Deficient Mismatch Repair Status Research Articles

Introducing Neoadjuvant Immunotherapy for Colorectal Cancer: Advancing the Frontier.

To give surgeons a review of the current and future use of neoadjuvant immunotherapy in patients with localized colorectal cancer. Immunotherapy has revolutionized the standard of care in oncology and improved survival outcomes in several cancers. However, the applicability of immunotherapy is still an ongoing challenge. Some cancer types are less responsive to immunotherapy, and the heterogeneity in responses within cancer types is poorly understood. Clinical characteristics of the patient, the timing of immunotherapy in relation to surgery, diversities in the immune responses, clonal heterogeneity, different features of the tumor microenvironment, and genetic alterations are some factors among many that may influence the efficacy of immunotherapy. In this narrative review, we describe the major types of immunotherapy used to treat localized colorectal cancer. Furthermore, we discuss the prediction of response to immunotherapy in relation to biomarkers and radiological assessment. Finally, we consider the future perspectives of clinical implications and response patterns, as well as the potential and challenges of neoadjuvant immunotherapy in localized colorectal cancer. Establishing mismatch repair status at the time of diagnosis is central to the potential use of neoadjuvant immunotherapy, in particular immune checkpoint inhibitors, in localized colorectal cancer. To date, efficacy is primarily seen in patients with deficient mismatch repair status and POLE mutations, although a small group of patients with proficient mismatch repair does respond. In conclusion, neoadjuvant immunotherapy shows promising complete response rates, which may open a future avenue of an organ-sparing watch-and-wait approach for a group of patients.

Predicting Mismatch Repair Deficiency Status in Endometrial Cancer through Multi-Resolution Ensemble Learning in Digital Pathology.

For molecular classification of endometrial carcinoma, testing for mismatch repair (MMR) status is becoming a routine process. Mismatch repair deficiency (MMR-D) is caused by loss of expression in one or more of the 4 major MMR proteins: MLH1, MSH2, MSH6, PHS2. Over 30% of patients with endometrial cancer have MMR-D. Determining the MMR status holds significance as individuals with MMR-D are potential candidates for immunotherapy. Pathological whole slide image (WSI) of endometrial cancer with immunohistochemistry results of MMR proteins were gathered. Color normalization was applied to the tiles using a CycleGAN-based network. The WSI was divided into tiles at three different magnifications (2.5 × , 5 × , and 10 ×). Three distinct networks of the same architecture were employed to include features from all three magnification levels and were stacked for ensemble learning. Three architectures, InceptionResNetV2, EfficientNetB2, and EfficientNetB3 were employed and subjected to comparison. The per-tile results were gathered to classify MMR status in the WSI, and prediction accuracy was evaluated using the following performance metrics: AUC, accuracy, sensitivity, and specificity. The EfficientNetB2 was able to make predictions with an AUC of 0.821, highest among the three architectures, and an overall AUC range of 0.767 - 0.821 was reported across the three architectures. In summary, our study successfully predicted MMR classification from pathological WSIs in endometrial cancer through a multi-resolution ensemble learning approach, which holds the potential to facilitate swift decisions on tailored treatment, such as immunotherapy, in clinical settings.

Survival of patients with microsatellite instability-high and Lynch syndrome-associated pancreatic ductal adenocarcinomas.

640 Background: Pancreatic ductal adenocarcinoma (PDAC) remains a challenging disease due to its aggressive nature, late-stage diagnosis, and limited treatment options. There is an increased interest in cancers which harbor microsatellite instability (MSI) due to their susceptibility to immune checkpoint inhibitors. MSI in PDAC is rare, and little is known about survival in this subtype of pancreas cancers. Our aim was to assess overall survival in surgically resected high microsatellite instability (MSI-H), mismatch repair deficient (MMRd), and Lynch Syndrome (LS) associated PDACs treated in our center. Methods: Patients with surgically resected PDACs from 1990 to 2023 were identified. A total of 936 cases were sequenced utilizing MSK-IMPACT, a targeted next generation sequencing platform. Patients with germline or sporadic pathogenic variants or likely pathogenic variants in one of the DNA MMR genes MLH1, MSH2, MSH6, PMS2, or 3’ end of EpCAM were identified. MSI-H, MMRd, and LS-associated cases were matched to patients with microsatellite stable or MMR proficient, non-LS-associated PDAC in a 1:2 ratio with a direct match on age (±5 years), gender, and year of surgery (±3 years). Kaplan-Meier curves were used to visualize the data. A generalized estimating equation (GEE) cox model with robust sandwich estimator was used to compare matched cohorts. Results: 17 patients with MSI-H, MMRd or LS-associated surgically resected PDACs were identified. Five patients were classified as MSI-H, 3 patients were MSI-indeterminate, and 9 patients were microsatellite stable. Eight patients were found to have pathogenic germline variants in LS-associated genes. The remaining nine patients had sporadic pathogenic DNA MMR gene variants ( MLH1 n=3, MSH6 n=6). Median age at surgery was 66 (interquartile range (IQR) 60-77), 41% of the patients were female, and median year of surgery was 2014. MSI-H, MMRd or LS-associated PDACs were matched to 34 control patients. The median survival time of the cases was 12 years vs. 1.9 years in the control group. Five-year survival rate was 81% (IQR 60-100%) and 18% (7.4%-43%), respectively. LS-associated, MSI-H or MMRd status in resectable PDAC was a strong predictor of good prognosis (hazard ratio 0.17, 95% CI 0.07-0.38, p value <0.001). Conclusions: MSI-H, MMRd or LS-associated PDACs displayed significantly better survival compared to their MSI-stable, MMR proficient, non-LS-associated counterparts, in the era before routine use of immunotherapy. It is expected that survival will be increased further with more frequent availability of immunotherapy.

