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Human epidermal growth factor receptor 2 ( HER2 , also known as ERBB2 ) amplification or overexpression occurs in approximately 20% of advanced gastric or gastro-oesophageal junction adenocarcinomas 1 – 3 . More than a decade ago, combination therapy with the anti-HER2 antibody trastuzumab and chemotherapy became the standard first-line treatment for patients with these types of tumours 4 . Although adding the anti-programmed death 1 (PD-1) antibody pembrolizumab to chemotherapy does not significantly improve efficacy in advanced HER2-negative gastric cancer 5 , there are preclinical 6 – 19 and clinical 20 , 21 rationales for adding pembrolizumab in HER2-positive disease. Here we describe results of the protocol-specified first interim analysis of the randomized, double-blind, placebo-controlled phase III KEYNOTE-811 study of pembrolizumab plus trastuzumab and chemotherapy for unresectable or metastatic, HER2-positive gastric or gastro-oesophageal junction adenocarcinoma 22 ( https://clinicaltrials.gov , NCT03615326). We show that adding pembrolizumab to trastuzumab and chemotherapy markedly reduces tumour size, induces complete responses in some participants, and significantly improves objective response rate. Interim analysis of a phase III clinical trial of HER2-positive gastric adenocarinoma shows pembrolizumab plus trastuzumab and chemotherapy improves response rates compared with trastuzumab and chemotherapy alone.

Latin Americans are highly heterogeneous regarding the type of Native American ancestry. Consideration of specific associations with common diseases may lead to substantial advances in unraveling of disease etiology and disease prevention. Here we investigate possible associations between the type of Native American ancestry and leading causes of death. After an aggregate-data study based on genome-wide genotype data from 1805 admixed Chileans and 639,789 deaths, we validate an identified association with gallbladder cancer relying on individual data from 64 gallbladder cancer patients, with and without a family history, and 170 healthy controls. Native American proportions were markedly underestimated when the two main types of Native American ancestry in Chile, originated from the Mapuche and Aymara indigenous peoples, were combined together. Consideration of the type of Native American ancestry was crucial to identify disease associations. Native American ancestry showed no association with gallbladder cancer mortality (P = 0.26). By contrast, each 1% increase in the Mapuche proportion represented a 3.7% increased mortality risk by gallbladder cancer (95%CI 3.1-4.3%, P = 6×10-27). Individual-data results and extensive sensitivity analyses confirmed the association between Mapuche ancestry and gallbladder cancer. Increasing Mapuche proportions were also associated with an increased mortality due to asthma and, interestingly, with a decreased mortality by diabetes. The mortality due to skin, bladder, larynx, bronchus and lung cancers increased with increasing Aymara proportions. Described methods should be considered in future studies on human population genetics and human health. Complementary individual-based studies are needed to apportion the genetic and non-genetic components of associations identified relying on aggregate-data.

Background/Objectives: Pain management in colorectal cancer is influenced by genetic variability in opioid receptor genes (OPRM1 and OPRD1), potentially affecting opioid efficacy and adverse drug reactions (ADRs). This study evaluated the association of OPRM1 (rs1799971 and rs510769) and OPRD1 (rs2236861) polymorphisms with pain severity, opioid efficacy, and ADRs in Chilean colorectal cancer patients. Methods: The genotypes of OPRM1 and OPRD1 polymorphisms and clinical data from 69 colorectal cancer patients were analyzed. Associations between genotypes, ADRs, and pain severity (maximum Visual Analog Scale, VAS) were evaluated under inheritance models. Results: The OPRM1 rs1799971 G allele was significantly associated with pain presence (p = 0.008), while OPRD1 rs2236861 was linked to ADR risk (p = 0.042). Allelic distribution analysis revealed higher frequencies of the OPRD1 G allele and OPRM1 rs510769 T allele in patients with ADRs and pain, respectively. For OPRM1 rs510769, the dominant model showed a significant association with pain severity (p = 0.033), while the overdominant model revealed a trend toward significance (p = 0.0504). Logistic regression model tests showed no significant predictive associations for the maximum VAS or ADRs under inheritance models. Conclusions: Genetic variations in OPRM1 and OPRD1 may play a role in pain perception and ADRs in colorectal cancer patients. These findings contribute to the understanding of pharmacogenomic factors in opioid therapy, emphasizing the need for further research to validate the clinical utility of these genetic markers.

