell death. With no known resistance mechanism, alpha-particle emitting isotopes represent a promising tool in cancer management. In targeted alpha therapy (TAT), an alpha-particle emitting isotope is attached to a tumor-targeting antibody (hereafter TAT antibody), ensuring specific delivery to the tumor. By substituting the alpha-particle emitting isotope (Actinium-225, 225Ac) with a diagnostic isotope (Zirconium-89, 89Zr), the in-vivo distribution of the TAT antibody can be monitored using PET/SPECT/CT. The aim of this work was to set up robust labeling and PET/SPECT protocols to evaluate TAT in CLM using novel experimental models.

METHODS: For SPECT-imaging of 225Ac daughter isotopes, the combined gamma emission spectra were gated at 218 keV ± 20% and 440 keV ± 20% for Francium-221 and Bismuth-213, respectively. 89Zr was labeled to a desferrioxamine* (DFO*) conjugated TAT antibody, which recognizes both the murine and human antigen. Indium-111 (111In) labeling was performed through diethylenetriaminepentaacetic acid (DTPA) conjugated to an isotype antibody. Radiochemical purity and protein integrity were assessed by size exclusion HPLC, iTLC and SDS-PAGE. For orthotopic CLM model development, 106 cells of human colorectal cancer cell lines HT-55 or LS1034 were injected in the spleen of female Rj:NMRI-Foxn1nu mice, followed by splenectomy. Tumor growth was monitored by T2-weighted MR-imaging. Non-tumor bearing mice (n = 12, 3 per group) were injected with 4 MBq of 10, 20, 50 or 100 µg 89Zr-TAT antibody to evaluate biodistribution and the mice scanned on day 2, 4 and 6 after iv injection.

RESULTS: Francium-221 and Bismuth-213 could be separately visualized after free Actinium-225 administration (i.v.). 89Zr and 111In were routinely labeled to their respective antibody with up to 500 MBq/mg with >95% radiochemical purity. 89Zr-DFO*-TAT antibody showed >95% radiochemical purity and >95% protein integrity after 7 days stability test in serum, shown by iTLC and SDS-PAGE. SPECT/CT of 89Zr-DFO*-TAT antibody in non-tumor bearing mice showed little uptake in healthy tissues apart from the liver due to hepatic antibody clearance. Orthotopic models of CLM show reproducible development of metastases for HT-55 and LS1034 within 3 weeks.

CONCLUSION: Robust labeling methods, PET/SPECT imaging protocols and suitable animal models of CLM were established. Results of our dual-isotope SPECT/CT imaging of our 89Zr-DFO*-TAT antibody in comparison with an 111In-labeled isotype antibody, together with efficacy data of the TAT, will be presented at the meeting.

Citation Format: Frans V. Suurs, Alexander Kristian, Gebregziabher Petros, Yuan Zeng Feng, Karianne G. Fleten, Roger M. Bjerke, Alan Cuthbertson, Kjersti Flatmark. SPECT-imaging guided development and evaluation of targeted alpha therapy (TAT) for colorectal liver metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2467.

Abstract 1346: T cell receptor repertoire sequencing reveals chemotherapy-driven clonal expansion in colorectal liver metastases

Background: Colorectal liver metastasis (CLM) is a leading cause of cancer-related mortality in the industrialized world, and only a small fraction of patients are eligible for curative resections. While immune checkpoint inhibition (ICI) has resulted in major breakthroughs in some cancers, the response in microsatellite stable (MSS) colorectal cancer has been disappointing. High density of infiltrating T cells has been associated with improved overall survival and response to ICI. We previously found that T cell infiltration varied considerably in a cohort of MSS CLM cases, which could reflect varying sensitivity to ICI treatment. The aim of this study was to quantify and characterize T cell infiltration in CLM using T cell receptor (TCR) repertoire sequencing (TCRR-seq).

Methods: Resection specimens were collected from 85 patients with CLM included in the Oslo CoMet trial (NCT01516710). Of these, 37 and 13 patients had received neoadjuvant chemotherapy (NACT) within a short or long interval, respectively, prior to resection, while 35 had not (no-NACT group). TCRR-seq libraries were prepared from DNA extracted from CLM tissue using the hsTCRB kit from Adaptive Biotechnologies, which allows both quantitative and qualitative analysis of TCR repertoires. The T cell fraction relative to the total number of cells was estimated for each CLM sample. Repertoire clonality was analyzed using Hill diversity profiles, a mathematical framework for determining species diversity derived from the ecological literature. Network analyses were conducted to analyze convergence of clonal T cell receptor amino acid sequences in each repertoire.

Results: The mean CLM T cell fraction was 8.1% (0.4-31.3%), and tumors with high T cell fraction had more monoclonal repertoires (p=1.86E-6). Interestingly, CLM from patients in the short interval group had increased T cell infiltration compared to the no-NACT and long interval groups (mean 10.5% and 6.3%, respectively; p=0.04), and these repertoires were also more monoclonal (p=0.003). Network analysis revealed that clonally expanded T cells tended to exhibit little overall receptor similarity to other T cells in the repertoire. Clonally expanded T cells were overall also private (unique) to each patient.

Conclusion: A short interval between exposure to cytotoxic chemotherapy and surgical resection was associated with increased T cell infiltration in CLM samples, and the increase was associated with clonal expansion. The findings suggest that chemotherapy could be a driver of clonal expansion in this setting, possibly by induction of immunogenic cell death. Furthermore, the CLM neo-antigen landscape appears to be diverse and private to the individual patient.

Citation Format: Eirik Høye, Vegar Johansen Dagenborg, Annette Torgunrud, Christin Lund-Andersen, Åsmund Avdem Fretland, Susanne Lorenz, Bjørn Edwin, Eivind Hovig, Anne Hansen Ree, Kjersti Flatmark. T cell receptor repertoire sequencing reveals chemotherapy-driven clonal expansion in colorectal liver metastases [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1346.

