Fluoropyrimidine type, patient age, tumour sidedness and mutation status as determinants of benefit in patients with metastatic colorectal cancer treated with EGFR monoclonal antibodies: individual patient data pooled analysis of randomised trials from the ARCAD database

BACKGROUND

KRAS mutations in metastatic colorectal cancer (mCRC) are used as predictive biomarkers to select therapy with EGFR monoclonal antibodies (mAbs). Other factors may be significant determinants of benefit.

METHODS

Individual patient data from randomised trials with a head-to-head comparison between EGFR mAb versus no EGFR mAb (chemotherapy alone or best supportive care) in mCRC, across all lines of therapy, were pooled. Overall survival (OS) and progression-free survival (PFS) were compared between groups. Treatment effects within the predefined KRAS biomarker subsets were estimated by adjusted hazard ratio (HRadj) and 95% confidence interval (CI). EGFR mAb efficacy was measured within the KRAS wild-type subgroup according to BRAF and NRAS mutation status. In both KRAS wild-type and mutant subgroups, additional factors that could impact EGFR mAb efficacy were explored including the type of chemotherapy, line of therapy, age, sex, tumour sidedness and site of metastasis.

RESULTS

5675 patients from 8 studies were included, all with known mCRC KRAS mutation status. OS (HRadj 0.90, 95% CI 0.84-0.98, p = 0.01) and PFS benefit (HRadj 0.73, 95% CI 0.68-0.79, p < 0.001) from EGFR mAbs was observed in the KRAS wild-type group. PFS benefit was seen in patients treated with fluorouracil (HRadj 0.75, 95% CI 0.68-0.82) but not with capecitabine-containing regimens (HRadj 1.04, 95% CI 0.86-1.26) (pinteraction = 0.002). Sidedness also interacted with EGFR mAb efficacy, with survival benefit restricted to left-sided disease (pinteraction = 0.038). PFS benefits differed according to age, with benefits greater in those under 70 (pinteraction = 0.001). The survival benefit was not demonstrated in those patients with mutations found in the KRAS, NRAS or BRAF genes. The presence of liver metastases interacted with EGFR mAb efficacy in patients with KRAS mutant mCRC (pinteraction = 0.004).

CONCLUSION

The benefit provided by EGFR mAbs in KRAS WT mCRC is associated with left-sided primary tumour location, younger patient age and absence of NRAS or BRAF mutations. Survival benefit is observed with fluorouracil but not capecitabine. Exploratory results support further research in KRAS mutant mCRC without liver metastases.

Image-based consensus molecular subtyping in rectal cancer biopsies and response to neoadjuvant chemoradiotherapy

The development of deep learning (DL) models to predict the consensus molecular subtypes (CMS) from histopathology images (imCMS) is a promising and cost-effective strategy to support patient stratification. Here, we investigate whether imCMS calls generated from whole slide histopathology images (WSIs) of rectal cancer (RC) pre-treatment biopsies are associated with pathological complete response (pCR) to neoadjuvant long course chemoradiotherapy (LCRT) with single agent fluoropyrimidine. DL models were trained to classify WSIs of colorectal cancers stained with hematoxylin and eosin into one of the four CMS classes using a multi-centric dataset of resection and biopsy specimens (n = 1057 WSIs) with paired transcriptional data. Classifiers were tested on a held out RC biopsy cohort (ARISTOTLE) and correlated with pCR to LCRT in an independent dataset merging two RC cohorts (ARISTOTLE, n = 114 and SALZBURG, n = 55 patients). DL models predicted CMS with high classification performance in multiple comparative analyses. In the independent cohorts (ARISTOTLE, SALZBURG), cases with WSIs classified as imCMS1 had a significantly higher likelihood of achieving pCR (OR = 2.69, 95% CI 1.01-7.17, p = 0.048). Conversely, imCMS4 was associated with lack of pCR (OR = 0.25, 95% CI 0.07-0.88, p = 0.031). Classification maps demonstrated pathologist-interpretable associations with high stromal content in imCMS4 cases, associated with poor outcome. No significant association was found in imCMS2 or imCMS3. imCMS classification of pre-treatment biopsies is a fast and inexpensive solution to identify patient groups that could benefit from neoadjuvant LCRT. The significant associations between imCMS1/imCMS4 with pCR suggest the existence of predictive morphological features that could enhance standard pathological assessment.

CHARIOT: a phase I study of berzosertib with chemoradiotherapy in oesophageal and other solid cancers using time to event continual reassessment method

BACKGROUND

Berzosertib (M6620) is a highly potent (IC50  =  19 nM) and selective, first-in-class ataxia telangiectasia-mutated and Rad3-related protein kinase (ATR) inhibitor. This trial assessed the safety, preliminary efficacy, and tolerance of berzosertib in oesophageal cancer (A1 cohort) with RT and advanced solid tumours (A2 cohort) with cisplatin and capecitabine.

METHODS

Single-arm, open-label dose-escalation (Time-to-Event Continual Reassessment Method) trial with 16 patients in A1 and 18 in A2. A1 tested six dose levels of berzosertib with RT (35 Gy over 15 fractions in 3 weeks).

RESULTS

No dose-limiting toxicities (DLTs) in A1. Eight grade 3 treatment-related AEs occurred in five patients, with rash being the most common. The highest dose (240 mg/m2) was determined as the recommended phase II dose (RP2D) for A1. Seven DLTs in two patients in A2. The RP2D of berzosertib was 140 mg/m2 once weekly. The most common grade ≥3 treatment-related AEs were neutropenia and thrombocytopenia. No treatment-related deaths were reported.

CONCLUSIONS

Berzosertib combined with RT is feasible and well tolerated in oesophageal cancer patients at high palliative doses. Berzosertib with cisplatin and capecitabine was well tolerated in advanced cancer. Further investigation is warranted in a phase 2 setting.

CLINICAL TRIALS IDENTIFIER

EU Clinical Trials Register (EudraCT) - 2015-003965-27 ClinicalTrials.gov - NCT03641547.

Improving radiotherapy in immunosuppressive microenvironments by targeting complement receptor C5aR1

An immunosuppressive microenvironment causes poor tumor T cell infiltration and is associated with reduced patient overall survival in colorectal cancer. How to improve treatment responses in these tumors is still a challenge. Using an integrated screening approach to identify cancer-specific vulnerabilities, we identified complement receptor C5aR1 as a druggable target, which when inhibited improved radiotherapy, even in tumors displaying immunosuppressive features and poor CD8+ T cell infiltration. While C5aR1 is well-known for its role in the immune compartment, we found that C5aR1 is also robustly expressed on malignant epithelial cells, highlighting potential tumor cell-specific functions. C5aR1 targeting resulted in increased NF-κB-dependent apoptosis specifically in tumors and not normal tissues, indicating that, in malignant cells, C5aR1 primarily regulated cell fate. Collectively, these data revealed that increased complement gene expression is part of the stress response mounted by irradiated tumors and that targeting C5aR1 could improve radiotherapy, even in tumors displaying immunosuppressive features.

Evaluation of hypofractionated adaptive radiotherapy using the MR Linac in localised pancreatic cancer: protocol summary of the Emerald-Pancreas phase 1/expansion study located at Oxford University Hospital, UK

INTRODUCTION

Online adaptive MR-guided radiotherapy allows for dose escalation to pancreatic cancer while sparing surrounding critical organs. We seek to evaluate the safety of delivering hypofractionated five-fraction, three-fraction and single-fraction MR-guided stereotactic ablative radiotherapy (SABR) to the pancreas.

METHODS AND ANALYSIS

This is a single-centre three-arm phase 1 non-randomised safety study. Patients with localised pancreatic cancer will receive either 50 Gy in five (biological equivalent dose (BED10)=100 Gy), 39 Gy in three (BED10=90 Gy) or 25 Gy in a single fraction (BED10=87.5 Gy) MR-guided daily online adaptive radiotherapy. Each fractionation regimen will be assessed as independent cohorts to determine tolerability, assessed continuously using Bayesian conjugate posterior beta distributions. The primary endpoint of the study is to establish the safety of five-fraction, three-fraction and single-fraction MR-guided hypofractionation SABR in localised pancreatic cancer by assessing dose-limiting toxicities. Secondary endpoints include overall survival, progression-free survival, local control rates, overall control rate, resection rates, long-term toxicities and freedom from second-line chemotherapy. This study plans to also explore imaging and immune biomarkers that may be useful to predict outcome and personalise treatment. The trial will recruit up to 60 patients with a safety run-in.

ETHICS AND DISSEMINATION

The trial is approved by the West Midlands-Black Country Research Ethics Committee 22/WM/0122. The results will be disseminated via conference presentations, peer-reviewed scientific journals and submission to regulatory authorities. The data collected for the study, including individual participant data, will be made available to researchers on request to the study team and with appropriate reason, via octo-enquiries@oncology.ox.ac.uk. The shared data will be deidentified participant data and will be available for 3 years following publication of the study. Data will be shared with investigator support, after approval of a proposal and with a signed data access agreement.

TRIAL REGISTRATION NUMBER

ISRCTN10557832.

Efficacy of early PET-CT directed switch to carboplatin and paclitaxel based definitive chemoradiotherapy in patients with oesophageal cancer who have a poor early response to induction cisplatin and capecitabine in the UK: a multi-centre randomised controlled phase II trial

Background

The utility of early metabolic response assessment to guide selection of the systemic component of definitive chemoradiotherapy (dCRT) for oesophageal cancer is uncertain.

Methods

In this multi-centre, randomised, open-label, phase II substudy of the radiotherapy dose-escalation SCOPE2 trial we evaluated the role of ¹⁸F-Fluorodeoxyglucose positron emission tomography (PET) at day 14 of cycle 1 of three-weekly induction cis/cap (cisplatin (60 mg/m²)/capecitabine (625 mg/m² days 1-21)) in patients with oesophageal squamous cell carcinoma (OSCC) or adenocarcinoma (OAC). Non-responders, who had a less than 35% reduction in maximum standardised uptake value (SUV_max) from pre-treatment baseline, were randomly assigned to continue cis/cap or switch to car/pac (carboplatin AUC 5/paclitaxel 175 mg/m²) for a further induction cycle, then concurrently with radiotherapy over 25 fractions. Responders continued cis/cap for the duration of treatment. All patients (including responders) were randomised to standard (50Gy) or high (60Gy) dose radiation as part of the main study. Primary endpoint for the substudy was treatment failure-free survival (TFFS) at week 24. The trial was registered with International Standard Randomized Controlled Trial Number 97125464 and ClinicalTrials.govNCT02741856.