Lung cancer is a leading cause of cancer-related deaths in Latin America, with non-small cell lung cancer (NSCLC) being the most prevalent. The current study aimed to report real-world data on epidermal growth factor receptor (EGFR) mutational testing and treatment regimens at diagnosis and progression in patients with metastatic NSCLC across four Latin American countries (Argentina, Chile, Colombia and Uruguay). A retrospective, multicenter, observational study was conducted in patients with NSCLC using medical records from participating countries. The study population was categorized into two cohorts: Cohort 1 comprised of newly diagnosed, treatment-naïve patients with stage IV NSCLC; and cohort 2 comprised of stage IV NSCLC EGFR mutation (EGFRm)-positive patients who had progressed after first- or second-generation EGFR-tyrosine kinase inhibitor (TKI) treatment. Measures included demographic variables, health characteristics, treatment regimen, molecular testing rate and turnaround time at diagnosis and at progression for cohorts 1 and 2, respectively. Descriptive statistics were used to summarize all study measures. Of the 462 patients enrolled, 431 were newly diagnosed or treatment naïve with metastatic NSCLC. In cohort 1, the majority of patients with private health insurance (57.31%) underwent molecular diagnosis while only 41.3% of patients within the public sector had access to testing. The average molecular testing rate in cohort 1 varied across countries, with Argentina having the highest testing rate (79%) and Uruguay the lowest (27.63%). EGFRm was observed in 22% of patients. Cohort 2 comprised 31 patients who had progressed after first- or second-generation EGFR-TKI treatment and of these, only 22 (70.97%) underwent testing after progression. Access to molecular testing is still a challenge impacting the choice of first-line treatment in Latin American patients with NSCLC. These findings underline the unmet needs of ensuring early diagnosis, molecular profiling and use of correct treatment to alleviate NSCLC burden in the region.

Colorectal cancer (CRC) is the second leading cause of cancer deaths globally. While ethnic differences in driver gene mutations have been documented, the South American population remains understudied at the genomic level, despite facing a rising burden of CRC. We analyzed tumors of 40 Chilean CRC patients (Chp) using next-generation sequencing and compared them to data from mainly Caucasian cohorts (TCGA and MSK-IMPACT). We identified 388 mutations in 96 out of 135 genes, with TP53 (45%), KRAS (30%), PIK3CA (22.5%), ATM (20%), and POLE (20%) being the most frequently mutated. TSC2 mutations were associated with right colon cancer (44.44% in RCRC vs. 6.45% in LCRC, p-value = 0.016), and overall frequency was higher compared to TCGA (p-value = 1.847 × 10[sup.−5]) and MSK-IMPACT cohorts (p-value = 3.062 × 10[sup.−2]). Limited sample size restricts definitive conclusions, but our data suggest potential differences in driver mutations for Chilean patients, being that the RTK-RAS oncogenic pathway is less affected and the PI3K pathway is more altered in Chp compared to TCGA (45% vs. 25.56%, respectively). The prevalence of actionable pathways and driver mutations can guide therapeutic choices, but can also impact treatment effectiveness. Thus, these findings warrant further investigation in larger Chilean cohorts to confirm these initial observations. Understanding population-specific driver mutations can guide the development of precision medicine programs for CRC patients.

Colorectal cancer (CRC) is the second leading cause of cancer deaths globally. While ethnic differences in driver gene mutations have been documented, the South American population remains understudied at the genomic level, despite facing a rising burden of CRC. We analyzed tumors of 40 Chilean CRC patients (Chp) using next-generation sequencing and compared them to data from mainly Caucasian cohorts (TCGA and MSK-IMPACT). We identified 388 mutations in 96 out of 135 genes, with TP53 (45%), KRAS (30%), PIK3CA (22.5%), ATM (20%), and POLE (20%) being the most frequently mutated. TSC2 mutations were associated with right colon cancer (44.44% in RCRC vs. 6.45% in LCRC, p-value = 0.016), and overall frequency was higher compared to TCGA (p-value = 1.847 × 10−5) and MSK-IMPACT cohorts (p-value = 3.062 × 10−2). Limited sample size restricts definitive conclusions, but our data suggest potential differences in driver mutations for Chilean patients, being that the RTK-RAS oncogenic pathway is less affected and the PI3K pathway is more altered in Chp compared to TCGA (45% vs. 25.56%, respectively). The prevalence of actionable pathways and driver mutations can guide therapeutic choices, but can also impact treatment effectiveness. Thus, these findings warrant further investigation in larger Chilean cohorts to confirm these initial observations. Understanding population-specific driver mutations can guide the development of precision medicine programs for CRC patients.

