Checkpoint inhibitors for gastroesophageal cancers: dissecting heterogeneity to better understand their role in first-line and adjuvant therapy.

Gastroesophageal adenocarcinoma (GEA) and squamous esophageal cancer (ESCC) are responsible for >1 million deaths annually globally. Until now, patients with metastatic GEA and ESCC could anticipate survival of <1 year. Anti- programmed cell death protein 1 (anti-PD-1) monotherapy has demonstrated modest efficacy in previously treated GEA and ESCC. In 2020, four pivotal trials have established anti-PD-1 therapy as a new standard of care for selected GEA and ESCC patients as first-line advanced and adjuvant therapy. In this review, we discuss the recent results of the CheckMate 649, ATTRACTION-4, KEYNOTE-590 and CheckMate 577 trials. We consider these results in the context of current standards of care and historical trials of immune checkpoint blockade in GEA and ESCC. We explore biomarker selection for anti-PD-1 therapy and appraise the future of combination therapies. In CheckMate 649, treatment with oxaliplatin-fluoropyrimidine chemotherapy plus nivolumab in patients with combined positive score ≥5 GEA tumors provided a clinically meaningful and statistically significant improvement in overall survival. The ATTRACTION-4 trial did not see a similar overall survival benefit, despite a clear improvement in progression-free survival. We review potential explanations for this result. KEYNOTE-590 showed profoundly improved survival when pembrolizumab was added to cisplatin-fluoropyrimidine chemotherapy in ESCC patients with combined positive score ≥10 tumors; this benefit was less convincing in unselected ESCC. Finally, CheckMate 577 provides proof-of-concept for the improvement in disease-free survival with adjuvant nivolumab in high-risk resected GEA and ESCC following trimodality therapy. Immune checkpoint blockade has come of age in GEA and ESCC, and will now be integrated into first-line and earlier lines of therapy, providing benefit for a larger proportion of patients. Biomarker standardization will be critical to select the patients most likely to benefit from treatment. For patients with immune evasive tumors, novel combinations under development show promise; however, global trials are needed.

Longitudinal tracking of 97 esophageal adenocarcinomas using liquid biopsy sampling.

BACKGROUND: The incidence of esophageal adenocarcinoma (EAC) is rapidly rising and has a 5-year survival rate of <20%. Beyond TNM (tumor-node-metastasis) staging, no reliable risk stratification tools exist and no large-scale studies have profiled circulating tumor DNA (ctDNA) at relapse in EAC. Here we analyze the prognostic potential of ctDNA dynamics in EAC, taking into account clonal hematopoiesis with indeterminate potential (CHIP). PATIENTS AND METHODS: A total of 245 samples from 97 patients treated with neoadjuvant chemotherapy and surgery were identified from the prospective national UK Oesophageal Cancer Clinical and Molecular Stratification (OCCAMS) consortium data set. A pan-cancer ctDNA panel comprising 77 genes was used. Plasma and peripheral blood cell samples were sequenced to a mean depth of 7082× (range 2196-28 524) and ctDNA results correlated with survival. RESULTS: Characteristics of the 97 patients identified were as follows: 83/97 (86%) male, median age 68 years (SD 9.5 years), 100% cT3/T4, 75% cN+. EAC-specific drivers had higher variant allele fractions than passenger mutations. Using stringent quality criteria 16/79 (20%) were ctDNA positive following resection; recurrence was observed in 12/16 (75%) of these. As much as 78/97 (80%) had CHIP analyses that enabled filtering for CHIP variants, which were found in 18/78 (23%) of cases. When CHIP was excluded, 10/63 (16%) patients were ctDNA positive and 9/10 of these (90%) recurred. With correction for CHIP, median cancer-specific survival for ctDNA-positive patients was 10.0 months versus 29.9 months for ctDNA-negative patients (hazard ratio 5.55, 95% confidence interval 2.42-12.71; P = 0.0003). Similar outcomes were observed for disease-free survival. CONCLUSIONS: We demonstrate in a large, national, prospectively collected data set that ctDNA in plasma following surgery for EAC is prognostic for relapse. Inclusion of peripheral blood cell samples can reduce or eliminate false positives from CHIP. In future, post-operative ctDNA could be used to risk stratify patients into high- and low-risk groups for intensification or de-escalation of adjuvant chemotherapy.

