Loss of CDX2 and high COX2 (PTGS2) expression in metastatic colorectal cancer.

Lack of expression of the tumour suppressor gene caudal-type homeobox 2 (CDX2) associates with poor outcomes in early stage colorectal cancer (CRC). Yet its prognostic value in the context of other prognostic biomarkers in metastatic CRC (mCRC) is unknown. Overexpressed cyclooxygenase-2 (COX2) has been reported in advanced CRC. However, CDX2 and COX2 relationship in mCRC remains undetermined. We aimed to assess their expression in mCRC tumours from a clinically characterised cohort and their influence on overall survival (OS) and progression-free survival (PFS) in first line. Among 720 consecutive mCRC patients, 346 had tumour samples appropriate for tissue microarray assembly and immunohistochemistry analyses. Clinical and survival data were retrospectively assessed. Loss of CDX2 expression was detected in 27 (7.8%) samples, enriched in poorly differentiated tumours (20%; p < 0.01) and in those with the BRAF p.V600E variant (40%; p < 0.01). Most tumours (93.4%) expressed COX2. COX2-negative samples were enriched in poorly differentiated mCRC. In unadjusted analyses, median OS (p < 0.001) and median PFS (p < 0.05) were inferior for patients with CDX2-negative versus CDX2-positive tumours. In conclusion, loss of CDX2 was significantly associated with poorly differentiated mCRC and BRAF p.V600E allele and a prognostic marker of worse OS.

New Functional Impairment After Hospital Discharge by Traumatic Brain Injury Mechanism in Younger Than 3 Years Old Admitted to the PICU in a Single Center Retrospective Study.

OBJECTIVES: Children who suffer traumatic brain injury (TBI) are at high risk of morbidity and mortality. We hypothesized that in patients with TBI, the abusive head trauma (AHT) mechanism vs. accidental TBI (aTBI) would be associated with higher frequency of new functional impairment between baseline and later follow-up. DESIGN: Retrospective single center cohort study. SETTING AND PATIENTS: Children younger than 3 years old admitted with TBI to the PICU at a level 1 trauma center between 2014 and 2019. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Patient characteristics, TBI mechanism, and Functional Status Scale (FSS) scores at baseline, hospital discharge, short-term (median, 10 mo [interquartile range 3-12 mo]), and long-term (median, 4 yr [3-6 yr]) postdischarge were abstracted from the electronic health record. New impairment was defined as an increase in FSS greater than 1 from baseline. Patients who died were assigned the highest score (30). Multivariable logistic regression was performed to determine the association between TBI mechanism with new impairment. Over 6 years, there were 460 TBI children (170 AHT, 290 aTBI), of which 13 with AHT and four with aTBI died. Frequency of new impairment by follow-up interval, in AHT vs. aTBI patients, were as follows: hospital discharge (42/157 [27%] vs. 27/286 [9%]; p < 0.001), short-term (42/153 [27%] vs. 26/259 [10%]; p < 0.001), and long-term (32/114 [28%] vs. 18/178 [10%]; p < 0.001). Sensory, communication, and motor domains were worse in AHT patients at the short- and long-term timepoint. On multivariable analysis, AHT mechanism was associated with greater odds (odds ratio [95% CI]) of poor outcome (death and new impairment) at hospital discharge (4.4 [2.2-8.9]), short-term (2.7 [1.5-4.9]), and long-term timepoints (2.4 [1.2-4.8]; p < 0.05). CONCLUSIONS: In patients younger than 3 years old admitted to the PICU after TBI, the AHT mechanism-vs. aTBI-is associated with greater odds of poor outcome in the follow-up period through to ~5 years postdischarge. New impairment occurred in multiple domains and only AHT patients further declined in FSS over time.

Current clinical practice in the management of Brazilian patients with potentially resectable pancreatic ductal adenocarcinoma (PDAC).

