Microsatellite Instability-high Status Research Articles

Dostarlimab (Jemperli)

We recommend that Jemperli in combination with carboplatin and paclitaxel be reimbursed by public drug plans for the first-line treatment of adult patients with primary advanced or recurrent mismatch repair deficient (dMMR) or microsatellite instability-high (MSI-H) endometrial cancer who are candidates for systemic therapy if certain conditions are met. Jemperli in combination with carboplatin and paclitaxel should only be covered to treat adult patients who have primary stage III or IV endometrial cancer, experience a first disease recurrence and have not previously received systemic anticancer therapy for advanced disease, and/or have received prior neoadjuvant adjuvant systemic anticancer therapy and experience a first recurrence at a minimum of 6 months after completion of treatment. Eligible patients should have confirmed dMMR or MSI-H status of their tumours before starting treatment with Jemperli and have a good performance status. Jemperli should only be reimbursed in combination with carboplatin and paclitaxel if prescribed by clinicians with expertise in advanced uterine cancer. Treatment should be supervised and administered in institutions with expertise in systemic therapy delivery. The cost of Jemperli should be reduced.

Neoadjuvant immunotherapy in microsatellite instability-high (MSI-H) duodenal adenocarcinoma leads to pathological complete response and paves the way for new strategies

Duodenal adenocarcinoma is a rare digestive cancer, often diagnosed at a late stage and harbours a poor prognosis. The arrival of immunotherapy has changed the prognosis of many neoplasia, including digestive adenocarcinomas with MSI-H status. Hereby, we describe three cases of MSI-H locally advanced duodenal adenocarcinoma who received neoadjuvant treatment with a PD1 inhibitor, pembrolizumab. A partial metabolic and endoscopic response was observed in all patients after 2 cycles. Duodenopancreatectomy was performed at the end of treatment (4–6 cycles), and anatomopathological analysis demonstrated pathological complete response in all patients. Our case series paves the way for prospectively exploring neoadjuvant immunotherapy in duodenal MSI-H adenocarcinoma and raises the question of organ sparing surgery in case of complete clinical response as observed in gastric and colo-rectal adenocarcinomas.

Neoadjuvant immunotherapy in a locally advanced colon cancer patient with MSI-H and suspected Lynch syndrome: A case report.

Carrilizumab, a PD-1 inhibitor, has shown therapeutic effectiveness in patients with late-stage or metastatic solid tumors exhibiting DNA mismatch repair deficiency (dMMR) or microsatellite instability-high (MSI-H). dMMR/MSI-H cancer patients are known to be responsive to PD-1 inhibitors. However, the use of carrilizumab for preoperative immunotherapy in early, unresectable MSI-H/dMMR primary colon cancer lesions is relatively underexplored. We present the case of a 46-year-old male who sought medical attention at our institution due to a history of hematochezia for two weeks, right-sided abdominal pain for one week, and loose stools. Imaging indicated duodenal involvement, and a biopsy confirmed ascending colon adenocarcinoma with MSI-H status. Given that the patient's family exhibited a history of more than three confirmed cases of colorectal cancer spanning two generations, Lynch syndrome was considered. After four cycles of PD-1 antagonist immunotherapy with carrilizumab, the patient's symptoms resolved, and physical examination revealed no abdominal tenderness or palpable masses. Following radical colectomy, the primary tumor exhibited a pathological complete response. This case highlights the potential of preoperative neoadjuvant immunotherapy to improve staging accuracy and increase surgical resection rates in T4b MSI-H colon cancer patients without distant metastasis, suggesting a need for reconsideration of the treatment approach.

Development and validation of a deep learning-based microsatellite instability predictor from prostate cancer whole-slide images

Microsatellite instability-high (MSI-H) is a tumor-agnostic biomarker for immune checkpoint inhibitor therapy. However, MSI status is not routinely tested in prostate cancer, in part due to low prevalence and assay cost. As such, prediction of MSI status from hematoxylin and eosin (H&E) stained whole-slide images (WSIs) could identify prostate cancer patients most likely to benefit from confirmatory testing to evaluate their eligibility for immunotherapy and need for Lynch syndrome testing. Prostate biopsies and surgical resections from prostate cancer patients referred to our institution were analyzed. MSI status was determined by next-generation sequencing. Patients sequenced before a cutoff date formed an algorithm development set (n = 4015, MSI-H 1.8%) and a paired validation set (n = 173, MSI-H 19.7%) that consisted of two serial sections from each sample, one stained and scanned internally and the other at an external site. Patients sequenced after the cutoff date formed a temporally independent validation set (n = 1350, MSI-H 2.3%). Attention-based multiple instance learning models were trained to predict MSI-H from H&E WSIs. The predictor achieved area under the receiver operating characteristic curve values of 0.78 (95% CI [0.69–0.86]), 0.72 (95% CI [0.63–0.81]), and 0.72 (95% CI [0.62–0.82]) on the internally prepared, externally prepared, and temporal validation sets, respectively, showing effective predictability and generalization to both external staining/scanning processes and temporally independent samples. While MSI-H status is significantly correlated with Gleason score, the model remained predictive within each Gleason score subgroup.

Epidemiological and clinicopathological features of KRAS, NRAS, BRAF mutations and MSI in Chinese patients with stage I-III colorectal cancer.