Adjuvant therapy following oesophagectomy for adenocarcinoma in patients with a positive resection margin.

BACKGROUND: The role of adjuvant therapy in patients with oesophagogastric adenocarcinoma treated by neoadjuvant chemotherapy is contentious. In UK practice, surgical resection margin status is often used to classify patients for receiving adjuvant treatment. The aim of this study was to assess the survival benefit of adjuvant therapy in patients with positive (R1) resection margins. METHODS: Two prospectively collected UK institutional databases were combined to identify eligible patients. Adjusted Cox regression analyses were used to compare overall and recurrence-free survival according to adjuvant treatment. Recurrence patterns were assessed as a secondary outcome. Propensity score-matched analysis was also performed. RESULTS: Of 616 patients included in the combined database, 242 patients who had an R1 resection were included in the study. Of these, 112 patients (46·3 per cent) received adjuvant chemoradiotherapy, 46 (19·0 per cent) were treated with adjuvant chemotherapy and 84 (34·7 per cent) had no adjuvant treatment. In adjusted analysis, adjuvant chemoradiotherapy improved recurrence-free survival (hazard ratio (HR) 0·59, 95 per cent c.i. 0·38 to 0·94; P = 0·026), with a benefit in terms of both local (HR 0·48, 0·24 to 0·99; P = 0·047) and systemic (HR 0·56, 0·33 to 0·94; P = 0·027) recurrence. In analyses stratified by tumour response to neoadjuvant chemotherapy, non-responders (Mandard tumour regression grade 4-5) treated with adjuvant chemoradiotherapy had an overall survival benefit (HR 0·61, 0·38 to 0·97; P = 0·037). In propensity score-matched analysis, an overall survival benefit (HR 0·62, 0·39 to 0·98; P = 0·042) and recurrence-free survival benefit (HR 0·51, 0·30 to 0·87; P = 0·004) were observed for adjuvant chemoradiotherapy versus no adjuvant treatment. CONCLUSION: Adjuvant therapy may improve overall survival and recurrence-free survival after margin-positive resection. This pattern seems most pronounced with adjuvant chemoradiotherapy in non-responders to neoadjuvant chemotherapy.

