MSS Group Research Articles

Molecular pathogenesis of microsatellite instability-high early-stage colorectal adenocarcinoma in India.

The prevalence of microsatellite instability (MSI) subtype among all colon cancers in India is about 30 %, approximately two times more than that of western population suggesting different molecular pathogeneses. A NanoString analysis-based Pan cancer differential expression (DE) profile was determined in a primary cohort of early-stage CRC (tumor=10, normal=7), and correlated against MSI status. Using RT-PCR, tumor-specific DE genes were validated in another cohort of MSI-high CRC (n=15). Among the most differentially expressed genes, AXIN2, ETV4, and RNF43 were tumor cell-specific signals, while a set of genes including COL11A1, COMP, INHBA, SPP1, MMP3, TLR2, and others were immune cell-specific signals, that had a differential expression between MSI and MSS groups. When overlapped with The Cancer Genome Atlas (TCGA) studies using the Tumor immune estimation resource tool (TIMER), and protein-protein interaction analysis by STRING.db, these genes were segregated to representative tumor cells and immune cells. On validation, the tumor-specific gene signals were inversely associated with TLR4 expression. The differential expression distribution of AXIN2, ETV4, and RNF43 among tumor and immune cells, suggests more than one pathological subset in the MSI-H subgroup of early-stage CRC in the Indian population.

Prognosis and immunotherapy efficacy in dMMR&MSS colorectal cancer patients and an MSI status predicting model.

The inconsistency between mismatch repair (MMR) protein immunohistochemistry (IHC) and microsatellite instability PCR (MSI-PCR) methods has been widely reported. We aim to investigate the prognosis and the effect of immunotherapy in dMMR by IHC but MSS by MSI-PCR (dMMR&MSS) colorectal cancer (CRC) patients. A microsatellite instability (MSI) predicting model was established to help find dMMR&MSS patients. MMR and MSI states were detected by the IHC and MSI-PCR in 1622 CRC patients (ZS6Y-1 cohort). Logistic regression analysis was used to screen clinical features to construct an MSI-predicting nomogram. We propose a new nomogram-based assay to find patients with dMMR&MSS, in which the MSI-PCR assay only detects dMMR patients with MSS predictive results. We applied the new strategy to a random cohort of 248 CRC patients (ZS6Y-2 cohort). The consistency of MMR IHC and MSI-PCR in the ZS6Y-1 cohort was 95.7% (1553/1622). Both pMMR&MSS and dMMR&MSS groups experienced significantly shorter overall survival (OS) than those in dMMR by IHC and MSI-H by MSI-PCR (dMMR&MSI-H) group (hazard ratio [HR] = 2.429, 95% confidence interval [CI]: 1.89-3.116, p < .01; HR = 21.96, 95% CI: 7.24-66.61, p < .01). The dMMR&MSS group experienced shorter OS than the pMMR&MSS group, but the difference did not reach significance (log rank test, p = .0686). In the immunotherapy group, the progression-free survival of dMMR&MSS patients was significantly shorter than that of dMMR&MSI-H patients (HR = 13.83, 95% CI: 1.508-126.8, p < .05). The ZS6Y-MSI-Pre nomogram (C-index = 0.816, 95% CI: 0.792-0.841, already online) found 66% (2/3) dMMR&MSS patients in the ZS6Y-2 cohort. There are significant differences in OS and immunotherapy effect between dMMR&MSI-H and dMMR&MSS patients. Our prediction model provides an economical way to screen dMMR&MSS patients.