Role of Mismatch Repair Deficiency Status and Microsatellite Instability in Relation to the Expression of Immune Checkpoint Proteins in Colorectal Cancer.

Introduction Colorectal cancer (CRC) is the third most common cancer in the world among men and second among women worldwide. One of the major molecular pathways responsible for the development of colorectal cancer (CRC) is the microsatellite instability (MSI) pathway. During carcinogenesis, the tumor cellsexpress programmed death ligand-1 (PD-L1), which reduces the immunogenicity leading to the escape of immune attack. Anti-PD-L1 interactionis an upcoming line of research for the treatment of colorectal carcinoma patients. Materials and methods The present study was an ambispective study where the mismatch repair deficiency status (MMR) and programmed death ligand-1 (PD-L1) expression were studied using immunohistochemistry and then later analyzed and compared with the clinicopathological parameters and MSI status in relation to the expression of programmed death ligand-1 (PD-L1) in neoplastic and immune cells in a total of 55 biopsy specimen. MMR expression was reported as retained or loss of nuclear staining, and PD-L1 expression was taken as positive with a cut-off of more than or equal to 5% membranous positivity in both tumor cells and immune cells. Results The analysis showed a significant correlation of microsatellite instability (MSI) status with two of the clinicopathological parameters, which were the site of the tumor (p-value<0.001) and M stage (p-value<0.001). PD-L1 expression in neoplastic cells showed no significant correlation with the clinicopathological parameters, whereas PD-L1 expression in immune cells showed a significant association with gender (p-value=0.043). Also, MSI status showed a significant association with PD-L1 expression in tumor cells (p-value <0.001).

Transcriptomic Profiling of Upper Tract Urothelial Carcinoma: Bladder Cancer Consensus Classification Relevance, Molecular Heterogeneity, and Differential Immune Signatures

Analyses of large transcriptomics data sets of muscle-invasive bladder cancer (MIBC) have led to a consensus classification. Molecular subtypes of upper tract urothelial carcinomas (UTUCs) are less known. Our objective was to determine the relevance of the consensus classification in UTUCs by characterizing a novel cohort of surgically treated ≥pT1 tumors. Using immunohistochemistry (IHC), subtype markers GATA3-CK5/6-TUBB2B in multiplex, CK20, p16, Ki67, mismatch repair system proteins, and PD-L1 were evaluated. Heterogeneity was assessed morphologically and/or with subtype IHC. FGFR3 mutations were identified by pyrosequencing. We performed 3’RNA sequencing of each tumor, with multisampling in heterogeneous cases. Consensus classes, unsupervised groups, and microenvironment cell abundance were determined using gene expression. Most of the 66 patients were men (77.3%), with pT1 (n = 23, 34.8%) or pT2-4 stage UTUC (n = 43, 65.2%). FGFR3 mutations and mismatch repair–deficient status were identified in 40% and 4.7% of cases, respectively. Consensus subtypes robustly classified UTUCs and reflected intrinsic subgroups. All pT1 tumors were classified as luminal papillary (LumP). Combining our consensus classification results with those of previously published UTUC cohorts, LumP tumors represented 57.2% of ≥pT2 UTUCs, which was significantly higher than MIBCs. Ten patients (15.2%) harbored areas of distinct subtypes. Consensus classes were associated with FGFR3 mutations, stage, morphology, and IHC. The majority of LumP tumors were characterized by low immune infiltration and PD-L1 expression, in particular, if FGFR3 mutated. Our study shows that MIBC consensus classification robustly classified UTUCs and highlighted intratumoral molecular heterogeneity. The proportion of LumP was significantly higher in UTUCs than in MIBCs. Most LumP tumors showed low immune infiltration and PD-L1 expression and high proportion of FGFR3 mutations. These findings suggest differential response to novel therapies between patients with UTUC and those with MIBC.