ANTECEDENTES: El papel del tratamiento adyuvante en pacientes con adenocarcinoma esofagogástrico tratados con quimioterapia neoadyuvante es polémico. En la práctica del Reino Unido, el estado del margen de resección quirúrgico se utiliza a menudo para identificar a los pacientes que reciben tratamiento adyuvante. El objetivo de este estudio fue evaluar el beneficio en la supervivencia del tratamiento adyuvante en pacientes con márgenes de resección positivos (R1). MÉTODOS: Se combinaron dos bases de datos de instituciones del Reino Unido que recogen información de forma prospectiva para identificar pacientes elegibles. Se utilizaron análisis de regresión de Cox ajustados para comparar la supervivencia global y la supervivencia libre de recidiva según el tratamiento adyuvante. Los patrones de recidiva se evaluaron como resultado secundario. También se realizó un análisis de emparejamiento por puntaje de propensión. RESULTADOS: De 616 pacientes incluidos en la base de datos combinada, se incluyeron en el estudio 242 pacientes con resección R1. De estos pacientes, 112 (46%) recibieron quimiorradioterapia adyuvante, 46 (19%) pacientes fueron tratados con quimioterapia adyuvante y 84 (35%) pacientes no recibieron ningún tratamiento. En el análisis ajustado, la quimiorradioterapia adyuvante mejoró la supervivencia libre de recidiva (cociente de riesgos instantáneos, hazard ratio, HR 0,59, i.c. del 95% 0,38-0,94; P = 0,026) con un beneficio tanto para la recidiva local (HR 0,48, i.c. del 95% 0,24-0,99; P = 0,047) como para la sistémica (HR 0,56, i.c. del 95% 0,33-0,94; P = 0,027). Cuando los pacientes se clasificaron según la respuesta tumoral a la quimioterapia neoadyuvante, los no respondedores (Mandard Grado 4/5) tratados con quimiorradioterapia adyuvante obtuvieron un beneficio en la supervivencia (HR 0,61, i.c. del 95% 0,38-0,97; P = 0,037). En el análisis por emparejamiento por puntaje de propensión, se observó un beneficio en la supervivencia global (HR 0,62, i.c. del 95% 0,39-0,98; P = 0,042) y en la supervivencia libre de recidiva (HR 0,51.i.c. del 95% 0,30-0,87; P = 0,004) con la quimiorradioterapia adyuvante frente a no recibir tratamiento adyuvante. CONCLUSIÓN: El tratamiento adyuvante puede mejorar la supervivencia global y la supervivencia libre de recidiva en pacientes con margen de resección positivo. Este patrón parece más pronunciado con la quimiorradioterapia adyuvante en pacientes que no responden a la quimioterapia.

A Dual-VENC Four-Dimensional Flow MRI Framework for Analysis of Subject-Specific Heterogeneous Nonlinear Vessel Deformation.

Advancement of subject-specific in silico medicine requires new imaging protocols tailored to specific anatomical features, paired with new constitutive model development based on structure/function relationships. In this study, we develop a new dual-velocity encoding coefficient (VENC) 4D flow MRI protocol that provides unprecedented spatial and temporal resolution of in vivo aortic deformation. All previous dual-VENC 4D flow MRI studies in the literature focus on an isolated segment of the aorta, which fail to capture the full spectrum of aortic heterogeneity that exists along the vessel length. The imaging protocol developed provides high sensitivity to all blood flow velocities throughout the entire cardiac cycle, overcoming the challenge of accurately measuring the highly unsteady nonuniform flow field in the aorta. Cross-sectional area change, volumetric flow rate, and compliance are observed to decrease with distance from the heart, while pulse wave velocity (PWV) is observed to increase. A nonlinear aortic lumen pressure-area relationship is observed throughout the aorta such that a high vessel compliance occurs during diastole, and a low vessel compliance occurs during systole. This suggests that a single value of compliance may not accurately represent vessel behavior during a cardiac cycle in vivo. This high-resolution MRI data provide key information on the spatial variation in nonlinear aortic compliance, which can significantly advance the state-of-the-art of in-silico diagnostic techniques for the human aorta.

Pan-Asian adapted ESMO Clinical Practice Guidelines for the management of patients with metastatic oesophageal cancer: a JSMO-ESMO initiative endorsed by CSCO, KSMO, MOS, SSO and TOS.

The most recent version of the European Society for Medical Oncology (ESMO) Clinical Practice Guidelines for the diagnosis, treatment and follow-up of oesophageal cancer was published in 2016, and covered the management and treatment of local/locoregional disease, limited disease, locally advanced disease and the management of advanced/metastatic disease. At the ESMO Asia Meeting in November 2017 it was decided by both ESMO and the Japanese Society of Medical Oncology (JSMO) to convene a special guidelines meeting immediately after the JSMO Annual Meeting in 2018. The aim was to adapt the ESMO 2016 guidelines to take into account the ethnic differences associated with the treatment of metastatic oesophageal cancer in Asian patients. These guidelines represent the consensus opinions reached by experts in the treatment of patients with metastatic oesophageal cancer representing the oncological societies of Japan (JSMO), China (CSCO), Korea (KSMO), Malaysia (MOS), Singapore (SSO) and Taiwan (TOS). The voting was based on scientific evidence, and was independent of both the current treatment practices and the drug availability and reimbursement situations in the individual participating Asian countries.

