MSI-high Tumors Research Articles

ASCL2 Affects the Efficacy of Immunotherapy in Colon Adenocarcinoma Based on Single-Cell RNA Sequencing Analysis.

Colon adenocarcinoma (COAD) is one of the leading causes of cancer-associated deaths worldwide. Patients with microsatellite instability-high (MSI-H) tumors were shown to highly benefit from immune checkpoint inhibitors (ICIs) than patients with microsatellite stable (MSS) tumors. Furthermore, the infiltration of immune cells and the expression of cancer stem cells (CSCs) in COAD were associated with the anti-tumor immune response. However, the potential mechanisms showing the relationship between microsatellite instability and CSCs or tumor-infiltrating immune cells (TIICs) have not been elucidated. Accumulating evidence reveals that achaete-scute family bHLH transcription factor 2 (ASCL2) plays a crucial role in the initiation and progression of COAD and drug resistance. However, the specific biological functions of ASCL2 in COAD remain unknown. In this study, we performed weighted gene co-expression network analysis (WGCNA) between MSS and MSI-H subsets of COAD. The results revealed that ASCL2 was a potential key candidate in COAD. Subsequently, the single-cell RNA-seq revealed that ASCL2 was positively associated with CSCs. Further, ASCL2 was shown to indirectly affect tumor immune cell infiltration by negatively regulating the expression of DUSP4. Finally, we inferred that the immunotherapy-sensitive role of ASCL2/DUSP4 axis on COAD is partly attributed to the activation of WNT/β-catenin pathway. In conclusion, this study revealed that ASCL2 was positively correlated to CSCs and tumor immune infiltration in COAD. Therefore, ASCL2 is a promising predictor of clinical responsiveness to anti-PD-1/PD-L1 therapy in COAD.

24P Somatic tumor testing informs on mismatch repair deficiency (MMR-D) phenotype in patients with endometrial cancer

24P Somatic tumor testing informs on mismatch repair deficiency (MMR-D) phenotype in patients with endometrial cancer

Updated efficacy and safety results from the phase 2 study of serplulimab, a novel anti-PD-1 antibody, in patients with previously treated unresectable or metastatic microsatellite instability-high or mismatch repair-deficient solid tumors.

2592 Background: Serplulimab is a novel humanized monoclonal antibody against PD-1. At ASCO 2021, we have presented the results from the phase 2 serplulimab study (NCT03941574) in patients with unresectable/metastatic microsatellite instability-high or mismatch repair-deficient (MSI-H/dMMR) solid tumors who have progressed on or been intolerant to standard therapies with a median follow-up of 7.7 months. Here, we report the updated efficacy and safety results together with the results from sensitivity analysis after another 6-month follow-up. Methods: In this single-arm, open-label, multicenter, phase 2 study, patients aged 18–75 years with histologically or cytologically confirmed unresectable or metastatic MSI-H/dMMR solid tumors were enrolled to receive 3 mg/kg of intravenous serplulimab every two weeks for up to two years. The primary endpoint was objective response rate (ORR) assessed by an independent radiological review committee (IRRC) per RECIST v1.1. Secondary endpoints included ORR assessed by the investigators, duration of response (DoR), progression-free survival (PFS), overall survival (OS), and safety. Results: As of July 10, 2021, 108 patients had received at least one dose of study treatment and were included in the safety set (SS). Among them, 68 patients with confirmed MSI-H (by local sites or central lab) were included in the main efficacy analysis population (MEAP); 58 patients with confirmed MSI-H (by central lab) and had no major protocol deviations were included in the sensitivity analysis population (SAP). The median follow-up duration was 13.5 months in the MEAP and 14.0 months in the SAP. IRRC-assessed ORR per RECIST v1.1 was 39.7% (95% CI 28.0–52.3; 3 complete response [CR]) in the MEAP and 43.1% (95% CI 30.2–56.8; 2 CR) in the SAP. Investigator-assessed ORRs were 38.2% (95% CI 26.7–50.8; 1 CR) and 41.4% (95% CI 28.6–55.1; 1 CR) in the MEAP and the SAP, respectively. Median DoR, PFS, and OS were not reached; 12-month OS rate was 74.5% (95% CI 62.2–83.3) in the MEAP and 82.4% (95% CI 69.7–90.1) in the SAP. In the SS, 57 (52.8%) patients had grade ≥3 treatment-emergent adverse events, most commonly anemia (9.3%). Thirteen (12.0%) patients had grade ≥3 immune-related adverse events. Three (2.8%) deaths (2 progressive disease and 1 intestinal obstruction) that might be related to serplulimab were reported. Conclusions: The encouraging antitumor activity and the manageable safety profile sustained after a longer duration of follow-up, supporting the further development of serplulimab as a potential tissue-agnostic antitumor treatment. Clinical trial information: NCT03941574.

Clinical and genomic distinction of class 1/2/3 BRAF-mutant colorectal cancer and differential prognosis.