Abstract 1279: Early radiologic signal of nivolumab responsiveness after short-course oxaliplatin-based chemotherapy in microsatellite-stable (MSS) metastatic colorectal cancer (mCRC)

Purpose: Immune checkpoint inhibition (ICI) may result in tumor response patterns that differ from efficacy measures of directly cytotoxic chemotherapies. Hence, the selection of patients for experimental ICI schedules, for instance in MSS-mCRC, calls for applicable and reliable signals of activity or early failure that enable treatment adaptation and maintain patient safety.

Experimental procedures: In the ongoing METIMMOX phase 2 study, we hypothesize that patients with previously untreated unresectable MSS-mCRC can obtain durable disease control to ICI when given short-course oxaliplatin-based chemotherapy (2 cycles of FLOX Q2W) before 2 cycles of nivolumab (240 mg Q2W) in a repeat sequential schedule to a total of 8 cycles. Patients have been randomly assigned to either this experimental study arm or a control arm of 8 FLOX cycles Q2W (standard-of-care; SoC), in both cases before treatment break until disease progression and reintroduction of a new treatment sequence. Radiologic response assessment is performed every 8 weeks with progression-free survival (PFS) as the primary end point.

Results: At analysis 10 November 2021, median PFS was 9.3 months (95% CI, 8.3-10.3) for SoC (n = 34) and 11.4 months (95% CI, 7.4-15.5) for the experimental therapy (n = 39) (p = 0.335; log-rank test). In the latter group, 37 patients had available response evaluation at minimum 8 weeks of study treatment, as 2 patients (compared to 4 in the control group) had discontinued treatment due to intolerable toxicity before the first post-baseline assessment. The control arm patients had deeper responses with mean 23% (SD, 19%) target lesion reduction compared to mean 8%(SD, 33%) reduction for the experimental schedule (p = 0.028; Student’s t-test). We categorized the experimental arm patients into those with ≥10% (n = 20) or <10% (n = 17) target lesion reduction at 8 weeks. Median PFS for the ≥10% group was 15.2 months (95% CI, 11.4-19.0) and for the <10% group 4.5 months (95% CI, 3.2-5.7), which was clearly superior and inferior to the control arm PFS (p = 0.007 for the ≥10% group and p = 0.019 for the <10% group; log-rank test). Categorisation of experimental arm patients set at higher than 10% target lesion change at the first radiologic response assessment did not identify patients with longer PFS.

Conclusions: While the SoC first-line chemotherapy resulted in deeper early responses, target lesion reduction of ≥10% at 8 weeks identified MSS-mCRC patients who held ICI responsiveness evoked by short-course oxaliplatin-based chemotherapy, with significantly improved PFS compared to the SoC. An early radiologic signal of clinical activity may guide the selection of patients to the safe continuation of investigational ICI schedules; however, we do not know if adopting it may compromise prognosis for patients with early ICI failure who can proceed with SoC.

Citation Format: Sebastian Meltzer, Anne Negård, Hanne Mari Hamre, Christian Kersten, Eva Hofsli, Marianne Grønlie Guren, Halfdan Sørbye, Kjersti Flatmark, Anne Hansen Ree. Early radiologic signal of nivolumab responsiveness after short-course oxaliplatin-based chemotherapy in microsatellite-stable (MSS) metastatic colorectal cancer (mCRC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1279.

ALK Inhibitors in Patients With ALK Fusion-Positive GI Cancers: An International Data Set and a Molecular Case Series

In GI cancers, anaplastic lymphoma kinase (ALK) rearrangements are extremely less frequent than in non–small-cell lung cancer but may be important to offer personalized strategies of treatment in selected patients. Data about the activity and efficacy of ALK inhibitors (ALKi) in GI cancers are scarce.

ALK inhibitors are active in patients with ALK fusion–positive GI cancers.

Impact of KRAS, BRAF and microsatellite instability status after cytoreductive surgery and HIPEC in a national cohort of colorectal peritoneal metastasis patients

BACKGROUND

Patients with metastatic colorectal cancer (mCRC) carrying BRAF (mutBRAF) or KRAS mutation (mutKRAS) have an inferior prognosis after liver or lung surgery, whereas the prognostic role in the context of peritoneal metastasis (PM) after cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) has been less investigated.

METHODS

In total, 257 patients with non-appendiceal PM-CRC were included from the Norwegian National Unit for CRS-HIPEC.

RESULTS

In total, 180 patients received CRS-HIPEC with Mitomycin C, 77 patients received palliative surgery only. In the CRS-HIPEC group, mutBRAF was found in 24.7%, mutKRAS 33.9% and double wild-type 41.4% without differences in survival. MSI was found in 29.3% of mutBRAF cases. Patients with mutBRAF/MSI had superior 5-year survival compared to mutBRAF with MSS (58.3% vs 25.2%, P = 0.022), and better 3-year disease-free survival (DFS) compared to mutKRAS (48.6% vs 17.2%, P = 0.049). Peritoneal Cancer Index and the number of lymph node metastasis were prognostic for OS, and the same two, location and gender prognostic for DFS in multivariate analysis.

CONCLUSIONS

PM-CRC with CRS-HIPEC patients has a surprisingly high proportion of mutBRAF (24.7%). Survival was similar comparing mutBRAF, mutKRAS and double wild-type cases, whereas a small subgroup with mutBRAF and MSI had better survival. Patients with mutBRAF tumours and limited PM should be considered for CRS-HIPEC.

MRI-based automatic segmentation of rectal cancer using 2D U-Net on two independent cohorts

BACKGROUND

Tumor delineation is time- and labor-intensive and prone to inter- and intraobserver variations. Magnetic resonance imaging (MRI) provides good soft tissue contrast, and functional MRI captures tissue properties that may be valuable for tumor delineation. We explored MRI-based automatic segmentation of rectal cancer using a deep learning (DL) approach. We first investigated potential improvements when including both anatomical T2-weighted (T2w) MRI and diffusion-weighted MR images (DWI). Secondly, we investigated generalizability by including a second, independent cohort.