BACKGROUND AND OBJECTIVES: We aimed to describe the routine clinical practice of physicians involved in the treatment of patients with localized pancreatic ductal adenocarcinoma (PDAC) in Brazil. METHODS: Physicians were invited through email and text messages to participate in an electronic survey sponsored by the Brazilian Gastrointestinal Tumor Group (GTG) and the Brazilian Society of Surgical Oncology (SBCO). We evaluated the relationship between variable categories numerically with false discovery rate-adjusted Fisher's exact test p values and graphically with Multiple Correspondence Analysis. RESULTS: Overall, 255 physicians answered the survey. Most (52.5%) were medical oncologists, treated patients predominantly in the private setting (71.0%), and had access to multidisciplinary tumor boards (MTDTB; 76.1%). Medical oncologists were more likely to describe neoadjuvant therapy as beneficial in the resectable setting and surgeons in the borderline resectable setting. Most physicians would use information on risk factors for early recurrence, frailty, and type of surgery to decide treatment strategy. Doctors working predominantly in public institutions were less likely to have access to MTDTB and to consider FOLFIRINOX the most adequate regimen in the neoadjuvant setting. CONCLUSIONS: Considerable differences exist in the management of localized PDAC, some of them possibly explained by the medical specialty, but also by the funding source of health care.

Influence of proton pump inhibitors on the pathological response of rectal cancer: a multicentre study.

Background: The standard neoadjuvant therapy for rectal cancer involves fluoropyrimidines and radiotherapy and, most recently, total neoadjuvant therapy (TNT). A drug-drug interaction between fluoropyrimidines and proton-pump inhibitors (PPI) was suggested, with a negative impact on oncological outcomes in breast, colon and gastric cancers. Little is known about such an effect on rectal tumours. We aimed to evaluate the impact of PPI utilisation on the pathological response after chemoradiation for rectal cancer. Materials and methods: Retrospective multicentre study of rectal cancer patients treated with neoadjuvant chemoradiotherapy with capecitabine (cohort 1) or 5-fluororuracil (5-FU) (cohort 2); TNT with oxaliplatin-based regimens was allowed. The pathological response was considered a complete (ypCR) or complete + partial (ypCR + ypPR) according to American Joint Committee on Cancer. PPI use was considered at any time during the neoadjuvant period if concomitant to fluoropyrimidines. Results: From January 2007 to November 2020, 251 patients received capecitabine and 196 5-FU. The rates of PPI use in cohorts 1 and 2 were 20.3% and 26.5%, respectively. TNT was offered to 18.3% in cohort 1. PPI use did not influence ypCR in cohort 1 (yes versus no: 29.4% versus 19.5%; p = 0.13) or 2 (yes versus no: 25.0% versus 26.4%; p = 1.0). Similar ypCR + ypPR were observed in both cohorts 1 (76.5% versus 72.0%; p = 0.60) and 2 (86.5% versus 76.4%; p = 0.16). PPI use was not associated with pathological response in multivariable analysis. PPI users experienced more grade 3 or higher diarrhoea and infections. Conclusion: PPI concomitant to capecitabine/5-FU chemoradiation did not influence the pathological response in rectal cancer but was associated with more treatment-related adverse events.

HORMONET: a phase II trial of tamoxifen for estrogen/progesterone receptor-positive neuroendocrine tumors.