3533 Background: Mutations occurring at the V600 amino acid of BRAF is the most common BRAF mutations in colorectal cancer (CRC), which lead to RAS-independent active monomers (Class 1) and are the targets of BRAF inhibitors. BRAF non-V600 mutants can be further classified as RAS-independent active dimers (Class 2) and RAS-dependent impaired kinase (Class 3). The clinical and genetic distinction of CRC patients carrying different subtypes of BRAF mutations remain to be revealed. Methods: A multicenter retrospective study investigated the mutational profiles of 2,118 CRC patients whose baseline tumor samples were analyzed between June 2015 and June 2020 using capture-based hybrid NGS targeting 400+ cancer-related genes. Clinical characteristics including age, sex, stage, and tumor location were analyzed. A public cBioPortal cohort of 471 metastatic CRC patients was used for survival analysis. Results: A total of 473 patients were identified to contain BRAF mutations and can be sub-grouped into Class 1 (N = 246), Class 2 (N = 29), Class 3 (N = 53), and others (N = 145). All Class 1 BRAF mutations were V600E, while the Class 2 and Class 3 mutations were predominantly G469 (52%) and D594 (56%), respectively. No difference in patient’s age, sex, and stage was observed among BRAF Class 1-3 subgroups, but the anatomical location of the tumor differed among subgroups, particularly between Class 1 and Class 3 BRAF-mutant patients significantly (p = 0.027). Specifically, 39% of tumors carrying Class 1 mutations occurred at the right colon, while the most frequent location of tumors with Class 3 mutations was rectum (58%). Mutational profiling revealed that KRAS and APC mutations were enriched in Class 2/3 compared to Class 1 BRAF-mutant patients, while RNF43 and SMAD4 mutations were more frequently observed in Class 1 patients. Mutations causing the activation of the Wnt or RTK/RAS signaling pathways were also more common in Class 2/3 subgroups comparing to Class 1 patients. Furthermore, based on the analysis of mutation allele frequency, Class 1 BRAF mutations tended to be drivers while Class 2/3 BRAF mutations were more likely to be passengers. In addition, mutational signature profiling showed that the NER signature was enriched in Class 1 BRAF-mutant patients but the APOBEC signature in Class2/3 classes. The tumor mutational burden of Class 2 BRAF tumors was higher than the other two subgroups (median: 10.4 vs 7.6 and 8.4), and microsatellite instability-high tumors were more common in Class 1 (11% vs 7% and 4%). In the cBioPortal cohort, Class 1 BRAF-mutant patients had the worst overall survival whereas Class 3 patients demonstrated the best prognosis. Conclusions: The clinical and genetic features of CRC patients harboring Class 2 and 3 BRAF mutations were different from those carrying Class 1 BRAF mutations in aspects including tumor location, concurrent mutations, mutational signatures, as well as survival outcomes.

Phase III study (daNIS-2) of the anti–TGF-β monoclonal antibody (mAb) NIS793 with nab-paclitaxel/gemcitabine (NG) versus NG alone in patients (pts) with first-line metastatic pancreatic ductal adenocarcinoma (mPDAC).

TPS4193 Background: Despite improving outcomes, current therapies for mPDAC have a modest impact on overall survival (OS) and new therapies are needed. PDAC is characterized by an abundance of intratumoral fibrosis, which may contribute to the lack of treatment efficacy and act as a mechanical barrier to effective penetration of therapeutics. TGF-β has a multifactorial role in tumorigenesis and maintaining an immunosuppressive tumor microenvironment (TME). Emerging evidence points to the role of TGF-β as a pivotal activator of cancer-associated fibroblasts that lead to the development of fibrotic networks. In preclinical models, TGF-β blockade alters the TME to facilitate an antitumor response, reduce stromal fibrosis, and augment the benefit of chemotherapy, providing rationale for combining TGF-β–targeting agents with chemotherapy. NIS793 is a potent, selective, human IgG2 mAb antagonist of TGF-β. This study investigates NIS793 in combination with NG vs NG alone in treatment-naïve pts with mPDAC. Methods: This is a phase III, randomized, double-blind, multicenter, two-arm study (NCT04935359) consisting of two stages: an initial safety run-in period followed by two-arm randomization. Eligible pts include adults with previously untreated mPDAC and an ECOG performance status ≤1. Pts with a tumor histology other than adenocarcinoma or with microsatellite instability-high tumors are ineligible. The aim of the safety run-in period is to assess the safety and tolerability of NIS793 + NG and confirm the recommended dose for the randomized phase of this study. Data will be analyzed once at least six evaluable pts have received NIS793 (intravenous [IV] 2100 mg every 2 weeks) + nab-paclitaxel (IV 125 mg/m2 on Days 1, 8, and 15) + gemcitabine (IV 1000 mg/m2 on Days 1, 8, and 15) for one 28-day cycle. Pts (N = 480) will be randomized 1:1 to NIS793 + NG or placebo + NG. Treatment will continue until unacceptable toxicity, disease progression, discontinuation by investigator or pt choice, death, or withdrawal of consent. The primary objective is to evaluate the OS of pts receiving NIS793 + NG vs NG alone; secondary objectives include assessing progression-free survival, the overall response rate, disease control rate, duration of response, and time to response (assessed locally per RECIST v1.1), as well as safety and tolerability, immunogenicity, pharmacokinetics, and patient-reported outcomes such as health-related quality of life. Efficacy will be assessed at screening, every 8 weeks for 1 year, and then every 12 weeks until disease progression. Blood samples will be taken at baseline and during treatment for pharmacokinetic and immunogenicity assessments. This study is ongoing and will enroll pts from approximately 149 sites across 28 countries. The first pt was treated on October 20, 2021. Clinical trial information: NCT04935359.

