Mismatch repair-deficient (MMRd) colorectal cancers (CRCs) have high mutation burdens, which make these tumours immunogenic and many respond to immune checkpoint inhibitors. The MMRd hypermutator phenotype may also promote intratumour heterogeneity (ITH) and cancer evolution. We applied multiregion sequencing and CD8 and programmed death ligand 1 (PD-L1) immunostaining to systematically investigate ITH and how genetic and immune landscapes coevolve. All cases had high truncal mutation burdens. Despite pervasive ITH, driver aberrations showed a clear hierarchy. Those in WNT/β-catenin, mitogen-activated protein kinase, and TGF-β receptor family genes were almost always truncal. Immune evasion (IE) drivers, such as inactivation of genes involved in antigen presentation or IFN-γ signalling, were predominantly subclonal and showed parallel evolution. These IE drivers have been implicated in immune checkpoint inhibitor resistance or sensitivity. Clonality assessments are therefore important for the development of predictive immunotherapy biomarkers in MMRd CRCs. Phylogenetic analysis identified three distinct patterns of IE driver evolution: pan-tumour evolution, subclonal evolution, and evolutionary stasis. These, but neither mutation burdens nor heterogeneity metrics, significantly correlated with T-cell densities, which were used as a surrogate marker of tumour immunogenicity. Furthermore, this revealed that genetic and T-cell infiltrates coevolve in MMRd CRCs. Low T-cell densities in the subgroup without any known IE drivers may indicate an, as yet unknown, IE mechanism. PD-L1 was expressed in the tumour microenvironment in most samples and correlated with T-cell densities. However, PD-L1 expression in cancer cells was independent of T-cell densities but strongly associated with loss of the intestinal homeobox transcription factor CDX2. This explains infrequent PD-L1 expression by cancer cells and may contribute to a higher recurrence risk of MMRd CRCs with impaired CDX2 expression. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Background The prognosis for patients with poorly-differentiated extra-pulmonary neuroendocrine carcinoma (PD -EP-NEC) is poor. A recognised first-line (1L) treatment for advanced disease is etoposide/platinum-based chemotherapy with no standard second-line (2L) treatment. Methods Patients with histologically-confirmed PD-EP-NEC (Ki-67 > 20%; Grade 3) received IV liposomal irinotecan (nal-IRI) (70 mg/m2 free base)/5-FU (2400 mg/m2)/folinic acid, Q14 days (ARM A), or IV docetaxel (75 mg/m2), Q21 days (ARM B), as 2L therapy. Primary endpoint was 6-month progression-free survival (PFS) rate (80% power to demonstrate one-sided 95% lower confidence interval excluded 15% (target level of efficacy: 30%)). Secondary endpoints: objective response rate (ORR), median PFS, overall survival (OS), toxicity and patient-reported quality -of-life (QoL) (ClinicalTrials.gov: NCT03837977). Findings Of 58 patients (29 each arm); 57% male, 90% ECOG PS 0/1, 10% PS 2, 89.7% Ki-67 & GE; 55%, primary site: 70.7% -gastrointestinal, 18.9%-other, 10.3%-unknown, 91.4%/6.9%/1.7% were resistant/sensitive/intolerant to 1L platinum-based treatment, respectively. The primary end-point of 6-month PFS rate was met by ARM A: 29.6% (lower 95% Confidence -Limit (CL) 15.7), but not by ARM B: 13.8% (lower 95%CL:4.9). ORR, median PFS and OS were 11.1% (95%CI:2.4-29.2) and 10.3% (95%CI:2.2-27.4%); 3 months (95%CI:2-6) and 2 months (95%CI:2-2); and 6 months (95%CI:3-10) and 6 months (95%CI:3-9) in ARMS A and B, respectively. Adverse events & GE; grade 3 occurred in 51.7% and 55.2% (1 and 6 discontinuations due to toxicity in ARMS A and B), respectively. QoL was maintained in ARM A, but not ARM B. Interpretation