MATERIAL AND METHODS

Two cohorts of rectal cancer patients (C1 and C2) from different hospitals with 109 and 83 patients, respectively, were subject to 1.5 T MRI at baseline. T2w images were acquired for both cohorts and DWI (b-value of 500 s/mm²) for patients in C1. Tumors were manually delineated by three radiologists (two in C1, one in C2). A 2D U-Net was trained on T2w and T2w + DWI. Optimal parameters for image pre-processing and training were identified on C1 using five-fold cross-validation and patient Dice similarity coefficient (DSC_p) as performance measure. The optimized models were evaluated on a C1 hold-out test set and the generalizability was investigated using C2.

RESULTS

For cohort C1, the T2w model resulted in a median DSC_p of 0.77 on the test set. Inclusion of DWI did not further improve the performance (DSC_p 0.76). The T2w-based model trained on C1 and applied to C2 achieved a DSC_p of 0.59.

CONCLUSION

T2w MR-based DL models demonstrated high performance for automatic tumor segmentation, at the same level as published data on interobserver variation. DWI did not improve results further. Using DL models on unseen cohorts requires caution, and one cannot expect the same performance.

A comprehensive framework for analysis of microRNA sequencing data in metastatic colorectal cancer

Although microRNAs (miRNAs) contribute to all hallmarks of cancer, miRNA dysregulation in metastasis remains poorly understood. The aim of this work was to reliably identify miRNAs associated with metastatic progression of colorectal cancer (CRC) using novel and previously published next-generation sequencing (NGS) datasets generated from 268 samples of primary (pCRC) and metastatic CRC (mCRC; liver, lung and peritoneal metastases) and tumor adjacent tissues. Differential expression analysis was performed using a meticulous bioinformatics pipeline, including only bona fide miRNAs, and utilizing miRNA-tailored quality control and processing. Five miRNAs were identified as up-regulated at multiple metastatic sites Mir-210_3p, Mir-191_5p, Mir-8-P1b_3p [mir-141–3p], Mir-1307_5p and Mir-155_5p. Several have previously been implicated in metastasis through involvement in epithelial-to-mesenchymal transition and hypoxia, while other identified miRNAs represent novel findings. The use of a publicly available pipeline facilitates reproducibility and allows new datasets to be added as they become available. The set of miRNAs identified here provides a reliable starting-point for further research into the role of miRNAs in metastatic progression.

Peptide vaccine targeting mutated GNAS: a potential novel treatment for pseudomyxoma peritonei

Background

Pseudomyxoma peritonei (PMP) is a rare, slow-growing abdominal cancer with no efficacious treatment options in non-resectable and recurrent cases. Otherwise, rare activating mutations in the GNAS oncogene are remarkably frequent in PMP and the mutated gene product, guanine nucleotide-binding protein α subunit (Gsα), is a potential tumor neoantigen, presenting an opportunity for targeting by a therapeutic cancer vaccine.

Methods

Tumor and blood samples were collected from 25 patients undergoing surgery for PMP (NCT02073500). GNAS mutation analysis was performed by next-generation targeted sequencing or digital droplet PCR. Responses to stimulation with Gsα mutated (point mutations R201H and R201C) 30 mer peptides were analyzed in peripheral blood T cells derived from patients with PMP and healthy donors. Fresh PMP tumor samples were analyzed by mass cytometry using a panel of 35 extracellular markers, and cellular subpopulations were clustered and visualized using the visual stochastic network embedding analysis tool.

Results

GNAS mutations were detected in 22/25 tumor samples (88%; R201H and R201C mutations detected in 16 and 6 cases, respectively). Strong T cell proliferation against Gsα mutated peptides was observed in 18/24 patients with PMP. Mass cytometry analysis of tumor revealed infiltration of CD3 +T cells in most samples, with variable CD4+:CD8 + ratios. A large proportion of T cells expressed immune checkpoint molecules, in particular programmed death receptor-1 and T cell immunoreceptor with Ig and ITIM, indicating that these T cells were antigen experienced.

Conclusion

These findings point to the existence of a pre-existing immunity in patients with PMP towards mutated Gsα, which has been insufficient to control tumor growth, possibly because of inhibition of antitumor T cells by upregulation of immune checkpoint molecules. The results form a rationale for exploring peptide vaccination with Gsα peptides in combination with immune checkpoint inhibiton as a possible curative treatment for PMP and other GNAS mutated cancers.

The circulating soluble form of the CD40 costimulatory immune checkpoint receptor and liver metastasis risk in rectal cancer

BACKGROUND

In colorectal cancer, the inflamed tumour microenvironment with its angiogenic activities is immune- tolerant and incites progression to liver metastasis. We hypothesised that angiogenic and inflammatory factors in serum samples from patients with non-metastatic rectal cancer could inform on liver metastasis risk.

METHODS

We measured 84 angiogenic and inflammatory markers in serum sampled at the time of diagnosis within the population-based cohort of 122 stage I-III patients. In a stepwise manner, the statistically strongest proteins associated with time to development of liver metastasis were analysed in the corresponding serum samples from 273 stage II-III rectal cancer patients in three independent cohorts.

RESULTS

We identified the soluble form of the costimulatory immune checkpoint receptor cluster of differentiation molecule 40 (sCD40) as a marker of liver metastasis risk across all patient cohorts-the higher the sCD40 level, the shorter time to liver metastasis. In patients receiving neoadjuvant treatment, the sCD40 value remained an independent variable associated with progression to liver metastasis along with the local treatment response. Of note, serum sCD40 was not associated with progression to lung metastasis.

CONCLUSIONS

Circulating sCD40 is a marker of liver metastasis risk in rectal cancer and may be developed for use in clinical practice.

Abstract 522: Immunogenic chemotherapy and immune checkpoint inhibition (ICI) in microsatellite-stable (MSS) metastatic colorectal cancer (mCRC): Biomarkers indicative of durable treatment response

Purpose: Cancer immune therapy has revolutionized patient outcome for the small mCRC subgroup with highly immunogenic disease. The majority of mCRC cases, however, are MSS with inherently low susceptibility to immune therapy. In our ongoing METIMMOX study (NCT03388190), MSS-mCRC patients are randomized to oxaliplatin-based immunogenic chemotherapy followed by ICI (experimental study arm) or the oxaliplatin-based standard-of-care (control arm). A subgroup of experimental arm patients has obtained durable major partial or complete responses. Such remarkable outcomes call for biomarkers that may help identifying MSS-mCRC patients who will benefit from such sequential therapy.