Anti-PD1, capecitabine, and oxaliplatin for the first-line treatment of dMMR esophagogastric cancer (AuspiCiOus-dMMR): A proof-of-principle study (AuspiCiOus).

TPS4163 Background: Doublet cytotoxic treatment demonstrates survival benefit over single drug therapies in patients with advanced esophagogastric cancer (EGC). Previous clinical data suggests an improved survival outcome in patients with microsatellite instability (MSI) treated with PD-1 inhibitor monotherapy or in combination with chemotherapy in first line palliative treatment. The positive effect of immunotherapy was only seen after a couple of months of treatment. This suggests that the patient might benefit from a short course of chemotherapy at the start of treatment. However, reports on the effects of cytotoxic treatment in MSI-high tumors range from beneficial to detrimental. Thus, the value of cytotoxic treatment, as well as the effect on the tumor immune microenvironment (TME) in MSI-high tumors is unclear. Therefore, in AuspiCious-dMMR we will study the effect of sequential treatment in patients with mismatch repair deficient (dMMR) EGC on the tumor immune microenvironment and, more specifically, the impact on the infiltration of cytotoxic T cells, before and after a short course of chemotherapy, and during treatment with PD-1 inhibition. Methods: AuspiCiOus is a multi-center, open-label, single arm (phase 2) study in patients with dMMR irresectable or metastatic EGC adenocarcinoma (NCT05177133). Patients are treated with Capecitabine and Oxaliplatin for two 3-weekly cycles, after which treatment is continued with retifanlimab (PD-1 inhibitor) for 4-weekly cycles up to progression or unacceptable toxicity, with a maximum of two years. Before treatment, after chemotherapy and after two cycles of immunotherapy fresh tumor biopsies are collected to study the primary outcome (T cell infiltration and the interferon-γ signature) as well as for translational research purposes (flow cytometry, nanostring profiling, (multicolor) immunohistochemistry and organoid culturing). Blood is collected at the same time points and on day 3 after the first course of immunotherapy for isolation of peripheral blood mononuclear cell, and determination of cytokine/chemokine profile, circulating stromal markers, and circulating tumor DNA. Also, fecal samples are collected to determine changes in the intestinal microbiome and patient reported outcome measures are used to determine quality of life. (s)AEs are assessed according to CTCAE v5 and tumor response is determined according to (i)RECIST 1.1. Key eligibility criteria are 1) histological confirmed diagnosis of untreated metastatic or irresectable HER2- adenocarcinoma of stomach or junction and 2) dMMR determination by IHC. Study is open for inclusion and three of planned 25 patients have been enrolled. Clinical trial information: NCT05177133.

Updated analysis from a phase 2 study of tislelizumab (TIS) monotherapy in patients (pts) with previously treated, locally advanced, unresectable/metastatic microsatellite instability-high (MSI-H)/mismatch repair-deficient (dMMR) solid tumors.