Feasibility of thoracoscopic monosubsegmentectomy for small ground-glass opacity dominant lung cancer

BackgroundMonosubsegmentectomy (MSS) involves removal of less lung parenchyma than monosegmentectomy (MS) does. However, the clinical efficacy of MSS in lung cancer treatment remains unclear, with concerns regarding insufficient surgical margins and increased complications. MethodsBetween February 2015 and December 2019, patients who underwent thoracoscopic MSS (n = 126) or MS (n = 678) for small ground-glass opacity (GGO) dominant lung cancer were examined. The primary endpoints were the procedure success rate (defined as resection with a surgical margin ≥2 cm or tumor size) and surgical margin. ResultsThere were no significant differences in age, sex, smoking history, or comorbidities between the groups. Both groups achieved a success rate of 100%. No significant group differences were observed in the number of lymph nodes removed (p = 0.060), overall complications (p = 0.147), or major complications (p = 0.450). The MSS group had a smaller surgical margin (median, 17 vs. 21mm, p < 0.001) and longer operative time (median, 138 vs. 130 min, p = 0.005) than the MS group did. Propensity score-matched analysis of 122 pairs of patients revealed consistent results. Surgical margins were further compared based on the number of resected subsegments. The 1 subsegment group had the smallest median surgical margin, followed by the 2 and 3 subsegments groups (17, 20, and 23 mm, p < 0.001). ConclusionsThoracoscopic MSS is an acceptable option for treating patients with small-sized GGO-dominant lung cancer. However, the close surgical margins and prolonged operative time should be considered.

Efficacy of PD-1 Inhibitors in First-Line Treatment for Advanced Gastroesophageal Junction and Gastric Cancer by Subgroups: A Systematic Review and Meta-Analysis

Background: PD-1 inhibitors have been approved for the first-line treatment of patients with advanced gastric cancer, gastroesophageal junction cancer, or esophageal adenocarcinoma. However, the results of several clinical trials are not entirely consistent, and the dominant population of first-line immunotherapy for advanced gastric/gastroesophageal junction cancer still needs to be precisely determined. Objective: This objective of this study is to evaluate the efficacy of anti-PD-1/PD-L1 therapy in advanced gastric/gastroesophageal junction adenocarcinoma patients through a systematic review and meta-analysis of relevant clinical trials. Method: The PubMed, Embase, and Cochrane Library electronic databases were searched up to August 1, 2022, for clinical trials of anti-PD-1/PD-L1 immunotherapy for the first-line treatment of advanced gastroesophageal cancer. Hazard ratios and 95% confidence intervals for overall survival, progression-free survival, and objective response rates were extracted and pooled for meta-analysis. Prespecified subgroups included the following: agent type, PD-L1 expression, and high microsatellite instability. Results: This study analyzed 5 RCTs involving 3,355 patients. Compared with the chemotherapy group, the combined immunotherapy group had a significantly higher objective response rate (OR = 0.63, 95% CI: 0.55–0.72, p < 0.00001) and prolonged overall survival (HR = 0.82, 95% CI: 0.76–0.88, p < 0.00001) and progression-free survival (HR = 0.75, 95% CI: 0.69–0.82, p < 0.00001). The combination of immunotherapy and chemotherapy prolonged OS in both MSI-H (HR = 0.38, p = 0.002) and MSS (HR = 0.78, p < 0.00001) populations, but there was a significant difference between groups (p = 0.02). However, in improving ORR, the benefit of ICI combined with chemotherapy in the MSS group and MSI-H group was not significantly different between groups (p = 0.52). Combination therapy with ICIs was more effective than chemotherapy alone in prolonging OS in the subgroup with a high CPS, regardless of the CPS cutoff for PD-L1. However, when the cutoff of CPS was 1, the difference between subgroups did not reach statistical significance (p = 0.12), while the benefit ratio of the MSI-H group was higher when the cutoff was 10 (p = 0.004) than when the cutoff value was 5 (p = 0.002). Conclusions: For first-line treatment of advanced gastroesophageal cancer, an ICI combination strategy is more effective than chemotherapy. The subgroup of patients with a CPS ≥10 has a more significant benefit, and CPS ≥10 has the potential to be used as an accurate marker of the dominant population of immuno-combined therapy.