The selection of appropriate treatment modalities based on the presence or absence of mutations in KRAS, NRAS, BRAF, and the microsatellite instability (MSI) status has become a crucial consensus in colorectal cancer (CRC) therapy. However, the distribution pattern of these genetic mutations and the prevalence of MSI status in Chinese stage I-III CRCs remain unclear. We retrospectively analyzed clinicopathological features, mutations in the KRAS, NRAS, and BRAF genes, as well as MSI status of 411 patients with stage I-III CRC who underwent surgery from June 2020 to December 2022 in the First Affiliated Hospital of Nanjing Medical University. The mutation rates of KRAS, NRAS, and BRAF were 48.9%, 2.2%, and 3.2%, respectively, and the microsatellite instability-high rate was 9.5%. KRAS mutation was independently associated with mucinous adenocarcinoma. Multivariate analysis suggested that tumor location and mucinous adenocarcinoma were independently associated with BRAF mutation. Only T stage was associated with NRAS mutations in the univariate analysis. Multivariate analysis revealed that factors such as larger tumor size, tumor location, younger age, and poor differentiation were independently associated with microsatellite instability-high status. The results illustrate the mutation frequencies of KRAS, NRAS, BRAF genes and MSI status in stage I-III CRC from the eastern region of China. These findings further validate the associations between these genes status and various clinicopathological characteristics.

Abstract 4101: Immune inhibition of murine colorectal cancer by a p53 peptide mucosal vaccine

Abstract Colorectal cancer (CRC) is among the most common cancers with high morbidity and mortality for patients despite multi-modality treatment options. Immune checkpoint inhibitors often have impact in the 15% of CRC patients with microsatellite instability-high status CRCs but have limited utility in the remaining 85% of CRC patients. Given the presence of p53 mutations in CRC, we pursued a vaccine approach against tumor cells expressing murine CRC Trp53 codon 270 missense alleles (codon 273 mutation in human cancer) using a combination of R270H p53 peptide, wild type p53 recombinant protein and used a mucosal adjuvant (MA) to drive epithelial immune responses. The vaccine (p53/MA) was studied in a CDX2-CreERT2 (tamoxifen-induced Cre-Lox) transgenic mouse CRC model where tumors arise in the cecum and proximal colon epithelium following combined ApcΔ580, KrasG12D, and Trp53R270H mutations (AKP model). The p53/MA vaccine treatment was administered intranasally to the mice at defined time points after tamoxifen tumor induction. p53/MA vaccinated animals had increased anti-p53 IgG (p<0.01), IgG2a (p<0.01), and IgG2b (p<0.001) in sera compared to control mice. The treatment enhanced antigen-specific Th1 and Th17 cellular immune responses, as shown by increasing of IFN-ɤ (p<0.05), IL-17a (p<0.01) and IL-2 (p<0.01) both in splenocytes and draining lymph nodes measured by Luminex assay. Vaccinated mice also showed significant more cells producing IFN-ɤ (p<0.001) and IL-17a (p<0.001) as analyzed by ELISpot. Importantly, the immunized animals had decreased tumor size/volume (p<0.001) and prolonged survival (p<0.05) compared to control animals that received only saline or MA respectively. Tumors from vaccinated mice also showed more mononuclear cell infiltrates than tumors from the control animals. In conclusion, novel p53/MA vaccinations can induce significant p53-specific immune responses and anti-tumor effects in the mouse AKP CRC model. Citation Format: Suhe Wang, Zhengyi Cao, Katarzyna W. Janczak, Ying Feng, Maranne Green, Eric R. Fearon, James R. Baker Jr. Immune inhibition of murine colorectal cancer by a p53 peptide mucosal vaccine [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4101.

Genomic analysis of oesophageal carcinoma (EC) to identify recurrent mutations in histone methyltransferases as a distinctive subset.

379 Background: Histone-lysine N-methyltransferase 2 (KMT2) family proteins methylate lysine 4 on the histone H3 tail at important regulatory regions in the genome and thereby impart crucial functions through modulating chromatin structures and DNA accessibility, which is associated with tumorigenesis and immune tolerance, indicating its possible correlation with the efficacy of immunotherapy. Recurrent mutations of KMT2 have been identified in EC, but data addressing the molecular features of KMT2 mutated (MT) EC are lacking. We aimed to understand the molecular profile of KMT2 -MT EC. Methods: A total of 787 oesophageal carcinoma [adenocarcinoma (EAC), N=604; squamous cell carcinoma (ESCC), N=183] were analyzed using next-generation sequencing (NGS) and immunohistochemistry (Caris Life Sciences, Phoenix, AZ). Tumor mutational burden (TMB) was calculated based on somatic nonsynonymous mutations, and mismatch repair deficiency (dMMR)/microsatellite instability-high (MSI-H) status was evaluated by a combination of IHC, Fragment analysis and NGS. Results: The mutation spectrum of KMT2A/C/D was significantly different between ESCC and EAC ( KMT2A, 2.7% vs. 1.2%; KMT2C, 3.8% vs. 1.2%; KMT2D, 14.2% vs. 2.0%, P <0.05). KMT2-MT EAC tumors showed significantly higher mutation rates in CIC (13% vs 1.1%), NF1 (12.5% vs 2.2%), FBXW7 (12% vs 3.4%), ATM (11.5% vs 2.6%) and BRCA1 (11.5% vs 1%, all q<0.05), compared to KMT2-WT tumors. However, in ESCC there were no significant differences in gene mutations between the KMT2-MT and WT groups. Significantly higher rates of dMMR/MSI-H (19.2% vs 1.0% in EAC, 5.4% vs. 0% in ESCC, both p<0.01) were seen in both KMT2-MT ESCC and EAC, compared to KMT2-WT cohorts, respectively. TMB was significantly higher in both KMT2-MT ESCC (median: 10 vs 8.6 mut/Mb, P=0.042) and EAC (23.9 vs 8.0 mut/Mb, P<0.0001), compared to KMT2-WT cohorts, respectively. A numerically longer immune-related overall survival was observed in KMT2 -MT EC patients, compared to KMT2 -WT EC patients (9.05 vs 6.98 months, HR=0.744, 95%CI: 0.52-1.07, P =0.11). Conclusions: This is the largest study to investigate the distinct genomic landscapes between KMT2 -MT and WT EC to date. Our data showed the KMT2 -MT EC has a distinctive genetic profile, indicated by higher TMB, and higher frequency of dMMR/MSI-H and gene mutations involved in DDR and epigenetic regulation. Understanding these molecular characteristics may be informative in the development of effective treatment strategies in KMT2 -MT EC.