e14556 Background: TIS is an anti-programmed cell death protein-1 antibody engineered to minimize binding to FcγR on macrophages to abrogate antibody-dependent phagocytosis. Primary results from this single-arm, multicenter, open-label, Phase 2 study evaluating TIS in pts with MSI-H/dMMR solid tumors, showed a clinically meaningful improvement in the objective response rate (ORR) for this patient population. Here we report results from the updated analysis (NCT03736889). Methods: Eligible adult pts with previously treated, locally advanced, unresectable/metastatic histologically confirmed MSI-H/dMMR solid tumors with ≥ 1 measurable lesion (RECIST v1.1) and an Eastern Cooperative Oncology Group performance status of ≤ 1 were enrolled. Pts received TIS 200 mg intravenously every 3 weeks until disease progression, unacceptable toxicity, or withdrawal. The efficacy analysis set were all pts who received any dose of TIS with measurable disease per independent review committee (IRC) at baseline. The primary endpoint was IRC-assessed ORR (RECIST v1.1). Secondary endpoints included duration of response (DoR), time to response (TTR), disease control rate (DCR), progression-free survival (PFS) (all IRC-assessed [RECIST v1.1]), overall survival (OS), and safety. Programmed death ligand 1 (PD-L1) immunohistochemistry assay (Ventana SP263) was applied retrospectively. Results: Between Sep 2018–Jul 2021, 80 pts were enrolled (median age 53 years; range 19–81 years) and 75 were included in the efficacy analysis set. In this updated efficacy analysis set, at a median follow-up of 15.2 months, ORRIRC was 46.7% (n = 35; 95% CI 35.1, 58.6) in all tumor types (1-sided p < 0.0001), including 5 complete responses (CR) and 30 partial responses (PR). ORRIRC was 39.1% (n = 18; 95% CI 25.1, 54.6) in colorectal cancer (CRC) pts (N = 46), 55.6% (n = 5; 95% CI 21.2, 86.3) in G/GEJC pts (N = 9), and 60.0% (n = 12; 95% CI 36.1, 80.9) in other pts (N = 20). Of the pts who responded (n = 35), one patient had disease progression. Median DoR was not reached, median TTRIRC was 11.9 weeks (range 8.4–98.9) and DCR was 72.0% (95% CI 60.4, 81.8). Median PFSIRC was not reached (95% CI 7.5, not estimable [NE]). Median OS (safety analysis set) was not reached (95% CI 28.7, NE). No clear association was observed between PD-L1 expression and clinical efficacy. Treatment-emergent adverse events (TEAEs) ≥ Grade 3 occurred in 48.8% (n = 39) of pts. The most common ≥ Grade 3 TEAE was anemia, 10.0% (n = 8). Immune-mediated TEAEs ≥ Grade 3 were 8.8% (n = 7). Conclusions: With a longer follow up time, TIS demonstrated clinically meaningful improvement in ORR in pts with MSI-H or dMMR solid tumors. TIS was generally well tolerated, with no new safety signals. These data support TIS as a new treatment option for this patient population. Clinical trial information: NCT03736889.

Anti PD-1 monoclonal antibody in patients with MSI-high and/or high tumor mutational burden for solid malignancies.

e15539 Background: High microsatellite instability (MSI-H) tumors have been associated with good responses to check-point inhibitors (CPI). With overall response rates (ORR) ranging between 36-46% among colorectal cancer (CRC) and other solid malignancies. Data regarding predictors of response and responses in non-CRC malignancies remains limited. We sought to evaluate the response to PD-1/PDL-1 CPI in patients with MSI-H and/or high TMB solid malignancies. Methods: Retrospective analysis of 16 patients (pts) who received 18 CPI-based therapies between October 2017 and February 2022. MSI-H and TMB status was assessed by CARIS, Guardant360 or INVITAE genetic testing. Primary objective was to determine objective response rate (ORR), defined as complete response (CR) or partial response (PR) by RECIST1.1. Secondary outcomes included progression-free survival(PFS); overall survival (OS), and duration of overall response (DOR). Results: A total of 16 pts were included. The median age of 72 years (range 53-83), 44% were male and 75% Hispanic. 44% of pts had RCR and 50% were previously treated, and 50% were stage IV at diagnosis. The most common mutations were BRCA2 31%, PIK3cA 31%, KRAS 25%, and GNAS 25%. The majority of pts received single-agent CPI therapy (72%). After a median follow-up of 52 months, 11 pts continued to receive therapy, 2 pts completed treatment. 3 pts died from progression of the disease. 1 pts switched from single-agent pembrolizumab to nivolumab-ipilimumab combination followed by nivolumab maintenance due to disease progression. 15 pts were evaluable for response with an ORR of 33%, including 33% among pts with CRC and 27% for non-CRC malignancies. (Table - Response rates) The OS was not reached (NR), with a PFS of 53 months (PFS of 64% at 1 year and 56% at 4 years). The median DOR was not reached (NR). The treatment was well tolerated and pts received a median of cycles was 19 (range 3-51) with no discontinuations due to toxicities. The molecular mutations, clinical characteristics, type of malignancy, MSI-H, or H-TMB status were not significantly associated with response to CPI after logistical regression analysis. Conclusions: CPIs are an effective treatment option for patients with MSI-H and/or High TMB, with an ORR of 33%. However, pts achieved durable responses, with a median DOR not reached. We identify a higher incidence of SD rates among CRC pts (67% vs. 18% non-CRC). We did not identify any predictors associated with response to CPI, likely due to the small number of pts. However, there was a tendency to highest response rates among pts with MSI-H and high TMB.[Table: see text]

Biomarkers of Response and Resistance to Immunotherapy in Microsatellite Stable Colorectal Cancer: Toward a New Personalized Medicine.