Findings

This substudy was closed on 1st August 2021 by the Independent Data Monitoring Committee on the grounds of futility and possible harm. To this point from 22nd November 2016, 103 patients from 16 UK centres had participated in the PET-CT substudy; 63 (61.2%; 52/83 OSCC, 11/20 OAC) of whom were non-responders. Of these, 31 were randomised to car/pac and 32 to remain on cis/cap. All patients were followed up until at least 24 weeks, at which point in OSCC both TFFS (25/27 (92.6%) vs 17/25 (68%); p = 0.028) and overall survival (42.5 vs. 20.4 months, adjusted HR 0.36; p = 0.018) favoured cis/cap over car/pac. There was a trend towards worse survival in OSCC + OAC cis/cap responders (33.6 months; 95%CI 23.1-nr) vs. non-responders (42.5 (95%CI 27.0-nr) months; HR = 1.43; 95%CI 0.67-3.08; p = 0.35).

Interpretation

In OSCC, early metabolic response assessment is not prognostic for TFFS or overall survival and should not be used to personalise systemic therapy in patients receiving dCRT.

Funding

Cancer Research UK.

Next generation radiotheranostics promoting precision medicine

Radiotheranostics is a field of rapid growth with some approved treatments including 131I for thyroid cancer, 223Ra for osseous metastases, 177Lu-DOTATATE for neuroendocrine tumors, and 177Lu-PSMA (prostate-specific membrane antigen) for prostate cancer, and several more under investigation. In this review, we will cover the fundamentals of radiotheranostics, the key clinical studies that have led to current success, future developments with new targets, radionuclides and platforms, challenges with logistics and reimbursement and, lastly, forthcoming considerations regarding dosimetry, identifying the right line of therapy, artificial intelligence and more.

Fluoropyrimidine-induced hand-foot syndrome and cardiotoxicity: recommendations for the use of the oral fluoropyrimidine S-1 in metastatic colorectal cancer

BACKGROUND

Fluoropyrimidines (FPs) are an essential part of the majority of systemic regimens in the treatment of metastatic colorectal cancer (CRC). The use of the oral FP S-1 has been approved by the European Medicines Agency as monotherapy or in combination with oxaliplatin or irinotecan, with or without bevacizumab, for the treatment of patients with metastatic CRC in whom it is not possible to continue treatment with another FP due to hand-foot syndrome (HFS) or cardiovascular toxicity (CVT). Subsequently, this indication has been included in the 2022 ESMO guidelines for metastatic CRC. Recommendations for use in daily practice are not available.

PATIENTS AND METHODS

Based on peer-reviewed published data on the use of S-1 in Western patients with metastatic CRC who switched from infusional 5-fluorouracil (5-FU) or capecitabine to S-1 for reasons of HFS or CVT, recommendations for its use were formulated by an international group of medical oncologists with expertise in the treatment of metastatic CRC and a cardio-oncologist.

RESULTS

In patients who experience pain and/or functional impairment due to HFS during treatment with capecitabine or infusional 5-FU, a switch to S-1 is recommended without prior dose reduction of capecitabine/5-FU. S-1 should preferably be initiated at full dose when HFS has decreased to grade ≤1. In patients with cardiac complaints, in whom an association with capecitabine or infusional 5-FU treatment cannot be excluded, capecitabine/5-FU should be discontinued and a switch to S-1 is recommended.

CONCLUSIONS

These recommendations should guide clinicians in daily practice in the treatment of patients with metastatic CRC with FP-containing regimens.

Machine learning for normal tissue complication probability prediction: Predictive power with versatility and easy implementation

Background and purpose

A popular Normal tissue Complication (NTCP) model deployed to predict radiotherapy (RT) toxicity is the Lyman-Burman Kutcher (LKB) model of tissue complication. Despite the LKB model's popularity, it can suffer from numerical instability and considers only the generalized mean dose (GMD) to an organ. Machine learning (ML) algorithms can potentially offer superior predictive power of the LKB model, and with fewer drawbacks. Here we examine the numerical characteristics and predictive power of the LKB model and compare these with those of ML.

Materials and methods

Both an LKB model and ML models were used to predict G2 Xerostomia on patients following RT for head and neck cancer, using the dose volume histogram of parotid glands as the input feature. Model speed, convergence characteristics and predictive power was evaluated on an independent training set.

Results

We found that only global optimization algorithms could guarantee a convergent and predictive LKB model. At the same time our results showed that ML models remained unconditionally convergent and predictive, while staying robust to gradient descent optimization. ML models outperform LKB in Brier score and accuracy but compare to LKB in ROC-AUC.

Conclusion

We have demonstrated that ML models can quantify NTCP better than or as well as LKB models, even for a toxicity that the LKB model is particularly well suited to predict. ML models can offer this performance while offering fundamental advantages in model convergence, speed, and flexibility, and so could offer an alternative to the LKB model that could potentially be used in clinical RT planning decisions.

Global colorectal cancer research, 2007-2021: Outputs and funding

The purpose of this study was to provide an evidence base for colorectal cancer research activity that might influence policy, mainly at the national level. Improvements in healthcare delivery have lengthened life expectancy, but within a situation of increased cancer incidence. The disease burden of CRC has risen significantly, particularly in Africa, Asia and Latin America. Research is key to its control and reduction, but few studies have delineated the volume and funding of global research on CRC. We identified research papers in the Web of Science (WoS) from 2007 to 2021, and determined the contributions of the leading countries, the research domains studied, and their sources of funding. We identified 62 716 papers, representing 5.7% of all cancer papers. This percentage was somewhat disproportionate to the disease burden (7.7% in 2015), especially in Eastern Europe. International collaboration increased over the time period in almost all countries except in China. Genetics, surgery and prognosis were the leading research domains. However, research on palliative care and quality-of-life in CRC was lacking. In Western Europe, the main funding source was the charity sector, particularly in the UK, but in most other countries government played the leading role, especially in China and the USA. There was little support from industry. Several Asian countries provided minimal contestable funding, which may have reduced the impact of their CRC research. Certain countries must perform more CRC research overall, especially in domains such as screening, palliative care and quality-of-life. The private-non-profit sector should be an alternative source of support.

BREAKWATER safety lead-in (SLI): Encorafenib (E) + cetuximab (C) + chemotherapy for BRAFV600E metastatic colorectal cancer (mCRC)

119

Background: Based on the phase 3 BEACON study (NCT02928224), BRAF inhibitor (i) encorafenib (E) + EGFRi cetuximab (C) was approved for the treatment (tx) of previously treated patients (pts) with BRAFV600E mCRC, with mPFS of 4.3 months (mo) and ORR of 19.5%. In the phase 2 ANCHOR study (NCT03693170), mPFS was 5.8 mo and ORR was 48% for 1L EC + binimetinib in BRAFV600E mCRC. To further assess 1L approaches, the ongoing phase 3 BREAKWATER study (NCT04607421) is evaluating EC ± chemotherapy vs standard-of-care chemotherapy in BRAFV600E mCRC. Here, we present updated safety and antitumor activity data as well as biomarker data from the BREAKWATER SLI. Methods: Inclusion criteria for the SLI were BRAFV600E mCRC (blood or tumor tissue), ≤1 prior systemic tx for mCRC, and ECOG PS 0/1. Pts previously treated with BRAFi/EGFRi or both oxaliplatin and irinotecan were excluded. Pts received E 300 mg daily + C 500 mg/m2 every 2 weeks (Q2W) + either mFOLFOX6 Q2W (n=27) or FOLFIRI Q2W (n=30) in 28-day cycles until disease progression or unacceptable toxicity. The primary endpoint was frequency of dose-limiting toxicities. Secondary endpoints included safety, pharmacokinetics, and antitumor activity. Exploratory endpoints included evaluation of plasma (circulating tumor DNA [ctDNA] genomic profiling) and tumor tissue (molecular profiling) biomarkers. Updated results from the BREAKWATER SLI will be presented, including overall safety and tolerability and antitumor activity. Biomarker data, including changes from baseline in BRAFV600E ctDNA following treatment (Cycle 1 Day 15, Cycle 2 Day 15 and Cycle 7 Day 1) and MSI status of pts, will also be presented. Expected conclusions will be included in the final abstract. Clinical trial information: NCT04607421 .

Biological Misinterpretation of Transcriptional Signatures in Tumor Samples Can Unknowingly Undermine Mechanistic Understanding and Faithful Alignment with Preclinical Data

PURPOSE

Precise mechanism-based gene expression signatures (GES) have been developed in appropriate in vitro and in vivo model systems, to identify important cancer-related signaling processes. However, some GESs originally developed to represent specific disease processes, primarily with an epithelial cell focus, are being applied to heterogeneous tumor samples where the expression of the genes in the signature may no longer be epithelial-specific. Therefore, unknowingly, even small changes in tumor stroma percentage can directly influence GESs, undermining the intended mechanistic signaling.

EXPERIMENTAL DESIGN

Using colorectal cancer as an exemplar, we deployed numerous orthogonal profiling methodologies, including laser capture microdissection, flow cytometry, bulk and multiregional biopsy clinical samples, single-cell RNA sequencing and finally spatial transcriptomics, to perform a comprehensive assessment of the potential for the most widely used GESs to be influenced, or confounded, by stromal content in tumor tissue. To complement this work, we generated a freely-available resource, ConfoundR; https://confoundr.qub.ac.uk/, that enables users to test the extent of stromal influence on an unlimited number of the genes/signatures simultaneously across colorectal, breast, pancreatic, ovarian and prostate cancer datasets.

RESULTS

Findings presented here demonstrate the clear potential for misinterpretation of the meaning of GESs, due to widespread stromal influences, which in-turn can undermine faithful alignment between clinical samples and preclinical data/models, particularly cell lines and organoids, or tumor models not fully recapitulating the stromal and immune microenvironment.

