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Table S1: Baseline patient demographics and disease characteristics. Table S2: mRNA/IHC AREG/EREG concordance table. Figure S1: AREG/EREG IHC scatterplot. Table S3: Prognostic effect of dichotomous AREG/EREG. Table S4: AREG/EREG and RECIST response rate. Table S5: AREG and EREG as individual continuous variables. Table S6: AREG/EREG predictive analyses adjusted for BRAF mutation, PTL and peritoneal metastases. Table S7: Exploratory analyses of different AREG/EREG cut points. Table S8: AREG/EREG IHC in biopsy and resection specimens.

Purpose:High tumor mRNA levels of the EGFR ligands amphiregulin (AREG) and epiregulin (EREG) are associated with anti-EGFR agent response in metastatic colorectal cancer (mCRC). However, ligand RNA assays have not been adopted into routine practice due to issues with analytic precision and practicality. We investigated whether AREG/EREG IHC could predict benefit from the anti-EGFR agent panitumumab.Experimental Design:Artificial intelligence algorithms were developed to assess AREG/EREG IHC in 274 patients from the PICCOLO trial of irinotecan with or without panitumumab (Ir vs. IrPan) in RAS wild-type mCRC. The primary endpoint was progression-free survival (PFS). Secondary endpoints were RECIST response rate (RR) and overall survival (OS). Models were repeated adjusting separately for BRAF mutation status and primary tumor location (PTL).Results:High ligand expression was associated with significant PFS benefit from IrPan compared with Ir [8.0 vs. 3.2 months; HR, 0.54; 95% confidence interval (CI), 0.37–0.79; P = 0.001]; whereas low ligand expression was not (3.4 vs. 4.4 months; HR, 1.05; 95% CI, 0.74–1.49; P = 0.78). The ligand-treatment interaction was significant (Pinteraction = 0.02) and remained significant after adjustment for BRAF-mutation status and PTL. Likewise, RECIST RR was significantly improved in patients with high ligand expression (IrPan vs. Ir: 48% vs. 6%; P < 0.0001) but not those with low ligand expression (25% vs. 14%; P = 0.10; Pinteraction = 0.01). The effect on OS was similar but not statistically significant.Conclusions:AREG/EREG IHC identified patients who benefitted from the addition of panitumumab to irinotecan chemotherapy. IHC is a practicable assay that may be of use in routine practice.

PURPOSE Despite extensive randomized evidence supporting the use of treatment breaks in metastatic colorectal cancer (mCRC), they are not universally offered to patients despite improvements in quality of life without detriment to overall survival (OS). FOCUS4-N was set up to explore the impact of oral maintenance therapy in patients who are responding to first-line therapy. METHODS FOCUS4 was a molecularly stratified trial program that registered patients with newly diagnosed mCRC. The FOCUS4-N trial was offered to patients in whom a targeted subtrial was unavailable or biomarker tests failed. Patients were randomly assigned using a 1:1 ratio between maintenance capecitabine and active monitoring (AM). The primary outcome was progression-free survival (PFS) with secondary outcomes including OS toxicity and tolerability. RESULTS Between March 2014 and March 2020, 254 patients were randomly assigned (127 to capecitabine and 127 to AM) across 88 UK sites. Baseline characteristics were balanced. There was strong evidence of efficacy for PFS (hazard ratio = 0.40; 95% CI, 0.21 to 0.75; P < .0001), but no significant improvement in OS (hazard ratio, 0.93; 95% CI, 0.69 to 1.27; P = .66) was observed. Compliance with treatment was good, and toxicity from capecitabine versus AM was as expected with grade ≥ 2 fatigue (25% v 12%), diarrhea (23% v 13%), and hand-foot syndrome (26% v 3%). Quality of life showed little difference between the groups. CONCLUSION Despite strong evidence of disease control with maintenance therapy, OS remains unaffected and FOCUS4-N provides additional evidence to support the use of treatment breaks as safe management alternatives for patients who are stable or responding to first-line treatment for mCRC. Capecitabine without bevacizumab may be used to extend PFS in the interval after 16 weeks of first-line therapy.

The international FOxTROT trial, recently published in the Journal of Clinical Oncology, (ref awaited) is the first randomised controlled trial testing neoadjuvant chemotherapy (NAC) with oxaliplatin and 5-fluorouracil in locally advanced but operable colon cancer. 1053 patients with operable, radiologically staged T3-T4, N1-2, M0 colon cancer were recruited from over 100 sites in the UK, Sweden and Denmark. Patients were randomised to 6 weeks of planned chemotherapy before resectional surgery, followed by adjuvant chemotherapy; or upfront surgery followed by adjuvant chemotherapy (total 18 weeks in both arms). NAC was safe and, compared with standard treatment, there was no increase in surgical complications, a higher R0 rate (95% vs 89%, p0.001), and significant primary and nodal pathological downstaging. The trial met its primary endpoint with fewer patients experiencing recurrent or residual disease at 2 years with NAC compared with control: (16.8% vs 21.2%, risk ratio=0.74, p=0.042). Rapid translation of these results into patient benefit is expected, particularly as the chemotherapeutic agents are already used routinely and do not incur any additional cost or toxicity. However, offering NAC as standard care for advanced colon cancer requires adaptations to current treatment pathways so presents organisational challenges. To date, the Leeds Cancer Centre, St James's University Hospital, UK has commenced 64 patients on the novel pathway following presentation and adoption of the FOxTROT results. Here, we describe our experience and share strategies developed across the MDT to minimise impact on person hours, service capacity and budget, whilst building patient safety and confidence.