A Belgian Population-Based Study Reveals Subgroups of Right-Sided Colorectal Cancer with a Better Prognosis Compared to Left-sided Cancer.

Patients with left-sided colorectal cancer (L-CRC) are known to have a significantly better prognosis than those with right-sided CRC (R-CRC). It has been hypothesized that RAS, BRAF mutations, or deficient mismatch repair status (MMR) might be responsible for the prognostic effect of primary tumor location (PTL). This study aims to evaluate the prognostic effect of PTL in the Belgian population and to determine the role of biomarkers (MMR, BRAF, and RAS status) in this effect. We performed a retrospective analysis of Belgian Cancer Registry data. First, we studied the prognostic effect of PTL on 5-year relative survival of 91 946 patients diagnosed with CRC (all stages) from 2004-2015. Second, we investigated the interaction between biomarkers and the prognostic effect of PTL in 1818 patients diagnosed with stage IV CRC in 2014-2015. L-CRC was associated with a significantly better 5-year relative survival compared to R-CRC in all stages and ages combined (68.4%, 95% CI, 67.7-69.1% vs 65.6%, 95% CI, 64.7-66.4%). Also, when stratified by age, sex, and stage, the prognosis of L-CRC was better compared to R-CRC in most subgroups. Only in stage II and certain subgroups of elderly patients, the opposite was observed. Furthermore, our data showed that none of the biomarkers had a significant interaction with the effect of PTL on survival. This population-based study confirms that L-CRC is associated with significantly better relative survival compared to R-CRC, in all stages and ages combined. Furthermore, in stage IV L-CRC is associated with a longer survival than R-CRC, regardless of MMR, RAS, and BRAF status.

Promising Therapeutic Impact of Immune Checkpoint Inhibitors in Type II Endometrial Cancer Patients with Deficient Mismatch Repair Status.

Type II endometrial cancer (EC) is responsible for most endometrial cancer-related deaths due to its aggressive nature, late-stage detection, and high tolerance to standard therapies. Thus, novel treatment strategies for type II EC are imperative. For patients with mismatch repair-deficient (dMMR) tumors, immunotherapy with immune checkpoint inhibitors represents a promising therapeutic strategy. However, the prevalence of dMMR tumors in type II EC patients remains unclear. In this study, using immunohistochemistry, we evaluated the expression of mismatch repair (MMR) proteins, tumor-infiltrating lymphocytes (CD8+), and immune checkpoint molecules (PD-L1) in 60 patients with type II EC (16, 5, 17, and 22 were endometrioid G3, serous, de-differentiated, and carcinosarcoma cases, respectively) to investigate the therapeutic effect of immune checkpoint inhibitors. Approximately 24 cases (40%) had a loss of MMR protein expression. The positivity rate of CD8+ (p = 0.0072) and PD-L1 (p = 0.0061) expression was significantly associated with the dMMR group. These results suggest immune checkpoint inhibitors (anti-PD-L1/PD-1 antibodies) could effectively treat type II EC with dMMR. The presence of dMMR might be a biomarker for a positive response to PD-1/PD-L1 immunotherapy in type II EC.

Diagnostic performance of Idylla MSI test in colorectal cancer biopsies

Universal testing for microsatellite instability (MSI) is recommended in colorectal cancer (CRC) to screen for Lynch syndrome and to guide optimal treatment and follow-up of the patients. Especially in neoadjuvant setting, where immuno-oncological treatments have recently shown excellent responses, identification of MSI status at biopsy is a prerequisite. Idylla MSI test offers a rapid and automated test to assess MSI-status from formalin-fixed paraffin-embedded tumor tissue sections. In this study, we compared the performance of the Idylla MSI test to mismatch repair (MMR) protein immunohistochemistry (IHC) using 117 CRC biopsies with previously known deficient MMR status. The concordance between Idylla and IHC was 99.0% (95/96) for biopsies with the recommended ≥ 20% tumor cell content. Further, 85.7% (18/21) of suboptimal CRC biopsy specimens (tumor cell content 5–15%) were diagnosed as MSI. Overall, we identified four discrepant cases of which three had tumor cell content less than 20%, explaining the discordant result. Our study shows that the Idylla MSI test offers a competent tool for MSI screening in CRC biopsy specimens.

CDK12 pathogenic mutations in African American and White patients with prostate cancer.