CONCLUSIONS

Efforts to faithfully align preclinical models of disease using phenotypically-designed GESs must ensure that the signatures themselves remain representative of the same biology when applied to clinical samples.

Clinical Trial Endpoints in Metastatic Cancer: Using Individual Participant Data to Inform Future Trials Methodology

Meta-analysis based on individual participant data (IPD) is a powerful methodology for synthesizing evidence by combining information drawn from multiple trials. Hitherto, its principal application has been in questions of clinical management, but an increasingly important use is in clarifying trials methodology, for instance in the selection of endpoints, as discussed in this review. In oncology, the Aide et Recherche en Cancérologie Digestive (ARCAD) Metastatic Colorectal Cancer Database is a leader in the use of IPD-based meta-analysis in methodological research. The ARCAD database contains IPD from more than 38 000 patients enrolled in 46 studies and continues to collect phase III trial data. Here, we review the principal findings of the ARCAD project in respect of endpoint selection and examine their implications for cancer trials. Analysis of the database has confirmed that progression-free survival (PFS) is no longer a valid surrogate endpoint predictive of overall survival in the first-line treatment of colorectal cancer. Nonetheless, PFS remains an endpoint of choice for most first-line trials in metastatic colorectal cancer and other solid tumors. Only substantial PFS effects are likely to translate into clinically meaningful benefits, and accordingly, we advocate an oncology research model designed to identify highly effective treatments in carefully defined patient groups. We also review the use of the ARCAD database in assessing clinical response including novel response metrics and prognostic markers. These studies demonstrate the value of IPD as a tool for methodological studies and provide a reference point for the expansion of this approach within clinical cancer research.

Using oxygen dose histograms to quantify voxelised ultra-high dose rate (FLASH) effects in multiple radiation modalities

Purpose.To introduce a methodology to predict tissue sparing effects in pulsed ultra-high dose rate radiation exposures which could be included in a dose-effect prediction system or treatment planning system and to illustrate it by using three published experiments.Methods and materials.The proposed system formalises the variability of oxygen levels as an oxygen dose histogram (ODH), which provides an instantaneous oxygen level at a delivered dose. The histogram concept alleviates the need for a mechanistic approach. At each given oxygen level the oxygen fixation concept is used to calculate the change in DNA-damage induction compared to the fully hypoxic case. Using the ODH concept it is possible to estimate the effect even in the case of multiple pulses, partial oxygen depletion, and spatial oxygen depletion. The system is illustrated by applying it to the seminal results by Town (Nat. 1967) on cell cultures and the pre-clinical experiment on cognitive effects by Montay-Gruelet al(2017Radiother. Oncol.124365-9).Results.The proposed system predicts that a possible FLASH-effect depends on the initial oxygenation level in tissue, the total dose delivered, pulse length and pulse repetition rate. The magnitude of the FLASH-effect is the result of a redundant system, in that it will have the same specific value for a different combination of these dependencies. The cell culture data are well represented, while a correlation between the pre-clinical experiments and the calculated values is highly significant (p < 0.01).Conclusions. A system based only on oxygen related effects is able to quantify most of the effects currently observed in FLASH-radiation.

The clinical relevance of tumor RAS/TP53 dual mutation in early and metastatic colorectal cancer (CRC)

3540

Background: The relevance of individual RAS (KRAS and NRAS) and TP53 mutations in CRC is well described, but the impact of the combination of both mutations together is less understood. RAS/TP53-mutant (mut) patients (pts) were selected in FOCUS 4-C for treatment with Adavosertib (Wee1 inhibitor) due to hypothesised sensitivity due to replication stress and loss of cell cycle checkpoint control. Initial analyses in CRC suggest that RAS/TP53-mut pts may be prognostically distinct from either mutation alone. Here we examine the impact of RAS/TP53-mut status in both early stage and metastatic CRC (mCRC). Methods: RAS and TP53 mutational status were assessed by whole gene targeted NGS or PCR in hotspot regions. Pts with RAS/TP53 status in the following studies were included after exclusion of BRAF-V600E mutants and MSI-H cases: for early-stage, QUASAR2 trial (N = 408) and an Australian community cohort (N = 654); for mCRC, FOCUS (N = 373) and FOCUS4 (N = 721). Biomarker prevalence, clinical characteristics and outcome data in the RAS/TP53-mut group were compared to pts not showing dual RAS/TP53-mut. Results: The prevalence of RAS/TP53-mut was greater in mCRC compared to early CRC (43.9% vs 25.4% respectively, p < 0.001). In early-stage (II & III) cohorts combined, RAS/TP53-mut pts were more likely to be female, have a right-sided primary tumour, and involved lymph nodes. In early CRC RAS/TP53-mut pts had worse outcome: DFS HR = 1.49[1.19-1.88], p = 0.001, and OS HR = 1.48[1.16-1.89], p = 0.001. In FOCUS, RAS/TP53-mut mCRC pts had inferior PFS with 1st line chemotherapy than not dual RAS/TP53-mut: 6.9 vs 8.6 months (HR = 1.44[1.17-1.79], p = 0.001), and also shorter post-progression survival (HR = 1.49, p = 0.001), and overall survival (14.9 vs 18.9 mths [HR = 1.60, p < 0.0005]). Consistently, during 16 weeks of induction chemotherapy for mCRC pts in FOCUS4, 27.4% of RAS/TP53-mut pts had progressive disease, compared with 18.4% in not dual RAS/TP53-mut; PFS from study registration was reduced in RAS/TP53-mut (5.3 vs 6.1 mths;HR = 1.53[1.22-1.94],p < 0.001), but no statistically significant difference in OS (13.6 vs 17.6 mths;HR = 1.27,p = 0.23). Outcomes by each of the four biomarker groups (RAS/TP53 dual mut; RASwt/TP53mut; RASmut/TP53 wt; RAS/TP53 dual wt) will be presented but in all cases the dual mut subgroup had the worst outcomes compared to the other three groups, marginally better than BRAF-V600E CRC. Conclusions: RAS/TP53 dual mutation status provides useful and readily available prognostic information in both early and mCRC, independent of MSI and BRAF status. It is associated with increased risk of recurrence in early CRC, and a higher risk of chemotherapy resistance and inferior outcomes in mCRC. Evaluation of treatment strategies in this sizeable patient group and further understanding of the underlying mechanism of poor outcomes are urgently required.

Molecular Subtyping Resource: a user-friendly tool for rapid biological discovery from transcriptional data

Generation of transcriptional data has dramatically increased in the past decade, driving the development of analytical algorithms that enable interrogation of the biology underpinning the profiled samples. However, these resources require users to have expertise in data wrangling and analytics, reducing opportunities for biological discovery by 'wet-lab' users with a limited programming skillset. Although commercial solutions exist, costs for software access can be prohibitive for academic research groups. To address these challenges, we have developed an open source and user-friendly data analysis platform for on-the-fly bioinformatic interrogation of transcriptional data derived from human or mouse tissue, called Molecular Subtyping Resource (MouSR). This internet-accessible analytical tool, https://mousr.qub.ac.uk/, enables users to easily interrogate their data using an intuitive 'point-and-click' interface, which includes a suite of molecular characterisation options including quality control, differential gene expression, gene set enrichment and microenvironmental cell population analyses from RNA sequencing. The MouSR online tool provides a unique freely available option for users to perform rapid transcriptomic analyses and comprehensive interrogation of the signalling underpinning transcriptional datasets, which alleviates a major bottleneck for biological discovery. This article has an associated First Person interview with the first author of the paper.

BREAKWATER safety lead-in (SLI): Encorafenib + cetuximab (EC) ± chemotherapy for first-line (1L) treatment (tx) of BRAF V600E-mutant (BRAFV600E) metastatic colorectal cancer (mCRC)

134

Background: Currently, there are no 1L tx options indicated specifically for patients (pts) with BRAFV600E mCRC. Based on results of BEACON CRC (NCT02928224), BRAF inhibitor encorafenib + EGFR inhibitor cetuximab was approved for tx of previously treated pts with BRAFV600E mCRC. BREAKWATER (NCT04607421), an ongoing, open-label, global, multicenter, randomized phase 3 study, evaluates 1L EC ± chemotherapy for tx of pts with BRAFV600E mCRC. Here we present preliminary data on safety and pharmacokinetics (PK) from the BREAKWATER SLI, which aimed to identify the chemotherapy backbone for EC for the phase 3 portion of BREAKWATER. Methods: SLI inclusion criteria were BRAFV600E mCRC (determined using tumor tissue or blood); evaluable disease (RECIST v1.1); ≤1 prior systemic tx for mCRC; European Cooperative Oncology Group performance status (ECOG PS) 0/1; and adequate bone marrow, hepatic, and renal function. Pts previously treated with BRAF/EGFR inhibitors or both oxaliplatin and irinotecan were excluded. Pts received encorafenib 300 mg daily + cetuximab 500 mg/m2 every 2 weeks (Q2W) + either FOLFIRI Q2W or mFOLFOX6 Q2W in 28-day cycles. The primary endpoint was frequency of dose-limiting toxicities (DLTs). PK were a secondary endpoint. Data cutoff date: Sep 13, 2021. Results: 57 pts were enrolled (EC + FOLFIRI, n = 30; EC + mFOLFOX6, n = 27). Median (range) age was 57 (28–78) years; 25% were Asian; 65% had ECOG PS 0; 37% had ≥3 organs involved; 58% were treatment naive. At cutoff date, tx was ongoing in 45 (79%) pts. Median (range) duration of tx for encorafenib in EC + FOLFIRI and EC + mFOLFOX6 was 15 (0–31) and 14 (0–27) weeks, respectively. One DLT was observed: grade 4 neutropenia in 1 pt in EC + FOLFIRI. Tx-emergent all-cause serious adverse events (AEs) occurred in 20% and 19% and grade ≥3 AEs in 33% and 56% of pts in EC + FOLFIRI and EC + mFOLFOX6, respectively. The table shows frequent (all grade in ≥30% pts or grade ≥3 in ≥10% with either tx) tx-emergent all-cause AEs. One pt died due to disease progression. In EC + FOLFIRI, in the presence of steady-state encorafenib, AUCinf of irinotecan and its active metabolite, SN-38, significantly decreased ̃25% and ̃40%, respectively, compared with values in the absence of encorafenib. In EC + mFOLFOX6, oxaliplatin PK was not significantly altered by steady-state encorafenib. Conclusions: Based on these data, BREAKWATER phase 3 will compare EC ± mFOLFOX6 with mFOLFOX6/FOLFOXIRI/CAPOX ± bevacizumab. Clinical trial information: NCT04607421. [Table: see text]