Purpose: High tumor mRNA levels of the EGFR ligands amphiregulin (AREG) and epiregulin (EREG) are associated with anti-EGFR agent response in metastatic colorectal cancer (mCRC). However, ligand RNA assays have not been adopted into routine practice due to issues with analytic precision and practicality. We investigated whether AREG/EREG IHC could predict benefit from the anti-EGFR agent panitumumab. Experimental Design: Artificial intelligence algorithms were developed to assess AREG/EREG IHC in 274 patients from the PICCOLO trial of irinotecan with or without panitumumab (Ir vs. IrPan) in RAS wild-type mCRC. The primary endpoint was progression-free survival (PFS). Secondary endpoints were RECIST response rate (RR) and overall survival (OS). Models were repeated adjusting separately for BRAF mutation status and primary tumor location (PTL). Results: High ligand expression was associated with significant PFS benefit from IrPan compared with Ir [8.0 vs. 3.2 months; HR, 0.54; 95% confidence interval (CI), 0.37–0.79; P = 0.001]; whereas low ligand expression was not (3.4 vs. 4.4 months; HR, 1.05; 95% CI, 0.74–1.49; P = 0.78). The ligand-treatment interaction was significant (Pinteraction = 0.02) and remained significant after adjustment for BRAF-mutation status and PTL. Likewise, RECIST RR was significantly improved in patients with high ligand expression (IrPan vs. Ir: 48% vs. 6%; P < 0.0001) but not those with low ligand expression (25% vs. 14%; P = 0.10; Pinteraction = 0.01). The effect on OS was similar but not statistically significant. Conclusions: AREG/EREG IHC identified patients who benefitted from the addition of panitumumab to irinotecan chemotherapy. IHC is a practicable assay that may be of use in routine practice.

BACKGROUND: Primary tumour location (PTL) is being adopted by clinicians to guide treatment decisions in metastatic colorectal cancer (mCRC). Here we test PTL as a predictive marker for panitumumab efficacy, and examine its relationship with an extended biomarker profile. We also examine rectal tumours as a separate location. PATIENTS AND METHODS: mCRC patients from the second-line PICCOLO trial of irinotecan versus irinotecan/panitumumab (IrPan). PTL was classified as right-PTL, left-PTL or rectal-PTL. PTL was assessed as a predictive biomarker for IrPan effect in RAS-wild-type (RAS-wt) patients (compared with irinotecan alone), then tested for independence alongside an extended biomarker profile (BRAF, epiregulin/amphiregulin (EREG/AREG) and HER3 mRNA expression). RESULTS: PTL data were available for 1180 patients (98.5%), of whom 558 were RAS-wt. High HER3 expression was independently predictive of panitumumab overall survival improvement, but PTL and EREG/AREG were not. IrPan progression-free survival (PFS) improvement compared with irinotecan was seen in left-PTL [hazard ratio (HR) = 0.61, P = 0.002) but not right-PTL (HR = 0.98, P = 0.90) (interaction P = 0.05; RAS/BRAF-wt interaction P = 0.10), or in rectal-PTL (HR = 0.82, P = 0.20) (interaction P = 0.14 compared with left-PTL; RAS/BRAF-wt interaction P = 0.04). Patients with right-PTL and high EREG/AREG or HER3 expression, had IrPan PFS improvement (high EREG/AREG HR = 0.20, P = 0.04; high HER3 HR = 0.33, P = 0.10) compared with irinotecan. Similar effect was seen for rectal-PTL patients (high EREG/AREG HR = 0.44, P = 0.03; high HER3 HR = 0.34, P = 0.05). CONCLUSIONS: RAS-wt patients with left-PTL are more likely to have panitumumab PFS advantage than those with right-PTL or rectal-PTL. However, an extended biomarker panel demonstrated significant heterogeneity in panitumumab PFS effect within a tumour location. AREG/EREG and HER3 mRNA expression identifies patients with right-PTL or rectal-PTL who achieve similar PFS effect with panitumumab as left-colon patients. Testing could provide a more reliable basis for clinical decision making. Further validation and development of these biomarkers is required to optimise routine patient care. CLINICAL TRIAL REGISTRATION: ISRCTN identifier: ISRCTN93248876. ispartof: ANNALS OF ONCOLOGY vol:31 issue:8 pages:1021-1029 ispartof: location:England status: published

203 Background: AREG and EREG are ligands of EGFR. AI assisted IHC evaluation of tumor AREG/EREG expression predicted benefit from anti-EGFR therapy in a retrospective analysis of the PICCOLO trial of second-line irinotecan ± panitumumab. Here, we sought to validate those findings through an analysis of patients who received anti-EGFR therapy during routine care for mCRC. Methods: Patients (pts) with available archival FFPE tumor tissue who received panitumumab or cetuximab ± chemotherapy at any time for treatment of mCRC at 8 UK cancer centers were eligible. Central RAS testing by next generation sequencing (NGS) was performed for pts where extended RAS testing had not been previously undertaken. RAS-mutant (mut) and RAS-unknown pts were excluded from the primary analysis population. AREG and EREG positive tumor cells were identified by IHC, performed locally at 6 of 8 sites. Pathologists annotated tumor areas on digital images of glass slides. AI algorithms calculated the percentage of tumor cells staining positive for AREG and EREG within tumor areas. More than 20% AREG and/or EREG tumor cell positivity was regarded as high biomarker expression, the optimal cut-point identified in PICCOLO. Study endpoints were progression-free survival (PFS), overall survival (OS), and locally reported response rate (RR) and disease control rate (DCR). Results: Of 541 pts recruited, 494 (91.3%) had adequate archival tissue for analysis. Central RAS testing was successfully performed in 255 of 393 (64.9%) pts without existing extended RAS results, leading to 45 exclusions, leaving 449 pts in the primary analysis population. 26 (5.8%) pts were BRAF-mut. 110 (24.5%) received concomitant FOLFOX and 304 (67.7%) FOLFIRI. After adjustment for additional prognostic factors, high AREG/EREG expression (n = 360; 80.2%) was associated with significantly prolonged PFS (HR 0.73; 95% CI, 0.56-0.95; p = 0.02), OS (HR 0.66 [0.50-0.86]; p = 0.002), and DCR (OR 1.92 [1.05-3.54]; p = 0.04), but not RR (unadjusted OR 1.39 [0.83-2.33]; p = 0.21). Median PFS in the high vs low biomarker groups was 8.5 vs 4.4 months; median OS 16.4 vs 8.9 months. The significant difference in OS (high vs low) was maintained in the subgroup with right-sided primary tumor location (n = 107; 23.8%) (HR 0.56 [0.37-0.86]; p = 0.007). Conclusions: High tumor AREG/EREG expression was associated with significantly prolonged PFS, OS and DCR among a cohort of pts treated with anti-EGFR therapy during routine care of mCRC. The prognostic effect observed validates the predictive effect of AREG/EREG seen in the PICCOLO trial, where AREG/EREG had no prognostic effect in patients receiving chemotherapy alone. A prospective biomarker-led trial is in set-up to support the use of AREG/EREG IHC in clinical practice.