Background: Nearly 30% of neuroendocrine tumors (NETs) have evidence of immunohistochemical (IHC) expression of estrogen (ER) and/or progesterone (PR) receptors. Therefore, targeting ER/PR may offer an effective NET-directed treatment to select patients. Methods: We conducted a multicenter Simon two-stage single-arm phase II trial of tamoxifen in patients with metastatic, progressive NETs. Eligible patients had positive IHC expression of ER and/or PR ⩾ 1%. Prior therapy with somatostatin analogs was required for progressing/functioning cases. Main exclusion criterion was aggressive disease requiring cytotoxic therapy. The primary end point was disease control rate (DCR) at week 24 by Response Evaluation Criteria in Solid Tumors version 1.1. We planned to enroll 23 patients in the first stage, to reach a DCR at week 24 of 70% (versus 50%); if ⩾12 patients reached the primary end point, a total of 37 would be included. Results: From February 2019 to February 2022, 23 out of 59 patients were eligible and enrolled: 15 (65%) were females; the most common sites were pancreas (11; 48%) and small bowel (6; 26%). In all, 13 patients (56.5%) had G2 NETs. At a median follow-up of 27 months, 13 patients (56.5%) had stable disease at week 24 and median progression-free survival (PFS) was 7.9 months [interquartile range (IQR): 3.7-12.1]. The best response was stable disease in 13 patients, with most patients experiencing minor tumor growth. Median PFS times were not significantly different according to ER/PR < or ⩾30% (p = 0.49) or ER versus PR expression (p = 0.19). One patient experienced grade 2 constipation. Conclusion: Tamoxifen for ER-/PR-positive NETs patients is safe but offers modest antitumor effects. Trial registry name: Study of Tamoxifen in Well Differentiated Neuroendocrine Tumors and Hormone Receptor Positive Expression (HORMONET). URL: https://clinicaltrials.gov/ct2/show/NCT03870399?term=03870399&draw=2&rank=1. Registration number: NCT03870399.

Therapy Sequencing in Patients With Advanced Neuroendocrine Neoplasms.

Neuroendocrine neoplasms (NENs) comprise a beautifully complicated, exciting landscape of histologies and clinical behaviors. However, the nuanced complexity of low- and high-grade variants can easily overwhelm both patients and providers. In this chapter, we review the ever-expanding literature on both functioning and nonfunctioning small bowel and pancreatic NENs, touching on somatostatin analogs, hepatic-directed therapies, small molecules, radiopharmaceuticals, immunotherapy, cytotoxic chemotherapy, and new promising agents. Furthermore, we suggest some strategies to address the most challenging scenarios seen in clinical practice, including sequencing of agents, treatment of carcinoid syndrome, and options for well-differentiated high-grade disease.

Metastatic pheochromocytoma and paraganglioma: a retrospective multicentre analysis on prognostic and predictive factors to chemotherapy.

Background: Prognostic and predictive markers in metastatic pheochromocytoma and paraganglioma (mPPGL) are unknown. We aimed to evaluate epidemiology of mPPGL, and prognostic factors of overall survival (OS) and predictive markers of treatment duration with first-line chemotherapy (TD1L). Patients and methods: Retrospective multicentre study of adult patients with mPPGL treated in Latin American centres between 1982 and 2021. Results: Fifty-eight patients were included: 53.4% were female, median age at diagnosis of mPPGL was 36 years and 12.1% had a family history of PPGL. The primary site was adrenal, non-adrenal infradiaphragmatic and supradiaphragmatic in 37.9%, 34.5% and 27.6%, respectively. 65.5% had a functioning tumour and 62.1% had metachronous metastases. Positive uptakes were found in 32 (55.2%) 68Gallium positron emission tomography (PET/CT), 27 (46.6%) 2-deoxy-2-[fluorine-18]fluoro-D-glucose PET/CT and 37 (63.8%) of 131Iodine-metaiodobenzylguanidine (MIBG) tests. Twenty-three (40%) patients received first-line chemotherapy, with cyclophosphamide, vincristine and dacarbazine used in 12 (52%) of patients. At a median follow-up of 62.8 months, median TD1L was 12.8 months. Either functional exams, tumour functionality, pathological characteristics or primary tumour location were significantly associated with response or survival. Yet, negative MIBG, Ki67 ≥ 10%, infradiaphragmatic location and functional tumours were associated with numerically inferior OS. Conclusions: In patients with mPPGL, prognostic and predictive factors to chemotherapy are still unknown, but negative MIBG uptake, Ki67 ≥ 10%, infradiaphragmatic location and functional tumours were numerically linked to worse OS. Our results should be further validated in larger and independent cohorts.