38 Background: African American (AA) men are underrepresented in prostate cancer (PC) trials but have a greater probability of both developing and dying from prostate cancer (PC) than other populations. CDK12 mutations in PC are associated with aggressive disease, increased metastasis, and decreased overall survival. Some preliminary data has suggested that CDK12 mutations may be more common in AA men. This study reports data from next-generation sequencing (NGS) of tissue from a large population of patients with PC in the real-world setting to investigate frequency of pathogenic CDK12 mutations in AA men and White men. Methods: De-identified records from patients with primary PC who underwent NGS with Tempus xT (solid tumor, 648 genes, 500× coverage, full transcriptome RNAseq for a subset of patients) were analyzed to characterize the frequency and types of pathogenic CDK12 mutations, and co-mutation in other assessed genes. Results were compared between patients identified as AA and White. Patients were excluded if they were Microsatellite Instability high (MSI-H), Tumor Mutational Burden (TMB) ≥10, or Mismatch Repair deficient (MMR-d). Results: Genomic profiles were analyzed from tissue samples of 6121 unique patients; of 3,555 patients with known race, 646 (18%) were AA, 2657 (75%) were White, and 252 (7%) were of other races. Of these patients, 3026 were AA or White after excluding 277 patients with known MSI-H, TMB≥10, or MMR-d status. AA were younger at diagnosis than Whites (median 63 vs 66 years; p&lt;0.001). Tissue samples from AA men were significantly more likely than those from Whites to express a pathogenic CDK12 mutation (42 [7.2%] vs 93 [3.8%], p&lt;0.001). The majority of the variants identified were truncating mutations. There were no differences in truncating vs. non-truncating alterations between White and AA men, nor were there differences in the prevalence or distribution of co-mutations between the two populations. Conclusions: AA men with PC show a higher frequency of pathogenic CDK12 mutations than Whites in a large real-world population. Co-mutations did not vary by race, and the alterations were most likely to be truncating mutations in both races.

Deep learning–assisted colonoscopy images for prediction of mismatch repair deficiency in colorectal cancer.

24 Background: Deficient mismatch repair (or microsatellite instability) is a major predictive biomarker for the efficacy of immune checkpoint inhibitors of colorectal cancer. However, routine testing is time-consuming and incur substantial costs. We developed and validated a deep learning-based classifiers (MMR-Scopy) to detect mismatch repair-deficient status from routine colonoscopy images. Methods: We retrospectively obtained the colonoscopy images from the imaging database at Endoscopic Center of the Sixth Affiliated Hospital of Sun Yat-sen University. Colorectal cancer images from patients that had undergone colonoscopy procedures, surgery and the mismatch repair immunohistochemistry test were eligible for this study. Colonoscopy images from a prospective trial (Neoadjuvant PD-1 blockade by toripalimab with or without celecoxib in mismatch repair-deficient or microsatellite instability-high locally advanced colorectal cancer, PICC) were used to test MMR-Scopy. The primary outcome was dMMR status. The primary performance metrics were accuracy, negative predictive value (NPV), and area under the receiver operating characteristic curve (AUROC). Results: A total of 5226 eligible images from 892 tumors from the consecutive patients were utilized to develop and validate the deep learning model. 2105 CRC images from 306 tumors were randomly selected to form model development dataset with a class-balanced approach. 3121 images of 488 pMMR tumors and 98 dMMR tumors were used to form the independent dataset. The MMR-Scopy model achieved an AUROC of 0.948 (95% CI 0.919- 0.977) on the test dataset. On the independent validation dataset, the AUROC was 0.807 (0.760- 0.854), and the NPV in was 94.2% (95% CI 0.918-0.967). On the PICC dataset, the model identified 29 tumors among the 33 dMMR tumors (87.88%). Conclusions: MMR-Scopy achieved a high NPV in detecting dMMR colorectal cancers. This model might serve as an automatic screening tool, one that might potentially assist doctors in determining a new treatment strategy. [Table: see text]

FOXM1 and MMR genes immunohistochemical expression in colorectal cancer: promising prognostic insights and candidate therapeutic targets

Abstract Background and objectives Colorectal cancer (CRC) high mortality in developing countries necessitates the delineation of the underlying mechanisms compromising its prognosis despite of current advances. Mismatch repair (MMR) genes protein expression is established as a surrogate to categorize CRC MMR status with different prognostic and therapeutic considerations, variations are observed not only among different classes but also within the same class. FOXM1 is involved in multitask carcinogenesis and is recently targeted in some cancers. Our objective was to study FOXM1 expression in different CRC subclasses to exploit any potential inferences of its role. Material and methods This retrospective study encompassed 51 CRC specimens received in Ain Shams University Hospital, immunohistochemical studies for microsatellite stability genes to determine MMR status and FOXM1 expression were performed. Results were statistically compared and correlated to the clinicopathological prognostic indices. Results FOXM1 expression was statistically significant when correlated to lymphovascular invasion and nodal metastasis. Despite failing to establish a statistical correlation with FOXM1 expression level yet a suggestive tendency of overexpression with precursor tubulovillous adenoma, mucinous and signet ring CRC, grade 3, PT3 was noted. FOXM1 high expression concorded with MMR deficient status, mounting to a statistical significance in right CRCs, this association was disrupted when nodal status was tested. Conclusion FOXM1 shows varying expression in CRC subclasses, variations did not follow a consistent synergistic pattern thus the effect of FOXM1 on prognostic indicators likely involves molecular coded cross-talks with mismatch repair genes as well as others. We offer innovative insights for prognostic aptitudes of FOXM1 that might pave promising utility in future if further validated.