204 Background: High CD3+ (all) and CD8+ (cytotoxic) T cell densities in the core (CT) and invasive margin (IM) of primary CRCs have been shown to be associated with superior prognosis at all stages of disease. Their predictive effect on benefit from adjuvant chemotherapy in early stage CRC has not been tested. Methods: FFPE samples from participants (pts) in the QUASAR trial (adjuvant fluorouracil/folinic acid vs observation in stage 2/3 CRC) were analysed for CD3 and CD8 immunohistochemistry (IHC). Pathologists annotated the core and peritumor areas on digital slide images. Artificial intelligence (AI) algorithms delineated the CT and IM, and calculated the densities (cells/mm2) of each marker in each region (CD3-CT, CD3-IM, CD8-CT, CD8-IM). Pts were randomly partitioned into test and validation sets (1:1). In the test set, each measure’s prognostic effect on recurrence-free interval (RFI) (primary endpoint), colorectal cancer mortality (CCM) and overall survival (OS) in each trial arm was assessed. Maximum likelihoods methods were used to develop optimal cut-points. Analyses were repeated in the validation set. Analysis of 425 pts in each set would give > 95% power (α = 0.05, 2-sided) to detect a twofold difference in recurrence risk. In predictive analyses, 2-year recurrence rate was the primary outcome; biomarker-treatment interactions were assessed. Results: Tumor tissue from 868 pts (797 [92%] stage 2; 531 [61%] colon) was analysed, with evaluable results for CD3-CT in 851 (98.0%), CD3-IM in 833 (96.0%), CD8-CT in 849 (97.0%) and CD8-IM in 820 (94.5%) pts. In the test set, optimal cut-points of 318, 798, 81 and 186 cells/mm2 were defined for CD3-CT, CD3-IM, CD8-CT and CD8-IM respectively. The recurrence rate in the high-risk group was twice that in the low-risk group for all measures (CD3-CT: rate ratio [RR] 2.00, [95%CI 1.33-2.94], p = 0.0008; CD3-IM: 2.38, [1.59-3.57], p < 0.00001; CD8-CT: 2.17, [1.59-3.57], p = 0.0001; CD8-IM: 2.13 [1.43-3.23], p = 0.0001), which was closely replicated in the validation set (CD3-CT: RR 1.96, [1.30-2.94], p = 0.002; CD3-IM: 1.79, [1.18-2.70], p = 0.005; CD8-CT: 1.72, [1.18-2.56], p = 0.005; CD8-IM: 1.72 [1.15-2.56], p = 0.008). In multivariate analyses, prognostic effects were similar in colon and rectal cancers, and in stage 2 and 3 disease. CD3/8 counts were not predictive of benefit from adjuvant chemotherapy, with similar efficacy in the high and low risk groups. Conclusions: AI-assisted CD3 and CD8 counts were strongly associated with tumor recurrence rates. With no biomarker-treatment interactions, proportional reductions in recurrence with chemotherapy were similar in high and low-risk disease. Hence, numbers of high-risk patients needed to treat to prevent one recurrence were about half the number for low-risk patients.

141 Background: Treatment for patients (pts) with metastatic colorectal cancer (mCRC) with unresectable liver metastases (mets) is usually chemotherapy (CT) +/- local ablative treatments. Immunotherapy (IO) effect is disappointing in mCRC with pMMR status so testing strategies to promote immune activation is key. Previous studies show that local ablative treatments may induce local immune activation and prime for IO response. Methods: This multi-center non-randomised early phase II study aims to test whether local liver therapy in combination with durvalumab and tremelimumab (durv/trem) will lead to immune response in liver metastases untreated locally. Eligible pts had non-resectable liver predominant mCRC and at least stable disease following 3-6 months first- or second line CT. Liver mets were amenable to radiofrequency ablation (RFA) or stereotactic radiotherapy (SBRT) allowing a total ablated volume of at least 25 cm3. At least 2 measurable liver or 1 liver and 1 extrahepatic lesions were left untreated locally. Tremelimumab 75 mg and durvalumab 1500 mg were given for 4 cycles followed by durvalumab 1500 mg every 4 weeks. During cycle 1, RFA and SBRT were performed concurrently.Primary endpoint was ORR per iRECIST in lesions untreated locally; secondary endpoints included feasibility and safety and progression free survival (PFS). According to an optimal Simon’s two-stage design to reject a ORR ≤ 10% with power of 90% under a ORR of 25% using a one-sided alpha of 5%, the study should be early stopped if there were ≤2 responses among the 21 first patients enrolled in the per protocol (PP) population (stage I) while ≥ 11 responses among 66 patients were needed to declare success. Results: Between March 2019 and March 2021, 23 pts were recruited from 6 centers in 4 countries; 21 pts started protocol treatment; 13 pts were treated with RFA; 8 pts with SBRT but 1 pt was ineligible out of 21. In the PP population (20 pts), median age was 57. Response to previous systemic CT was PR (75%) and SD (25%). No pt had prior surgery or local treatment to the liver. 60% had limited extra-hepatic disease (up to 2 sites). Median treatment duration was 85.0 days; all 20 pts received planned local ablative treatment. At best response assessment, 0% of patients had a CR or PR, 45% had SD and 55% PD. Median PFS was 2.2 months (95% CI: 1.8-3.6). At a median follow up of 11 months, 55% of pts had died. The study was closed due to futility. In patients treated with RFA + durv/trem, 30.8% had grade 3 toxicity; for SBRT +durv/trem it was 50%. Conclusions: In this phase II trial, combining IO with local ablative therapy in liver predominant mCRC did not result in responses in lesions untreated locally. Further strategies are required to improve IO response in this clinical setting. Clinical trial information: 2017-001375-22 .