nal-IRI/5-FU/folinic acid, but not docetaxel, met the primary endpoint, with manageable toxicity and maintained QoL, with no difference in OS. ORR and median PFS were similar in both arms. This study provides prospective efficacy, toxicity and QoL data in the 2L setting in a disease group of unmet need, and represents some of the strongest evidence available to recommend systemic treatment to these patients. Funding Servier. Copyright & COPY; 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Total neoadjuvant therapy (TNT) incorporates (chemo)-radiotherapy ((C)RT) and chemotherapy (ChT) prior to surgery for locally advanced rectal cancer (LARC). Recent phase 3 trials reported that this approach improves pathologic complete response rate and disease-specific survival by reducing the risk of metastatic progression. We report real-world data on tolerability and early outcome data of patients treated with TNT in our institution. Patients with LARC diagnosed and treated using the TNT approach at the Royal Free London between August 2017 and October 2022 were retrospectively identified from the radiotherapy planning system. Baseline demographic, clinic, imaging, and follow-up data were collated from electronic patient records. 43 patients were identified. Median age was 62 years (range 43-83). All patients had ECOG performance status 0-1. Rectal cancer staging was T3/T4 in 37 patients (86%) and 17 (40%) had N2 involvement on MRI. The majority of patients had high-risk features with 33 (77%) having threatened circumferential resection margin and 26 (60%) with radiological extramural vascular invasion. 5 patients (12%) had pelvic side wall lymph node disease. All except 3 patients had the RT-ChT sequence. 37 patients (86%) had long course CRT 45-50.4Gy in 25-28 fractions with concurrent capecitabine and 6 (14%) had short course RT 25Gy in 5 fractions. ChT regimens used were CAPOX (39 patients), FOLFOX (2), FOLFOXIRI (1) and 5-FU (1). Median number of cycles was 4 (range 3-8). 35 (81%) patients had a dose-reduction of ChT. Majority of dose reductions were for oxaliplatin due to concerns about long-term neurotoxicity. Grade 3+ toxicity occurred in 2 patients due to enterocolitis. Post-treatment MRI was done at median of 13 weeks and 23 weeks from start of radiotherapy. 22 patients (51%) had TRG1 (radiologic complete response (CR)) on post-TNT MRI. 9 patients opted to defer surgery and began active surveillance. Of these, 1 patient had a successful salvage surgery due to local progression. 26 surgical outcomes were available at point of analysis. Surgery was performed after a median of 11 weeks after the last chemotherapy. Median post-operative hospital stay was 11 days. 25 patients (96%) had an R0 resection and 8 patients (31%) had a pathologic CR. 5 patients received adjuvant ChT. At point of analysis 4 patients with MRI TRG1 without evidence of luminal disease on flexible sigmoidoscopy had surgery (including the patient with local progression following surveillance). Excluding the patient with progressive disease, 1 of 3 patients had evidence of residual disease on post-operative histology. After a median follow up of 17 months (range 7-59), 2 (5%) patients had local progression and 9 (21%) patients had distant metastatic progression. TNT approach for LARC was generally well-tolerated in this UK cohort with good completion rate of neoadjuvant treatment. In patients who underwent surgery, a high rate of R0 resection and complete pathologic response was seen despite majority of patients having a dose reduction of chemotherapy. Early outcomes in this high-risk rectal cancer cohort are similar to those reported in recent trials. Further follow-up is required to assess long-term oncological outcomes.