Pan-Asian adapted ESMO Clinical Practice Guidelines for the management of patients with metastatic gastric cancer: a JSMO-ESMO initiative endorsed by CSCO, KSMO, MOS, SSO and TOS.

The most recent version of the European Society for Medical Oncology (ESMO) Clinical Practice Guidelines for the diagnosis, treatment and follow-up of gastric cancer (GC) was published in 2016, and covered the management and treatment of local, locoregional, locally advanced and metastatic disease. At the ESMO Asia Meeting in November 2017 it was decided by both ESMO and The Japanese Society of Medical Oncology (JSMO) to convene a special guidelines meeting immediately after the JSMO Annual Meeting in 2018. The aim was to adapt the ESMO 2016 guidelines to take into account the ethnic differences associated with the treatment of metastatic GC in Asian patients. These guidelines represent the consensus opinions reached by experts in the treatment of patients with metastatic GC representing the oncological societies of Japan (JSMO), China (CSCO), Korea (KSMO), Malaysia (MOS), Singapore (SSO) and Taiwan (TOS). The voting was based on scientific evidence and was independent of both the current treatment practices and the drug availability and reimbursement situations in the individual participating Asian countries.

Quality assurance of surgery in the randomized ST03 trial of perioperative chemotherapy in carcinoma of the stomach and gastro-oesophageal junction.

BACKGROUND: The UK Medical Research Council ST03 trial compared perioperative epirubicin, cisplatin and capecitabine (ECX) chemotherapy with or without bevacizumab (B) in gastric and oesophagogastric junctional cancer. No difference in survival was noted between the arms of the trial. The present study reviewed the standards and performance of surgery in the context of the protocol-specified surgical criteria. METHODS: Surgical and pathological clinical report forms were reviewed to determine adherence to the surgical protocols, perioperative morbidity and mortality, and final histopathological stage for all patients treated in the study. RESULTS: Of 1063 patients randomized, 895 (84·2 per cent) underwent resection; surgical details were available for 880 (98·3 per cent). Postoperative assessment data were available for 873 patients; complications occurred in 458 (52·5 per cent) overall, of whom 71 (8·1 per cent) developed complications deemed to be life-threatening by the responsible clinician. The most common complications were respiratory (211 patients, 24·2 per cent). The anastomotic leak rate was 118 of 873 (13·5 per cent) overall; among those who underwent oesophagogastrectomy, the rate was higher in the group receiving ECX-B (23·6 per cent versus 9·9 per cent in the ECX group). Pathological assessment data were available for 845 patients. At least 15 nodes were removed in 82·5 per cent of resections and the median lymph node harvest was 24 (i.q.r. 17-34). Twenty-five or more nodes were removed in 49·0 per cent of patients. Histopathologically, the R1 rate was 24·9 per cent (208 of 834 patients). An R1 resection was more common for proximal tumours. CONCLUSION: In the ST03 trial, the performance of surgery met the protocol-stipulated criteria. Registration number: NCT00450203 ( http://www.clinicaltrials.gov).

Peri-operative therapy for operable gastroesophageal adenocarcinoma: past, present and future.