Outcomes inPatients with newly diagnosed mCRC were registered into FOCUS4 and tested forFOCUS4-C was conducted between April 2017 and Mar 2020 during which time 718 patients were registered; 247 (34%) wereIn this phase II randomized trial, adavosertib improved PFS compared with AM and demonstrates potential as a well-tolerated therapy for

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 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.

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.

TPS3645 Background: The prognostic advantage of early stage deficient-MMR/MSI-High CRC is lost after relapse, so there is a pressing clinical need to maximize the chance of cure in the early stages where prevalence of dMMR is higher comprising approximately 12% of Stage 3 and 20% of Stage 2 CRC. The efficacy of adjuvant checkpoint inhibition in this patient group has yet to be demonstrated in the context of micrometastatic disease without a supporting immune-competent microenvironment. Longitudinal studies especially in the neoadjuvant setting would optimally interrogate post-immunotherapy changes both in time and space. The NEOPRISM-CRC (NEOadjuvant PembRolizumab In Stratified Medicine – ColoReCtal) study is a Phase II Trial to determine whether neoadjuvant Pembrolizumab stratified to tumour mutation burden (TMB) is efficacious and safe. It will also be a platform to explore the relationships between possible predictive novel biomarkers and response to Pembrolizumab in blood, tumour tissue and microbiome. Methods: The study population consists of subjects with newly diagnosed operable dMMR/MSI-H CRC. Patients must be fit and eligible for planned curative surgery based on a) radiological node positive T1-4 CRC or b) high risk T3 defined as EITHER ≥ 5mm of extramural depth of invasion or unequivocal EMVI on imaging (regardless of depth), or T4 disease. They will receive one of two pre-operative regimens depending upon their TMB based on the FoundationOne®CDx test (FM1CDx). All patients will have one 21 day cycle of Pembrolizumab 200 mg IV. Prior to cycle 2 and with the result of the FM1CDx test, patients will continue their treatment as follows: A) TMB-high (defined as ≥20 mutations per Mb) or TMB-medium (defined as 6-19 mutations per Mb), or MSI-H on PCR if FM1CDx test is not evaluable: A further 2 cycles of Pembrolizumab 200 mg IV every 21 days. B) TMB-low (defined as ≤5 mutations per Mb), or if FM1CDx and PCR tests are not evaluable: No further Pembrolizumab given. Surgery to remove the CRC will be performed 4-6 weeks after the last dose of Pembrolizumab in both arms. Following resection patients may receive adjuvant chemotherapy in accordance with local institutional guidelines. The primary end point is pathological complete response rate (pCR). Secondary endpoints include 3 year RFS, OS, safety and health-related quality of life. Up to 32 patients will be registered over a 18-24 month period assuming that the pCR with 3 cycles of Pembrolizumab will be ≥ 33% for patients with high or medium TMB based on the FM1CDx profile, and intend to rule out a percentage ≤10%. To reach 80% power with 5% statistical significance, 19 patients are required in the high/medium TMB arm. The trial will be considered a success if at least 5/19 patients have a pCR after 3 cycles of Pembrolizumab. Enrolment will commence in March 2022. Clinical trial information: NCT05197322.

TPS3633 Background: Meta-analysis of 6 RCTs indicates that anti-EGFR agents are ineffective in rPTL RAS-wt aCRC (Arnold D, et al. Ann Oncol. 2017;28:1713-1729). However, data from the phase III PICCOLO and COIN trials suggest high tumor expression of the EGFR ligands, EREG and AREG, confers sensitivity to anti-EGFR agents in a subset of this population (Adams RA, et al. J Clin Oncol. 2012;30(30_suppl):32-32; Seligmann JF, et al. Ann Oncol. 2020;31:1021-1029). More data is needed before ligand assessment can be integrated into routine care: to date, EREG/AREG mRNA has only been assessed retrospectively, and feasibility of timely delivery of results must be demonstrated. The ARIEL trial aims to determine whether first-line chemotherapy plus cetuximab or panitumumab is more effective than chemotherapy alone in achieving early tumor shrinkage (ETS) after 8 weeks of treatment in patients (pts) with EREG/AREG-high rPTL RAS-wt aCRC. Methods: ARIEL is a multicentre, phase IV, open label, biomarker enrichment RCT. Pts with previously untreated rPTL RAS-wt (or RAS-unknown) aCRC are eligible for registration and EREG/AREG assessment using archival FFPE tumor tissue. Those confirmed as RAS-wt EREG/AREG-high (expression above 30th centile based on PICCOLO)3 are eligible for randomization to chemotherapy alone (fluoropyrimidine backbone plus irinotecan or oxaliplatin) vs chemotherapy (FOLFOX or FOLFIRI) plus anti-EGFR therapy (panitumumab or cetuximab) (options at physician’s discretion). Pts with EREG/AREG-low tumors are not eligible for randomization but may consent to translational research and follow-up. The primary endpoint is ETS at 8 weeks (≥30%, yes vs no). Secondary endpoints are depth of response at 16 weeks, overall survival, overall treatment utility, pt-reported quality of life, cost per QALY, pt acceptability of trial procedures, and safety. Pre-trial work-up included cross-validation of the EREG/AREG RT-qPCR assay at trial laboratories in Leeds and Birmingham, UK demonstrating reproducibility of biomarker results. Recruitment to an internal pilot phase is currently ongoing to demonstrate feasibility of timely delivery of biomarker results to sites (lower limit of 90% CI of mean result delivery time for first 20 pts must include 3 weeks). Mean monthly recruitment rate will be assessed at 18 months to determine likelihood of completion of the trial within the 3 year recruitment period. ARIEL is funded by the UK National Institute for Health Research (NIHR) and opened the first of 40 sites in February 2022. 440 pts will be registered for biomarker assessment in order to randomize 162 pts. All pts will be followed-up to 1 year post-randomisation, with a final assessment in all pts when the last pt has completed a year of follow-up (median 3.5 years). ARIEL is participating in the NIHR Associate PI scheme. Clinical trial information: 11061442.