BREAKWATER: Randomized phase 3 study of encorafenib (enco) + cetuximab (cet) ± chemotherapy for first-line treatment (tx) of BRAF V600E-mutant (BRAFV600) metastatic colorectal cancer (mCRC)

TPS211

Background: Approximately 10% of patients (pts) with mCRC have BRAF mutations (mostly V600E). First-line tx options for BRAFV600E mCRC are limited to cytotoxic chemotherapy ± anti-VEGF or anti-EGFR; or immune checkpoint inhibitors in pts with MSI-H tumors. In Europe, Japan, and USA, the combination of BRAF inhibitor enco + EGFR inhibitor cet is approved for tx of BRAFV600E mCRC after prior therapy. In BEACON CRC, enco + cet resulted in a median overall survival (OS) of 9.3 months (95% confidence interval [CI]: 8.0–11.3) and an objective response rate (ORR) of 19.5% (95% CI: 14.5%–25.4%) in previously treated pts with BRAFV600E mCRC (median follow-up: 12.8 months); 57.4% of pts had grade 3/4 adverse events (AEs), and 9% discontinued due to AEs. Given the poor prognosis of pts with BRAFV600E mCRC and based on the efficacy and tolerability of enco + cet from BEACON CRC, the BREAKWATER study will evaluate the efficacy and safety of enco + cet ± chemotherapy in tx-naive pts with BRAFV600E mCRC. Methods: BREAKWATER is an open-label, global, multicenter, randomized, phase 3 study with a safety lead-in (SLI). Approximately 60 and 870 pts will be enrolled in the SLI and phase 3 parts of the study, respectively. Pts must have mCRC with BRAF V600E-mutation (determined using tumor tissue or blood); ECOG performance status 0/1; and adequate bone marrow, hepatic, and renal function. Pts in the SLI must have evaluable disease (RECIST v1.1) and have received ≤ 1 prior tx regimen; those previously treated with a BRAF or EGFR inhibitor, or both oxaliplatin and irinotecan, will be excluded. Pts in the phase 3 study must have measurable disease and be tx naive for metastatic disease. Study tx and endpoints are shown in the table. Enrollment began on 06-Jan-2021. Clinical trial information: NCT04607421. [Table: see text]

Molecular subtype-specific efficacy of anti-EGFR therapy in colorectal cancer is dependent on the chemotherapy backbone

BACKGROUND

Patient selection for addition of anti-EGFR therapy to chemotherapy for patients with RAS and BRAF wildtype metastatic colorectal cancer can still be optimised. Here we investigate the effect of anti-EGFR therapy on survival in different consensus molecular subtypes (CMSs) and stratified by primary tumour location.

METHODS

Retrospective analyses, using the immunohistochemistry-based CMS classifier, were performed in the COIN (first-line oxaliplatin backbone with or without cetuximab) and PICCOLO trial (second-line irinotecan with or without panitumumab). Tumour tissue was available for 323 patients (20%) and 349 (41%), respectively.

RESULTS

When using an irinotecan backbone, anti-EGFR therapy is effective in both CMS2/3 and CMS4 in left-sided primary tumours (progression-free survival (PFS): HR 0.44, 95% CI 0.26-0.75, P = 0.003 and HR 0.12, 95% CI 0.04-0.36, P < 0.001, respectively) and in CMS4 right-sided tumours (PFS HR 0.17, 95% CI 0.04-0.71, P = 0.02). Efficacy using an oxaliplatin backbone was restricted to left-sided CMS2/3 tumours (HR 0.57, 95% CI 0.36-0.96, P = 0.034).

CONCLUSIONS

The subtype-specific efficacy of anti-EGFR therapy is dependent on the chemotherapy backbone. This may provide the possibility of subtype-specific treatment strategies for a more optimal use of anti-EGFR therapy.

Treatment breaks in first line treatment of advanced colorectal cancer: An individual patient data meta-analysis

BACKGROUND

Intermittent systemic anti-cancer therapy in patients with advanced colorectal cancer (aCRC) may improve quality of life without compromising overall survival (OS). We aimed to use individual patient data meta-analysis (IPDMA) from multiple randomised controlled trials evaluating intermittent strategies to inform clinical practice. We also aimed to validate whether thrombocytosis as a predictive biomarker identified patients with significantly reduced OS receiving a complete treatment break.

PATIENTS AND METHODS

An IPDMA of intermittent strategy impact on survival was undertaken, including all relevant trials in which data were available. Intermittent strategies were classified into two groups: a planned stopping of all therapy ("treatment break strategy"; 6 trials; 2,907 patients) or to the same treatment omitting oxaliplatin ("maintenance strategy"; 3 trials; 1,271 patients). The primary analysis sample was of patients successfully completing induction therapy. Additionally, a pre-planned analysis of the predictive value of thrombocytosis on survival under a continuous versus an intermittent strategy was undertaken.

RESULTS

All trials had comparable inclusion criteria. The overall IPDMA of intermittent therapy versus continuous therapy demonstrated no detriment in OS (HR = 1.03 [95% CI 0.93-1.14]), whether from complete break (HR 1.04 [95% CI 0.87-1.26]) or maintenance strategies (HR 0.99 [95% CI 0.87-1.13]). Thrombocytosis was confirmed as a marker of poor prognosis in aCRC, but did not predict for OS detriment from treatment break strategies (interaction HR = 0.97 [95% CI 0.66-1.40] compared to continuous therapy).

CONCLUSION

The highest levels of evidence from this IPDMA indicate no detriment in survival for patients receiving an intermittent therapy strategy, either for maintenance or complete break strategies. Although, thrombocytosis is confirmed as a marker of poor prognosis, it is not predictive of poor outcome for patients treated with intermittent therapy. An intermittent chemotherapy strategy can therefore be applied irrespective of baseline platelet count and does not result in inferior OS compared to continuous chemotherapy.

Incorporating oxygenation levels in analytical DNA-damage models-quantifying the oxygen fixation mechanism

Purpose.To develop a framework to include oxygenation effects in radiation therapy treatment planning which is valid for all modalities, energy spectra and oxygen levels. The framework is based on predicting the difference in DNA-damage resulting from ionising radiation at variable oxygenation levels.Methods.Oxygen fixation is treated as a statistical process in a simplified model of complex and simple damage. We show that a linear transformation of the microscopic oxygen fixation process allows to extend this to all energies and modalities, resulting in a relatively simple rational polynomial expression. The model is expanded such that it can be applied for polyenergetic beams. The methodology is validated using Microdosimetric Monte Carlo Damage Simulation code (MCDS). This serves as a bootstrap to determine relevant parameters in the analytical expression, as MCDS is shown to be extensively verified with published empirical data. Double-strand break induction as calculated by this methodology is compared to published proton experiments. Finally, an example is worked out where the oxygen enhancement ratio (OER) is calculated at different positions in a clinically relevant spread out Bragg peak (SOBP) dose deposition in water. This dose deposition is obtained using a general Monte Carlo code (FLUKA) to determine dose deposition and locate fluence spectra.Results.For all modalities (electrons, protons), the damage categorised as complex could be parameterised to within 0.3% of the value calculated using microdosimetric Monte Carlo. The proton beam implementation showed some variation in OERs which differed slightly depending on where the assessment was made; before the SOBP, mid-SOBP or at the distal edge. Environment oxygenation was seen to be the more important variable.Conclusions.An analytic expression calculating complex damage depending on modality, energy spectrum, and oxygenation levels was shown to be effective and can be readily incorporated in treatment planning software, to take into account the impact of variable oxygenation, forming a first step to an optimised treatment based on biological factors.

Abstract LB129: Stratification of radiotherapy and fluoropyrimidine-based chemotherapy from multi-omic profiling in rectal cancer biopsies

Neoadjuvant chemoradiotherapy is commonly used to treat rectal cancer but patients have different levels of response and/or toxic effects.

As part of the Stratification in COloRecTal cancer (S:CORT) programme, we collected 257 rectal biopsies from two cohorts: Grampian (single hospital) and Aristotle (clinical trial). All patients had been subsequently treated with identical regimen of neoadjuvant radiotherapy and capecitabine. We performed trancriptomic, mutation and copy number profiling and aimed to identify biomarkers associated with the robust pathological endpoint of complete response (CR). Key biological determinants were identified by linear regression of different pre-defined, hypothesis-driven biomarkers for radiotherapy response, adjusted by the known confounders T and N stage. A novel RNA signature was derived using a personalised bioinformatical pipeline using a wide range of machine learning approaches. Results were validated in a publicly available transcriptomic cohort of 107 patients treated with similar dose of radiotherapy and 5-fluorouracil infusion. Further comparision of the biological determinants and the novel RNA signature were performed in the same cohorts and also TCGA by linear regression. Previously published transcriptomic signatures were retrieved and assessed in the validation, unseen cohort.

Grampian and Aristotle cohorts had similar statistical power and showed similar associations of CR with biological candidates, 10 of them being significant or borderline (p&lt;0.1). Accordingly, both cohorts were merged into a single discovery set to better assess which ones would show additive, independent association. Following multivariable stepwise regression the final model was composed of the immune biomarkers cytotoxic lymphocytes and CMS1 for radiosensitivity while the stromal TGFb Fibroblasts and epithelial APC mutations were for radioresistance. The first three variables were validated in the transcriptomic validation set (Cyt lymph OR 7.09, p=0.01; CMS1 OR 5.39, p=0.02; TGFb Fib OR 0.27, p=0.04). In parallel, a 33-gene signature, trained in the discovery cohort by a comprehensive machine learning pipeline, showed excellent predictive ability in the validation cohort (0.9 AUC; 88% accuracy, 90% sensitivity, 86% specificity). Most genes were associated with at least one of the four biological features identified in the discovery set, validation set and a third cohort of colorectal cancer resections. Our novel signature showed much better predictive ability than other previously published transcriptomic signatures in the validation, unseen cohort.