293 Background: NET-02 was a multi-centre, randomised (1:1), non-comparative phase II trial of nal-IRI/5-FU/folinic acid (ARM A) or docetaxel (ARM B) in pts with progressive PD-EP-NEC, aimed at selecting a treatment for evaluation in a phase III trial. Primary analysis (N = 58) showed ARM A, but not ARM B, achieved the target 6-month progression-free survival rate primary endpoint (McNamara et al. ASCO 2022). HRQoL was a secondary endpoint in NET-02. Methods: HRQoL was assessed using the EORTC QLQ-C30 and GINET21 (at baseline (BL), 6-weekly intervals and at disease progression). The mean change from BL was estimated for each scale by timepoint and treatment arm. Results are presented where there were ≥4 responses per time point. Scores were considered stable if they did not change by > 10 points from BL. The mean BL C30 scores for all pts were compared to United Kingdom (UK) population normative C30 data using a 2-sample t-test. Results: Fifty-four of 58 pts (93%) completed a BL questionnaire; of these, 39 (72%) completed ≥1 post-BL questionnaire, with 21 (51%) completing questionnaires at progression. Global health status (GHS) and all functional scales in ARM A remained stable from BL to intervals pre-progression, with a sustained improvement in role functioning observed post-BL. In ARM B, GHS and all C30 functional scales decreased by > 10 points between BL and week 18 (worsening of QoL). Both arms had a > 10-point increase from BL in constipation and diarrhoea in ≥1 post-BL time point. In ARM A, pain, insomnia and financial problems decreased from BL. No C30 symptom scales in ARM B were consistently lower post-BL. Patterns of change in GINET21 mean score were similar in both arms: body image, disease-related worries, information/communication, sexual function and social function all had a > 10-point reduction in score from BL (indicating improvement in symptoms/problems); endocrine and gastrointestinal symptoms remained stable; muscle/bone pain varied across time points, initially showing a reduction in pain followed by an increase, compared to BL. In comparison to the UK C30 norms (BL all pts), 11 of 15 C30 scales did not significantly differ (P > 0.05). Mean scores for fatigue and appetite loss were significantly higher than UK C30 norms (worse symptoms in pts from NET-02) (P = 0.03, P = 0.0003 respectively). However, emotional functioning and GHS were significantly better in pts from NET-02 (P = 0.001, P = 0.03 respectively). Role and social functioning were lower in pts from NET-02 (both P = 0.06) (poorer level of functioning). Conclusions: HRQoL was maintained and potentially improved with nal-IRI/5-FU/folinic acid, but not docetaxel. Compared to the UK general population, BL QoL did not substantially differ in pts from NET-02. Clinical trial information: NCT03837977.

Introduction Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) is considered to be a rare condition associated with lung neuroendocrine tumours (NET), and its natural history is poorly described. We aimed to assess the prevalence and clinicopathologic characteristics of DIPNECH in the lung NET population, and to investigate predictors of time-to-progression (TTP) and overall survival (OS). Methods We retrospectively identified patients diagnosed with DIPNECH between April 2005 and December 2020. Clinical data were collected from medical records. The relationship between baseline characteristics and TTP and OS was analysed using the Kaplan-Meier method. Univariate analysis was performed using the Cox proportional hazards model. Results Of 311 patients with well-differentiated lung NETs, 61 (20%) had DIPNECH and were included in the study. Baseline demographics described 95% female, 59% never smokers and mean body mass index 34.4 kg m(-2); 77% were typical carcinoids (TC), 13% atypical carcinoids (AC), and 10% both TC and AC (multicentric). At presentation, 54% of patients were asymptomatic. Multicentric NETs were demonstrated in 16 (26%) on histopathology, and a further 32 (52%) had synchronous NETs suggested on imaging (multiple nodules >= 5 mm). Seven (11%) patients developed metastases and the median OS from time of first metastasis was 37 months. AC histopathology and NET TNM stage >= IIA were associated with poorer TTP and OS. Of the DIPNECH cohort, the 15-year survival rate was 86%. Conclusions DIPNECH may be more prevalent in the lung NET population than previously appreciated, especially in women. Although our results confirm that DIPNECH is predominantly an indolent disease associated with TC, 23% developed AC and these patients may warrant closer observation.

OBJECTIVES:There is a pressing need to develop clinical management pathways for grade 3 (G3) gastroenteropancreatic neuroendocrine neoplasms (GEP NEN).METHODS:We performed a retrospective study on patients with metastatic G3 GEP NEN. The relationship between baseline characteristics and progression-free survival and overall survival was analyzed using the Kaplan-Meier method. Univariate and multivariate analyses were performed using the Cox proportional hazards model.RESULTS:We included 142 patients (74 well-differentiated neuroendocrine tumors [WDNETs], 68 poorly differentiated neuroendocrine carcinomas [PDNECs]). Patients with WDNET had prolonged survival compared with PDNEC (median, 24 vs 15 months, P = 0.0001), which persisted in both pancreatic and nonpancreatic cohorts. Well-differentiated morphology, Ki-67 <50% and positive somatostatin receptor imaging were independently associated with prolonged survival. Of the subgroup treated with first-line platinum-based chemotherapy, response rates were favorable (partial response, 47%; stable disease, 30%); there was no significant difference in response rates nor progression-free survival between WDNET and PDNEC despite significantly prolonged overall survival in the WDNET cohort.CONCLUSIONS:Our study corroborates the knowledge of 2 prognostically distinct subgroups within the World Health Organization 2019 G3 GEP NEN population, observed in both pancreatic and nonpancreatic gastrointestinal cohorts. Definitive management pathways are needed to reflect the differences between G3 WDNET and PDNEC.