Human epidermal growth factor receptor 2 (ERBB2/HER2) amplification or overexpression occurs in approximately 20% of advanced gastric or gastroesophageal junction adenocarcinomas1–3. Over a decade ago, combination therapy with the anti–HER2 antibody trastuzumab and chemotherapy became the standard first-line treatment for these patients4. Although adding the anti–programmed death 1 (PD-1) antibody pembrolizumab to chemotherapy does not significantly improve efficacy in advanced HER2-negative gastric cancer5, there are preclinical6–19 and clinical20,21 rationales for adding pembrolizumab in HER2-positive disease. Here we describe results of the protocol-specified first interim analysis of the randomized, double-blind, placebo-controlled phase III KEYNOTE-811 study of pembrolizumab plus trastuzumab and chemotherapy for unresectable or metastatic, HER2-positive gastric or gastroesophageal junction adenocarcinoma (ClinicalTrials.gov, NCT03615326)22. We show that adding pembrolizumab to trastuzumab and chemotherapy dramatically reduces tumour size, induces complete responses in some participants, and significantly improves objective response rate.

A strong association between the proportion of indigenous South American Mapuche ancestry and the risk of gallbladder cancer (GBC) has been reported in observational studies. Chileans show the highest incidence of GBC worldwide, and the Mapuche are the largest indigenous people in Chile. We set out to assess the confounding-free effect of the individual proportion of Mapuche ancestry on GBC risk and to investigate the mediating effects of gallstone disease and body mass index (BMI) on this association. Genetic markers of Mapuche ancestry were selected based on the informativeness for assignment measure, and then used as instrumental variables in two-sample Mendelian randomization analyses and complementary sensitivity analyses. Results suggested a putatively causal effect of Mapuche ancestry on GBC risk (inverse variance-weighted (IVW) risk increase of 0.8% per 1% increase in Mapuche ancestry proportion, 95% CI 0.4% to 1.2%, p = 6.7 × 10−5) and also on gallstone disease (3.6% IVW risk increase, 95% CI 3.1% to 4.0%), pointing to a mediating effect of gallstones on the association between Mapuche ancestry and GBC. In contrast, the proportion of Mapuche ancestry showed a negative effect on BMI (IVW estimate −0.006 kg/m2, 95% CI −0.009 to −0.003). The results presented here may have significant implications for GBC prevention and are important for future admixture mapping studies. Given that the association between the individual proportion of Mapuche ancestry and GBC risk previously noted in observational studies appears to be free of confounding, primary and secondary prevention strategies that consider genetic ancestry could be particularly efficient.

•Genetic variants in ABCB1/4 are associated with gallbladder cancer risk in Chileans.•Conferred risk effects and allele frequencies were similar in Chile and North India.•Chileans with large proportions of Mapuche ancestry showed strong associations. The first large-scale genome-wide association study of gallbladder cancer (GBC) recently identified and validated three susceptibility variants in the ABCB1 and ABCB4 genes for individuals of Indian descent. We investigated whether these variants were also associated with GBC risk in Chileans, who show the highest incidence of GBC worldwide, and in Europeans with a low GBC incidence. This population-based study analysed genotype data from retrospective Chilean case-control (255 cases, 2042 controls) and prospective European cohort (108 cases, 181 controls) samples consistently with the original publication. Our results confirmed the reported associations for Chileans with similar risk effects. Particularly strong associations (per-allele odds ratios close to 2) were observed for Chileans with high Native American (=Mapuche) ancestry. No associations were noticed for Europeans, but the statistical power was low. Taking full advantage of genetic and ethnic differences in GBC risk may improve the efficiency of current prevention programs.

Latin Americans have a rich genetic make-up that translates into heterogeneous fractions of the autosomal genome in runs of homozygosity (FROH) and heterogeneous types and proportions of indigenous American ancestry. While autozygosity has been linked to several human diseases, very little is known about the relationship between inbreeding, genetic ancestry, and cancer risk in Latin Americans. Chile has one of the highest incidences of gallbladder cancer (GBC) in the world, and we investigated the association between inbreeding, GBC, gallstone disease (GSD), and body mass index (BMI) in 4029 genetically admixed Chileans. We calculated individual FROH above 1.5 Mb and weighted polygenic risk scores for GSD, and applied multiple logistic regression to assess the association between homozygosity and GBC risk. We found that homozygosity was due to a heterogeneous mixture of genetic drift and consanguinity in the study population. Although we found no association between homozygosity and overall GBC risk, we detected interactions of FROH with sex, age, and genetic risk of GSD that affected GBC risk. Specifically, the increase in GBC risk per 1% FROH was 19% in men (p-value = 0.002), 30% in those under 60 years of age (p-value = 0.001), and 12% in those with a genetic risk of GSD above the median (p-value = 0.01). The present study highlighted the complex interplay between inbreeding, genetic ancestry, and genetic risk of GSD in the development of GBC. The applied methodology and our findings underscored the importance of considering the population-specific genetic architecture, along with sex- and age-specific effects, when investigating the genetic basis of complex traits in Latin Americans.