The immune, stromal and epithelial components of rectal tumours are important players for prediction of CR to radiotherapy in rectal cancer. A 33-gene transcriptomic biomarker can be used to effectively select patients that are highly likely to achieve CR allowing organ preservation while modulation of the relevant biological features in the other patients may be tested to improve their poor outcome with current treatment strategies.

Citation Format: Enric Domingo, Sanjay Rathee, Andrew Blake, Leslie M. Samuel, Graeme I. Murray, David Sebag-Montefiore, Simon Gollins, Nicholas West, Rubina Begum, Marian Duggan, Laura White, Susan Richman, Philip Quirke, James Robineau, Keara Redmond, Aikaterini Chatzipli, Ultan McDermott, Ian Tomlinson, Philip Dunne, Francesca Buffa, Tim Maughan. Stratification of radiotherapy and fluoropyrimidine-based chemotherapy from multi-omic profiling in rectal cancer biopsies [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 LB129.

Impact of geography on prognostic outcomes of 21,509 patients with metastatic colorectal cancer enrolled in clinical trials: an ARCAD database analysis

BACKGROUND

Benchmarking international cancer survival differences is necessary to evaluate and improve healthcare systems. Our aim was to assess the potential regional differences in outcomes among patients with metastatic colorectal cancer (mCRC) participating in international randomized clinical trials (RCTs).

DESIGN

Countries were grouped into 11 regions according to the World Health Organization and the EUROCARE model. Meta-analyses based on individual patient data were used to synthesize data across studies and regions and to conduct comparisons for outcomes in a two-stage random-effects model after adjusting for age, sex, performance status, and time period. We used mCRC patients enrolled in the first-line RCTs from the ARCAD database, which provided enrolling country information. There were 21,509 patients in 27 RCTs included across the 11 regions.

RESULTS

Main outcomes were overall survival (OS) and progression-free survival (PFS). Compared with other regions, patients from the United Kingdom (UK) and Ireland were proportionaly over-represented, older, with higher performance status, more frequently male, and more commonly not treated with biological therapies. Cohorts from central Europe and the United States (USA) had significantly longer OS compared with those from UK and Ireland (p = 0.0034 and p < 0.001, respectively), with median difference of 3-4 months. The survival deficits in the UK and Ireland cohorts were, at most, 15% at 1 year. No evidence of a regional disparity was observed for PFS. Among those treated without biological therapies, patients from the UK and Ireland had shorter OS than central Europe patients (p < 0.001).

CONCLUSIONS

Significant international disparities in the OS of cohorts of mCRC patients enrolled in RCTs were found. Survival of mCRC patients included in RCTs was consistently lower in the UK and Ireland regions than in central Europe, southern Europe, and the USA, potentially attributed to greater overall population representation, delayed diagnosis, and reduced availability of therapies.

Stromal composition predicts recurrence of early rectal cancer after local excision

AIMS

After local excision of early rectal cancer, definitive lymph node status is not available. An alternative means for accurate assessment of recurrence risk is required to determine the most appropriate subsequent management. Currently used measures are suboptimal. We assess three measures of tumour stromal content to determine their predictive value after local excision in a well-characterised cohort of rectal cancer patients without prior radiotherapy.

METHODS AND RESULTS

A total of 143 patients were included. Haematoxylin and eosin (H&E) sections were scanned for (i) deep neural network (DNN, a machine-learning algorithm) tumour segmentation into compartments including desmoplastic stroma and inflamed stroma; and (ii) digital assessment of tumour stromal fraction (TSR) and optical DNA ploidy analysis. 3' mRNA sequencing was performed to obtain gene expression data from which stromal and immune scores were calculated using the ESTIMATE method. Full results were available for 139 samples and compared with disease-free survival. All three methods were prognostic. Most strongly predictive was a DNN-determined ratio of desmoplastic to inflamed stroma >5.41 (P < 0.0001). A ratio of ESTIMATE stromal to immune score <1.19 was also predictive of disease-free survival (P = 0.00051), as was stromal fraction >36.5% (P = 0.037).

CONCLUSIONS

The DNN-determined ratio of desmoplastic to inflamed ratio is a novel and powerful predictor of disease recurrence in locally excised early rectal cancer. It can be assessed on a single H&E section, so could be applied in routine clinical practice to improve the prognostic information available to patients and clinicians to inform the decision concerning further management.

BREAKWATER: Randomized phase 3 study of encorafenib (enco) + cetuximab (cetux) ± chemotherapy for first-line (1L) treatment (tx) of BRAF V600E-mutant (BRAFV600E) metastatic colorectal cancer (mCRC)

TPS3619

Background: Approximately 10% of patients (pts) with mCRC have BRAF mutations (mostly V600E). 1L tx options for BRAFV600E mCRC are limited to cytotoxic chemotherapy ± anti-VEGF or anti-EGFR, or immune checkpoint inhibitors in pts with MSI-H tumors. In Europe, Japan, and USA, the combination of BRAF inhibitor enco + EGFR inhibitor cetux is approved for tx of BRAFV600E mCRC after prior therapy. In BEACON CRC, enco + cetux resulted in a median overall survival (OS) of 9.3 months (95% confidence interval [CI]: 8.0–11.3) and an objective response rate (ORR) of 19.5% (95% CI: 14.5%–25.4%) in previously treated pts with BRAFV600E mCRC (median follow-up: 12.8 months); 57.4% of pts had grade 3/4 adverse events (AEs); 9% discontinued due to AEs. Given the poor prognosis of pts with BRAFV600E mCRC and based on the efficacy and tolerability of enco + cetux from BEACON CRC, BREAKWATER will evaluate efficacy and safety of enco + cetux ± chemotherapy in tx-naive pts with BRAFV600E mCRC. Methods: BREAKWATER is an open-label, global, multicenter, randomized, phase 3 study with a safety lead-in (SLI). Approximately 60 and 870 pts will be enrolled in the SLI and phase 3 parts of the study, respectively. Pts must have BRAFV600E mCRC (determined using tumor tissue or blood); ECOG performance status 0/1; and adequate bone marrow, hepatic, and renal function. Pts in the SLI must have evaluable disease (RECIST v1.1) and have received ≤ 1 prior tx regimen; those previously treated with a BRAF or EGFR inhibitor, or both oxaliplatin and irinotecan, will be excluded. Pts in the phase 3 study must have measurable disease and be tx naive for metastatic disease. Study tx and endpoints are shown in the table. Enrollment began on 6 January 2021. Clinical trial information: NCT04607421. [Table: see text]

Global BRAF testing practices in metastatic colorectal cancer (mCRC)

e15523

Background: The BRAF V600E mutation is a marker of poor prognosis in patients with mCRC. Targeted therapy, such as encorafenib + cetuximab, is approved in the US/Europe for the treatment of BRAF V600E-mutated mCRC and demonstrated improved survival vs historical standard of care (SOC). Determining BRAF mutation status in mCRC is recommended by NCCN and ESMO guidelines; although adherence to these guidelines may not be uniform. This report’s objective is to communicate global survey results of mCRC BRAF testing practices. Identifying regions where BRAF testing is not SOC may help identify where education efforts are needed to improve effective treatment decision making. Methods: Oncology treatment centers were identified from a registry and from public information. Centers were selected for research experience, historic data quality, and estimated numbers of mCRC patients. A BRAF testing practices survey using an online platform of verified centers was conducted from March to November 2020; 425 sites in 39 countries responded. Results: BRAF testing is performed as SOC most commonly in Northern and Western Europe (97%) and East Asia (95%). Conversely, BRAF testing as SOC is least common in Eastern Europe (47%) and South America (52%). Surveyed regions generally test patients when confirming advanced disease prior to first-line (1L) treatment (35% to 78%) or at initial histological diagnosis (9% to 41%). Most regions test tumor tissue; few test both tumor tissue and blood; and none conduct blood mutation testing only. Testing practices in the US by type of site (academic vs community) will be presented. Conclusions: BRAF testing has global variability, impacting treatment decisions. Increased awareness and routine testing may lead to informed decisions regarding targeted therapies, such as encorafenib + cetuximab (where approved), in patients with BRAF V600E-mutant mCRC.[Table: see text]

Oral maintenance capecitabine versus active monitoring for patients with metastatic colorectal cancer (mCRC) who are stable or responding after 16 weeks of first-line treatment: Results from the randomized FOCUS4-N trial

3504

Background: There is extensive randomised evidence supporting the use of treatment breaks in mCRC, but breaks from treatment are not universally offered to patients despite reductions in toxicity, without detriment to OS. Prior trials have shown that the combination of Cp and bevacizumab extend PFS but not OS. FOCUS4-N explores oral maintenance Cp monotherapy in patients with disease control on first line therapy. Methods: FOCUS4 was a molecularly stratified trial programme registering patients with newly diagnosed mCRC from 88 hospitals in the UK. Whilst undergoing 16 wks of first line treatment, a sample of tumour was sent for laboratory testing to stratify their disease into molecular subtypes: MSI, BRAF, PIK3CA, TP53 and RAS mutations. For some molecular groups, a targeted therapy subtrial was available but entry into the FOCUS4-N trial was offered to those in whom a targeted subtrial was unavailable. Patients were randomised 1:1 between maintenance Cp therapy or AM. The primary outcome was PFS assessed using 8-wkly RECIST reported CT scans with quality of life (using EQ5D 8 weekly) and OS as secondary outcomes. Toxicity and tolerability were assessed 4-wkly. On progression, from the nadir, patients recommenced first line treatment. Cox regression was used to assess efficacy by intention-to-treat (ITT) with adjustment for tumour location, WHO status, metastatic burden, first line treatment and biomarker subtype. Results: Between March 2014 and March 2020, 254 patients were randomised (127 to Cp and 127 to AM). Baseline characteristics were balanced between groups but event rates were higher than anticipated in the AM group and the final analysis was triggered early as a result of the COVID-19 pandemic halting recruitment. The table presents results for PFS and OS. Compliance with treatment was good with per-protocol analysis results very similar to ITT (PFS HR=0.38 (95% CI 0.28-0.51)). Toxicity from Cp v AM was as expected with G≥2 fatigue (25% v 12%), diarrhoea (23% v 13%) and hand-foot syndrome (26% v 3%). Quality of life showed no statistically significant differences between the two arms. Conclusions: Despite strong evidence of prolongation of PFS with maintenance therapy, OS remains unaffected and FOCUS4-N provides additional evidence to support the use of treatment breaks as a safe management alternative for patients who are stable or responding well to first line treatment for mCRC. Cp without bevacizumab may be used to extend PFS, in the interval after 16 weeks of combination therapy. Clinical trial information: ISRCTN#90061546. [Table: see text]

Lack of an association between gallstone disease and bilirubin levels with risk of colorectal cancer: a Mendelian randomisation analysis

BACKGROUND

Epidemiological studies of the relationship between gallstone disease and circulating levels of bilirubin with risk of developing colorectal cancer (CRC) have been inconsistent. To address possible confounding and reverse causation, we examine the relationship between these potential risk factors and CRC using Mendelian randomisation (MR).