Experimental procedures: Study enrollment began August 2018. Patients with unresectable, previously untreated MSS-mCRC have been randomized to the Nordic FLOX regimen (standard-of-care) or repeat sequential 2 FLOX cycles and 2 cycles of nivolumab (240 mg Q2W). At analysis October 2020, 48 patients were evaluable for progression-free survival (PFS). Serum collected at baseline and after the first 2 FLOX and 2 nivolumab cycles were analyzed for 42 immune factors with the Luminex multiplex immunoassay. The Significance Analysis for Microarrays method was applied to select the most significant proteins. Diffusion-weighted magnetic resonance imaging (DW-MRI) of the liver was performed at baseline and after the first 2 FLOX cycles. Using a b-value of 1000 s/mm2, the intensity ratio of a representative metastatic lesion relative to normal parenchymal tissue in the liver was calculated at each recording.

Results: At this early time of analysis, with median follow-up of 8.6 (range, 1-21) months, median PFS for the entire groups of control and experimental arm patients was identical (6.4 and 6.6 months, respectively). We selected 13 experimental arm patients with long (median 13.6 months) or short (median 5.6 months) PFS for the serum protein analysis and 9 patients with liver DW-MRI. High serum CD40L levels (> median 47.6 ng/ml) at baseline or CD23 levels (> median 15.7 ng/ml) after the first 2 FLOX and 2 nivolumab cycles were both associated with improved PFS (p < 0.001 and p < 0.007; log-rank test). The baseline DW-MRI intensity of the peripheral hyperintense rim of the metastatic lesion (2.0- to 2.8-fold higher than the corresponding parenchymal value) diminished towards the parenchymal intensity (1.2- to 1.6-fold higher) after the first 2 FLOX cycles in patients with longer PFS than the median for all study patients. The rim intensity did not change in patients with short PFS.

Conclusions: Three potential response markers in serum or at DW-MRI (one at baseline, one following the induction immunogenic chemotherapy, and one following the subsequent ICI) were identified for MSS-mCRC at this early time of the METIMMOX study conduct.

Citation Format: Anne Hansen Ree, Sebastian Meltzer, Kine M. Bakke, Hanne M. Hamre, Christian Kersten, Eva Hofsli, Marianne Grønlie Guren, Halfdan Sorbye, Christin Johansen, Anne Negård, Kathrine Røe Redalen, Kjersti Flatmark. Immunogenic chemotherapy and immune checkpoint inhibition (ICI) in microsatellite-stable (MSS) metastatic colorectal cancer (mCRC): Biomarkers indicative of durable treatment response [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 522.

Low Concordance Between T-Cell Densities in Matched Primary Tumors and Liver Metastases in Microsatellite Stable Colorectal Cancer

Background

The subtype, density and location of tumor infiltrating T-cells are being explored as prognostic and predictive biomarkers in primary colorectal cancer (pCRC) and colorectal liver metastases (CLM). Very limited data exist comparing findings in pCRC and matched CLM.

Patients and methods

Fifty-eight patients with available pCRC and matched CLM (57/58 microsatellite stable) were included in this OSLO-COMET substudy. In immunohistochemically stained sections, total (T_tot), helper (TH), cytotoxic (CTL), and regulatory (Treg) T-cells were manually counted in hotspots from the invasive margin (IM), intratumor (IT), and tumor adjacent regions to determine T-cell densities.

Results

A striking accumulation of T-cells was found in IM of both pCRC and CLM with much lower densities in the IT region, exemplified by T_tot of 2838 versus 340 cells/mm², respectively, in CLM. The correlation at the individual level between T-cell densities in pCRC and corresponding CLM was poor for all regions and T-cell subtypes; for instance, the correlation coefficient (R²) for IM T_tot was 0.07. The IT TH : CTL and Treg : TH ratios were 2.94 and 0.44, respectively, in pCRC, and 1.84 and 0.24, respectively, in CLM.

Conclusion

The observed accumulation of T-cells in the IM regions of pCRC and CLM with low penetration to the IT regions, combined with high TH : CTL and Treg : TH ratios, point to the presence of an immune suppressive microenvironment. T-cell densities of CLM differed markedly from the matched pCRC, indicating that to evaluate T-cell biomarkers in metastasis, the commonly available pCRC cannot serve as a surrogate for the metastatic tumor.

Increased Local Inflammatory Response to MOC31PE Immunotoxin After Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy

Background

Despite extensive cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS-HIPEC), most patients with resectable peritoneal metastases from colorectal cancer experience disease relapse. MOC31PE immunotoxin is being explored as a novel treatment option for these patients. MOC31PE targets the cancer-associated epithelial cell adhesion molecule, and kills cancer cells by distinct mechanisms, simultaneously causing immune activation by induction of immunogenic cell death (ICD).

Methods

Systemic and local cytokine responses were analyzed in serum and intraperitoneal fluid samples collected the first three postoperative days from clinically comparable patients undergoing CRS-HIPEC with (n = 12) or without (n = 26) intraperitoneal instillation of MOC31PE. A broad panel of 27 pro- and antiinflammatory interleukins, chemokines, interferons, and growth factors was analyzed using multiplex technology.

Results

The time course and magnitude of the systemic and local postoperative cytokine response after CRS-HIPEC were highly compartmentalized, with modest systemic responses contrasting substantial intraperitoneal responses. Administration of MOC31PE resulted in changes that were broader and of higher magnitude compared with CRS-HIPEC alone. Significantly increased levels of innate proinflammatory cytokines, such as interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF) as well as an interesting time response curve for the strong T-cell stimulator interferon (IFN)-γ and its associated chemokine interferon gamma-induced protein/chemokine (C-X-C motif) ligand 10 (IP-10) were detected, all associated with ICD.

Conclusions

Our study revealed a predominately local rather than systemic inflammatory response to CRS-HIPEC, which was strongly enhanced by MOC31PE treatment. The MOC31PE-induced intraperitoneal inflammatory reaction could contribute to improve remnant cancer cell killing, but the mechanisms remain to be elucidated in future studies.