TPS4158 Background: The prognosis for pts with PD-EP-NEC is poor. First-line treatment for advanced disease is etoposide/platinum-based chemotherapy, analogous to that of high grade lung NEC, with no standard second-line treatment, and is an area of unmet need. Methods: This is a multi-centre, randomised, phase II trial of nal-IRI; 80mg/m2 intravenously (IV) over 90 mins, prior to 5-FU; 2400 mg/m2 infusion over 46 hrs and folinic acid, Q14 days, or docetaxel; 75mg/m2 IV over 60 mins, Q21 days, as second-line therapy in pts with progressive PD-EP-NEC (Ki-67 > 20%), with the overall aim of selecting a treatment for continuation to a phase III trial. The standard arm is that used in high-grade lung NEC, of which docetaxel is a second-line therapy option (NCCN guidelines) and combination regimens such as Irinotecan/5-FU are a second-line therapy option currently used without trial evidence for this subset of pts. Pts must have had prior treatment with first-line platinum-based chemotherapy, have documented disease progression and have an ECOG performance status of ≤2. This study plans to recruit 102 pts from 16 UK centres (over 37 mths). Primary endpoint is 6-mth progression-free survival (PFS) rate; trial is designed to have an 80% chance of demonstrating that the one-sided 95% confidence interval of the 6 mth PFS rate excludes 15%, if the true rate is at least 30%, where 30% is the required level of efficacy, and a rate of < 15% would give grounds for rejection. If both treatment arms exceed the required level of efficacy to warrant further evaluation in a phase III trial, treatment with the higher PFS rate at 6 mths will be selected. Secondary endpoints include overall survival, objective response rate, toxicity, quality of life, serum neuron-specific enolase. Exploratory endpoints include quantification of circulating tumour cells (CTCs), circulating tumour deoxyribonucleic acid (ctDNA) and molecular profiling of CTCs, ctDNA and tumour tissue, and generation of CTC-derived xenografts. This trial is open and has enrolled 6 pts at time of submission. Clinical trial information: 10996604.

Background Bone metastases are associated with a worse outcome in patients with neuroendocrine tumours (NETs). Tumour overexpression of C-X-C chemokine receptor 4 (CXCR4) appears predictive of skeletal involvement. We investigated the role of circulating tumour cells (CTCs) and CXCR4 expression on CTCs as potential predictors of skeleton invasion. Methods Blood from patients with metastatic bronchial, midgut or pancreatic NET (pNET) was analysed by CellSearch. CXCR4 immunohistochemistry was performed on matched formalin-fixed paraffin-embedded (FFPE) samples. Results Two hundred and fifty-four patients were recruited with 121 midgut and 119 pNETs, of which 51 and 36% had detectable CTCs, respectively. Bone metastases were reported in 30% of midgut and 23% of pNET patients and were significantly associated with CTC presence ( p = 0.003 and p < 0.0001). In a subgroup of 40 patients, 85% patients with CTCs had CTCs positive for CXCR4 expression. The proportion of CXCR4-positive CTCs in patients with bone metastases was 56% compared to 35% in those without ( p = 0.18) it. Staining for CXCR4 on matched FFPE tissue showed a trend towards a correlation with CXCR4 expression on CTCs ( p = 0.08). Conclusions CTC presence is associated with bone metastases in NETs. CXCR4 may be involved in CTC osteotropism and present a therapeutic target to reduce skeletal morbidity.