P-187 Epidermal growth factor receptor inhibitors (EGFRi) in patients with left-side, RAS wildtype metastatic colorectal cancer: Clinician use and outcomes for patients

Current treatment for metastatic colorectal cancer (mCRC), includes anti-epidermal growth factor receptor inhibitors (EGFRi) for RAS wildtype cancers. With improved outcomes has come added complexity for clinician treatment selection and sequencing. Head-to-head studies support first-line EGFRi use over bevacizumab in combination with chemotherapy for patients with a left-side primary. In January 2015, the EGFRi cetuximab gained government approval for first-line use in Australia, with routine RAS testing increasing in turn. In clinical practice, around 50% of patients do not receive second-line treatment, suggesting many patients miss out on this treatment option if reserved for second-line and later treatment. Clinical data from July 2009 to July 2021 was reviewed from TRACC (Treatment of Recurrent and Advanced Colorectal Cancer), a prospective, comprehensive, multi-site Australasian registry, to identify patients with RAS wildtype, left-side primary mCRC who received first-line treatment. Intent (curative vs palliative), biologic use and chemotherapy backbone were described over time. Patients who received first-line palliative intent doublet chemotherapy who were ECOG 0 or 1 at diagnosis were further characterised. Second-line treatment groups were analysed according to biologic and sequence used. Fisher’s exact test was used for significance tests and Kaplan Meier curves for survival analyses. 800 patients had left-side primary RAS wildtype mCRC and received first-line chemotherapy. 166 (20%) received first-line EGFRi plus chemotherapy, 352 (43%) received bevacizumab plus chemotherapy, and 282 (35%) received chemotherapy alone. Patients diagnosed after government EGFRi approval in January 2015 were more likely to be treated with first-line EGFRi plus chemotherapy than first-line bevacizumab plus chemotherapy (36% vs 30%, p < 0.001). While patients receiving first-line EGFRi were younger (60 vs 62 years, p=0.006) with fewer comorbidities (Charlson Comorbidity Index ≥ 3 in 13% vs 20%, p=0.048), ECOG status, de novo metastatic disease, deficient mismatch repair status or site of metastases were not different between the two groups. Overall, 148 (19%) left-side primary RAS wildtype patients never received any biologic agent. Of the palliative intent cohort (n = 490), median progression-free survival (PFS) was 11.6, 10.5 and 9.2 months for EGFRi plus doublet chemotherapy, bevacizumab plus doublet chemotherapy, and doublet chemotherapy alone respectively. EGFRi plus doublet chemotherapy had significantly longer PFS than doublet chemotherapy alone (HR 0.70 [0.52 - 0.95], p=0.022), but did not reach statistical significance compared to the bevacizumab group. However, median overall survival for the palliative intent cohort was significantly improved in the EGFRi group compared to bevacizumab group (53.2 vs 30.0 months; HR 0.70 [0.52 – 0.95]). When sequencing agents at progression, second-line PFS trended longer for those receiving EGFRi then bevacizumab, as compared to those receiving bevacizumab then EGFRi (7.9 vs 6.0 months; p=0.25). In this community series, first-line EGFRi plus doublet chemotherapy significantly improved OS when compared with bevacizumab plus doublet chemotherapy for left-side RAS wildtype mCRC patients. This was despite not demonstrating a PFS benefit in first-line, suggesting treatment sequencing may impact biologic efficacy. Despite EGFRi use increasing over time, 1 in 5 patients with left-side RAS wildtype mCRC never received any biologic agent.

Validated biomarker assays confirm that ARID1A loss is confounded with MMR deficiency, CD8+ TIL infiltration, and provides no independent prognostic value in endometriosis-associated ovarian carcinomas.