Supplementary Information

The online version contains supplementary material available at 10.1245/s10434-021-10022-0.

Repeat sequential oxaliplatin-based chemotherapy (FLOX) and nivolumab versus FLOX alone as first-line treatment of microsatellite-stable (MSS) metastatic colorectal cancer (mCRC): Initial results from the randomized METIMMOX study

3556

Background: Immune checkpoint blockade (ICB) has revolutionized patient outcome for the small mCRC subgroup with highly immunogenic disease. The majority of mCRC cases, however, are MSS without innate ICB susceptibility. In our ongoing METIMMOX study, we hypothesize that MSS mCRC can be transformed into an immunogenic condition by short-course oxaliplatin-based therapy (FLOX), enabling patients with unresectable, previously untreated metastases to obtain durable disease control when adding ICB therapy. Here we present the protocol-planned interim analysis. Methods: Eligibility criteria include infradiaphragmatic metastasis and C-reactive protein < 60 mg/L. At analysis 15 January 2021, 54 patients stratified according to primary tumor sidedness and mutational status and evaluable for the primary end point (progression-free survival; PFS) had been randomly assigned to a standard-of-care schedule of 8 FLOX cycles Q2W (control arm) or repeat sequential 2 FLOX cycles and 2 nivolumab cycles (240 mg Q2W) to a total of 8 cycles (experimental arm), for both arms before treatment break until disease progression and reintroduction of a new treatment sequence. Radiologic response assessment is every 8 weeks. Safety, tolerability, objective response rate, and duration of response are among secondary end points. Results: At median follow-up of 6.4 (range, 0.5-20) months, patients were well balanced between the treatment arms with regard to the predefined strata and single-organ or multiple-organ metastases. Median PFS for the entire groups of control and experimental arm patients was 5.6 (range, 0.5-15; n = 26) and 6.6 (range, 0.5-20; n = 28) months, respectively. The number of FLOX-related CTCAE grade 3 or higher adverse events, including 2 deaths after initial FLOX administration, was comparable in the two arms. Twelve immune-related grade 3-4 adverse events (no new safety signals) were recorded. In the experimental arm, 4 (16%) patients, all RAS/BRAF-mutant cases, had experienced complete response and 9 (32%) patients had ongoing objective response at 8 months. The control arm cases had 0 with complete response and 6 (23%) with ongoing objective response at 8 months, 1 of whom had proceeded to curative-intent liver surgery. Conclusions: MSS mCRC patients may hold the opportunity of ICB responsiveness evoked by short-course oxaliplatin-based chemotherapy. The search for predictive biomarkers of ICB responsiveness is ongoing in the specifically designed METIMMOX correlative study program. Clinical trial information: NCT03388190.

Metastases in locally advanced rectal cancer undergoing curatively intended treatment

BACKGROUND

The main cause of mortality in locally advanced rectal cancer (LARC) is metastatic progression. The aim of the present study was to describe frequency, pattern and outcome of metastatic disease in a cohort of LARC patients after curative resection.

METHODS

This was a single-centre cohort study of 628 LARC cases after neoadjuvant chemoradiotherapy/radiotherapy (CRT/RT) and surgery. Data, including the first site of metastasis, was registered in an institutional database linked to the National Cancer Registry.

RESULTS

Metastases were diagnosed in 270 patients (43.0%) with liver and lungs as the first site in 113 and 96 cases, respectively. Involved resection margins, high tumour stage and poor response to CRT/RT were associated with metastasis development and inferior overall survival (OS). Metastasectomy was performed in 76 (67.3%) patients with liver metastases and 28 (29.2%) patients with lung metastases. Five-year OS was 89% in patients without metastases and 32% in metastatic cases. In patients selected for metastasectomy, 5-year OS was 69% and 53% for lung and liver metastases, respectively. Corresponding numbers without metastasectomy were 12% and 0%.

CONCLUSION

In this large LARC cohort undergoing curatively intended treatment, liver and lung metastases occurred at similar frequencies. Liver as the first metastatic site was associated with inferior long-term outcome, while selection for metastasectomy was associated with better OS, with more than half of the resected patients being alive five years after LARC surgery. Our results show that the presence of resectable metastatic disease at diagnosis should not exclude a curative therapeutic approach in LARC.

Omics analyses in peritoneal metastasis-utility in the management of peritoneal metastases from colorectal cancer and pseudomyxoma peritonei: a narrative review

High-throughput "-omics" analysis may provide a broader and deeper understanding of cancer biology to define prognostic and predictive biomarkers and identify novel therapy targets. In this review we provide an overview of studies where the peritoneal tumor component of peritoneal metastases from colorectal cancer (PM-CRC) and pseudomyxoma peritonei (PMP) were analyzed. Most of the available data was derived from DNA mutation analysis, but a brief review of findings from transcriptomic and protein expression analysis was also performed. Studies reporting genomic analysis of peritoneal tumor samples from 1,779 PM-CRC and 623 PMP cases were identified. The most frequently mutated genes in PM-CRC were KRAS, APC, SMAD4, BRAF, and PIK3CA, while in PMP KRAS, GNAS, FAT4, TGFBR1, TP53 and SMAD3/4 mutations were most commonly identified. Analyses were performed by single-gene analyses and to some extent targeted next-generation sequencing, and a very limited amount of broad explorative data exists. The investigated cohorts were typically small and heterogeneous with respect to the methods used and to the reporting of clinical data. This was even more apparent regarding transcriptomic and protein data, as the low number of cases examined and quality of clinical data would not support firm conclusions. Even for the most frequently mutated genes, the results varied greatly; for instance, KRAS mutations were reported at frequencies between 20-57% in PM-CRC and 38-100% in PMP. Such variation could be caused by random effects in small cohorts, heterogeneity in patient selection, or sensitivity of applied technology. Although a large number of samples have been subjected to analysis, cross-study comparisons are difficult to perform, and combined with small cohorts and varying quality and detail of clinical information, the observed variation precludes useful interpretation in a clinical context. Although omics data in theory could answer questions to aid management decisions in PM-CRC and PMP, the existing data does not presently support clinical implementation. With the necessary technologies being generally available, the main challenge will be to obtain sufficiently large, representative cohorts with adequate clinical data and standardized reporting of results. Importantly, studies where the focus is specifically on peritoneal disease are needed, where the study designs are aligned with clearly defined research questions to allow robust conclusions. Such studies are highly warranted if patients with PM-CRC and PMP are to derive benefit from recent advances in precision cancer medicine.