METHODS

We used two-sample MR to examine the relationship between genetic liability to gallstone disease and circulating levels of bilirubin with CRC in 26,397 patients and 41,481 controls. We calculated the odds ratio per genetically predicted SD unit increase in log bilirubin levels (ORSD) for CRC and tested for a non-zero causal effect of gallstones on CRC. Sensitivity analysis was applied to identify violations of estimator assumptions.

RESULTS

No association between either gallstone disease (P value = 0.60) or circulating levels of bilirubin (ORSD = 1.00, 95% confidence interval (CI) = 0.96-1.03, P value = 0.90) with CRC was shown.

CONCLUSIONS

Despite the large scale of this study, we found no evidence for a causal relationship between either circulating levels of bilirubin or gallstone disease with risk of developing CRC. While the magnitude of effect suggested by some observational studies can confidently be excluded, we cannot exclude the possibility of smaller effect sizes and non-linear relationships.

Circulating biomarkers and outcomes from a randomised phase 2 trial of gemcitabine versus capecitabine-based chemoradiotherapy for pancreatic cancer

BACKGROUND

The Phase 2 SCALOP trial compared gemcitabine with capecitabine-based consolidation chemoradiotherapy (CRT) in locally advanced pancreatic cancer (LAPC).

METHODS

Thirty-five systematically identified circulating biomarkers were analysed in plasma samples from 60 patients enroled in SCALOP. Each was measured in triplicate at baseline (prior to three cycles of gemcitabine-capecitabine induction chemotherapy) and, for a subset, prior to CRT. Association with overall survival (OS) was determined using univariable Cox regression and optimal thresholds delineating low to high values identified using time-dependent ROC curves. Independence from known prognostic factors was assessed using Spearman correlation and the Wilcoxon rank sum test prior to multivariable Cox regression modelling including independent biomarkers and known prognostic factors.

RESULTS

Baseline circulating levels of C-C motif chemokine ligand 5 (CCL5) were significantly associated with OS, independent of other clinicopathological characteristics. Patients with low circulating CCL5 (CCL5low) had a median OS of 18.5 (95% CI 11.76-21.32) months compared to 11.3 (95% CI 9.86-15.51) months in CCL5high; hazard ratio 1.95 (95% CI 1.04-8.65; p = 0.037).

CONCLUSIONS

CCL5 is an independent prognostic biomarker in LAPC. Given the known role of CCL5 in tumour invasion, metastasis and the induction of an immunosuppressive micro-environment, targeting of CCL5-mediated pathways may offer therapeutic potential in pancreatic cancer.

CLINICAL TRIAL REGISTRATION

The SCALOP trial was registered with ISRCTN, number 96169987 (registered 29 May 2008).

Global BRAF testing practices in metastatic colorectal cancer

128

Background:The BRAF V600E mutation is a marker of poor prognosis in patients with metastatic colorectal cancer (mCRC). Targeted therapy, such as encorafenib plus cetuximab, is approved in the US/Europe for the treatment (tx) of BRAF V600E-mutated mCRC and demonstrated improved survival vs historical standard of care (SOC). Determining BRAF mutation status in mCRC is recommended by NCCN and ESMO guidelines although adherence to guidelines may not be uniform. This report’s objective is to communicate global survey results of mCRC BRAF testing practices. Identifying regions where BRAF testing is not SOC may help identify where education efforts are needed improve effective tx decision making. Methods: Oncology tx centers were identified from a registry and public information. Centers were selected for research experience, historic data quality, and estimated mCRC patients. A BRAF testing practices survey using an online platform of verified centers was conducted March-August 2020; 395 centers/38 countries have responded thus far. Results: Respondents indicated BRAF-mutation testing is performed as SOC for patients with mCRC in most regions; Eastern Europe and South America are exceptions: only 47% (45/95) and 45% (9/20) of centers, respectively routinely performed mutation testing. Most test tumor tissue, few test both tumor tissue or blood, and none conduct blood mutation testing only. Most regions perform BRAF testing at initial diagnosis or confirmation of advanced disease. Individual country statistics will be presented. Conclusions: BRAF testing has global variability, impacting tx decisions. Increased awareness and routine testing may lead to informed decisions regarding targeted therapies, such as encorafenib plus cetuximab where approved, in patients with BRAF V600E-mutant mCRC.

[Table: see text]

Tumor bulk as a prognostic biomarker and predictor of benefit from anti-EGFR therapy in patients with metastatic colorectal cancer: Analysis of 476 patients from the ARCAD Clinical Trials Program

108

Background: Primary tumor sidedness has emerged as a prognostic and predictive biomarker for patients (pts) with metastatic colorectal cancer (mCRC). Tumor bulk has also been postulated to predict response to anti-EGFR therapy. We sought to evaluate the role of tumor bulk as a predictive biomarker to anti-EGFR therapy in pts with left- (LS) and right-sided (RS) mCRC. Methods: Data from 476 pts with mCRC enrolled across 2 first-line trials of anti-EGFR plus chemotherapy versus chemotherapy were pooled. Pts were included if there was available information on tumor sidedness and tumor bulk. All were KRAS wild-type and BRAF wild-type or unknown BRAF status. The right colon was defined as the cecum through the transverse colon, and the left colon as the splenic flexure through the rectum. Tumor bulk was the mean tumor size of target lesions at baseline, bulky defined as > 3.5 cm. Overall survival (OS) and progression-free survival (PFS) were assessed using Kaplan-Meier and Cox models adjusting for performance status (PS), platelet count, primary tumor (PT) resection, number of metastatic sites, and stratified by study. Results: Pts with bulky tumors (211, 44%) had higher PS, white blood cell and platelet counts, higher CEA, fewer sites of metastatic disease, more liver than lung metastases, and fewer had PT resection. OS and PFS medians in months (mos) are presented in the table with 95% confidence intervals (95%CIs). Bulky tumors had inferior median OS compared with non-bulky (mOS, 17.9 vs. 21.3 mos, HRadj 1.33, 95% CI 1.05-1.69, P = 0.016) although median PFS was similar (mPFS, 8.6 vs. 8.7 mos, HRadj 1.15, 95% CI 0.92-1.42, P = 0.21). Conclusions: Tumor bulk is an independent prognostic factor for OS in KRAS wild-type and BRAF wild-type or unknown BRAF status pts. Pts with non-bulky RS tumors have survival outcomes similar to pts with bulky LS tumors. Although the mPFS for pts with RS tumors treated with anti-EGFR therapy was the lowest across subgroups, this finding was not statistically significant. Further research is warranted into whether pts with bulky RS tumors benefit from anti-EGFR therapy. Clinical trial information: NCT00182715, NCT00640081. [Table: see text]

Abstract 3867: STAT1-related antigen processing and presentation dictates prognosis in the fibroblast-rich subtype of stage II/III colon cancer

Background: Molecular subtyping of colon cancer (CC) has repeatedly identified a poor-prognostic group of patients, characterized by high levels of stroma (particularly fibroblast) in the tumor microenvironment. To date, the benefit of standard 5FU-based adjuvant chemotherapy in these high-fibroblast (HiFi) patients has been unclear. Given TGF-β signaling is associated with HiFi tumors, a number of recent clinical trials have focussed on targeting TGF-β in these patients. While these efforts are ongoing, we set out to identify novel therapeutically-relevant biological signaling within HiFi tumors.

Methods: Untreated stage II (n=215) and stage II/III (n=258) tumors were assigned a fibroblast score, using single-sample gene set enrichment analysis, enabling stratification into HiFi and LoFi groups based on their histology and transcriptome. Supervised stratification, based on relapse-free survival, within the HiFi group allowed for in silico discovery, interrogation and independent validation of the HiFi-specific biology underpinning relapse. Upstream regulators of these processes were identified as potential therapeutic targets, and assessed in an in vitro co-culture model, to confirm mechanistic signaling, and an in vivo HiFi model, to confirm efficacy.

Results: We confirmed the poor prognosis of the HiFi group (p = 0.008), followed by discovery and independent validation of the prognostic value of STAT1-related signaling in stratifying HiFi tumors based on disease relapse (HR 0.2 (0.1-0.5) and 0.09 (0.02-0.47)). This signaling was significantly associated with activation of antigen processing and presentation in specific immune lineages (p &lt; 0.001). In line with the upstream regulator analysis, treatment with poly I:C (a TLR3 agonist) increased STAT1-related signaling and antigen processing in an in vitro macrophage-stromal co-culture system.

Conclusions: We have found that increased levels of STAT1-related signaling, resulting in antigen processing and presentation in specific subclasses of immune cells, is associated with reduced risk of recurrence in the otherwise poor-prognostic HiFi subtype of CC. Using in silico and in vitro methods, we demonstrate that poly I:C is a potential therapeutic option for patients with stromal-rich tumors. Results from ongoing in vivo validation in a HiFi mouse model will provide preclinical evidence of the utility of poly I:C in this setting and support a phase II clinical trial.