Immune Checkpoint Inhibitors Targeting the PD-1/PD-L1 Pathway in Advanced, Recurrent Endometrial Cancer: A Scoping Review with SWOT Analysis.

Results of recent clinical trials using the immune check point inhibitors (ICI) pembrolizumab or dostarlimab with/without lenvatinib has led to their approval for specific molecular subgroups of advanced recurrent endometrial cancer (EC). Herein, we summarise the clinical data leading to this first tissue-agnostic approval. As this novel therapy is not yet available in the United Kingdom standard care setting, we explore the strengths, weaknesses, opportunities, and threats (SWOT) of ICI treatment in EC. Major databases were searched focusing on clinical trials using programmed cell death protein 1 (PD-1) and its ligand (PD-L1) ICI which ultimately contributed to anti-PD-1 approval in EC. We performed a data quality assessment, reviewing survival and safety analysis. We included 15 studies involving 1609 EC patients: 458 with mismatch repair deficiency (MMRd)/microsatellite instability-high (MSI-H) status and 1084 with mismatch repair proficiency/microsatellite stable (MMRp/MSS) status. Pembrolizumab/dostarlimab have been approved for MMRd ECs, with the addition of lenvatinib for MMRp cases in the recurrent setting. Future efforts will focus on the pathological assessment of biomarkers to determine molecular phenotypes that correlate with response or resistance to ICI in order to identify patients most likely to benefit from this treatment.

Pan-Cancer Prevalence of Microsatellite Instability-High (MSI-H) Identified by Circulating Tumor DNA and Associated Real-World Clinical Outcomes.

Immune checkpoint inhibitors are approved for advanced solid tumors with microsatellite instability-high (MSI-H). Although several technologies can assess MSI-H status, detection and outcomes with circulating tumor DNA (ctDNA)-detected MSI-H are lacking. As such, we examined pan-cancer MSI-H prevalence across 21 cancers and outcomes after ctDNA-detected MSI-H. Patients with advanced cancer who had ctDNA testing (Guardant360) from October 1, 2018, to June 30, 2022, were retrospectively assessed for prevalence. GuardantINFORM, which includes anonymized genomic and structured payer claims data, was queried to assess outcomes. Patients who initiated new treatment within 90 days of MSI-H detection were sorted into immunotherapy included in treatment (IO) or no immunotherapy included (non-IO) groups. Real-world time to treatment discontinuation (rwTTD) and real-world time to next treatment (rwTTNT) were assessed in months as proxies of progression-free survival (PFS); real-world overall survival (rwOS) was assessed in months. Cox regression tests analyzed differences. Colorectal cancer, non-small-cell lung cancer (NSCLC), prostate cancer, gastroesophageal cancer, and uterine cancer (UC) were assessed independently; all other cancers were grouped. In total, 1.4% of 171,881 patients had MSI-H detected. Of 770 patients with outcomes available, rwTTD and rwTTNT were significantly longer for patients who received IO compared with non-IO for all cancers (P ≤ .05; hazard ratio [HR] range, 0.31-0.52 and 0.25-0.54, respectively) except NSCLC. rwOS had limited follow-up for all cohorts except UC (IO 39 v non-IO 23 months; HR, 0.18; P = .004); however, there was a consistent trend toward prolonged OS in IO-treated patients. These data support use of a well-validated ctDNA assay to detect MSI-H across solid tumors and suggest prolonged PFS in patients treated with IO-containing regimens after detection. Tumor-agnostic, ctDNA-based MSI testing may be reliable for rapid decision making.

Different prognostic values of KRAS exon 2 submutations and BRAF V600E mutation in microsatellite stable (MSS) and unstable (MSI) stage III colon cancer: an ACCENT/IDEA pooled analysis of seven trials