ARID1A (BAF250a) is a component of the SWI/SNF chromatin modifying complex, plays an important tumour suppressor role, and is considered prognostic in several malignancies. However, in ovarian carcinomas there are contradictory reports on its relationship to outcome, immune response, and correlation with clinicopathological features. We assembled a series of 1623 endometriosis-associated ovarian carcinomas, including 1078 endometrioid (ENOC) and 545 clear cell (CCOC) ovarian carcinomas, through combining resources of the Ovarian Tumor Tissue Analysis (OTTA) Consortium, the Canadian Ovarian Unified Experimental Resource (COEUR), local, and collaborative networks. Validated immunohistochemical surrogate assays for ARID1A mutations were applied to all samples. We investigated associations between ARID1A loss/mutation, clinical features, outcome, CD8+ tumour-infiltrating lymphocytes (CD8+ TILs), and DNA mismatch repair deficiency (MMRd). ARID1A loss was observed in 42% of CCOCs and 25% of ENOCs. We found no associations between ARID1A loss and outcomes, stage, age, or CD8+ TIL status in CCOC. Similarly, we found no association with outcome or stage in endometrioid cases. In ENOC, ARID1A loss was more prevalent in younger patients (p = 0.012) and was associated with MMRd (p < 0.001) and the presence of CD8+ TILs (p = 0.008). Consistent with MMRd being causative of ARID1A mutations, in a subset of ENOCs we also observed an association with ARID1A loss-of-function mutation as a result of small indels (p = 0.035, versus single nucleotide variants). In ENOC, the association with ARID1A loss, CD8+ TILs, and age appears confounded by MMRd status. Although this observation does not explicitly rule out a role for ARID1A influence on CD8+ TIL infiltration in ENOC, given current knowledge regarding MMRd, it seems more likely that effects are dominated by the hypermutation phenotype. This large dataset with consistently applied biomarker assessment now provides a benchmark for the prevalence of ARID1A loss-of-function mutations in endometriosis-associated ovarian cancers and brings clarity to the prognostic significance. © 2021 The Pathological Society of Great Britain and Ireland.

The THE FREQUENCY OF MISMATCH REPAIR DEFICIENCY IN COLORECTAL CARCINOMA DETERMINED BY IMMUNOHISTOCHEMISTRY

Objective: To determine the frequency of mismatch repair deficiency in colorectal carcinoma determined by immunohistochemistry.&#x0D; Study Design: Cross-sectional study.&#x0D; Place and Duration of Study: Department of Histopathology, Armed Forces Institute of Pathology, Rawalpindi, from Aug 2018 to Jan 2019.&#x0D; Methodology: A total of 101 patients of adenocarcinoma of colorectum who underwent surgical resections and their characteristic and clinical data were recorded. Immunohistochemical stains were performed using antibodies MLH1, MSH2, PMS2 and MSH6. Results were interpreted and mismatch repair deficiency status of all patients was determined. Patients with loss of expression for MLH1, MSH2, PMS2 and MSH6 antibodies were observed and noted.&#x0D; Results: In this study, out of 101 patients with CRC, 71 (70.3%) were male and 30 (29.7%) female. The mean age was (54 years ± 15.9). Amongst the 101 cases loss of immunohistochemical staining for MMR proteins was noted in 19 patients (18.8%). The combined loss of all four antibodies was seen in one case, loss of MLH1 and PMS2 in 7, MSH2 and MSH6 in 5 and MLH1 only in 6 patients. However, no mismatch repair deficiency was detected in remaining 82 cases. According to statistical analysis no significant association between mismatch repair deficiency and variables was found.&#x0D; Conclusion: The frequency of mismatch repair deficiency in colorectal carcinoma patients was found to be 18.8% in our population.

Abstract 484: Immune checkpoint inhibitor therapy for metastatic colorectal cancer: Real-world practice patterns and predictors of overall survival

Abstract There is well-established evidence of a therapeutic role for immune checkpoint inhibitors (ICIs) in mismatch repair deficient (MMR-D) metastatic colorectal cancer (mCRC). However, factors associated with receipt and response to ICIs in the real-world setting are not well-characterized. Using electronic health record-derived, de-identified data from the nationwide Flatiron Health database, we selected 568 patients diagnosed with mCRC between January 2013 and December 2019 who received at least one line of ICI therapy in their treatment course (median age: 62.9 years, 50.2% male, 69.4% White, 44% stage IV at diagnosis, 41.2% MMR-D). Overall survival (OS) was defined as the time period from start of ICI therapy until death or last patient activity. Differences in sociodemographic (e.g. age, sex), clinical (e.g. stage at diagnosis, anatomic site) and molecular (e.g. MMR status) characteristics between patients who did and did not receive ICI therapy were compared using chi-square or t-tests. Univariate and multivariate Cox regression models were used to identify predictive factors associated with OS among patients treated with ICIs. Median OS from start of ICI therapy was 8.95 months, while the 1-year probability of survival was 42.6%. Compared to patients who did not receive ICI therapy (n=18,366), patients who received ICIs were initially diagnosed at earlier stage (I-III), were more likely to have MMR-D tumors (p&amp;lt;0.001), and were more likely to have colon cancer (p&amp;lt;0.001). Among patients who received ICIs, MMR-D status (vs. mismatch repair proficient [MMR-P]; HR=0.33, 95%CI=0.22-0.51, p=1x10-6), albumin level ≥3 g/dL (vs. &amp;lt;3 g/dL; HR=0.34, 95%CI=0.21-0.53, p=2x10-6) and concurrent antibiotic intake (yes vs. no; HR=0.51, 95%CI=0.34-0.75, p=8x10-4) were statistically significantly associated with higher OS, while stage IV disease at diagnosis (vs. stage I-III; HR=1.80, 95%CI=1.22-2.66, p=0.003) was significantly associated with lower OS. Patients with MMR-P tumors who received an early line of ICI therapy (1 or 2) or a combination therapy (e.g. ICIs + chemotherapy) had significantly higher OS than patients who received ICIs at a later line (&amp;gt;2) or ICIs alone (p=0.0074 and 0.0057, respectively). In the multivariable model, high albumin level (HR=0.27, 95%CI=0.16-0.45, p=5x10-7) and antibiotic intake (HR=0.46, 95%CI=0.29-0.74, p=0.001) remained statistically significantly associated with higher OS among patients with MMR-P tumors. Our findings support that MMR status is a key predictor for OS in mCRC patients treated with ICI therapy and provide insights into additional specific clinical features that may predict response to ICIs in a real-world setting. Citation Format: Shahla Bari, Marco Matejcic, Richard Kim, Hao Xie, Estrella Carballido, Ibrahim Sahin, Benjamin Powers, Seth Felder, Stephanie Schmit. Immune checkpoint inhibitor therapy for metastatic colorectal cancer: Real-world practice patterns and predictors of overall survival [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 484.