Citation Format: Amy M. McCorry, Niamh A. Leonard, Rene Jackstadt, Dustin J. Flanagan, Owen J. Sansom, Tim Maughan, Simon Leedham, Emma M. Kerr, Aideen E. Ryan, Mark Lawler, Philip D. Dunne, ACRCelerate and S:CORT consortia. STAT1-related antigen processing and presentation dictates prognosis in the fibroblast-rich subtype of stage II/III colon cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3867.

A phase 1 trial of the safety, tolerability and biological effects of intravenous Enadenotucirev, a novel oncolytic virus, in combination with chemoradiotherapy in locally advanced rectal cancer (CEDAR)

BACKGROUND

Chemoradiotherapy remains the standard of care for locally advanced rectal cancer. Efforts to intensify treatment and increase response rates have yet to yield practice changing results due to increased toxicity and/or absence of increased radiosensitization. Enadenotucirev (EnAd) is a tumour selective, oncolytic adenovirus which can be given intravenously. Pre-clinical evidence of synergy with radiation warrants further clinical testing and assessment of safety with radiation.

METHODS

Eligibility include histology confirmed locally advanced rectal cancer that require chemoradiation. The trial will use a Time-to-Event Continual Reassessment Model-based (TiTE-CRM) approach using toxicity and efficacy as co-primary endpoints to recommend the optimal dose and treatment schedule 30 patients will be recruited. Secondary endpoints include pathological complete response the neoadjuvant rectal score. A translational program will be based on a mandatory biopsy during the second week of treatment for 'proof-of-concept' and exploration of mechanism. The trial opened to recruitment in July 2019, at an expected rate of 1 per month for up to 4 years.

DISCUSSION

Chemoradiation with Enadenotucirev as a radiosensitiser in locally Advanced Rectal cancer (CEDAR) is a prospective multicentre study testing a new paradigm in radiosensitization in rectal cancer. The unique ability of EnAd to selectively infect tumour cells following intravenous delivery is an exciting opportunity with a clear translational goal. The novel statistical design will make efficient use of both toxicity and efficacy data to inform subsequent studies.

TRIAL REGISTRATION

ClinicalTrial.gov, NCT03916510. Registered 16th April 2019.

Treatment effects (TEs) of EGFR monoclonal antibodies (mAbs) in metastatic colorectal cancer (mCRC) patients (pts) with KRAS, NRAS, and BRAF mutation (MT) status: Individual patient data (IPD) meta-analysis of randomized trials from the ARCAD database

4090

Background: EGFR mAbs have become incorporated into clinical practice for the management of mCRC over the last decade. KRAS and NRAS mutations are used as predictive biomarkers and BRAF V600E mutations are associated with an adverse prognosis. The observed TE within biomarker subpopulations has varied between studies. Methods: IPD from randomized trials with head-to-head comparison between EGFR mAb versus no EGFR mAb (chemotherapy alone or BSC) in mCRC, across all lines of therapy (first, second and later), were pooled. Biomarker subpopulations are defined in the table. Overall survival (OS) and progression-free survival (PFS) were compared between groups by Cox model, stratified by studies and adjusted by age, gender, and performance status. TEs were estimated by adjusted hazard ratio (HRadj) and 95% confidence interval (CI). Within each biomarker subgroup, EGFR mAb efficacy was explored according to multiple exploratory factors, including line of therapy, type of backbone chemo, gender, sidedness and site of metastasis. Interaction tests were performed. P-values < 0.01 were considered statistically significant to account for multiple comparisons. Results: 5729 pts from 8 studies with data available for ≥ 1 biomarker were analysed. PFS benefits (median 9.2 mos in EGFR mAbs, 8.0 mos in no EGFR mAbs) were confirmed in triple-WT pts, but not for OS (refer to table). No OS/PFS benefits were observed for pts with any of the MT tumors. Exploratory analyses showed a potential detrimental TE of EGFR mAbs in KRAS MT mCRC with liver metastasis (OS: HRadj 1.22, p = .003, pinteraction .0056; PFS: HRadj 1.24, p = .0009, pinteraction .0008). These results were confirmed within the subgroup of pts with all 3 biomarkers available. Conclusions: This is the largest IPD analysis to explore the predictive value of RAS/BRAF biomarkers in mCRC. Our findings demonstrate that there is no evidence of efficacy of EGFR mAbs in KRAS, BRAF and/or NRAS MT mCRC. EGFR mAbs might have a detrimental effect in KRAS MT mCRC with liver metastases. [Table: see text]

A phase II open label, randomised study of ipilimumab with temozolomide versus temozolomide alone after surgery and chemoradiotherapy in patients with recently diagnosed glioblastoma: the Ipi-Glio trial protocol

BACKGROUND

Median survival for patients with glioblastoma is less than a year. Standard treatment consists of surgical debulking if feasible followed by temozolomide chemo-radiotherapy. The immune checkpoint inhibitor ipilimumab targets cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and has shown clinical efficacy in preclinical models of glioblastoma. The aim of this study is to explore the addition of ipilimumab to standard therapy in patients with glioblastoma.

METHODS/DESIGN

Ipi-Glio is a phase II, open label, randomised study of ipilimumab with temozolomide (Arm A) versus temozolomide alone (Arm B) after surgery and chemoradiotherapy in patients with recently diagnosed glioblastoma. Planned accrual is 120 patients (Arm A: 80, Arm B: 40). Endpoints include overall survival, 18-month survival, 5-year survival, and adverse events. The trial is currently recruiting in seven centres in the United Kingdom.

TRIAL REGISTRATION

ISRCTN84434175. Registered 12 November 2018.

Prognostic and predictive impact of primary tumor sidedness in first-line trials for advanced colorectal cancer: An analysis of 7,828 patients in the ARCAD database

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Background: Unplanned subgroup analyses from several studies have suggested primary tumor sidedness (PTS) as a potential prognostic and predictive parameter in metastatic colorectal cancer (mCRC). We aimed to investigate the prognostic and predictive impact of PTS on outcomes. Methods: PTS data of 7,828 mCRC patients (pts) from 10 first-line randomized trials in the ARCAD database were pooled. PTS was defined as right-sided (RS) or left-sided (LS) if tumor arose from the cecum to the hepatic flexure or from the splenic flexure to the rectum, respectively; transverse colon cancers were not included. Overall survival (OS) and progression-free survival (PFS) were assessed using Kaplan-Meier and Cox models adjusting for age, sex, performance status (PS), prior radiation/chemo, and stratified by treatment arm. Predictive value was tested by interaction term between PTS and treatment (anti-EGFR plus chemotherapy vs. chemotherapy alone). Results: Compared to RS pts (2407, 31%), LS pts (5421, 69%) had better OS (median: 21.6 v 16.8 mos; HRadj: 0.73, 95% CI 0.69-0.78, P < .001) and PFS (median 8.4 v 7.2 mos; HRadj: 0.81, 95% CI 0.76-0.86, P < .001). Results were consistent among subgroups defined by age, sex, PS, metastatic sites and chemo backbone (irinotecan- and oxaliplatin-based). Interaction between PTS and KRAS mutation was significant (Pinteraction< .001): LS is associated with better prognosis only among KRAS wild-type (wt) (HRadj: OS 0.62, 95% CI, 0.55-0.70; PFS 0.71, 95% CI 0.63-0.80), but not among KRAS mutated pts. Among KRAS wt pts, survival benefit from anti-EGFR was observed for LS, but not for RS (table). Conclusions: The prognostic value of PTS is restricted to the KRAS wt population. PTS is predictive of anti-EGFR efficacy, with a significant improvement of survival for LS mCRC pts. These results suggest treatment stratification in mCRC studies by both PTS and KRAS status.

[Table: see text]

Translational analysis from SCALOP trial: CCL5 as a prognostic biomarker and a potentially actionable target in locally advanced pancreatic cancer (LAPC)

740

Background: SCALOP was a multi-centre phase II RCT where 114 patients with LAPC were received 3 cycles of Gemcitabine and Capecitabine (GEMCAP) and those with stable/responding disease (n = 74) were randomised to Gem-RT or Cap-RT. The trial showed superiority of Cap-RT. Baseline blood samples of randomised patients were analysed for 35 circulating biomarkers. In vivo study was undertaken with candidate biomarker (CCL5) to test actionability. Methods: Patient bloods were tested using R&D multiplexed magnetic Luminex assays and IGF-1, TGF-b1 and b-NGF DuoSet ELISA. Orthotropic KrasG12D;P53R172H;PDXcre (KPC) tumors were implanted in Bl6-mice and treated with Gem, CCR5-inhibitor (CCR5i) maraviroc (MV), PD1 inhibitor (PD1i), PD1i+MV alone and in combination with MRI guided small animal Radiotherapy (RT). Immunophenotyping was performed by IHC and Aurora Cytek spectral flow cytometry. Results: Baseline biomarker data was available on 63/74 randomised patients. Of the 35 biomarkers tested, only CCL5 was found to be significantly associated with OS with a median OS of 18.5 (95% CI: 11.76-21.32) vs 11.3 (9.86-15.51) months (low vs high), and HR 1.37 (95% CI:1.04-3.65; p = 0.037) in the Cox multivariable model. Treatment of orthotopic KPC tumors revealed that combination of MV+PD1i+RT resulted in tumour growth inhibition and a switch of tumour macrophages from M2 to M1 accompanied by increase in infiltration of cytotoxic CD8+ Tcells and NK cells. Conclusions: Previous pre-clinical studies reported CCL5-CCR5 axis as a poor prognostic marker and a possible cause of immune-resistance in pancreatic cancer. Herein we have demonstrated in prospectively collected clinical trial blood samples that high circulating CCL5 is associated with poor prognosis in LAPC. CCR5 inhibitor in combination with RT+PD1i may overcome immune-resistance, and should be tested in clinical trials. Clinical trial information: 96169987 .