The prognostic value of KRAS and BRAFV600E mutations in stage III colon cancer (CC) remains controversial and has never been clearly analyzed in patients with microsatellite instability-high (MSI-H) tumors due to sample size limitations. Data are also lacking for KRAS submutations and prognosis. We examined clinicopathological variables and prognosis in patients with surgically resected stage III CC who participated in seven clinical trials from the ACCENT/IDEA databases. Associations between KRAS exon 2 and BRAFV600E mutations and time to recurrence (TTR), overall survival (OS), and survival after recurrence (SAR) were assessed using a Cox model. We also analyzed the prognostic value of KRAS exon 2 submutations. Among 8460 patients, 11.4% had MSI-H status. In the MSI-H group, BRAFV600E, KRAS exon 2 mutants, and double-wild-type statuses were detected in 40.6%, 18.1%, and 41.3%, respectively, whereas and in the microsatellite stable (MSS) group, these were detected in 7.7%, 38.6%, and 53.8%, respectively. In the MSS group, 5-year TTR rates of 61.8%, 66.3%, and 72.9% were observed among patients with BRAFV600E, KRAS exon 2 mutants, and those who were DWT, respectively [adjusted hazard ratio (HR)= 1.58 and 1.31, both P < 0.001]. In the MSI-H group, 5-year TTR rates did not differ significantly among the mutated subgroups. Similar results were found for OS. However, survival after relapse was significantly shorter in the KRAS exon 2- and BRAFV600E-mutated patients in both MSS (adjusted HR= 2.06 and 1.15; both P < 0.05) and MSI-H (adjusted HR= 1.99 and 1.81; both P < 0.05) groups. In the MSS group, KRAS exon 2 mutations were associated with TTR, but only p.G12C, p.G12D, and p.G13D were associated with poor outcomes after disease recurrence. Testing for both KRAS and BRAFV600E mutations in stage III patients should be considered as they can better define individual patient prognosis, and may also enable patient selection for (neo)adjuvant trials dedicated to specific molecular subtypes with poor prognosis.

Concordance of microsatellite instability and mismatch repair status in paired biopsies and surgical specimens of resectable gastroesophageal adenocarcinoma: time for a call to action.

Reliability of mismatch repair proteins and microsatellite instability assessment is essential in order to define treatment strategy and identify candidates to immune checkpoint inhibitors in locally advanced gastroesophageal carcinoma. We evaluated the concordance of deficient mismatch repair (dMMR) and microsatellite instability-high (MSI-H) status between endoscopic biopsies and surgical specimens. Consecutive patients with resectable gastric or gastroesophageal junction adenocarcinoma classified as MSI-H/dMMR by polymerase chain reaction (PCR) or immunohistochemistry (IHC) and operated at three referral Institutions were included. The primary endpoint was the rate of concordance between biopsy and surgical samples. If needed, central revision by IHC/PCR was performed by specialized pathologists from coordinating Institutions. Thirteen (19.7%) out of 66 patients showed discordant MSI-H/dMMR results in the original pathology reports. In most cases (11, 16.7%) this was due to the diagnosis of proficient mismatch repair status on biopsies. Among the ten cases available for central review, four were due to sample issues, fourwere reclassified as dMMR, onecase showed dMMR status but was classified as microsatellite stable by PCR, one was linked to misdiagnosis of endoscopic biopsy by the local pathologist. Heterogeneity of mismatch repair proteins staining was observed in two cases. Available methods can lead to conflicting results in MSI-H/dMMR evaluation between endoscopic biopsies and surgical samples of gastroesophageal adenocarcinoma. Strategies aiming to improve the reliability of assessment should be primarily focused on the optimization of tissue collection and management during endoscopy and adequate training of dedicated gastrointestinal pathologists within the multidisciplinary team.

Metastatic breast cancer (MBC) with ultra-high tumor mutational burden (UHTMB): A comprehensive genomic profiling (CGP) study.

1036 Background: Pts with MBC whose tumors feature high TMB (≥ 10 mutations/Mb) are eligible for on label immune checkpoint inhibitor (ICI) treatment. This study evaluated the genomic landscape of MBC with “Ultra high” TMB, defined at &gt; 20 mutations/Mb. Methods: 2049 MBC underwent hybrid capture-based CGP to evaluate all classes of genomic alterations (GA), TMB, microsatellite instability (MSI) and trinucleotide mutational signatures. HER2 IHC results were available in a subset of pts. PD-L1 expression on immunocytes was determined by IHC (Ventana SP142). Results: 45/2049 (2.2%) of MBC were UHTMB. 45 (100%) pts had metastatic disease. 38 (84%) had documented Stage IV disease and 7 documented axillary LN metastases at the time of sequencing. Local breast tumor was used for CGP in 19 (42.2%) MBC and metastatic site biopsy was used in 26 (57.8%). When compared with 2004 non-UHTMB pts with UHTMB were older (mean 64.6 yrs vs 58.2 yrs p &lt; .0001), more often had lobular histology (40.0% vs 14.5% p &lt; .0001) and ER+ disease (86.6% vs 70.0%). Of the 35 UHTMB cases with HER2 IHC data available, 11 (31.4%%) were HER2 IHC negative (0+), 21 (60.0%) were HER2-low status (9 1+ and 12 2+/ISH negative) and 3 (8.6%) were HER2 IHC positive (3+). 1/3 HER2 IHC2+ cases and 2/45 (4.4%) of all UHTMB cases were positive for HER2 copy number gain on CGP. UHTMB cases had more driver GA/tumor (mean 9.8 vs 5.7 p &lt; .0001) and were less often TNBC (13.3% vs 27.0% p = .041) compared to non-UHTMB high cancers. Mutation signature analysis revealed APOBEC was predominant in UHTMB samples (82.5%); MMR signature was also observed in 10% of cases. MSI high status was significantly more frequent in UHTMB high cases (11.6% vs 0.4% p &lt; .0001). GA more frequently identified in UHTMB cases included CDH1 (45.5% vs 14.3% p &lt; .0001), PIK3CA (81.8% vs 37.9% p &lt; .0001), CDKN2A (11.4% vs 3.2% p = .017), ARID1A (25.0% vs 5.0% p &lt; .0001) and NF1 (20.5% vs 5.9% p = .0014). PD-L1 ( CD274) gene amplification (2.3% vs 1.3%) or protein expression by the Ventana SP142 assay (57.14% vs 51.10%) were not significantly different among groups. Conclusions: UHTMB MBC is a rare, yet clinically important subset of clinically advanced breast cancer driven by APOBEC mutagenesis, with high incidence of ER+ lobular histology and frequent alterations in CDH1 and PIK3CA. In addition to potential benefit from ICI based treatment, UHTMB MBC present with a high frequency of HER2-low status which may impact therapy decisions for this rare disease. [Table: see text]