Long-Term Oncologic Outcomes After Laparoscopic Versus Open Resection for Colorectal Liver Metastases : A Randomized Trial

BACKGROUND

Despite the recent worldwide dissemination of laparoscopic liver surgery, no high-level evidence supports the oncologic safety of this approach.

OBJECTIVE

To evaluate long-term oncologic outcomes after laparoscopic versus open liver resection in patients with colorectal metastases.

DESIGN

A single-center, assessor-blinded, randomized controlled trial (OSLO-COMET [Oslo Randomized Laparoscopic Versus Open Liver Resection for Colorectal Metastases Trial]). (ClinicalTrials.gov: NCT01516710).

SETTING

Oslo University Hospital, the only provider of liver surgery for the 3 million inhabitants of southeastern Norway.

PARTICIPANTS

Patients with resectable colorectal liver metastases were randomly assigned to have open or laparoscopic liver resection.

INTERVENTION

From February 2012 to January 2016, a total of 280 patients were included in the trial (laparoscopic surgery: n = 133; open surgery: n = 147).

MEASUREMENTS

The primary outcome was postoperative morbidity within 30 days. Five-year rates of overall and recurrence-free survival were predefined secondary end points.

RESULTS

At a median follow-up of 70 months, rates of 5-year overall survival were 54% in the laparoscopic group and 55% in the open group (between-group difference, 0.5 percentage point [95% CI, -11.3 to 12.3 percentage points]; hazard ratio, 0.93 [CI, 0.67 to 1.30]; P = 0.67). Rates of 5-year recurrence-free survival were 30% in the laparoscopic group and 36% in the open group (between-group difference, 6.0 percentage points [CI, -6.7 to 18.7 percentage points]; hazard ratio, 1.09 [CI, 0.80 to 1.49]; P = 0.57).

LIMITATION

The trial was not powered to detect differences in secondary end points and was not designed to address a noninferiority hypothesis for survival outcomes.

CONCLUSION

In this randomized trial of laparoscopic and open liver surgery, no difference in survival outcomes was found between the treatment groups. However, differences in 5-year overall survival up to about 10 percentage points in either direction cannot be excluded. This trial should be followed by pragmatic multicenter trials and international registries.

PRIMARY FUNDING SOURCE

The South-Eastern Norway Regional Health Authority.

Simultaneous pelvic exenteration and liver resection for primary rectal cancer with synchronous liver metastases: results from the PelvEx Collaborative

AIM

At presentation, 15-20% of patients with rectal cancer already have synchronous liver metastases. The aim of this study was to determine the surgical and survival outcomes in patients with advanced rectal cancer who underwent combined pelvic exenteration and liver (oligometastatic) resection.

METHOD

Data from 20 international institutions that performed simultaneous pelvic exenteration and liver resection between 2007 and 2017 were accumulated. Primarily, we examined perioperative outcomes, morbidity and mortality. We also assessed the impact that margin status had on survival.

RESULTS

Of 128 patients, 72 (56.2%) were men with a median age of 60 years [interquartile range (IQR) 15 years]. The median size of the liver oligometastatic deposits was 2 cm (IQR 1.8 cm). The median duration of surgery was 406 min (IQR 240 min), with a median blood loss of 1090 ml (IQR 2010 ml). A negative resection margin (R0 resection) was achieved in 73.5% of pelvic exenterations and 66.4% of liver resections. The 30-day mortality rate was 1.6%, and 32% of patients had a major postoperative complication. The 5-year overall survival for patients in whom an R0 resection of both primary and metastatic disease was achieved was 54.6% compared with 20% for those with an R1/R2 resection (P = 0.006).

CONCLUSION

Simultaneous pelvic exenteration and liver resection is feasible, with acceptable morbidity and mortality. Simultaneous resection should only be performed where an R0 resection of both pelvic and hepatic disease is anticipated.

Experimental Treatment of Mucinous Peritoneal Metastases Using Patient-Derived Xenograft Models

Mucinous peritoneal metastases (PM) generally respond poorly to systemic treatment, and there is a clear unmet need for new treatment strategies to improve survival and quality of life for patients with PM. In this work, the growth inhibitory effect of five drugs (oxaliplatin (OXA; 5 mg/kg), irinotecan (IRI; 60 mg/kg), cabazitaxel (CBZ; 15 or 30 mg/kg), regorafenib (REG; 10, 30 or 60 mg/kg), and capecitabine (CAP; 359 or 755 mg/kg) was investigated in three orthotopic patient-derived xenograft models that mimic mucinous PM. Drugs were administered intraperitoneally (i.p.) as monotherapy weekly for 4 weeks (OXA, IRI), as one single i.p. injection (CBZ), or orally (REG, CAP) daily 5 of 7 days per week for four weeks, and i.p. tumor growth and survival were monitored and compared between treatment groups. The i.p. administered drugs (OXA, IRI, CBZ) had the strongest growth inhibitory effect, with OXA being most efficacious, completely inhibiting tumor growth in the majority of the animals. CBZ and IRI also strongly inhibited tumor growth, but with more variation in efficacy between the models. A moderate reduction in tumor growth was observed in all models treated with REG, while CAP had little to no growth inhibitory effect. Targeted next-generation-sequencing has identified mutational profiles typically associated with PM (mutations in KRAS, GNAS, and BRAF oncogenes), supporting the representativeness of the models. The results presented in this work support the continued exploration of i.p. treatment protocols for PM, with OXA remaining and CBZ emerging as particularly interesting candidates for further studies.