Simple SummaryImmune Checkpoint Inhibitors (ICIs) have demonstrated clinical efficacy in Microsatellite Instability High Colorectal Cancer (MSI-H CRC). However, in Microsatellite Stable (MSS) CRC, ICIs monotherapy provides limited clinical benefit. Therefore, efforts must be made to understand the highly heterogeneous CRC microenvironment and to find predictive biomarkers of response in order to adequately select CRC patients who may respond to ICIs-based therapies.Immune Checkpoint Inhibitors (ICIs) are well recognized as a major immune treatment modality for multiple types of solid cancers. However, for colorectal cancer (CRC), ICIs are only approved for the treatment of Mismatch-Repair-Deficient and Microsatellite Instability-High (dMMR/MSI-H) tumors. For the vast majority of CRC, that are not dMMR/MSI-H, ICIs alone provide limited to no clinical benefit. This discrepancy of response between CRC and other solid cancers suggests that CRC may be inherently resistant to ICIs alone. In translational research, efforts are underway to thoroughly characterize the immune microenvironment of CRC to better understand the mechanisms behind this resistance and to find new biomarkers of response. In the clinic, trials are being set up to study biomarkers along with treatments targeting newly discovered immune checkpoint molecules or treatments combining ICIs with other existing therapies to improve response in MSS CRC. In this review, we will focus on the characteristics of response and resistance to ICIs in CRC, and discuss promising biomarkers studied in recent clinical trials combining ICIs with other therapies.

Microsatellite Instability and Metastatic Colorectal Cancer - A Clinical Perspective.

Approximately 4-5% of patients with metastatic colorectal cancer (mCRC) have mismatch repair deficient (dMMR)/microsatellite instability-high (MSI-H) tumours. These tumours present challenges in the clinical practice due to variant response to fluoropyrimidine-based chemotherapy and, perhaps, also non-immunologic targeted therapies. Recently, a breakthrough in the treatment of dMMR/MSI-H mCRC has been achieved with several clinical trials showing dramatic long-term benefit of immunotherapy using checkpoint inhibitors. Nevertheless, several questions remain regarding the optimisation of immunotherapy regimens and the use of biomarkers to identify populations set to derive the greatest benefit from immunotherapy. Combination regimens and/or the use of immunotherapy as a maintenance after induction non-immunologic systemic therapy may be the way forward to improve outcomes.

Ovarian Endometrioid and Clear Cell Carcinomas with Low Prevalence of Microsatellite Instability: A Unique Subset of Ovarian Carcinomas Could Benefit from Combination Therapy with Immune Checkpoint Inhibitors and Other Anticancer Agents.

Ovarian cancer has the highest mortality rate among all gynecological malignancies; therefore, a novel treatment strategy is needed urgently. Utilizing immune checkpoint inhibitors has been considered for microsatellite instability (MSI)-high (MSI-H) tumors. However, the prevalence of MSI-H tumors in ovarian endometrioid and clear cell carcinomas remains unclear. Here, polymerase chain reaction was used to analyze 91 cases of ovarian endometrioid and clear cell carcinomas for the MSI status and the relationship between MSI-H, immune checkpoint molecules, and clinicopathological factors (including patient survival). Only 5 of 91 (5%) cases were MSI-H endometrioid carcinomas. In these cases, CD-8 expression was significantly higher (p = 0.026), confirming an enhanced immune response. From the survival curve, no statistical correlations were found between the MSI-H group and the microsatellite stable (MSS) group; however, the MSS group trended towards better progression-free survival than the MSI-H group (p = 0.056). Patients with PD-L1 expression had shorter overall survival than those without (p = 0.022). Thus, MSI-H is a rare event and not a favorable prognostic factor in ovarian endometrioid and clear cell carcinomas. Thus, to improve the prognosis of ovarian endometrioid carcinoma and clear cell carcinomas, a combination therapy of immune checkpoint inhibitors and other molecular targeted therapies may be required.

Comparative analysis of microsatellite instability by next-generation sequencing, MSI PCR and MMR immunohistochemistry in 1942 solid cancers

Checkpoint inhibitor approval for microsatellite instability-high (MSI-H) tumours has made MSI as a therapeutically important biomarker. Next-generation sequencing (NGS)-based MSI detection is being widely used for assessing MSI. However, MSI tumours detected using NGS and their relevance to MSI-polymerase chain reaction (PCR) and mismatch repair deficiency (dMMR) are unclear. In 1942 solid cancer cases tested using NGS-based comprehensive cancer panel with 523 genes (1.94 mb), the MSI score, tumour mutation burden (TMB; ≥ 10 mutations/mb), and frameshift mutations were analysed. GeneScan analyses of five mononucleotide markers (MSI-PCR) and MMR protein immunohistochemistry (IHC) were compared with the NGS-MSI results. With a ≥ 12% MSI score as a cut-off for MSI-H, two MSS cases were classified as MSI-H. With a ≥ 20% cut-off, 10 cases categorised as MSS by NGS were MSI-H/dMMR by MSI-PCR and MMR IHC. To avoid discrepant cases, we adopted a high MSI cut-off and a borderline MSI category. Finally, MSI-H (≥ 20%), borderline MSI (≥ 7% and < 20%), and MSS (< 7%) were found in 35 (1.8%), 24 (1.2%), and 1883 (97%) cases, respectively. All MSI-H cases by NGS were MSI-H/dMMR by MSI-PCR and MMR IHC. Of the 24 borderline MSI cases by NGS, MSI-H/dMMR was 9 (37.5%) cases, MSS/dMMR was 1 (4.2%) case, and 11 (45.8%) of them had high TMB. All MSS cases by NGS were MSS/pMMR by MSI-PCR/IHC, and 257 (13.6%) had high TMB. With those arbitrary cut-off points, 10 (0.5%) MSS cases using NGS were discrepant with MSI-PCR or MMR IHC, and all were borderline MSI cases. The mean number of frameshift mutations was significantly higher in the MSI-H group (28.3) than in the borderline MSI (7.7) or MSS (1.3) groups (p < 0.001). In conclusion, to facilitate therapeutic decision-making for NGS, cut-off points for MSI can be defined based on MSI-PCR/dMMR confirmation.