Polyamine metabolism patterns characterized tumor microenvironment, prognosis, and response to immunotherapy in colorectal cancer

BackgroundChanges in Polyamine metabolism (PAM) have been shown to establish a suppressive tumor microenvironment (TME) and substantially influence the progression of cancer in the recent studies. However, newly emerging data have still been unable to fully illuminate the specific effects of PAM in human cancers. Here, we analyzed the expression profiles and clinical relevance of PAM genes in colorectal cancer (CRC).MethodsBased on unsupervised consensus clustering and principal component analysis (PCA) algorithm, we designed a scoring model to evaluate the prognosis of CRC patients and characterize the TME immune profiles, with related independent immunohistochemical validation cohort. Through comparative profiling of cell communities defined by single cell sequencing data, we identified the distinct characteristics of polyamine metabolism in the TME of CRC.ResultsThree PAM patterns with distinct prognosis and TME features were recognized from 1224 CRC samples. Moreover, CRC patients could be divided into high- and low-PAMscore subgroups by PCA-based scoring system. High PAMscore subgroup were associated to more advanced stage, higher infiltration level of immunosuppressive cells, and unfavorable prognosis. These results were also validated in CRC samples from other public CRC datasets and our own cohort, which suggested PAM genes were ideal biomarkers for predicting CRC prognosis. Notably, PAMscore also corelated with microsatellite instability-high (MSI-H) status, higher tumor mutational burden (TMB), and increased immune checkpoint gene expression, implying a potential role of PAM genes in regulating response to immunotherapy. To further confirm above results, we demonstrated a high-resolution landscape of TME and cell–cell communication network in different PAM patterns using single cell sequencing data and found that polyamine metabolism affected the communication between cancer cells and several immune cells such as T cells, B cells and myeloid cells.ConclusionIn total, our findings highlighted the significance of polyamine metabolism in shaping the TME and predicting the prognosis of CRC patients, providing novel strategies for immunotherapy and the targeting polyamine metabolites.

Penile squamous cell carcinoma (PSCC) with elevated tumor mutational burden (TMB): A genomic landscape study.

4 Background: TMB has emerged as a major biomarker of efficacy in immune checkpoint inhibitor (ICPI) therapies in the neoadjuvant, adjuvant and metastatic disease setting in a wide variety of malignancies, but not in PSCC. Methods: 397 clinically advanced (local major recurrence and/or metastatic disease) PSCC underwent hybrid capture-based comprehensive genomic profiling (CGP) to evaluate all classes of genomic alterations (GA). Tumor mutational burden (TMB) was determined on up to 1.1 Mb of sequenced DNA and microsatellite instability (MSI) was determined on up to 114 loci. Trinucleotide mutation signatures were evaluated (Alexandrov, et al. 2013). Genome-wide loss of heterozygosity (gLOH) was determined using validated pipelines and excluding whole-arm and whole-chromosome events. TMB was categorized into three cohorts: &lt;10 mutations/Megabase [muts/Mb] (low), 10-19 muts/Mb (high), and &gt;20 muts/Mb (very high). Tumor cell PD-L1 expression was determined by IHC (Dako 22C3) and defined as tumor proportion score (TPS) &gt;1. The presence of HPV16/18 was determined by next generation sequencing (NGS). Statistical comparisons were corrected for multiple comparisons using the Bonferonni method. Results: There were 339 (85.4%) TMB low, 40 (10.1%) TMB 10-19 and 18 (4.5%) TMB very high PSCC cases in this study. The mean age of PSCC with very high TMB at 70.1 yrs was older than for TMB low at 63.4 yrs (p=.08). There were no significant differences in genomic ancestry among the 3 groups. The TMB 10-19 and TMB very high tended to feature an APOBEC genomic mutational signature more than the TMB low PSCC cases (74 and 76% vs 44%). MSI high status was absent in the TMB low PSCC, but was present in 7.5% of the TMB 10-19 and 11.8% of the TMB very high cases. gLOH levels above 16% were similar in all 3 groups and ranged from 6.2 to 9.4%. GA associated with differences in TMB status in the PSCC cases included higher PIK3CA GA in TMB 10-19 (40.0%) vs TMB low (18.3%; p=.035) and TMB very high (66.7%) vs TMB low (p=.0002). CDKN2A GA were higher in TMB low (45.7%) than in the combined TMB 10-19 + very high (25.9%; p=.049). GA in KMT2D were higher in the combined TMB 10-19 + very high (29.3%) than the TMB low PSCC (7.7%; p=0002). FGFR3 GA were similar in all 3 groups. PD-L1 expression was not significantly different among the 3 groups with TMB low (78.3%), TMB 10-19 (64.2%) and TMB very high (54.5%). HPV identification was more frequent as TMB increased: 28.3% for the TMB low, 50.0% for the TMB high and 58.8% for the TMB very high groups. Conclusions: The evaluation of PSCC by CGP based on TMB levels revels significant differences in biomarkers for the near 15% of cases that have TMB &gt;10 muts/Mb. Further study of TMB as a biomarker in ICPI-based clinical trials for advanced PSCC appear warranted.