High tumor mRNA levels of the EGFR ligands amphiregulin (AREG) and epiregulin (EREG) are associated with anti-EGFR agent response in metastatic colorectal cancer (mCRC). However, ligand RNA assays have not been adopted into routine practice due to issues with analytic precision and practicality. We investigated whether AREG/EREG IHC could predict benefit from the anti-EGFR agent panitumumab.Artificial intelligence algorithms were developed to assess AREG/EREG IHC in 274 patients from the PICCOLO trial of irinotecan with or without panitumumab (Ir vs. IrPan) inHigh ligand expression was associated with significant PFS benefit from IrPan compared with Ir [8.0 vs. 3.2 months; HR, 0.54; 95% confidence interval (CI), 0.37-0.79;AREG/EREG IHC identified patients who benefitted from the addition of panitumumab to irinotecan chemotherapy. IHC is a practicable assay that may be of use in routine practice.

The presence of peritoneal metastases in patients with advanced colorectal cancer is associated with poor prognosis but the mechanisms for this are unclear. This review summarises the current knowledge of the pathophysiology, clinical features, prevalence, prognosis, and molecular biology of peritoneal metastases and the risk factors for the development of peritoneal metastases following resection of a primary colorectal tumour. Furthermore, the evidence for treatment strategies are described including cytoreductive surgery, hyperthermic intraperitoneal chemotherapy, early post-operative intraperitoneal chemotherapy, sequential post-operative intraperitoneal chemotherapy and emerging novel strategies. Active areas of research should include the identification of individuals at high risk of peritoneal metastases after curative resection of primary tumour, development of a surveillance program for high-risk patients, optimisation of systematic therapies and further investigation of the use of intraperitoneal chemotherapy.

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]

111 Background: High tumor mRNA levels of the EGFR ligands, AREG and EREG are associated with anti-EGFR agent response in patients (pts) with RAS-wt mCRC, regardless of tumor location. However, ligand RNA assays have not been adopted into routine clinical practice due to issues with analytical precision and practicality. Here we test whether AREG and EREG expression assessed by IHC can predict benefit from Pan. Methods: A retrospective biomarker study within the PICCOLO trial (NCT00389870; irinotecan [Ir] ± Pan in fluoropyrimidine-resistant RAS-wt mCRC). AREG and EREG positive tumor cells were assessed by IHC in all RAS-wt patients with available tumor tissue. Pathologists annotated tumor areas on digital images of glass slides. Artificial intelligence (AI) algorithms calculated the percentage of tumor cells staining positive for AREG and EREG within the tumor areas. More than 50% AREG and/or EREG tumor cell positivity was regarded as high ligand expression. The primary endpoint was progression-free survival (PFS) and secondary endpoints were RECIST response rate (RR) and overall survival (OS). Results: 274 RAS-wt pts had available tumor tissue. High ligand expression (n = 132) was associated with significant PFS benefit from IrPan compared with Ir (8.0 vs 3.2 months; HR 0.54 [0.37-0.79]; p = 0.001); whereas low ligand expression (n = 142) was not (3.4 vs 4.4 months; HR 1.05 [95% CI, 0.74-1.49]; p = 0.78). The ligand-treatment interaction was significant (p = 0.02) and independent of BRAF-mutation status and primary tumor location. Likewise RR was significantly improved in pts with high ligand expression (IrPan vs Ir: 48% vs 6%; risk ratio, 7.8 [2.90-20.69]; p < 0.0001) but not those with low ligand expression (IrPan vs Ir: 25% vs 14%; risk ratio, 1.8 [95% CI, 0.89-3.65]; p = 0.10) (interaction p = 0.01). Lesser effect was seen on OS. Conclusions: IHC assessment of AREG and EREG identified pts who did or did not benefit from Pan, as has been previously demonstrated through mRNA quantification. IHC represents a more practicable technique as it can be provided at the point of care and is associated with shorter turn-around times. AREG and EREG IHC may be of use in routine practice to identify patients who would benefit from anti-EGFR therapy and those for whom alternative treatment strategies should be explored.

4013 Background: FOxTROT has reported marked down-staging, reduced perioperative morbidity and a trend towards fewer recurrences with 6 wks of oxaliplatin-fluoropyrimidine neoadjuvant chemotherapy (NAC) in CC (Seymour, ASCO 2019 abstract 3504). Using updated data, we investigate the contribution of panitumumab (Pan) and tumour markers to efficacy of NAC. Methods: 1053 pts with radiologically-staged T3-4, N0-2, M0 CC were randomly allocated (2:1) to either 6 wks of NAC and 18 wks of postoperative adjuvant chemotherapy (AC) or 24 wks of AC. 279 pts with RAS-wt tumours were also randomised 1:1 to receive Pan or not with NAC. The primary endpoint was freedom from recurrence or residual disease at 2 years for NAC vs AC, and depth of extramural spread for the Pan randomisation; secondary endpoints include safety, histological downstaging, CC-specific survival and OS. Results: Of 699 allocated pre-and-postoperative chemotherapy, 674 (97%) started and 612 (88%) completed NAC. 684/699 (97.8%) pre-and-postoperative and 349/354 (98.6%) control patients underwent tumour resection. There was marked T- and N-down-staging and tumour regression with NAC (all p

Imatinib therapy has improved outcomes in advanced GISTs. Current guidelines suggest monitoring with CT scanning every 12 weeks. There are no validated biomarkers to assist disease evaluation. We identified 50 patients treated with imatinib for GIST in a single tertiary center. We assessed the prognostic value of D-dimers by Cox regression, and the utility as a biomarker for radiological progression (rPD) using receiver-operator curve (ROC) analysis. In asymptomatic patients with D-dimer levels