Early age of onset and broad cancer spectrum persist in MSH6- and PMS2-associated Lynch syndrome

PurposeThis study aimed to characterize MSH6/PMS2-associated mismatch repair–deficient (MMR-D)/microsatellite instability-high (MSI-H) tumors, given revised guidelines suggesting more modest phenotypes. MethodsPatients who consented to Institutional Review Board–approved protocols of tumor/germline sequencing or Lynch syndrome registry at a single institution from February 2005 to January 2021 with germline, heterozygous MSH6/PMS2 pathogenic/likely pathogenic variants were identified. Clinical data were abstracted and correlated with MMR/microsatellite instability status using nonparametric tests. ResultsWe identified 243 patients (133 sequencing, 110 registry) with germline MSH6/PMS2 pathogenic/likely pathogenic variants; 186 (77%) had >1 cancer. Of 261 pooled tumors, colorectal cancer (CRC) and endometrial cancer (EC) comprised 55% and 43% of cancers in MSH6 and PMS2, respectively; 192 tumors underwent molecular assessments and 122 (64%) were MMR-D/MSI-H (77 in MSH6, 45 in PMS2). MMR-D/MSI-H cancers included CRC (n = 56), EC (n = 35), small bowel cancer (n = 6), ovarian cancer (n = 6), urothelial cancer (n = 5), pancreas/biliary cancer (n = 4), gastric/esophageal cancer (n = 3), nonmelanoma skin tumors (n = 3), prostate cancer (n = 2), breast cancer (n = 1), and central nervous system/brain cancer (n = 1). Among MMR-D/MSI-H CRC and EC, median age of diagnosis was 51.5 (range = 27-80) and 55 (range = 39-74) years, respectively; 9 of 56 (16%) MMR-D/MSI-H CRCs were diagnosed at age <35 years. ConclusionMSH6/PMS2 heterozygotes remain at risk for a broad spectrum of cancers, with 16% of MMR-D/MSI-H CRCs presenting before upper threshold of initiation of colonoscopy per guidelines.

The immune microenvironment in gastric adenocarcinoma.

Like most solid tumours, the microenvironment of epithelial-derived gastric adenocarcinoma (GAC) consists of a variety of stromal cell types, including fibroblasts, and neuronal, endothelial and immune cells. In this article, we review the role of the immune microenvironment in the progression of chronic inflammation to GAC, primarily the immune microenvironment driven by the gram-negative bacterial species Helicobacter pylori. The infection-driven nature of most GACs has renewed awareness of the immune microenvironment and its effect on tumour development and progression. About 75-90% of GACs are associated with prior H. pylori infection and 5-10% with Epstein-Barr virus infection. Although 50% of the world's population is infected with H. pylori, only 1-3% will progress to GAC, with progression the result of a combination of the H. pylori strain, host susceptibility and composition of the chronic inflammatory response. Other environmental risk factors include exposure to a high-salt diet and nitrates. Genetically, chromosome instability occurs in ~50% of GACs and 21% of GACs are microsatellite instability-high tumours. Here, we review the timeline and pathogenesis of the events triggered by H. pylori that can create an immunosuppressive microenvironment by modulating the host's innate and adaptive immune responses, and subsequently favour GAC development.

Metastatic colorectal carcinoma with signet-ring cells: Clinical, histological and molecular description from an Association des Gastro-Entérologues Oncologues (AGEO) French multicenter retrospective cohort.