Clinicopathological and Survival Characteristics of Mismatch Repair Status and PD-1 Expression in Serous Ovarian Cancer.

To evaluate the clinicopathological characteristics of mismatch repair (MMR) deficiency and its clinical outcomes by performing immunohistochemistry (IHC) for MMR genes in the serous ovarian cancer (SOC) tumour sections. A retrospective case-control study. Place and Duration of the Study: Gynecology Department of Kanuni Sultan Süleyman Training and Research Hospital, and Department of Medical Oncology of Medipol University, between March 2001 and January 2020. IHC was carried out for MLH1, MSH2, MSH6, and PMS2 on full-section slides from 127 SOCs to evaluate the MMR status. MMR-negative and MMR-low groups together were defined as MMR deficient and called microsatellite instability-high (MSI-H). The MSI status and expression of programmed cell death-1 (PD-1) were compared in SOCs with different MMR statuses. A significantly higher frequency of MMR-deficient SOCs was diagnosed at early stages compared with the patients in the MSS group (38.6% and 20.6%, respectively, p=0.022). The frequency of cases with PD-1 expression was significantly higher in the MSI-H group (76.2%) than in the MSS counterparts (58.8%, p=0.028). Patients in the MSI-H group had significantly longer DFS (25.6 months) and OS (not reached) than those in the MSS group (16 months and 48.9 months, p=0.039 and p=0.026, respectively). MSI-H SOCs were diagnosed at an earlier stage as compared to MMR proficient cases. The presence of PD-1 expression was significantly higher in cases presenting MMR deficiency compared with MMR-proficient cases. MSI status was significantly associated with DFS and OS. Serous ovarian cancer, Microsatellite instability, Mismatch repair deficiency.

A deep learning model for the prediction of microsatellite instability and pathogenic POLE mutations in colorectal cancer using histopathologic images.

3543 Background: Immunotherapy has brought about a landmark change in anti-tumor treatment in the past years. High microsatellite instability (MSI-H) is now the only clinically approved biomarker predicting response to immunotherapy in CRC. Increasing evidence suggests that POLE mutations in the exonuclease domain could drive an ultra-mutational phenotype and improve the treatment outcomes of ICI in solid tumors. In this study, we set out to apply a deep learning model using H&amp;E-stained, formalin-fixed, paraffin-embedded (FFPE) whole slide images (WSIs) of CRC primary tumors. Methods: The deep learning model is developed and validated through five-fold cross-validation using WSI of primary tumors from 506 CRC patients and externally validated using 52 WSIs from a prospective cohort. The microsatellite status, tumor mutation burden (TMB) and POLE genotype were determined by next-generation sequencing (NGS). Patients with MSS status and a low TMB (＜20Mutations/Mb) were admitted to the MSS group, and CRCs with a POLE mutation which was defined as an oncogenic mutation referring to the POLE functional mutation list at OncoKB( POLE (oncokb.org) were admitted to the POLE mutant group. Clustering-constrained-attention multiple-instance learning (CLAM) model is employed as the base model, and we conduct the model ensemble by performing a large-scale hyper-parameter search, selecting five models with the highest value in one of the performance metrics, including the AURoC, accuracy, precision, recall, and f1 score, and finally averaging the predictions of the five models. Results: The internal dataset included 237 MSS, 142 MSI-H, and 127 POLE mutant CRC. The three groups had significant differences in primary location (p ＜ 0.0001), histology (p ＜ 0.0001), tumor differentiation (p = 0.002), tumor stage (p ＜ 0.0001), Crohn's-like reaction (p ＜ 0.0001) and tumor growth pattern (p = 0.001). The cross-validation performance of the ensemble model (M E) in the internal dataset achieves an AURoC of 0.944 for three-way classification task (POLE vs. MSI-H vs. MSS) and 0.940 for two-way classification task (POLE &amp; MSI-H vs. MSS) which were superior to the performance of each single CLAM model. To demonstrate the generalizability of the deep learning model, a domestic perspective cohort consisting of 20 MSS, 17 MSI-H, and 15 POLE mutant CRC H&amp;E images were used to validate the external performance. And the M E retained robust performance on the external dataset, with an AURoC of 0.904 for three-way classification task and 0.836 for two-way classification task. Conclusions: A CLAM-based deep learning model could directly predict the MSI-H and POLE mutation from histological images that could be used to stratify CRC patients for immunotherapy with faster turnaround time and lower costs compared with traditional sequencing methods.