Single and multi-hit PIK3CA short variant (SV) genomic alterations (GA) in clinically advanced prostate cancer (CAPC): A genomic landscape study.

258 Background: Tumors harboring 2 or more PIK3CA Short variants (SV) (“Multi-hit”) have been described in breast cancer as linked to enhanced clinical outcome from anti-PIK3CA targeted therapies including alpelisib and investigational agents in clinical trials. The landscape and clinical implications of multi-hit PIK3CA alterations in other tumors, including in CAPC, are underexplored. Methods: 19,978 CAPC samples underwent hybrid capture based comprehensive genomic profiling (CGP) to evaluate all classes of GA and determine tumor mutational burden (TMB), microsatellite instability (MSI), genomic ancestry, signature and loss of heterozygosity (gLOH). Tumor cell PD-L1 expression was determined by IHC (Dako 22C3). Results: 18,741 (93.8%) CAPC were PIK3CA wild type (WT), 1,155 (5.8%) featured a single PIK3CA SV and 82 (0.4%) featured multi-hit PIK3CA SVs. The median ages of CAPC patients with single hit (69.1 yrs) or multi-hit (68.7 yrs) PIK3CA SV were older than the PIK3CA WT (67.6 yrs) CAPC (p&lt;.0001 for both). At 14.0%, African ancestry was more frequent in PIK3CA WT CAPC than in single-hit (10.4%; p=.001) and multi-hit (10.2%; not significant). Single-hit (81.4%; p&lt;.0001) and multi-hit (85.2% p=.05) PIK3CA SV CAPC featured significantly more MMR trinucleotide genomic signatures than PIK3CA WT (64.8%). Single-hit (2.7%; p=.02) and multi-hit (5.8% p=.05) PIK3CA SV CAPC featured significantly more POLE trinucleotide genomic signatures than PIK3CA WT (0.4%). MSI high status was significantly more common in both PIK3CA single-hit (12.4% vs 2.5%; p&lt;.0001) and multi-hit (35.4% vs 2.5%; p&lt;.0001). Mean TMB was also significantly higher in single-hit PIK3CA (11.1 vs 3.5 mut/Mb; p&lt;.0001) and multi-hit (42.9 vs 3.5 mut/Mb; p&lt;.0001). Noteworthy differences in GA of potential importance for CAPC pts included significantly higher frequencies of GA in BRCA2 in multi-hit vs WT (18.3% vs 8.5%; p=.019), ATM in multi-hit vs WT (13.4% vs 5.6%; p=.02) and PTEN in single-hit vs WT (40.2% vs 30.1%; p&lt;.0001) and lower frequencies of GA in CDK12 (3.6% vs 5.6%; p=.009) and SPOP (7.4% vs 9.8%; p=.012) in single-hit vs WT. There were no differences in gLOH or PD-L1 expression among the 3 groups. Conclusions: Although uncommon, the identification of multi-hit PIK3CA GA in CAPC highlights a potentially unique subtype of this disease that may be associated with enhanced responsiveness to anti-PIK3CA targeted therapy strategies.

INFINITY: A multicentre, single-arm, multi-cohort, phase II trial of tremelimumab and durvalumab as neoadjuvant treatment of patients with microsatellite instability-high (MSI) resectable gastric or gastroesophageal junction adenocarcinoma (GAC/GEJAC).

358 Background: In resectable GAC/GEJAC, MSI status is associated with better survival and potential lack of benefit from chemotherapy. Given the high responsiveness of MSI tumors to immunotherapy, neoadjuvant or definitive dual CTLA-4/PD(L)-1 inhibition may allow omission of chemotherapy or surgery. Methods: INFINITY is a multicentre, single-arm, multi-cohort phase II trial (NCT04817826) investigating the activity and safety of tremelimumab+durvalumab as neoadjuvant (Cohort 1) or definitive (Cohort 2) treatment for MSI, mismatch repair deficient (dMMR) and EBV-negative resectable GAC/GEJAC. In Cohort 1, patients (pts) received a 12-week treatment with single high dose tremelimumab 300 mg and durvalumab 1500 mg q4 weeks (T300/D) for 3 cycles followed by surgery. The primary endpoint was pCR rate (ypT0N0) with negative ctDNA after T300/D. Secondary endpoints: disease-free survival, overall survival, quality of life. Exploratory: correlation of pCR with clinical variables, PDL-1 CPS assessed by IHC 22C3, tumor mutational burden (TMB) by Foundation One, liquid biopsies and other biomarkers. Cohort 2 investigates non operative management after same treatment regimen. Results: Overall, 18 pts with MSI/dMMR resectable cT2-4 any N GAC/GEJAC were recruited in Cohort 1. One withdrew consent and 2 achieved a complete clinical-pathological response at radiology and endoscopy (ongoing) and refused surgery. Among 15 evaluable patients, 1 had disease progression and 14 underwent resection. pCR rate was 60% (9/15) and major-complete pathological response (&lt;10% viable cells) was 80%. All pts with pCR had negative ctDNA status pre-surgery. pCR rate was 1/6 (17%) in T4 vs 8/9 (89%) in T2-3 tumors (p=0.011), whereas no correlation was found with baseline N status. PDL-1 CPS was not associated with outcomes and TMB had a non-significant trend of correlation with pCR (median TMB 26 in non-pCR vs 40 in pCR group, p=0.2). Grade≥3 immune-related AEs occurred in 3 pts of safety population (n=18): colitis, pneumonitis, liver toxicity, all resolved with high dose steroids and did not impair surgery. Two pts died after surgery for other reasons than disease or AEs, whereas no disease relapses were observed in remaining pts. QoL and additional translational analyses on RNA-seq, digital spatial profiling and ctDNA monitoring will be presented. Conclusions: Pre-operative T300/D for 3 months was safe and provided promising proof of efficacy in MSI, dMMR GAC/GEJAC pts. These results open the way to investigate NOM in pts with clinical, pathological and molecular (ctDNA minimal residual disease) complete response after T300/D. Enrollment in Cohort 2 has started after IDMC evaluation and protocol. amendment to include only pts with cT2-3 tumors confirmed at staging laparoscopy. Clinical trial information: NCT04817826 .