Surgery represents the only chance of cure for patients with gastroesophageal adenocarcinoma; however, surgery alone does not cure most patients. Over the past decade, several multimodality adjunctive treatments have improved survival for patients with operable gastroesophageal adenocarcinoma who are undergoing surgical resection; these include peri-operative chemotherapy, neoadjuvant chemoradiotherapy, adjuvant chemotherapy and adjuvant chemoradiotherapy. More recently, the results of several large randomised trials are leading to a shift in the peri-operative treatment of gastroesophageal cancer, away from anthracycline-based and towards taxane-based chemotherapy regimens. Emerging data support an increased focus on patients who are at high risk for poor operative outcomes such as R1 resection, and on patients who are at high risk for relapse following surgery such as those with lymph node metastases (N1+). Future developments may include use of fluorodeoxyglucose-positron emission tomography to inform a switch to non-cross resistant chemotherapy pre-operatively and substitution of alternative treatments for chemotherapy in high risk post-operative node positive patients. Conversely, in molecularly selected subgroups such as microsatellite unstable gastroesophageal cancer, peri-operative or adjuvant chemotherapy may not be helpful, and treatments such as immunotherapy may be considered. In this review, the most up-to-date clinical trials and translational research in the field of operable gastroesophageal cancer are discussed; with a focus on how best to risk stratify patients with operable disease for peri-operative treatment plus surgery, and how novel therapies might be integrated into standard treatments in order to improve survival outcomes in this patient group.

A seven-Gene Signature assay improves prognostic risk stratification of perioperative chemotherapy treated gastroesophageal cancer patients from the MAGIC trial.

Background: Following neoadjuvant chemotherapy for operable gastroesophageal cancer, lymph node metastasis is the only validated prognostic variable; however, within lymph node groups there is still heterogeneity with risk of relapse. We hypothesized that gene profiles from neoadjuvant chemotherapy treated resection specimens from gastroesophageal cancer patients can be used to define prognostic risk groups to identify patients at risk for relapse. Patients and methods: The Medical Research Council Adjuvant Gastric Infusional Chemotherapy (MAGIC) trial (n = 202 with high quality RNA) samples treated with perioperative chemotherapy were profiled for a custom gastric cancer gene panel using the NanoString platform. Genes associated with overall survival (OS) were identified using penalized and standard Cox regression, followed by generation of risk scores and development of a NanoString biomarker assay to stratify patients into risk groups associated with OS. An independent dataset served as a validation cohort. Results: Regression and clustering analysis of MAGIC patients defined a seven-Gene Signature and two risk groups with different OS [hazard ratio (HR) 5.1; P < 0.0001]. The median OS of high- and low-risk groups were 10.2 [95% confidence interval (CI) of 6.5 and 13.2 months] and 80.9 months (CI: 43.0 months and not assessable), respectively. Risk groups were independently prognostic of lymph node metastasis by multivariate analysis (HR 3.6 in node positive group, P = 0.02; HR 3.6 in high-risk group, P = 0.0002), and not prognostic in surgery only patients (n = 118; log rank P = 0.2). A validation cohort independently confirmed these findings. Conclusions: These results suggest that gene-based risk groups can independently predict prognosis in gastroesophageal cancer patients treated with neoadjuvant chemotherapy. This signature and associated assay may help risk stratify these patients for post-surgery chemotherapy in future perioperative chemotherapy-based clinical trials.

Lymph node regression and survival following neoadjuvant chemotherapy in oesophageal adenocarcinoma.

BACKGROUND: The aim was to define the pathological response in lymph nodes following neoadjuvant chemotherapy for oesophageal adenocarcinoma and to quantify any associated survival benefit. METHODS: Lymph nodes retrieved at oesophagectomy were examined retrospectively by two pathologists for evidence of a response to chemotherapy. Patients were classified as lymph node-negative (either negative nodes with no evidence of previous tumour involvement or negative with evidence of complete regression) or positive (allocated a lymph node regression score based on the proportion of fibrosis to residual tumour). Lymph node responders (score 1, complete response; 2, less than 10 per cent remaining tumour; 3, 10-50 per cent remaining tumour) and non-responders (score 4, more than 50 per cent viable tumour; 5, no response) were compared in survival analyses using Kaplan-Meier and Cox regression analysis. RESULTS: Among 377 patients, 256 had neoadjuvant chemotherapy. Overall, 68 of 256 patients (26·6 per cent) had a lymph node response and 115 (44·9 per cent) did not. The remaining 73 patients (28·5 per cent) had negative lymph nodes with no evidence of regression. Some patients had a lymph node response in the absence of a response in the primary tumour (27 of 99, 27 per cent). Lymph node responders had a significant survival benefit (P < 0·001), even when stratified by patients with or without a response in the primary tumour. On multivariable analysis, lymph node responders had decreased overall (hazard ratio 0·53, 95 per cent c.i. 0·36 to 0·78) and disease-specific (HR 0·42, 0·27 to 0·66) mortality, and experienced reduced local and systemic recurrence. CONCLUSION: Lymph node regression is a strong prognostic factor and may be more important than response in the primary tumour.