Current Treatment of Potentially Resectable Pancreatic Ductal Adenocarcinoma: A Medical Oncologist's Perspective.

Pancreatic cancer has traditionally been associated with a dismal prognosis, even in early stages of the disease. In recent years, the introduction of newer generation chemotherapy regimens in the adjuvant setting has improved the survival of patients treated with upfront resection. However, there are multiple theoretical advantages to deliver early systemic therapy in patients with localized pancreatic cancer. So far, the evidence supports the use of neoadjuvant therapy for patients with borderline resectable pancreatic cancer. The benefit of this treatment sequence for patients with resectable disease remains elusive. In this review, we summarize the data on adjuvant therapy for pancreatic cancer and describe which evidence backs the use of neoadjuvant therapy. Additionally, we address important issues faced in clinical practice when treating patients with localized pancreatic cancer.

Brazilian Society of Surgical Oncology: Guidelines for the management of anal canal cancer.

BACKGROUND: Anal canal squamous cell carcinoma (SCC) is a relatively uncommon neoplasia, and it is mostly a local-regional cancer, of low metastatic potential (only 15%), resulting in cure in most cases treated with definitive chemoradiation. On the other hand, its incidence has been steadily increasing over the last decades, which makes it an important public health problem. In an effort to provide surgeons and oncologists who treat patients with anal cancer with the most updated information based on the best scientific evidence, the Brazilian Society of Surgical Oncology (SBCO) has produced the present guideline for the management of anal canal SCC, focused on the main topics related to daily clinical practice. OBJECTIVES: The SBCO developed the present guidelines to provide recommendations on the main topics related to the management of anal canal squamous cell carcinoma (SCC) based on current scientific evidence. METHODS: Between October 2022 and January 2023, 14 experts met to develop the guidelines for the management of anal canal cancer. A total of 30 relevant topics were distributed among the participants. The methodological quality of a final list with 121 sources was evaluated, all the evidence was examined and revised, and the management guidelines were formulated by the 14-expert committee. To reach a final consensus, all the topics were reviewed in a meeting that was attended by all the experts. RESULTS: The proposed guidelines contained 30 topics considered to be highly relevant in the management of anal canal cancer, covering subjects related to screening recommendations, preventive measures, tests required for diagnosing and staging, treatment strategies, response assessment after chemoradiotherapy, surgical technique-related aspects, and follow-up recommendations. In addition, screening and response assessment algorithms, and a checklist were proposed to summarize the important information and offer an updated tool to assist surgeons and oncologists who treat anal canal cancer and in providing the best care to their patients. CONCLUSION: These guidelines summarize recommendations based on the most current scientific evidence on relevant aspects of anal canal cancer management and are a practical guide to help surgeons and oncologists who treat anal canal cancer make the best therapeutic decisions.

A systematic review of therapeutic strategies in gastroenteropancreatic grade 3 neuroendocrine tumors.