Mutational analysis of microsatellite-stable gastrointestinal cancer with high tumour mutational burden: a retrospective cohort study.

Genomic signatures contributing to high tumour mutational burden (TMB-H) independent from mismatch-repair deficiency (dMMR) or microsatellite instability-high (MSI-H) status are not well studied. We aimed to characterise molecular features of microsatellite stable (MSS) TMB-H gastrointestinal tumours. Molecular alterations of 48 606 gastrointestinal tumours from Caris Life Sciences (CARIS) identified with next-generation sequencing were compared among MSS-TMB-H, dMMR/MSI-H, and MSS-TMB-low (L) tumours, using χ2 or Fisher's exact tests. Antitumour immune response within the tumour environment was predicted by analysing the infiltration of immune cells and immune signatures using The Cancer Genome Atlas database. The Kaplan-Meier method and the log-rank test were used to evaluate the impact of gene alterations on the efficacy of immune checkpoint inhibitors in MSS gastrointestinal cancers from the CARIS database, a Memorial Sloan Kettering Cancer Center cohort, and a Peking University Cancer Hospital cohort. MSS-TMB-H was observed in 1600 (3·29%) of 48 606 tumours, dMMR/MSI-H in 2272 (4·67%), and MSS-TMB-L in 44 734 (92·03%). Gene mutations in SMAD2, MTOR, NFE2L2, RB1, KEAP1, TERT, and RASA1 might impair antitumour immune response despite TMB-H, while mutations in 16 other genes (CDC73, CTNNA1, ERBB4, EZH2, JAK2, MAP2K1, MAP2K4, PIK3R1, POLE, PPP2R1A, PPP2R2A, PTPN11, RAF1, RUNX1, STAG2, and XPO1) were related to TMB-H with enhanced antitumour immune response independent of dMMR/MSI-H, constructing a predictive model (modified TMB [mTMB]) for immune checkpoint inhibitor efficacy. Patients with any mutation in the mTMB gene signature, in comparison with patients with mTMB wildtype tumours, showed a superior survival benefit from immune checkpoint inhibitors in MSS gastrointestinal cancers in the CARIS cohort (n=95, median overall survival 18·77 months [95% CI 17·30-20·23] vs 7·03 months [5·73-8·34]; hazard ratio 0·55 [95% CI 0·31-0·99], p=0·044). In addition, copy number amplification in chromosome 11q13 (eg, CCND1, FGF genes) was more prevalent in MSS-TMB-H tumours than in the dMMR/MSI-H or MSS-TMB-L subgroups. Not all mutations related to TMB-H can enhance antitumour immune response. More composite biomarkers should be investigated (eg, mTMB signature) to tailor treatment with immune checkpoint inhibitors. Our data also provide novel insights for the combination of immune checkpoint inhibitors and drugs targeting cyclin D1 or FGFs. US National Cancer Institute, Gloria Borges WunderGlo Foundation, Dhont Family Foundation, Gene Gregg Pancreas Research Fund, San Pedro Peninsula Cancer Guild, Daniel Butler Research Fund, Victoria and Philip Wilson Research Fund, Fong Research Project, Ming Hsieh Research Fund, Shanghai Sailing Program, China National Postdoctoral Program for Innovative Talents, China Postdoctoral Science Foundation, National Natural Science Foundation of China.

Genomic and transcriptomic analysis of MSI-H colorectal cancer patients with targetable alterations identifies clinical implications for immunotherapy.

Targetable alterations such as BRAFV600E mutation and NTRK fusion are enriched in microsatellite instability-high (MSI-H) colorectal cancer (CRC). MSI-H with targetable alterations (MSI-H altered) might present unique opportunities for both targeted therapy and immunotherapy. We systematically evaluated the molecular characteristics and immune-related features of MSI-H altered and MSI-H without targetable alterations (MSI-H wt) CRC patients in our study. Among 1938 continuously enrolled CRC patients, 126 patients with MSI-H status (6.50%) were included in this retrospective study. Genomic and transcriptomic data were investigated by next-generation sequencing (NGS) and gene expression profiling (GEP), respectively. BRAFV600E, NTRK1, and FGFR2 mutations were the most frequent targetable alterations in MSI-H CRC patients. The MSI-H altered phenotype was significantly associated with older age (p< 0.001), right side (p=0.024) and females (p= 0.036). No lynch syndrome (LS) patients were identified in MSI-H altered group. The tumor mutational burden (TMB), and tumor neoantigen burden (TNB) of MSI-H altered and wt subgroups were comparable (p<0.05). Subsequently, transcriptomic study analysis further revealed MSI-H altered CRC patients were linked to an immune-active tumor microenvironment with higher levels of Teff IFN-gamma, CYT, and MERCK 18 signatures, and lower levels of the IPRES gene signature, EMT and TGF Beta signatures. In addition, case study supported MSI-H CRC patient harboring targetable alterations might also achieved a long-term disease-free survival benefit from immunotherapy. Our study preliminary revealed MSI-H altered as a novel subtype of MSI-H CRC patients with unique molecular signatures and immune-active tumor microenvironment. Given the accessibility of immune checkpoint inhibitors (ICIs) treatment, our results might provide clinical evidence for immunotherapy in MSI-H CRC patients with targetable alterations.