Histological and mechanical differences in the skin of patients with rectal prolapse.

INTRODUCTION: It is still an enigma that some patients develop rectal prolapse whilst others with similar risk factors do not. Biomechanical assessment of the skin may provide further insight into the aetiology of this complex condition. Elastin fibres are an abundant and integral part of many extracellular matrices and are especially critical for providing the property of elastic recoil to tissues. The significance of elastin fibres is clearly reflected by the numerous human conditions in which a skin phenotype occurs as a result of elastin fibre abnormalities. METHOD: Between January and June 2013, skin specimens were obtained prospectively during surgery on 20 patients with rectal prolapse and 21 patients without prolapse undergoing surgery for other indications. Expression levels of elastin in the skin were measured by Orcein staining, and Image J. Tensile tests were performed using the Zwick Roell device, with custom ceramic clamps. For statistical analysis, Student's t test was used. RESULTS: Histological analysis of prolapse vs control showed percentage dermal elastin fibres of 9 vs 5.8 % (p = 0.001) in males and 6.5 vs 5.3 % (p = 0.05) in females. Patients with more severe prolapse (external) had a significantly (p = 0.05) higher percentage dermal elastin fibres 6.9 vs 6.1 % than internal prolapse. Young's modulus of patients with prolapse was lower in males (3.3 vs 2.8, p = 0.05) and females (3.1 vs 2.7, p = 0.05). CONCLUSION: Patients with prolapse have a higher concentration of elastin fibres in the skin, and these differences are quantitatively demonstrated through mechanical testing. This suggests that the aetiology may be a result of a dysfunction of elastin fibre assembly.

Expression of fibulin-5 in the skin of patients with rectal prolapse.

AIM: Components of connective tissue other than collagen have been found to be involved in patients with rectal prolapse. The organization of elastic fibres differs between controls and subsets of patients with rectal prolapse, and their importance for maintaining the structural and functional integrity of the pelvic floor has been demonstrated in transgenic mice, with animals which have a null mutation in fibulin-5 (Fbln5(i/i)) developing prolapse. This study aimed to compare fibulin-5 expression in the skin of patients with and without rectal prolapse. METHOD: Between January 2013 and February 2014, skin specimens were obtained during surgery from 20 patients with rectal prolapse and from 21 without prolapse undergoing surgery for other indications. Fibroblasts from the skin were cultured and the level of fibulin-5 expression was determined on cultured fibroblasts, isolated from these specimens by quantitative real-time polymerase chain reaction. Immunohistochemistry was performed on fixed tissue specimens to assess fibulin-5 expression. RESULTS: Fibulin-5 mRNA expression and fibulin-5 staining intensity were significantly lower in young male patients with rectal prolapse compared with age-matched controls [fibulin-5 mean ± SD mRNA relative units, 1.1 ± 0.41 vs 0.53 ± 0.22, P = 0.001; intensity score, median (range), 2 (0-3) vs 1 (0-3), P = 0.05]. There were no significant differences in the expression of fibulin-5 in women with rectal prolapse compared with controls. CONCLUSION: Fibulin-5 may be implicated in the aetiology of rectal prolapse in a subgroup of young male patients.