Epidermal growth factor receptor (EGFR) (HER1) signaling depends on ligand binding and dimerization with itself or other HER receptors. We previously showed in a randomized trial that high EGFR ligand expression is predictive of panitumumab benefit in advanced colorectal cancer. Tumor expression of HER3 may further refine the RAS wild-type (wt) population benefitting from anti-EGFR agents.To examine HER3 messenger RNA expression as a prognostic and predictive biomarker for anti-EGFR therapy in a randomized clinical trial of panitumumab.The study was a prospectively planned retrospective biomarker study of pretreatment samples from the PICCOLO trial that tested the addition of panitumumab to irinotecan therapy in patients with KRAS wt advanced colorectal cancer who experienced failure with prior fluoropyrimidine treatment. HER3 was assessed as a prognostic marker, then as a predictive biomarker in patients with RAS wt, first as a continuous variable and then as a binary (high vs low) variable. Relationship with MEK-AKT pathway mutations and EGFR ligands epiregulin and amphiregulin (EREG/AREG) were also assessed.Primary end point was progression-free survival (PFS); secondary end points were response rate and overall survival (OS).In 308 patients (mean age at randomization, 61.6 years; 193 men) higher HER3 was weakly prognostic for OS (hazard ratio [HR] per 2-fold change, 0.91; 95% CI, 0.83-0.99; P = .04) but not PFS (HR, 0.93; 95% CI, 0.83-1.05; P = .25). Higher HER3 was predictive, being associated with prolonged PFS on irinotecan plus panitumumab (IrPan) (HR, 0.71; 95% CI, 0.61-0.82; P .001), but not irinotecan (HR, 0.96; 95% CI, 0.82-1.13; P = .65) in patients with RAS wt, with significant interaction between biomarker and treatment (P = .001). Similar interaction was seen for OS (P = .004). In an exploratory binary model, dividing the population at the 66th percentile, HER3 was predictive of panitumumab benefit: in patients with high HER3 expression, median PFS was 8.2 months (IrPan) vs 4.4 months (irinotecan) (HR, 0.33; 95% CI, 0.19-0.58; P .001). Patients with low HER3 expression gained no benefit in PFS: 3.3 months (IrPan) vs 4.3 months (irinotecan) (HR, 0.96; 95% CI, 0.67-1.38; P = .84), with significant interaction (P = .002). The binary model was also predictive for OS, with significant interaction (P = .01). Combining HER3 and ligand data, patients with HER3-high, AREG/EREG-high tumors gained markedly from panitumumab (PFS HR, 0.24; 95% CI, 0.11-0.51; P .005 and OS HR, 0.36; 95% CI, 0.18-0.73; P = .004). Conversely, patients with HER3-low, AREG/EREG-low tumors did not benefit (PFS HR, 1.14; 95% CI, 0.73-1.79; P = .57 and OS HR, 1.44; 95% CI, 0.92-2.26; P = .11).High HER3 expression identified patients with RAS wt who gained markedly from panitumumab, and those who did not, with statistically significant biomarker-treatment interactions for PFS and OS. This finding provides insight into the mechanism of anti-EGFR agents and is of potential clinical utility.

To improve strategies for the treatment of BRAF-mutant advanced colorectal cancer (aCRC) patients, we examined individual data from patients treated with chemotherapy alone in three randomised trials to identify points on the treatment pathway where outcomes differ from BRAF wild-types.2530 aCRC patients were assessed from three randomised trials. End-points were progression-free survival, response rate, disease control rate, post-progression survival (P-PS) and overall survival. Treatments included first-line oxaliplatin/fluorouracil (OxFU) and second-line irinotecan. Clinicians were unaware of BRAF-status.231 patients (9.1%) had BRAF-mutant tumours. BRAF-mutation conferred significantly worse survival independent of associated clinicopathological factors known to be prognostic. Compared with wild-type, BRAF-mutant patients treated with first-line OxFU had similar DCR (59.2% versus 72%; adjusted OR = 0.76, P = 0.24) and PFS (5.7 versus 6.3 months; adjusted HR = 1.14, P = 0.26). Following progression on first-line chemotherapy, BRAF-mutant patients had a markedly shorter P-PS (4.2 versus 9.2 months, adjusted HR = 1.69, P 6 months; OS = 24.0 months); however, 36.5% progressed rapidly through first-line chemotherapy and thereafter, with OS = 4.7 months.BRAF-mutant aCRC confers a markedly worse prognosis independent of associated clinicopathological features. Chemotherapy provides meaningful improvements in outcome throughout treatment lines. Post-progression survival is markedly worse and vigilance is required to ensure appropriate delivery of treatment after first-line progression.

Mucinous epithelial ovarian cancers (mEOC) are a relatively rare subset of ovarian cancers. Despite a relatively favourable outcome in early disease, the more frequent advanced presentation is associated with poorer response to platinum/taxane chemotherapies, and poorer survival, compared to serous ovarian cancers. We consider some of the fundamental clinico-pathological and molecular features, and existing clinical trial data regarding mEOC. Underlying molecular differences, between mEOC and serous cancers may contribute to the observed clinical differences, including an increased prevalence of K-RAS mutations in mEOC, more in keeping with gastrointestinal tumours. This observation contributes to the rationale for a trial (“mEOC”) investigating the use of “ovarian” versus “gastrointestinal” style chemotherapy. Looking to potential future approaches, we speculate upon the potential impact of emerging technologies on the future investigation and management of mEOC.

e15635Background: High peripheral blood NLR is a poor prognostic marker in cancer patients. We investigated the relationship between NLR and measured IRs in patients with chemo-naive aCRC and the m...

Background: Whilst RAS mutations predict which aCRC patients (pts) will not benefit from anti-EGFR agents, RAS-wt status does not reliably predict who will. Several studies report that high EGFR ligand expression (EREG/AREG) is predictive of anti-EGFR agent benefit but progression towards clinical utility is limited by lack of consensus on a clinical dichotomisation point and additional tumor material required. Here we explore EGFR copy number as a biomarker of prognosis and predictor of Pan benefit in a randomised trial in aCRC. Methods: EGFR CN, EREG/AREG RNA expression, RAS/RAF mutations were assessed in tumor from 275 pts randomised to 2nd-line irinotecan (Ir) or IrPan (PICCOLO, Lancet Onc 14:749-59). EGFR CN status was measured by the Affymetrix OncoScan array, analysed using Biodiscovery Nexus software and defined as normal (2 copies) or gain (>2 copies). Prognostic analysis was in Ir alone pts. Predictive analysis, in the 234 RAS-wt pts, compared baseline values with outcomes using Cox proportional hazards models. Results: 196 (71.3%) pts were classified as EGFR gain and 79 (28.7%) as normal. EGFR gain was significantly associated with high EREG and AREG RNA expression (both p

Anticancer drugs directed against the microtubule, including taxanes and vinca alkaloids, have been the backbone of many chemotherapy regimes for decades. These drugs have, however, significant limitations, which have prompted the development of novel microtubule targeting agents (MTAs). This article will discuss MTAs for anticancer therapies and recent debates regarding their mechanisms of action. Furthermore, the limitations of taxanes, including hypersensitivity reactions, neurotoxicity, drug resistance and lack of validated biomarkers to guide therapy will be discussed, all of which have driven the development of novel agents. The mechanisms of action and drug development of new generations of MTAs will also be outlined. Agents demonstrating utility in Phase III clinical trials, including eribulin, ixabepilone, cabazitaxel and trastuzumab–DM1 will be highlighted, as well as novel agents currently in development and future directions for MTAs.