Metastatic signet-ring cell colorectal carcinoma is rare. We analyzed its clinicopathological and molecular features, prognostic factors and chemosensitivity. Retrospective study from 2003 to 2017 in 31 French centers, divided into three groups: curative care (G1), chemotherapy alone (G2), and best supportive care (G3). Tumors were most frequently in the proximal colon (46%), T4 (71%), and poorly differentiated (86%). The predominant metastatic site was peritoneum (69%). Microsatellite instability and BRAF mutation were found in 19% and 9% (mainly right-sided) of patients and RAS mutations in 23%. Median overall survival (mOS) of the patients (n=204) was 10.1 months (95%CI: 7.9;12.8), 45.1 for G1 (n=38), 10.9 for G2 (n=112), and 1.8 months for G3 (n=54). No difference in mOS was found when comparing tumor locations, percentage of signet-ring cell contingent and microsatellite status. In G1, relapse-free survival was 14 months (95%CI: 6.5-20.9). In G2, median progression-free survival (PFS) was 4.7 months (95%CI: 3.6;5.9]) with first-line treatment. Median PFS was higher with biological agents than without (5.0vs 3.9 months, p=0.016). mSRCC has a poor prognosis with specific location and molecular alterations resulting in low chemosensitivity. Routine microsatellite analysis should be performed because of frequent MSI-high tumors in this population.

Immune Checkpoint Inhibitors in Advanced Prostate Cancer: Current Data and Future Perspectives.

Simple SummaryThe treatment landscape of advanced prostate cancer (PCa) is constantly improving with the approval of many new therapeutic options. Immunotherapy in PCa has been investigated with disappointing results. This review aims to evaluate the potential role of immunotherapy in both castration-sensitive and castration-resistant PCa, discussing the immunobiology of PCa, the results of the current literature, and the ongoing clinical trials. Potential prognostic and/or predictive factors and future perspectives are also discussed.In the last 10 years, many new therapeutic options have been approved in advanced prostate cancer (PCa) patients, granting a more prolonged survival in patients with metastatic disease, which, nevertheless, remains incurable. The emphasis on immune checkpoint inhibitors (ICIs) has led to many trials in this setting, with disappointing results until now. Therefore, we discuss the immunobiology of PCa, presenting ongoing trials and the available clinical data, to understand if immunotherapy could represent a valid option in this disease, and which subset of patients may be more likely to benefit. Current evidence suggests that the tumor microenvironment needs a qualitative rather than quantitative evaluation, along with the genomic determinants of prostate tumor cells. The prognostic or predictive value of immunotherapy biomarkers, such as PD-L1, TMB, or dMMR/MSI-high, needs further evaluation in PCa. Monotherapy with immune checkpoint inhibitors (ICIs) has been modestly effective. In contrast, combined strategies with other standard treatments (hormonal agents, chemotherapy, PARP inhibitors, radium-223, and TKIs) have shown some results. Immunotherapy should be better investigated in biomarker-selected patients, particularly with specific pathway aberrations (e.g., AR-V7 variant, HRD, CDK12 inactivated tumors, MSI-high tumors). Lastly, we present new possible targets in PCa that could potentially modulate the tumor microenvironment and improve antitumor activity with ICIs.

Clinicopathological features of PD-L1 protein expression, EBV positivity, and MSI status in patients with advanced gastric and esophagogastric junction adenocarcinoma in Japan

ABSTRACT This real-world study examined the prevalence of programmed death ligand-1 (PD-L1) expression and assessed the frequency of microsatellite instability-high (MSI-H) status and Epstein-Barr virus (EBV) positivity in Japanese patients with advanced gastric and gastroesophageal junction (GEJ) adenocarcinoma. This multicenter (5 sites), retrospective, observational study (November 2018–March 2019) evaluated Japanese patients with advanced gastric and GEJ adenocarcinoma after surgical resection (Stage II/III at initial diagnosis) or unresectable advanced cancer (Stage IV). The primary objectives were prevalence of PD-L1 expression (combined positive score [CPS] ≥1), MSI status, and EBV positivity. Tumor specimens of 389/391 patients were analyzed (male, 67.1%; mean age, 67.6 ± 12.2 years); 241/389 (62%) were PD-L1 positive, 24/379 (6.3%) had MSI-H tumors, and 13/389 (3.3%) were EBV positive. PD-L1 expression was higher in tumor-infiltrating immune cells than in tumor cells for lower CPS cutoffs. Among patients with MSI-H tumors and EBV-positive tumors, 19/24 (79.2%) and 9/13 (69.2%), respectively, were PD-L1 positive. A greater proportion of patients with MSI-H tumors (83.3% [20/24]) were PD-L1 positive than those with MSI-low/stable tumors (60.8% [216/355]; p = .0297); similarly, an association was observed between history of H pylori infection and PD-L1 expression. A higher proportion of patients with MSI-H tumors demonstrated PD-L1 expression with a CPS ≥10 (66.7% [16/24]) vs those with MSI-low/stable tumors (24.8% [88/355]; p < .0001). The prevalence of PD-L1 positivity among Japanese patients was comparable to that in previous pembrolizumab clinical trials and studies in gastric cancer. Particularly, higher PD-L1 expression was observed in MSI-H tumors.

Clinical Validity of Plasma-Based Genotyping for Microsatellite Instability Assessment in Advanced GI Cancers: SCRUM-Japan GOZILA Substudy.