Background: Gastroenteropancreatic (GEP) neuroendocrine neoplasms with Ki-67 > 20% were subdivided in the most recent 2019 World Health Organization histopathological classification into grade 3 (G3) neuroendocrine tumors (NETs), described as well-differentiated tumors, and neuroendocrine carcinomas, which are described as poorly differentiated tumors. This classification met the demand noted for different prognoses between these subgroups, prompting the need for treatment recommendations for well-differentiated G3 tumors. Methods: We systematically searched medical literature databases and oncology conferences for studies on G3 GEP NET to describe epidemiology, diagnosis, molecular features, and treatments used. We excluded studies that did not discriminate G3 NET data. Data were tabulated and described, and a quality analysis of the reports was performed. Results: We found 23 published studies and six abstracts; 89.7% of studies were retrospective, six were composed exclusively of G3 NETs. Among 761 patients, the median number of patients per study was 15, most were male and older than 60 years, and functional imaging tests were positive in more than 80% of cases. Overall, the scientific evidence supporting the treatment of G3 GEP NETs is limited. For localized disease, resection remains the standard treatment but there is no evidence to support neoadjuvant or adjuvant therapy. For advanced disease, capecitabine and temozolomide seems to be the most effective option, with a response rate, median progression-free survival, and median overall survival up to 37.9%, 20.6 months, and 41.2 months, respectively. Conclusion: The latest available data on the epidemiology, diagnosis, molecular changes, and treatment of G3 GEP NET are described. Yet, the level of evidence for treatment recommendations is low, as most studies are retrospective. A treatment algorithm for G3 GEP NET is proposed.

HPV virus and biomarkers of resistance to chemoradiation in circulating tumor cells from patients with squamous cell carcinoma of the anus.

Localized anal cancer is mostly represented by squamous cell carcinoma of the anus (SCCA) and is cured in ≥80 % of cases by chemoradiation (CRT). Development of techniques for detection/evaluating circulating tumor cells (CTCs) for diagnosis/ prognosis/response to therapy can change the manner we treat/follow SCCA patients. OBJECTIVE: to detect CTCs from patients with SCCA and evaluate the presence of HPV virus, p16 expression and markers related to resistance to CRT (RAD23B/ ERCC1/ TYMS) in CTCs at baseline and after CRT. METHODS: CTCs were isolated/quantified by ISET®, protein expressions were analyzed by immunocytochemistry and HPV DNA was detected by chromogenic in situ hybridization. RESULTS: We enrolled 15 patients: median age was 61 (43-73) years, the majority was women (10/15). CTCs were detected in all patients at baseline (median= 0.4 (0.4-3.33) CTCs/mL) and in 8/9 patients, after CRT (median= 2.33 (0-7.0) CTCs/mL). DNA from HPV was found in CTCs in 14/15 patients (93.33 %) at baseline and in 7/9 (77.7 %) after treatment. At a median follow-up of 22.20 (1.45-38.55) months, three patients expressed ERCC1 in CTCs after treatment, with one of them having disease recurrence. CONCLUSION: We showed that detection of HPV in CTCs from patients with non-metastatic SCCA is feasible and appears to be a sensitive diagnostic method. These results may be clinically useful for better monitoring these patients. However, future larger cohorts may demonstrate whether there is any correlation between the presence of HPV and the expression of screening markers for CRT in SCCA.

Impact of Granulocyte Colony-Stimulating Factor (G-CSF) on the Outcomes of Patients With Metastatic Pancreatic Adenocarcinoma (MPA) During First-Line Treatment With FOLFIRINOX: A Single-Center Retrospective Analysis.

INTRODUCTION: The role of primary prophylaxis (PP) with granulocyte colony-stimulating factor (G-CSF) for patients with metastatic pancreatic adenocarcinoma (MPA) treated with FOLFIRINOX is unknown. We aimed to compare the frequencies of grades 3 or 4 neutropenia (G3/4N) and febrile neutropenia (FN) and survival outcomes according to the use of PP. METHODS: This is a retrospective study. We included patients with pathologically confirmed MPA treated with FOLFIRINOX in first-line. Patients who received primary prophylaxis (PP group) were compared to patients who received secondary or no G-CSF (no-PP group). Overall survival (OS) and progression-free survival (PFS) were evaluated using the standard Cox proportional hazard model. To account for potential biases, we performed sensitivity analyses excluding patients who received secondary prophilaxis and treating G-CSF as a time-dependent covariate in extended Cox proportional hazard models. RESULTS: The study population consisted of 123 patients. PP was used by 75 patients (61.0%). G3/4 N occurred more frequently among patients without PP (10.7 vs 41.7%; P < .001). There was no difference in the frequency of FN between groups (5.3 vs 8.3%; P = .710). In multivariate analysis, PP was associated with a trend toward improved OS (HR = .66; 95% confidence interval [95% CI] .41 - 1.07; P = .094). In the multivariate model excluding patients with secondary prophylaxis (HR = .54; 95% CI 0.32 - .91; P = .022) and in the time-dependent model (HR = .47; 95% CI 0.28 - .80; P = .005), PP was associated with statistically superior OS. CONCLUSIONS: Despite the reduction in the frequency of G3/4N, the risk of FN among patients treated with FOLFIRINOX without G-CSF is too low to justify its use in a routine basis. However, given the potential of G-CSF to improve survival in this setting, further studies are warranted to assess its role during treatment with FOLFIRINOX for patients with MPA.