3561Background: RAS mut status predicts lack of benefit from anti-EGFR agents in aCRC, but its impact on prognosis and chemotherapy outcomes is less clear. Previously we have reported that the poor...

Importance RAS wild-type (wt) status is necessary but not sufficient for response to anti-epidermal growth factor receptor (EGFR) agents in advanced colorectal cancer (aCRC). RNA expression of EGFR ligands epiregulin (EREG) and amphiregulin (AREG) may correlate with EGFR-targeted therapy efficacy in aCRC, so may represent a much-needed additional predictive marker for these drugs. Objective To examine a novel ligand model in a randomized clinical trial of panitumumab, irinotecan, and ciclosporin in colorectal cancer (PICCOLO) with with the a priori hypothesis that high tumor expression of either AREG or EREG would predict panitumumab therapy benefit in RAS -wt patients; and low expression, lack of efficacy. Design, Setting, and Participants Prospectively planned retrospective biomarker study from the PICCOLO trial, which tested the addition of panitumumab to irinotecan therapy in patients with KRAS wt aCRC who experienced failure with prior fluoropyrimidine treatment. The analysis was conducted between 2012 and 2014. A predefined dichotomous model classified tumors as “high expressor” (either EREG or AREG in top tertile for messenger RNA level) or “low expressor” (neither EREG nor AREG in top tertile). Ligand expression was assessed as a prognostic and predictive biomarker. Expression of AREG/EREG and RAS and BRAF mutations were assessed in archival tumor tissue. Main Outcomes and Measures Primary end point was progression-free survival (PFS); secondary end points were response rate and overall survival (OS). Results Of the 696 PICCOLO trial patients in the irinotecan–vs–irinotecan with panitumumab randomization, 331 had sufficient tumor tissue available and measurement of ligand expression was successful in 323. High ligand expression was not prognostic for OS (hazard ratio [HR], 0.79 [95% CI, 0.58-1.09]; P = .15) or PFS (HR, 0.93 [95% CI, 0.68-1.27]; P = .64). The primary population had RAS wt aCRC (n = 220); for RAS wt patients with high ligand expression, median (interquartile range [IQR]) PFS was 8.3 [4.0-11.0] months (irinotecan with panitumumab) vs 4.4 [2.8-6.7] months (irinotecan alone); HR, 0.38 [95% CI, 0.24-0.61]; P RAS wt patients with low ligand expression, median (IQR) PFS was 3.2 [2.7-8.1] months (irinotecan with panitumumab) vs 4.0 [2.7-7.5] months (irinotecan); HR, 0.93 [95% CI, 0.64-1.37]; P = .73; interaction test results were significant [ P = .01]). Less marked effects were seen for response rate (interaction P = .17) and OS (interaction P = .11). Conclusions and Relevance High ligand expression is a predictive marker for panitumumab therapy benefit on PFS in RAS wt patients; conversely, patients with low ligand expression gained no benefit. The current “opt-in” strategy for anti-EGFR therapy in all patients with RAS wt aCRC should be questioned. Expression of EREG/AREG is a useful biomarker for anti-EGFR therapy; optimization for clinical use is indicated. Trial Registration isrctn Identifier:ISRCTN93248876

Ovarian cancer is an important health concern worldwide. The majority of patients present with advanced disease, and despite initial chemosensitivity, most relapse and die from their disease. Better therapeutic options are urgently required. Maximal surgical debulking in combination with platinum/taxane chemotherapy has been the standard of care in advanced ovarian cancer since the mid-1990s. Trials investigating the addition of a third chemotherapeutic agent have disappointingly failed to demonstrate benefit. Intra-peritoneal therapy demonstrated improvements in outcomes in some trials, but at the cost of increased toxicity and inconvenience. Encouragingly, prospective data has now demonstrated benefits with bevacizumab in both the first-line and relapsed settings; however, interpretation is complex, particularly considering recent data demonstrating non-inferiority of neo-adjuvant chemotherapy with delayed primary surgery, and other data demonstrating a substantial improvement in outcome as a result of first-line paclitaxel dose fractionation. This article reviews the recent advances in ovarian cancer treatment and discusses current management and key areas for future research.

3583 Background: EGFR pathway activation is important in aCRC, but EGFR expression is not predictive for anti-EGFR drug efficacy. Signalling occurs across ErbB receptors and EGFR may mediate oncoge...

3509 Background: BRAF-mut aCRC pts have poor overall survival (OS). To investigate this phenomenon, we have examined individual patient data from pts treated with chemotherapy alone in 3 RCTs to id...

Aim: Links between inflammation, the immune response and cancer outcomes are compelling. The dNLR, calculated from a standard blood count, is a simple measure of inflammatory response, and in retrospective series high dNLR has been reported to be associated with poorer outcomes in aCRC. We examined dNLR as a prognostic marker, and assessed its predictive utility for two treatments in large phase III trials in aCRC. Methods: 2484 patients (pts) were studied, from the FOCUS (Lancet 370:143, 2007) and PICCOLO trials (Lancet Oncol 14:749, 2013). dNLR was calculated from the pre-randomisation blood count and prospectively defined as “high” (≥2) or “low” ( Results: 52.8% pts had high dNLR; 47.2% had low dNLR. High dNLR was independently associated with reduced OS in both trials (FOCUS: n = 1810 HR 1.51, p 25% after 6 weeks of chemotherapy was associated with a higher risk of disease progression at 12 weeks (OR = 1.6, p = 0.02) and inferior PFS (HR = 1.34, p Conclusions: The dNLR provides prognostic information and may provide an early warning when chemotherapy is failing. It might also help identify patients who could be treated safely with less intensive 1st line chemotherapy, but confirmatory data are required. Given that dNLR is readily and freely calculated from routine clinical data, its integration into routine patient evaluation should be considered following further validation. Disclosure: All authors have declared no conflicts of interest.