Molecularly matched therapy in the context of sensitivity, resistance, and safety; patient outcomes in end-stage cancer - the MetAction study

Background: In precision cancer medicine, the challenge is to prioritize DNA driver events, account for resistance markers, and procure sufficient information for treatment that maintains patient safety. The MetAction project, exploring how tumor molecular vulnerabilities predict therapy response, first established the required workflow for DNA sequencing and data interpretation (2014-2015). Here, we employed it to identify molecularly matched therapy and recorded outcome in end-stage cancer (2016-2019).Material and methods: Metastatic tissue from 26 patients (16 colorectal cancer cases) was sequenced by the Oncomine assay. The study tumor boards interpreted called variants with respect to sensitivity or resistance to matched therapy and recommended single-agent or combination treatment if considered tolerable. The primary endpoint was the rate of progression-free survival 1.3-fold longer than for the most recent systemic therapy. The objective response rate and overall survival were secondary endpoints.Results: Both common and rare actionable alterations were identified. Thirteen patients were found eligible for therapy following review of tumor sensitivity and resistance variants and patient tolerability. The interventions were inhibitors of ALK/ROS1-, BRAF-, EGFR-, FGFR-, mTOR-, PARP-, or PD-1-mediated signaling for 2-3 cases each. Among 10 patients who received treatment until radiologic evaluation, 6 (46% of the eligible cases) met the primary endpoint. Four colorectal cancer patients (15% of the total study cohort) had objective response. The only serious adverse event was a transient colitis, which appeared in 1 of the 2 patients given PD-1 inhibitor with complete response. Apart from those two, overall survival was similar for patients who did and did not receive study treatment.Conclusions: The systematic MetAction approach may point forward to a refined framework for how to interpret the complexity of sensitivity versus resistance and patient safety that resides in tumor sequence data, for the possibly improved outcome of precision cancer medicine in future studies. ClinicalTrials.gov, identifier: NCT02142036.

Estimating the Prevalence of Pseudomyxoma Peritonei in Europe Using a Novel Statistical Method

Background

The determination of the incidence and prevalence of rare diseases is important for economists and health-care providers. Pseudomyxoma peritonei (PMP) is a rare, slow-growing abdominal cancer that represents a substantial burden on both patients and health-care systems. The incidence rate was previously approximated at 1–2 people per million per year; this incidence has never been challenged, and the prevalence has not been estimated.

Methods

Epidemiological data from Norway and England were obtained and analysed to calculate a minimum incidence rate based on the number of patients having a first surgical intervention for PMP. A novel method was then used to determine a prevalence rate for PMP, incorporating incidence, death, and cure rates in a multi-year analysis that accounted for the increasing population of Europe over a 10-year period.

Results

An incidence rate of 3.2 people per million per year was calculated, with a corresponding estimated prevalence rate of 22 people per million per year. By this calculation, 11,736 people in Europe were estimated to be living with PMP in 2018.

Conclusion

Incidence and prevalence are essential tools for assessment of the financial and human cost of a disease. For rare diseases, such as PMP, the lack of accurate registries presents a particular challenge in determining such health-related statistical parameters. Based on our calculations, a significant number of people are living with PMP in Europe, underlining the need for appropriate resource allocation to ensure that adequate health-care measures are provided.

MirGeneDB 2.0: the metazoan microRNA complement

Small non-coding RNAs have gained substantial attention due to their roles in animal development and human disorders. Among them, microRNAs are special because individual gene sequences are conserved across the animal kingdom. In addition, unique and mechanistically well understood features can clearly distinguish bona fide miRNAs from the myriad other small RNAs generated by cells. However, making this distinction is not a common practice and, thus, not surprisingly, the heterogeneous quality of available miRNA complements has become a major concern in microRNA research. We addressed this by extensively expanding our curated microRNA gene database - MirGeneDB - to 45 organisms, encompassing a wide phylogenetic swath of animal evolution. By consistently annotating and naming 10,899 microRNA genes in these organisms, we show that previous microRNA annotations contained not only many false positives, but surprisingly lacked >2000 bona fide microRNAs. Indeed, curated microRNA complements of closely related organisms are very similar and can be used to reconstruct ancestral miRNA repertoires. MirGeneDB represents a robust platform for microRNA-based research, providing deeper and more significant insights into the biology and evolution of miRNAs as well as biomedical and biomarker research. MirGeneDB is publicly and freely available at http://mirgenedb.org/.

Abstract B46: Gene expression in colorectal liver metastases: Distinct immune signatures and opportunities for immune modulating therapy

Colorectal cancer (CRC) is one of the most common cancers and a leading cause of cancer death in the Western world. Up to 50% of CRC patients develop metastatic disease and the liver is the most common site. The recently identified consensus molecular subtypes (CMS1-4) based on analyses of primary CRC have prognostic and therapeutic implications, but it is unclear whether these molecular subtypes are valid for metastatic disease. The tumor microenvironment plays a major role in the dynamic shaping of the tumor phenotype and the clinical impact of the immune contexture within given CMS subgroups is emerging. In this study we performed gene expression profiling of a CLM cohort for patient stratification. Surgically resected CLMs (n=44) were analyzed by genome-wide transcription profiling. Clustering approaches were applied to define subgroups. Differential gene expression analyses were performed to reveal altered expression patterns in subgroups selected by clinicopathologic parameters. Functional annotation of gene signatures was conducted. Validation in public data sets and by proteomic analyses (RPPA) is ongoing. Quantification of T-cell subsets by immunohistochemistry was scored. The CMS classifier tool revealed the cohort to be highly enriched for CMS2 and thus of limited stratification utility. In contrast, intrinsic subgroups were revealed by alternative computational approaches. Distinct immune profiles were associated with the subgroups identified. Unsupervised clustering based on high-variance genes identified a 55-gene cluster that split the cohort near evenly. Functional annotation of the 55 genes identified one subgroup to display dysregulated cholesterol/lipid homeostasis with reciprocal links to immune regulatory genes. Supervised clustering using EMT/mesenchymal signatures identified a mesenchymal subgroup (20% of the samples). Functional annotation suggested coexistence of immunosuppression with the mesenchymal phenotype. Elevated expression of immune checkpoint molecules including TIM-3, and M2 macrophage markers correlated with the EMT/mesenchymal signature. The subgroup showed relative high density of T-cell subset infiltration (CD3, CD4, CD8, FOXP3). In differential gene expression analysis, CLMs exposed to neoadjuvant chemotherapy showed activation of interferon gamma (IFNG) signaling and genes linked to immunogenic cell death. Co-expression of immune regulatory genes suggested counterbalance of the immune responses triggered by IFNG. Immune-related gene expression signatures were associated with the CLM subgroups identified. These observations underline the integration and importance of the immune interactome in CLM. The coordinated expression of immunosuppressive factors suggests not only a rationale for immune therapy, but also that development of immune-modulating strategies may be required to increase efficacy of current therapy for selected CLM patients.