RHAMM in liver metastases of stage IV colorectal cancer with mismatch-repair proficient status correlates with tumor budding, cytotoxic T-cells and PD-1/PD-L1

BackgroundDuring the last decades, the management for metastatic colorectal cancer patients has improved due to novel therapeutic approaches. A mismatch-repair deficient status seems to favour a better response to checkpoint inhibitor therapy, but the question arises whether a specific subgroup of stage IV patients with mismatch-repair (MMR) proficient status should also be considered. RHAMM (Receptor for Hyaluronic Acid Mediated Motility/HAMMR/CD168) is characterized by tumor progression and immunogenicity. Therefore, the aim of this study is to determine whether RHAMM within the CRLM of MMR-proficient patients correlate with a more immunological microenvironment, represented by cytotoxic T-cells, PD-1 and PD-1. MethodsTwo patient cohorts of liver metastases from MMR colorectal cancers were included into the study (n = 81 and 76) using ngTMA® technology and immunohistochemically analyzed for RHAMM, cytotoxic T-cells (CD8+), PD-1/PD-L1, intrametastatic budding (IMB) and perimetastatic budding (PMB). ResultsRHAMM-positive IMB was linked to a higher PD-L1 expression (r = 0.32; p = 0.233 and r = 0.28; p = 0.044) in the center and periphery of the metastasis and RHAMM-positive PMB was associated with a higher expression of PD-1 (r = 0.33; p = 0.0297), and especially PD-L1 (r = 0.604; p < 0.0001 and r = 0.43; p = 0.003) in the center and periphery of the metastasis. IMB and PMB were additionally associated with a higher count of CD8+ T-cells (p < 0.0001; r = 0.58; p < 0.0001; r = 0.53). ConclusionsThe RHAMM status can be assessed in IMB/PMB either in biopsies or in resections of colorectal cancer liver metastases. A positive RHAMM status in IMB and/or PMB may be a potential indicator for a checkpoint inhibitor therapy for stage IV colorectal cancer patients with MMR proficient status.

Clinicopathologic Factors Associated with Mismatch Repair Status Among Filipino Patients with Young-Onset Colorectal Cancer.

IntroductionYoung-onset colorectal cancer is recognized as a distinct disease that may be sporadic or hereditary in nature. Microsatellite instability testing is recommended as a routine procedure in evaluating colorectal cancer specimens, especially in young-onset disease, because of implications in management. Immunohistochemistry of mismatch repair proteins serves as an inexpensive alternative to microsatellite instability testing with the added advantage of monitoring protein expression levels that may suggest underlying genetic or epigenetic alterations. This descriptive study aimed to determine the frequencies of proficient and deficient mismatch repair status among Filipino young-onset colorectal cancer patients, and to investigate their clinicopathologic profile.MethodsTumor tissues were prospectively collected from patients from two tertiary hospitals in the Philippines. Patients of age ≤45 years with resected adenocarcinoma of the colon or rectum were recruited.ResultsSeventy-seven out of 124 patients had tumor samples sent for immunohistochemistry. Of these, 61 samples (79%) were found to have proficient status while 16 samples (21%) had deficient status. Mismatch repair protein deficiencies, when present, more commonly involved MSH2 and MSH6 (9%) rather than MLH1 and PMS2 (5%). The deficient group had a mean age of 37.1 years and a female preponderance (56.25%), presenting as locally advanced ascending or descending colon tumors with mucinous histology in half of the population. The mismatch repair proficient group presented as locally advanced rectal and sigmoid tumors but with fewer mucinous adenocarcinomas (26.2%) compared to the deficient group. In both the mismatch repair proficient and deficient patients with family history reports, most did not have any known relative with cancer (75.4% and 68.75%, respectively).ConclusionThis is the first attempt to perform mismatch repair testing among young-onset colorectal cancer patients in the Philippines and to gather data on their clinicopathologic characteristics. However, the limited sample size precludes conclusive results for the associations of mismatch repair with clinicopathologic features.