Induction oxaliplatin capecitabine followed by switch to carboplatin-paclitaxel based RT versus continuing oxaliplatin capecitabine RT in operable esophageal adenocarcinoma: Survival analysis of the randomized phase II neoscope trial

373

Background: Initial results of the NEOSCOPE trial comparing pre-operative CarPac vs OxCap based chemoradiotherapy (CRT) in patients with adenocarcinoma of the oesophagus or oesophagogastric junction showed comparable toxicity and improvement in pathological complete response (pCR) in favour of the CarPacRT. Here we report survival after a median follow-up of 40.7 months (95% CI: 45.1-53.6). Methods: NEOSCOPE was an open, randomised, ‘pick a winner’ phase II trial. Patients with resectable oesophageal adenocarcinoma ≥ cT3 and/or ≥ cN1 were randomised to OxCapRT (oxaliplatin 85 mg/m2 day 1, 15, 29; capecitabine 625 mg/m2 bd on days of RT) or CarPacRT (carboplatin AUC2; paclitaxel 50 mg/m2 day 1, 8, 15, 22, 29). RT dose was 45 Gy/25 fractions/5 weeks. Induction OxCap (2 cycles) was given prior to CRT. Surgery was performed 6–8 weeks after CRT.The primary endpoint was pCR, secondary endpoints were toxicity, PFS and OS. Results: Between Oct 2013 and Feb 2015, 85 patients were recruited from 17 UK centres. Median OS was not reached in the CarPacRT group and was 41.72 months (95% CI 19.58-.)in the OxCap group (HR 0.56[95% CI 0.29-1.07]; p=0.079). 3-year and 5-year OS rates were 74% (95% CI 58%-85%) and 54% (95% CI 34%-71%) (CarPacRT), and 52% (95% CI 35%-67%) and 39% (95% CI 21%-56%) (OxCapRT). Median PFS (not reached vs 35.3 months, HR=0.61 [95% CI 0.33-1.12]; p=0.111) and metastatic PFS (not reached vs 39.0 months, HR=0.61 [95% CI 0.32-1.14], p=0.118) both favoured the CarPacRT arm. Local recurrence rate was low (OxCapRT= 10%; CarPacRT= 7%). The OS benefit for CarPacRT was consistent across subgroups but not statistically significant. Conclusions: In this longer term analysis there was some evidence that induction OxCap followed by switch to CarPacRT was superior to continuing OxCapRT, with efficacy similar to that seen in other published studies such as ‘CROSS’ and ‘FLOT’. Taken together with the previously published pCR results CarPacRT rather than OxCapRT warrants inclusion in future trials. Funding: Cancer Research UK (C44694/A14614). Clinical trial information: NCT01843829.

Modifiable pathways for colorectal cancer: a mendelian randomisation analysis

BACKGROUND

Epidemiological studies have linked lifestyle, cardiometabolic, reproductive, developmental, and inflammatory factors to the risk of colorectal cancer. However, which specific factors affect risk and the strength of these effects are unknown. We aimed to examine the relationship between potentially modifiable risk factors and colorectal cancer.

METHODS

We used a random-effects model to examine the relationship between 39 potentially modifiable risk factors and colorectal cancer in 26 397 patients with colorectal cancer and 41 481 controls (ie, people without colorectal cancer). These population data came from a genome-wide association study of people of European ancestry, which was amended to exclude UK BioBank data. In the model, we used genetic variants as instruments via two-sample mendelian randomisation to limit bias from confounding and reverse causation. We calculated odds ratios per genetically predicted SD unit increase in each putative risk factor (ORSD) for colorectal cancer risk. We did mendelian randomisation Egger regressions to identify evidence of potential violations of mendelian randomisation assumptions. A Bonferroni-corrected threshold of p=1·3 × 10-3 was considered significant, and p values less than 0·05 were considered to be suggestive of an association.

FINDINGS

No putative risk factors were significantly associated with colorectal cancer risk after correction for multiple testing. However, suggestive associations with increased risk were noted for genetically predicted body fat percentage (ORSD 1·14 [95% CI 1·03-1·25]; p=0·0086), body-mass index (1·09 [1·01-1·17]; p=0·023), waist circumference (1·13 [1·02-1·26]; p=0·018), basal metabolic rate (1·10 [1·03-1·18]; p=0·0079), and concentrations of LDL cholesterol (1·14 [1·04-1·25]; p=0·0056), total cholesterol (1·09 [1·01-1·18]; p=0·025), circulating serum iron (1·17 [1·00-1·36]; p=0·049), and serum vitamin B12 (1·21 [1·04-1·42]; p=0·016), although potential pleiotropy among genetic variants used as instruments for vitamin B12 constrains the finding. A suggestive association was also noted between adult height and increased risk of colorectal cancer (ORSD 1·04 [95% CI 1·00-1·08]; p=0·032). Low blood selenium concentration had a suggestive association with decreased risk of colorectal cancer (ORSD 0·85 [95% CI 0·75-0·96]; p=0·0078) based on a single variant, as did plasma concentrations of interleukin-6 receptor subunit α (also based on a single variant; 0·98 [0·96-1·00]; p=0·035). Risk of colorectal cancer was not associated with any sex hormone or reproductive factor, serum calcium, or circulating 25-hydroxyvitamin D concentrations.

INTERPRETATION

This analysis identified several modifiable targets for primary prevention of colorectal cancer, including lifestyle, obesity, and cardiometabolic factors, that should inform public health policy.

FUNDING

Cancer Research UK, UK Medical Research Council Human Genetics Unit Centre, DJ Fielding Medical Research Trust, EU COST Action, and the US National Cancer Institute.

A systematic review of health economic evaluations of proton beam therapy for adult cancer: Appraising methodology and quality

BACKGROUND AND PURPOSE

With high treatment costs and limited capacity, decisions on which adult patients to treat with proton beam therapy (PBT) must be based on the relative value compared to the current standard of care. Cost-utility analyses (CUAs) are the gold-standard method for doing this. We aimed to appraise the methodology and quality of CUAs in this area.

MATERIALS AND METHODS

We performed a systematic review of the literature to identify CUA studies of PBT in adult disease using MEDLINE, EMBASE, EconLIT, NHS Economic Evaluation Database (NHS EED), Web of Science, and the Tufts Medical Center Cost-Effectiveness Analysis Registry from 1st January 2010 up to 6th June 2018. General characteristics, information relating to modelling approaches, and methodological quality were extracted and synthesized narratively.

RESULTS

Seven PBT CUA studies in adult disease were identified. Without randomised controlled trials to inform the comparative effectiveness of PBT, studies used either results from one-armed studies, or dose-response models derived from radiobiological and epidemiological studies of PBT. Costing methods varied widely. The assessment of model quality highlighted a lack of transparency in the identification of model parameters, and absence of external validation of model outcomes. Furthermore, appropriate assessment of uncertainty was often deficient.

CONCLUSION

In order to foster credibility, future CUA studies must be more systematic in their approach to evidence synthesis and expansive in their consideration of uncertainties in light of the lack of clinical evidence.

Abstract B40: High circulating CCL5 is associated with poor prognosis in locally advanced pancreatic cancer (LAPC): Biomarker analysis from the randomized phase II SCALOP trial

Background: SCALOP recruited 114 patients with LAPC. Induction chemotherapy consisted of 3 cycles of gemcitabine and capecitabine (GEMCAP). Patients with nonprogression (n=74) were randomized to GEM or CAP based CRT (50.4Gy/28 fractions). Blood samples collected at baseline were analyzed for 35 angiogenic and immune biomarkers reported to be of prognostic/predictive value in pancreatic cancer.

Methods: IGF-1, TGF-b1, and b-NGF were analyzed using R & D DuoSet ELISA systems and the signal detected using a POLARstar Omega plate reader. The remaining biomarkers were assessed using R & D multiplexed magnetic Luminex assays and measured using a Luminex Magpix. Assays were performed in triplicate.

Statistical Analysis: Univariate Cox proportional hazard models were used as continuous variable to determine the association with overall survival (OS). Multiple comparisons were adjusted using the False Discovery Rate (FDR). Those found to be significant at the q value &lt;0.2 were then further investigated for independence from existing clinical characteristics (i.e., CA19-9, WHO PS and age). Of those found to be independent, optimal thresholds delineating low to high values were found using the R “survivalROC” package based on time-dependent ROC curves from censored survival data and their corresponding area under the curve (AUC). The dichotomized biomarkers, split at the optimal threshold, were then associated with OS using univariate and multivariable Cox proportional hazard models.

Results: Biomarker data were available on 63/74 patients. 57% (36/63) were male, 56% (35/63) were age &lt;65, 59% (37/63) had WHO PS 0 compared to 1, 51% (32/63) received gemcitabine, median CA19.9 was 233IU/L (IQR 75,801) and median tumor diameter was 3.8cm (IQR 3, 4.8). Of the 35 biomarkers tested, only CCL5, IL3, and IFN had significant associations with OS. CCL5 and IL3 were then found to be independent of existing clinical characteristics and were taken forward, where their optimal thresholds were found to be 1.27 micg/ml (sensitivity 64%; specificity 100%) and 57.75 pg/ml (sensitivity 83%; specificity 100%), respectively. CCL5, but not IL3, was found to be significantly associated with OS once dichotomized at its optimal threshold, with a median OS of 18.5 (95% CI: 11.76-21.32) vs. 11.3 (9.86-15.51) months, HR 1.37 (95% CI:1.04-3.65; p=0.037) in the Cox multivariable model. Moreover, biomarker signatures incorporating both CCL5 and IL3 (continuous variable) with age, PS and CA19.9 were prognostic: CCL5 signature:19.2 vs. 10.8 mo (HR 2.79, p=0.001) IL3 signature: 18.5 vs. 11.2 mo (HR 2.35, p=0.006) CCL5/IL3 signature: 18.7 vs. 11.2 mo, (HR 2.25, p=0.11).

Conclusion: High circulating CCL5 has a significantly worse prognosis. This is consistent with preclinical literature that demonstrates the role of CCL5 in tumor invasion/metastasis and induction of an immunosuppressive microenvironment through Treg infiltration. We are currently conducting in vivo experiments involving CCR5 antagonists and immunotherapy in orthotopic mouse models.

Citation Format: Frances Willenbrock, Catrin Cox, Charlotte Wilhelm-Benartzi, Aswin Abraham, Robert Owens, Ahmad Sabbagh, Chris Hurt, Tim Maughan, Eric O'Neill, Somnath Mukherjee. High circulating CCL5 is associated with poor prognosis in locally advanced pancreatic cancer (LAPC): Biomarker analysis from the randomized phase II SCALOP trial [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2019 Sept 6-9; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2019;79(24 Suppl):Abstract nr B40.