In vitro selection and characterization of probiotic properties in eight lactobacillus strains isolated from cocoa fermentation.

Traditionally, probiotic microorganisms are isolated from human and animal intestinal microbiota. However, the demand for diversification of biofunctional products has driven the search for new sources of probiotic candidates, such as fermented foods and vegetables. The present study found that strains isolated from the fermentation of fine cocoa from southern Bahia have biotechnological potential for use as a probiotic, since they showed capacity for self-aggregation and co-aggregation, antimicrobial activity against intestinal pathogens and resistance to gastrointestinal transits. Scores of importance for each property were established in order to more accurately assess the probiotic potential of the strains. The tests carried out contemplate the criteria previously established for the selection of probiotic candidates.

Erratum: METNET: a phase II trial of metformin in patients with well-differentiated neuroendocrine tumours.

[This corrects the article on p. 1 in vol. 16.].

Antagonistic activity of Lactiplantibacillus plantarum 6.2 extracted from cocoa fermentation and its supernatant on Gardnerella vaginalis.

Search for alternative methods for the treatment of bacterial vaginosis has been growing, and probiotics being among them. The most well-known probiotic microorganisms are lactobacilli, which are naturally present in the vaginal microenvironment. Cocoa fermentation is a source of lactic acid bacteria, with lactobacilli being the most prominent. The aim of this study was to evaluate the antagonistic activity of Lactiplantibacillus plantarum 6.2 a strain of lactobacilli isolated from cocoa fermentation, and its cell-free supernatant on Gardnerella vaginalis. It was shown that Lpb. plantarum 6.2 and its supernatant, used at three concentrations, i.e., 40, 20 and 10 mg/mL, have a strong antagonistic activity against G. vaginalis, with a probable action of proteinaceous bacteriocins; the activity was lost after heat treatment. The ability to exclude and displace G. vaginalis from the adhesion site to vaginal HMVII epithelial cells was also demonstrated by the lactobacilli and the supernatant, with the latter showing a bactericidal effect. Thus, the Lpb. plantarum 6.2 strain presents itself as a good probiotic with potential to be used not only as a therapeutic alternative for vaginosis but also as a complement to existing therapies.

Plasma Angiotensin II Is Increased in Critical Coronavirus Disease 2019.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) employs angiotensin-converting enzyme 2 (ACE2) as its receptor for cell entrance, and studies have suggested that upon viral binding, ACE2 catalytic activity could be inhibited; therefore, impacting the regulation of the renin-angiotensin-aldosterone system (RAAS). To date, only few studies have evaluated the impact of SARS-CoV-2 infection on the blood levels of the components of the RAAS. The objective of this study was to determine the blood levels of ACE, ACE2, angiotensin-II, angiotensin (1-7), and angiotensin (1-9) at hospital admission and discharge in a group of patients presenting with severe or critical evolution of coronavirus disease 2019 (COVID-19). We showed that ACE, ACE2, angiotensin (1-7), and angiotensin (1-9) were similar in patients with critical and severe COVID-19. However, at admission, angiotensin-II levels were significantly higher in patients presenting as critical, compared to patients presenting with severe COVID-19. We conclude that blood levels of angiotensin-II are increased in hospitalized patients with COVID-19 presenting the critical outcome of the disease. We propose that early measurement of Ang-II could be a useful biomarker for identifying patients at higher risk for extremely severe progression of the disease.