Contrast-Enhanced CT Texture Analysis in Colon Cancer: Correlation with Genetic Markers.

Background: The purpose of the study was to determine whether contrast-enhanced CT texture features relate to, and can predict, the presence of specific genetic mutations involved in CRC carcinogenesis. Materials and methods: This retrospective study analyzed the pre-operative CT in the venous phase of patients with CRC, who underwent testing for mutations in the KRAS, NRAS, BRAF, and MSI genes. Using a specific software based on CT images of each patient, for each slice including the tumor a region of interest was manually drawn along the margin, obtaining the volume of interest. A total of 56 texture parameters were extracted that were compared between the wild-type gene group and the mutated gene group. A p-value of <0.05 was considered statistically significant. Results: The study included 47 patients with stage III-IV CRC. Statistically significant differences between the MSS group and the MSI group were found in four parameters: GLRLM RLNU (area under the curve (AUC) 0.72, sensitivity (SE) 77.8%, specificity (SP) 65.8%), GLZLM SZHGE (AUC 0.79, SE 88.9%, SP 65.8%), GLZLM GLNU (AUC 0.74, SE 88.9%, SP 60.5%), and GLZLM ZLNU (AUC 0.77, SE 88.9%, SP 65.8%). Conclusions: The findings support the potential role of the CT texture analysis in detecting MSI in CRC based on pre-treatment CT scans.

Survival of Locally Advanced MSI-high Gastric Cancer Patients Treated With Perioperative Chemotherapy: A Retrospective Cohort Study.

To evaluate the efficacy of chemotherapy in patients with microsatellite instability (MSI)-high gastric cancer. Although MSI-high gastric cancer is associated with a superior prognosis, recent studies question the benefit of perioperative chemotherapy in this population. Locally advanced gastric adenocarcinoma patients who either underwent surgery alone or also received neoadjuvant, perioperative, or adjuvant chemotherapy between 2000 and 2018 were eligible. MSI status, determined by next-generation sequencing or mismatch repair protein immunohistochemistry, was determined in 535 patients. Associations among MSI status, chemotherapy administration, overall survival (OS), disease-specific survival, and disease-free survival were assessed. In 535 patients, 82 (15.3%) had an MSI-high tumor and ∼20% better OS, disease-specific survival, and disease-free survival. Grade 1 (90%-100%) pathological response to neoadjuvant chemotherapy was found in 0 of 40 (0%) MSI-high tumors versus 43 of 274 (16%) MSS. In the MSI-high group, the 3-year OS rate was 79% with chemotherapy versus 88% with surgery alone ( P =0.48). In the MSS group, this was 61% versus 59%, respectively ( P =0.96). After multivariable interaction analyses, patients with MSI-high tumors had superior survival compared with patients with MSS tumors whether given chemotherapy (hazard ratio=0.53, 95% confidence interval: 0.28-0.99) or treated with surgery alone (hazard ratio=0.15, 95% confidence interval: 0.02-1.17). MSI-high locally advanced gastric cancer was associated with superior survival compared with MSS overall, despite worse pathological chemotherapy response. In patients with MSI-high gastric cancer who received chemotherapy, the survival rate was ∼9% worse compared with surgery alone, but chemotherapy was not significantly associated with survival.