Citation Format: Vigdis Nygaard, Vegar Johansen Dagenborg, Sheraz Yaqub, Åsmund Avdem Fretland, Olga Østrup, Laxmi Siwal-Pandit, Krzysztof Grzyb, Anne-Lise Børresen-Dale, Gunhild Mari Mælandsmo, Anne Hansen Ree, Bjørn Edwin, Kjersti Flatmark. Gene expression in colorectal liver metastases: Distinct immune signatures and opportunities for immune modulating therapy [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr B46.

Immune stimulatory effect of anti-EpCAM immunotoxin - improved overall survival of metastatic colorectal cancer patients

Introduction: In a recent phase I trial in a heterogeneous group of carcinoma patients with advanced disease, we did not observe objective responses by CT at 8 weeks in patients treated with either the anti-EpCAM immunotoxin MOC31PE alone or administered in combination with the immunosuppressor cyclosporin (CsA). We have now assessed overall survival (OS) data for the two groups to reveal potential differences, and to elucidate putative underlying mechanisms.Material and methods: The OS time of MOC31PE monotherapy (34 patients) and MOC31PE in combination with CsA (23 patients), was assessed. Pre- and post-treatment patient sera were analyzed in a multiplex immunoassay, and the immunogenic effects of MOC31PE were studied in vitro and in a dendritic cell maturation assay.Results: When the data were analyzed for all treated patients regardless of cancer type, the MOC31PE alone group had a median OS of 12.7 months (95% CI = 5.6-19.8 months) compared to 6.2 months (95% CI = 5.6-6.8 months) (p=.066) for the patients treated with MOC31PE + CsA group. For the subgroup of patients with colorectal cancer, the median OS survival was 16.3 months (95% CI = 5.6-27.0) for the MOC31PE only cohort (n = 15), compared to 6.0 months (CI = 5.8-6.2) (p < .001) for the combination group. The cytokine profile in patient sera and the in vitro immunological studies indicate that MOC31PE induced an immunogenic response leading to T-cell activation; a response that was suppressed in patients treated with MOC31PE + CsA.Conclusions: The results reveal a promising clinical benefit of anti-EpCAM immunotoxin treatment in patients with advanced disease, an effect apparently explained by a previously unknown immunogenic effect of MOC31PE.

Neoadjuvant chemotherapy is associated with a transient increase of intratumoral T-cell density in microsatellite stable colorectal liver metastases

Patients with colorectal liver metastases (CLM) commonly receive neoadjuvant chemotherapy (NACT) prior to surgical resection. NACT may induce immunogenic cell death with subsequent recruitment of T-cells to the tumor microenvironment, which could be exploited by immune checkpoint inhibition (ICI). In theory, this could expand the use of ICI to obtain responses also in microsatellite stable colorectal cancer, but evidence to suggest optimal treatment schedules are lacking. In this study, densities of total-, cytotoxic-, helper- and regulatory T-cells were quantified by immunohistochemistry in resected CLM from 92 patients included in the OSLO-COMET trial (NCT01516710). All but one patient had microsatellite stable tumors (91/92). Associations between T-cell densities and clinicopathological parameters were analyzed. Fluoropyrimidine-based NACT (in most cases with addition of oxaliplatin or irinotecan) was administered to 45 patients completed median 8 weeks prior to surgical resection. No overall association was found between NACT administration and intratumoral T-cell densities. However, within the NACT group, a short time interval (<9.5 weeks) between NACT completion and CLM resection was strongly associated with high intratumoral T-cell densities compared to the long-interval and no NACT groups (medians 491, 236, and 292 cells/mm², respectively; P < .0001). The results from this study suggest that the observed increase in intratumoral T-cells after NACT administration may be transient. The significance of this finding should be further explored to ensure that optimal treatment schedules are chosen for studies combining cytotoxic chemotherapy and ICI.

Immunogenic cell death by neoadjuvant oxaliplatin and radiation protects against metastatic failure in high-risk rectal cancer

OBJECTIVE

High rates of systemic failure in locally advanced rectal cancer call for a rational use of conventional therapies to foster tumor-defeating immunity.

METHODS

We analyzed the high-mobility group box-1 (HMGB1) protein, a measure of immunogenic cell death (ICD), in plasma sampled from 50 patients at the time of diagnosis and following 4 weeks of induction chemotherapy and 5 weeks of sequential chemoradiotherapy, both neoadjuvant modalities containing oxaliplatin. The patients had the residual tumor resected and were followed for long-term outcome.

RESULTS

Patients who met the main study end point-freedom from distant recurrence-showed a significant rise in HMGB1 during the induction chemotherapy and consolidation over the chemoradiotherapy. The higher the ICD increase, the lower was the metastatic failure risk (hazard ratio 0.26, 95% confidence interval 0.11-0.62, P = 0.002). However, patients who received the full-planned oxaliplatin dose of the chemoradiotherapy regimen had poorer metastasis-free survival (P = 0.020) than those who had the oxaliplatin dose reduced to avert breach of the radiation delivery, which is critical to maintain efficient tumor cell kill and in the present case, probably also protected the ongoing radiation-dependent ICD response from systemic oxaliplatin toxicity.

CONCLUSION

The findings indicated that full-dose induction oxaliplatin followed by an adapted oxaliplatin dose that was compliant with full-intensity radiation caused induction and maintenance of ICD and as a result, durable disease-free outcome for a patient population prone to metastatic progression.