Expression of PD-L1 in Microsatellite Instability High Tumours: A Retrospective Study

Introduction: Microsatellite Instability (MSI) is the hallmark of Lynch syndrome/Constitutional Mismatch Repair Deficiency (CMMRD) and is also found in many sporadic cancers like colorectal cancer, endometrial, gastric, small intestine, urothelial, central nervous system and sebaceous gland neoplasms. MSI is a predictive biomarker for immunotherapy and Immunohistochemistry (IHC) antibodies against four Mismatch Repair (MMR) proteins: MutL Homolog 1 (MLH1), MutS Homolog 2 (MSH2), MutS Homolog 6 (MSH6) and Postmeiotic Segregation increased 2 (PMS2) can identify the MSI status of the tumour. In addition to MSI, immune checkpoint programmed cell death protein 1 (PD-1) expression and its ligand PD-L1 are biomarkers that can predict response to immunotherapy. Considering this increasing interest to identify deficient MMR (dMMR) status in different cancers, authors have assessed the expression of PDL1 and status of MSI in various cancer types. Aim: To evaluate the expression of PD-L1 in MSI-high status tumours. Materials and Methods: This retrospective cross-sectional study was done in the Department of Pathology, Panimalar Medical College Hospital and Research Institute for a period of six months from July 2022 to December 2022. A total of 151 cases were identified for the period of three years from January 2020 to December 2022. The slides and blocks were retrieved from the archives. Tumour sections from the paraffin embedded tissues were deparaffinised and antigen retrieval was done. IHC using four antibodies (MLH1, MH2, MSH6 and PMS2) was performed on these slides to assess the MSI status. The slides were reviewed and were further subjected to PD-L1 IHC. PD-L1 expression on tumour cells was compared with the MSI status of different cancer types. The p-value was calculated using t-test and p&lt;0.5 was considered statistically significant. Statistical analysis was done using International Business Machines (IBM) Statistical Package for the Social Sciences (SPSS) software version 21.0. Results: A total of 151 cases were included in the present study. A positive nuclear stain for the four MMR proteins denote expression of wild type MMR proteins, hence MSI low status. A loss of nuclear expression denotes mutation of MMR proteins and hence MSI high (MSI-H) status. The MSI was high in nine out of 48 cases (18.75%) of colon cancer, three out of 15 cases (20%) of endometrial cancers, three out of 20 cases (15%) of gastric cancers. Rest were one out of sixteen cases of ovarian cancer, one out of two malignant melanoma and one out of three glioblastoma. Out of these, PD-L1 was positive in seven of the 18 MSI-H cases (38.88% of MSI-H cases). The MSI was low/ stable in the remaining 133 cases. The p-value of significance was 0.03 (statistically significant). Conclusion: This study shows a significant association of MSI-H with PD-L1 expression in tumours. Further large scale studies can help in assessing the role of PD-L1 as an effective therapeutic biomarker in MSI-high status patients who can benefit from targeted therapy

Outcomes of Immune Checkpoint Inhibitor Administration in Hospitalized Patients With Solid Tumor Malignancies.

More oncologists desire to treat their patients with immune checkpoint inhibitors (ICIs) in the inpatient setting as their use has become more widespread for numerous oncologic indications. This is cost-prohibitive to patients and institutions because of high drug cost and lack of reimbursement in the inpatient setting. We sought to examine current practice of inpatient ICI administration to determine if and in which clinical scenarios it may provide significant clinical benefit and therefore be warranted regardless of cost. We conducted a retrospective chart review of adult patients who received at least one dose of an ICI for treatment of an active solid tumor malignancy during hospitalization at a single academic medical center between January 2017 and June 2018. Patient, disease, and admission characteristics including mortality data were examined, and cost analysis was performed. Sixty-five doses of ICIs were administered to 58 patients during the study period. Nearly 40% and 80% of patients died within 30 days and 180 days of ICI administration, respectively. There was a trend toward longer overall survival in patients with good prognostic factors including positive programmed death-ligand 1 (PD-L1) expression or microsatellite instability-high (MSI-H) status. Slightly over 70% of patients were discharged within 7 days of ICI administration. The total cost of inpatient ICI administration over the 18-month study period was $615,016 US dollars. Inpatient ICI administration is associated with high costs and poor outcomes in acutely ill hospitalized patients with advanced solid tumor malignancies and therefore should largely be avoided. Careful discharge planning to expedite outpatient treatment after discharge will be paramount in ensuring patients with good prognostic features who will benefit most from ICI therapy can be promptly treated in the outpatient setting as treating very close to discharge in the inpatient setting appears to be unnecessary, regardless of tumor features.