Amide Proton Transfer-Weighted Imaging Combined With Intravoxel Incoherent Motion for Evaluating Microsatellite Instability in Endometrial Cancer.

Microsatellite instability (MSI), caused by mismatch repair (MMR) protein defects that lead to uncorrectable mismatch bases, results in the accumulation of gene mutations and ultimately to tumors. Preoperative prediction of MSI can provide a basis for personalized and precise treatment of endometrial cancer (EC) patients. To investigate amide proton transfer weighting (APTw) imaging combined with intravoxel incoherent motion (IVIM) in the assessment of MSI in EC. Retrospective. A total of 71 patients with EC (12 classified as the MSI group and 22 as the microsatellite stabilization [MSS] group after entering and leaving the group standard). A 3.0 T/IVIM, diffusion-weighted imaging (DWI) and APTw. Amide proton transfer (APT) value, apparent diffusion coefficient (ADC), pure diffusion coefficient (D), pseudo diffusion coefficient (D*), and perfusion fraction (f) were calculated and compared between MSI and MSS groups. The Kendall's W test; Mann-Whitney U-test; Chi-square test or Fisher's exact test; logistic regression analysis; Area under the receiver operating characteristic (ROC) curve (AUC); The Delong test; Pearson or Spearman correlation coefficients. The significance threshold was set at P < 0.05. APT and D* values of the MSI group were significantly higher than those of the MSS group. While ADC, D, and f values in the MSI group were significantly lower than those in the MSS group. The multivariate analysis revealed that only APT and D* values were independent predictors to evaluate the MSI status. And the ROC curves indicated that the combination of APT and D* values could distinguish the MSI status of EC with the highest diagnostic efficacy (AUC=0.973), even without significant difference to those by APT (AUC=0.894) or D* (AUC=0.920) value separately (P=0.149 and 0.078, respectively). Combination of APTw and IVIM imaging may serve as an effective noninvasive method for clinical assessment of MSI in EC. 3 TECHNICAL EFFICACY: Stage 2.

"My Surgical Success": Feasibility and Impact of a Single-Session Digital Behavioral Pain Medicine Intervention on Pain Intensity, Pain Catastrophizing, and Time to Opioid Cessation After Orthopedic Trauma Surgery-A Randomized Trial.

BACKGROUND:Behavioral pain treatments may improve postsurgical analgesia and recovery; however, effective and scalable options are not widely available. This study tested a digital perioperative behavioral medicine intervention in orthopedic trauma surgery patients for feasibility and efficacy for reducing pain intensity, pain catastrophizing, and opioid cessation up to 3 months after surgery.METHODS:A randomized controlled clinical trial was conducted at an orthopedic trauma surgery unit at a major academic hospital to compare a digital behavioral pain management intervention (“My Surgical Success” [MSS]) to a digital general health education (HE) intervention (HE; no pain management skills). The enrolled sample included 133 patients; 84 patients were randomized (MSS, n = 37; HE, n = 47) and completed study procedures. Most patients received their assigned intervention within 3 days of surgery (85%). The sample was predominantly male (61.5%), White (61.9%), and partnered (65.5%), with at least a bachelor’s degree (69.0%). Outcomes were collected at 1–3 months after intervention through self-report e-surveys and electronic medical record review; an intention-to-treat analytic framework was applied. Feasibility was dually determined by the proportion of patients engaging in their assigned treatment and an application of an 80% threshold for patient-reported acceptability. We hypothesized that MSS would result in greater reductions in pain intensity and pain catastrophizing after surgery and earlier opioid cessation compared to the digital HE control group.RESULTS:The engagement rate with assigned interventions was 63% and exceeded commonly reported rates for fully automated Internet-based e-health interventions. Feasibility was demonstrated for the MSS engagers, with >80% reporting treatment acceptability. Overall, both groups improved in the postsurgical months across all study variables. A significant interaction effect was found for treatment group over time on pain intensity, such that the MSS group evidenced greater absolute reductions in pain intensity after surgery and up to 3 months later (treatment × time fixed effects; F[215] = 5.23; P = .024). No statistically significant between-group differences were observed for time to opioid cessation or for reductions in pain catastrophizing (F[215] = 0.20; P = .653), although the study sample notably had subclinical baseline pain catastrophizing scores (M = 14.10; 95% confidence interval, 11.70–16.49).CONCLUSIONS:Study findings revealed that a fully automated behavioral pain management skills intervention (MSS) may be useful for motivated orthopedic trauma surgery patients and reduce postsurgical pain up to 3 months. MSS was not associated with reduced time to opioid cessation compared to the HE control intervention.