PURPOSECirculating tumor DNA (ctDNA) genotyping may guide targeted therapy for patients with advanced GI cancers. However, no studies have validated ctDNA genotyping for microsatellite instability (MSI) assessment in comparison with a tissue-based standard.PATIENTS AND METHODSThe performance of plasma-based MSI assessment using Guardant360, a next-generation sequencing–based ctDNA assay, was compared with that of tissue-based MSI assessment using a validated polymerase chain reaction–based method in patients with advanced GI cancers enrolled in GOZILA study, a nationwide ctDNA profiling study. The primary end points were overall percent agreement, positive percent agreement (PPA), and negative percent agreement. The efficacy of immune checkpoint inhibitor therapy was also evaluated.RESULTSIn 658 patients with advanced GI cancers who underwent both plasma and tissue testing for MSI, the overall percent agreement, PPA, and negative percent agreement were 98.2% (95% CI, 96.8 to 99.1), 71.4% (95% CI, 47.8 to 88.7), and 99.1% (95% CI, 98.0 to 99.7), respectively. In patients whose plasma samples had a ctDNA fraction ≥ 1.0%, the PPA was 100.0% (15/15; 95% CI, 78.2 to 100.0). Three patients with MSI-high (MSI-H) tumors detected only by ctDNA genotyping achieved clinical benefits after receiving anti–programmed cell death 1 therapy with the progression-free survival ranging from 4.3 to 16.7 months. One patient with an aggressive cancer of an unknown primary site benefited from pembrolizumab after rapid detection of MSI-H by ctDNA genotyping.CONCLUSIONctDNA genotyping was able to detect MSI with high concordance to validated tissue-based MSI testing, especially in patients with tumors that have sufficient ctDNA shedding. Furthermore, ctDNA genotyping enabled identification of patients with MSI-H tumors who benefited from immune checkpoint inhibitor treatment.

Defining hereditary upper tract urothelial carcinoma: Implications for genetic testing and clinical management.

523 Background: Despite being a rare cancer, upper tract urothelial carcinoma (UTUC) is the third most common core cancer associated with Lynch syndrome (LS) after colorectal and endometrial cancers. Yet, there is no established guideline to identify patients with UTUC who are at risk of carrying germline mutations in LS-associated genes. The objective of this study is to define selection criteria for patients with UTUC for LS screening. Methods: We retrospectively identified patients with UTUC who underwent germline sequencing of ≥77 cancer susceptibility genes using next generation sequencing (NGS) as part of a prospective matched tumor-normal genomic profiling initiative from 04/2015 to 04/2021. Mismatch repair protein status was evaluated by immunohistochemical (IHC) staining for MMR genes MSH2, MSH6, MLH1, and PMS2. Microsatellite instability (MSI) status was determined using NGS. Diagnostic performance of clinical and tumor-based screening criteria was assessed by the presence of germline pathogenic/likely pathogenic variants (PGVs) in MMR genes. Results: A total of 232 patients with UTUC underwent germline testing; median age of diagnosis was 67 years (interquartile range 59 – 73). Of these patients, 70% were male, 43% had UTUC diagnosed before the age of 65, 85% had high grade UTUC,12% had bilateral UTUC, 11% had metastasis at diagnosis, 10% and 31% had personal and family history of LS-associated cancers, respectively. PGVs in moderate or high-penetrance genes were identified in 31 (13%) patients including 6 (3%) in BRCA1/ 2 and 21 (9%) in MMR genes (13 MSH2, 4 MSH6, 4 MLH1). A total of 10/21 (48%) patients with MMR PGVs developed UTUC as their first cancer diagnosis. Of patients with MMR PVGs, 15/16 (94%) had MMR-deficient tumors and 12/18 (67%) had MSI-high tumors. Personal and family history of LS core cancers (p &lt; 0.001), age of diagnosis &lt; 65 (p = 0.008), MSI-high (p &lt; 0.001), and MMR-deficiency (p &lt; 0.001) were associated with MMR carrier status. Female gender (p = 0.7), HG UTUC (p = 0.5), and bilateral UTUC (p = 0.7) were not associated with MMR PGVs. Current NCCN genetic referral criteria for Lynch syndrome has high specificity in identifying patients with LS (100%) but missed 11/21 (52%) patients with UTUC and MMR PGVs. Conclusions: Current genetic referral guidelines for Lynch syndrome may miss a significant portion of patients with LS-associated UTUC. UTUC tumor should be investigated for MMR protein and MSI status with IHC or next generation sequencing methods to augment LS-screening of patients with UTUC and inform systemic treatment selection.

The Genomics of Colorectal Cancer in Populations with African and European Ancestry.

KRAS (particularly KRASG12D/G13), APC, and PIK3CA were more frequently altered in AFR who had a lower frequency of MSI-H tumors. There were no differences in actionable kinase driver alterations. In young-onset colorectal cancer, both ancestries had a similar frequency of MSI-H/TMB-H tumors, but strikingly different trends in APC. See related commentary by Eng and Holowatyj, p. 1187. This article is highlighted in the In This Issue feature, p. 1171.