Prognostic Value and Immunohistochemical Analysis of Mismatch Repair Deficiency in Patients with Stage II and III Colorectal Carcinoma-A Single-Center Study.

Background and objectives: Deficient mismatch repair (MMR) status is associated with good prognosis but poor therapeutic response to adjuvant chemotherapy in patients with colorectal cancer. However, there are some opposed arguments considering therapeutic outcomes in patients with evidenced MMR deficiency in colorectal cancer. The aim of the study was the investigation of prognostic value and immunohistochemical analysis of the MMR-deficiency tumors. Materials and Methods: The study enrolled 104 patients with resected stage II and III colorectal cancer samples from the period 2018–2019. Results: The tumors with deficient MMR status were significantly associated with age up to 50 years and right-sided localization (p < 0.001). During the follow-up period of 22.43 ± 6.66 months, 21 patients (20.2%) died, whereas 14 patients (13.5%) had relapses. The loss of mutL homologue 1/postmeiotic segregation increased 2 (MLH1/PMS2) expression, compared to proficient MMR tumors, was associated with shorter disease-free survival in patients with lymphovascular invasion (p < 0.05), perineural invasion (p < 0.01), stage III (p < 0.05) and high-grade tumor (p < 0.05). Conclusions: This retrospective pilot study of a single-center cohort of patients with stage II and III colorectal cancer highlights the clinical importance of using immunohistochemistry (IHC) analysis as a guide for diagnostic algorithm in a country with limited resources, but with a high prevalence of colorectal carcinoma in the young patients. MMR-deficiency tumors compared with proficient MMR colorectal cancer was not shown to be a significant predictor of disease-free and overall survival.

Utility of Discordant Mismatch Repair-Deficiency (MMR)/Microsatellite Instability (MSI) Testing in Screening Uterine Leiomyosarcoma Patient for Lynch/Other Familial Cancer Syndromes

Abstract Casestudy Lynch Syndrome (LS) is primarily linked to colorectal and endometrial cancers. Occasional sarcomas, including leiomyosarcoma, have been recognized within the spectrum of LS demonstrating mismatch repair-deficiency (MMR)/microsatellite instability (MSI) in this context. Results A 67-year-old female of bilineal Ashkenazi Jewish descent was recently diagnosed with uterine leiomyosarcoma in addition to metastatic papillary thyroid carcinoma at age 58. She met NCCN criteria for LS and BRCA1/2 (brother with renal cancer at age 64, father with colon cancer at age 60, paternal half-sister with rectal cancer at age 50 and maternal aunt with breast cancer). Studies have shown that immunohistochemistry (IHC) for MMR proteins and PCR-based MSI have comparable sensitivity and specificity with high concordance, but neither test alone is sufficient to capture all defective MMR tumors. Screening strategies vary depending on the level of clinical suspicion for LS. When high, a normal result by one method warrants testing via a second method or concurrent IHC plus PCR testing to minimize the impact of rare false normal results. Rarely, this strategy can yield discordant results, as in our case wherein MSI by PCR was stable (MSS) but IHC for MLH-1 and PMS-2 showed heterogeneous (patchy/focal) nuclear loss of protein expression. The latter is not always due to artefact but can correspond to MMR status differences within the tumor, requiring recognition to prevent false-positive/false-negative evaluations. Heterogenous MLH1 and/or PMS2 expression, may be suggestive of variable MLH1 methylation/second hit mutations, variable epitope expression or expression related to variable differentiation. Conclusion The clinical significance of this pattern was unclear in our patient whose initial genetic screen (including MLH1, PMS2, MSH2, MSH6, EPCAM) was negative. However, as studies have indicated that patients with indeterminate IHC findings can have MLH1 hypermethylation or germline mutations, she had justification to undergo extended genetic screening. A heterozygous pathogenic variant in BLM 2207_2212delinsTAGATTC (p.Tyr736Leufs*5) associated with autosomal recessive Bloom Syndrome (BS) was identified. Carriers of BS do not show symptoms of the disease, but they are at a greater than average risk of developing cancers.

Prevalence of mismatch repair deficiency and Lynch syndrome in a cohort of unselected small bowel adenocarcinomas

AimsPrevious estimates of the prevalence of mismatch repair (MMR) deficiency and Lynch syndrome in small bowel cancer have varied widely. The aim of this study was to establish the prevalence...