Outcome of laparoscopic ventral mesh rectopexy for external rectal prolapse.

AIM: The study assessed the efficacy of laparoscopic ventral mesh rectopexy (LVMR) for full thickness external rectal prolapse (ERP), including recurrent prolapse. METHOD: A prospective database identified all patients undergoing LVMR for ERP over the 16-year period to December 2013. Clinical outcome, Cleveland Clinic Incontinence Score (CCIS), quality of life (QOL) and patient-reported outcome were evaluated. RESULTS: In total, 190 LVMRs (87% women) were performed during the study period, with a median active follow-up of 29 (1-196) months; 120 had a follow-up > 5 years and 16 > 10 years. The median time from surgery was 73 (1-196) months. The 60-day mortality, recurrence and mesh-related complication rates were 1%, 3% and 3.7%. The mean improvement in CCIS was 8 (P < 0.0001). Sixty-two patients returned a complete sequence of QOL scores (Birmingham Bowel and Urinary Symptoms Questionnaire 22), which had improved by 46% at year 1 and were sustained at a median of 4 years (P < 0.001). Mean patient-reported outcome measures for satisfaction at final review in 119 responders was 9.1/10. Thirty-nine patients underwent LVMR for recurrent ERP following perineal repair. Of these, full thickness recurrence occurred in one and there were no mesh complications. The same sustained improvement in QOL was observed. CONCLUSION: LVMR for ERP is associated with low morbidity and recurrence and a long-term improvement in function and QOL. LVMR achieves the same benefits after a failed perineal procedure.

Phase II trial of domatinostat (4SC-202) in combination with avelumab in patients with previously treated advanced mismatch repair proficient oesophagogastric and colorectal adenocarcinoma: EMERGE.

BACKGROUND: Most oesophagogastric adenocarcinomas (OGAs) and colorectal cancers (CRCs) are mismatch repair proficient (MMRp), responding poorly to immune checkpoint inhibition. We evaluated the safety and efficacy of domatinostat (histone deacetylase inhibitor) plus avelumab (anti-PD-L1 antibody) in patients with previously treated inoperable, advanced/metastatic MMRp OGA and CRC. PATIENTS AND METHODS: Eligible patients were evaluated in a multicentre, open-label dose escalation/dose expansion phase II trial. In the escalation phase, patients received escalating doses of domatinostat [100 mg once daily (OD), 200 mg OD, 200 mg twice daily (BD)] orally for 14 days followed by continuous dosing plus avelumab 10 mg/kg administered intravenously 2-weekly (2qw) to determine the recommended phase II dose (RP2D). The trial expansion phase evaluated the best objective response rate (ORR) during 6 months by RECIST version 1.1 using a Simon two-stage optimal design with 2/9 and 1/10 responses required to proceed to stage 2 in the OGA and CRC cohorts, respectively. RESULTS: Patients (n = 40) were registered between February 2019 and October 2021. Patients in the dose escalation phase (n = 12) were evaluated to confirm the RP2D of domatinostat 200 mg BD plus avelumab 10 mg/kg. No dose-limiting toxicities were observed. Twenty-one patients were treated at the RP2D, 19 (9 OGA and 10 CRC) were assessable for the best ORR; 2 patients with CRC did not receive combination treatment and were not assessable for the primary endpoint analysis. Six patients were evaluated in the dose escalation and expansion phases. In the OGA cohort, the best ORR was 22.2% (95% one-sided confidence interval lower bound 4.1) and the median duration of disease control was 11.3 months (range 9.9-12.7 months). No responses were observed in the CRC cohort. No treatment-related grade 3-4 adverse events were reported at the RP2D. CONCLUSIONS: Responses in the OGA cohort met the criteria to expand to stage 2 of recruitment with an acceptable safety profile. There was insufficient signal in the CRC cohort to progress to stage 2. TRIAL REGISTRATION: NCT03812796 (registered 23rd January 2019).