Aim: Variations in tumour biology and outcomes depending upon PTL have been reported in aCRC. We tested effects of PTL in two phase III randomised trials. Methods: We studied 2075 pts, from FOCUS (1st-line; n = 1390; Lancet 370: 143-52) and PICCOLO (2nd-line; n = 685; Lancet Oncol 14:749-59). We compared: (1) right colon (RC) vs [left colon (LC) or rectum] and (2) LC vs rectum. Association of PTL with RAS/RAF, AREG/EREG and MMR was assessed where available. PTL was tested as a prognostic factor, then for predictive utility by testing PTL/treatment interactions on OS and PFS for: 1st line FU vs doublet (FOCUS); 1st-line irinotecan doublet vs oxaliplatin doublet (FOCUS); 2nd line irinotecan (Ir) +/- panitumumab (Pan) (KRAS-wt pts, PICCOLO). Results: PTL was RC in 575 (28%), LC in 801 (39%) and rectum in 699 (34%) pts. RC tumours had more BRAF mutations (n = 1136, 22% vs 6%, p Interaction test p-values for treatment comparisons Comparison Interaction Test p-values RC vs LC/rectum LC vs Rectum OS PFS OS PFS 1st line doublet vs single-agent FU (1334 pts) 0.39 0.84 0.48 0.8 1st line OxFU doublet vs IrFU doublet (452 pts) 0.99 0.67 0.18 0.50 2nd line Ir +/- Pan KRAS-WT (450 pts) 0.35 0.13 0.63 0.46 2nd line Ir +/- Pan KRAS/BRAF-WT (341 pts) 0.72 0.89 0.83 0.19 Conclusions: We confirm that RC tumours are biologically distinct, and have worse outcomes with 1st-line therapy. We did not find PTL to be predictive for the benefit of the drugs under test in these trials, so cannot recommend its use for selection of therapy. Better objective predictive biomarkers are required. Disclosure: All authors have declared no conflicts of interest.

9643 Background: Epidemiological evidence suggests diabetics are at increased risk of several cancers, with inferior cancer outcomes. There is little data to describe the experience of diabetic pat...

3520 Background: RNA expression of epiregulin (EREG) ligands EREG and/or amphiregulin (AREG) has shown correlation with the efficacy of EGFR-targeted therapy in advanced colorectal cancer (aCRC). T...

Background The discovery and validation of prognostic and predictive biomarkers in advanced colorectal cancer is crucial for the personalisation of therapy. Inflammation-based prognostic scores have been developed, including the neutrophil lymphocyte ratio (NLR), and the derived NLR (dNLR) calculated using a differential white cell count. The NLR has been assessed in several cancers; in a retrospective series of advanced colorectal cancer, higher NLR was associated with reduced survival and poorer outcomes with chemotherapy. We aimed to validate the usefulness of the dNLR as a prognostic and a predictive biomarker to anti-epidermal growth factor receptor (EGFR) agents in advanced colorectal cancer. Methods We studied patients from a phase 3, open-label, randomised controlled trial that assessed the addition of panitumumab to irinotecan in pretreated advanced colorectal cancer (PICCOLO trial). The prognostic analysis included all patients for whom dNLR data were available; a subset with KRAS wild-type tumours randomised to standard irinotecan with or without panitumumab was also analysed for predictive value. The dNLR was calculated from the prerandomisation blood count and categorised as high (≥2) or low ( Findings 1159 patients were included in the prognostic analysis, and 444 in the predictive analysis. In multivariate analysis, high dNLR was independently associated with reduced overall survival compared with low dNLR (hazard ratio 1·59, 95% CI 1·32–1·78; p KRAS, BRAF, NRAS , and PIK3CA ), and in the subset of 323 patients in this all-wild-type category panitumumab had a more marked effect on tumour response rate in patients with low dNLR (odds ratio 7·4, p Interpretation The dNLR seems to offer the clinician useful prognostic information. Since this information can easily be calculated from routine clinical data, its integration into routine patient assessment should be considered after further validation. We did not demonstrate significant predictive value for anti-EGFR therapy, but our finding of higher response with panitumumab in patients with a low dNLR is hypothesis generating. Further investigation in datasets from randomised controlled trials and exploratory translational work are warranted. Funding Cancer Research UK, Yorkshire Cancer Research.

119 Background: Treatment with palliative imatinib has improved outcomes in advanced GISTs, with a reported 2 year PFS of 50%. Guidelines suggest monitoring during imatinib by CT scan at 12 week intervals. There are no validated biomarkers to assist in disease evaluation. High d-dimer levels are associated with poor prognosis in several cancers and are predictive of disease progression during chemotherapy. In the diagnosis of venous thromboembolism, low D-dimer levels have a high negative predictive value (npv) for thrombosis. We investigated whether low d-dimers have a clinically useful npv for GIST progression. Methods: We retrospectively identified all patients treated with palliative Imatinib for GIST in a single tertiary referral centre using a systematic search of an electronic clinical database. Every 12 weeks during treatment patients were assessed by clinical evaluation, CT and a d-dimer measurement (HemosIL HS assay). The prognostic value of d-dimers was assessed by Cox regression. The clinical utility of d-dimers as a biomarker for radiological progression (rPD) was evaluated using radio operator curve (ROC) analysis. Results: 50 patients treated between Jan 2002 and June 2011 met criteria for inclusion. D-dimers were prognostic for progression free survival and overall survival, when analysed by level or over time (p Conclusions: D-dimers may have a useful role in disease monitoring for GIST patients treated with palliative imatinib, particularly as a negative predictor of progression. This may reduce the burden of CT scanning in a useful percentage of patients but will require further validation.