Cure Rates According to Dose-Intensity of Chemoradiation in T2N0 Squamous Cell Carcinoma of the Anal Canal.

BACKGROUND: Patients with T2N0 squamous cell carcinoma of the anal canal (SCCA) have comprised less than 30% of patients enrolled in phase III clinical trials of curative-intent definitive chemoradiation. We aimed to evaluate treatment outcomes of these patients according to dose-intensity of chemoradiation. MATERIALS AND METHODS: Retrospective multicenter study of patients with T2N0 SCCA, with the primary endpoint to compare the progression-free survival (PFS) of patients treated with full definitive chemoradiotherapy (f-CRT, CRT with 2 drugs) versus a nonstandard treatment (NST; radiotherapy only or CRT with 1 drug). Secondary outcomes were rates of complete response (CR), salvage surgery, and colostomy. PFS time was analyzed using the Kaplan-Meier method and differences in survival outcomes were assessed using the log-rank test and adjusted for prognostic covariates using a multivariable Cox regression model RESULTS: From March 2006 to January 2020, 74 patients were included. Most patients (n = 58; 78.4%) received f-CRT. In a median follow up time of 66.1 months, the unadjusted median PFS was 128.3 months (95% confidence interval [CI] 105.5-151.1) for f-CRT versus 74.1 months for NST (95% CI 45.8-102.4; P = .067). CR was achieved by 51 (87.9%) versus 11 (68.9%; P = .065) patients treated with f-CRT or an NST, respectively. Comparing f-CRT versus NST, the colostomy rates were higher for those treated with an NST: 5 (32.8%) versus 5 (9.5%; P = .019) CONCLUSION: For patients with T2N0 SCCA, f-CRT remains the standard treatment, offering higher CR and less likelihood of colostomy.

METNET: a phase II trial of metformin in patients with well-differentiated neuroendocrine tumours.

Background: Preclinical studies have suggested that metformin has anti-tumour effects, likely due to blockage of mammalian target of rapamycin pathway through adenosine monophosphate-activated protein kinase and decreased insulin levels. A retrospective study showed that metformin added to everolimus to treat type 2 diabetes mellitus offered longer progression-free survival (PFS) in patients with pancreatic neuroendocrine tumours (NET). Aims: To evaluate the efficacy and safety of metformin monotherapy in patients with advanced/metastatic well-differentiated NET (WD-NET) of gastroenteropancreatic (GEP) or pulmonary origin. Patients and methods: Single-arm phase II trial of metformin 850 mg PO twice daily until progression or intolerance for patients with progressive metastatic well-differentiated GEP or pulmonary NET. The primary endpoint was disease control rate (DCR) by RECIST 1.1 at 6 months. Secondary endpoints were response rate, PFS, toxicity and variations in glycaemic profiles (glycaemia, glycated haemoglobin and peptide C and insulin) at baseline, at 30 and 90 days. Results: From 2014 to 2019, 28 patients were enrolled: median age was 50 years; 84% had non-functional NET, 86% were of GEP origin and 62% had G2 NET. At the time of last follow-up, 26 patients had progression, with 13 (46%) presenting DCR at 6 months and a median PFS of 6.3 months (95% confidence interval: 3.2-9.3). There was no objective response, but one patient with refractory carcinoid syndrome had complete symptom relief, lasting for more than 5 years. Variations in glycaemic profiles were not associated with DCR at 6 months. Diarrhoea was the most common adverse event, being grade 3 or 4 in 10% of the cases. Conclusion: Metformin monotherapy offers modest anti-tumour activity in well-differentiated GEP or lung NET.