Molecular typing and clinical characteristics of synchronous multiple primary colorectal cancer.

3061 Background: Synchronous multiple primary colorectal cancer (sMPCC) is clinically rare while its incidence was increasing in the past decade. However, little was known about molecular and clinical features of sMPCC, which might be different from single primary colorectal cancer (CRC). Methods: From November 2012 to April 2021, 239 sMPCC from a total of 13276 CRC patients operated in the 6th Affiliated Hospital of Sun Yat-sen University were enrolled in this study. Mismatch repair (MMR) status in each lesion of all 239 patients was examined by immunohistochemistry (IHC). Totally 78 sMPCC patients and 94 single primary CRC patients conducted an 831-gene panel based next-generation sequencing (NGS) (OncoPanscan, Genetronhealth). Somatic mutations and potential pathogenic germline variants were analyzed. Microsatellite instability (MSI) and tumor mutation burden (TMB) were calculated. Results: We found that dMMR/MSI-H frequencies in sMPCC were significantly higher than those in single primary CRC, which were confirmed by both IHC (50/239 vs 872/13037, p &lt; 0.001) and NGS (17/78 vs 5/94, p = 0.0022). According to the MMR/MSI status at different lesion in sMPCC patients, they were further divided into all MSI-H, MSI-H &amp; MSS and all MSS group, with incidences of 16.7%, 4.2% and 79.1%, respectively. With NGS analysis, we found that the most enriched gene mutation type in sMPCC patients was C &gt; T (G &gt; A), and their most frequently mutated genes were APC (65%), KRAS (46%), TP53 (31%), PIK3CA (25%), EGFR (23%), ARID1A (18%), NF1 (18%), SOX9 (18%), FAT4 (16%), and TCF7L2 (15%), whereas those genes in single primary CRC patients were APC (71%), TP53 (64%), KRAS (40%), FBXW7 (20%), PIK3CA (13%), SMAD4 (12%), ARID1A (11%), FAT4 (11%), CREBBP (11%), and NF1 (10%). Moreover, we found that higher TMB was correlated with higher MSI in sMPCC rather than single primary CRC patients. Furthermore, we found that the mutated genes were different among three subgroups. The top 5 mutated genes in MSI-H group were APC (68%), FAT4 (64%), TCF7L2 (59%), KMT2B (55%), ARID1A (45%), whereas those in MSI-H &amp; MSS group were APC (57%), KMT2B (43%), KMT2C (43%), ATM (43%), PRKDC (43%), and those in MSS group were APC (66%), KRAS (49%), TP53 (36%), PIK3CA (21%), EGFR (20%). Finally, we also found that patients with pathogenic/likely pathogenic germline mutations were comparable between sMPCC and single primary CRC, indicating that sMPCC may not be resulted from germline changes. Conclusions: Our results revealed that incidences of dMMR/MSI-H in sMPCC were significantly higher than those in single primary CRC. We proposed that MMR/MSI status of each lesion in sMPCC patients should be verified before treatment and these patients could be divided into three subgroups according to their MMR/MSI status. Our findings indicated that sMPCC patients with different MMR/MSI status might be treated with personalized therapies for better management of their disease.

Homologous recombination deficiency is linked to shorter survival expectancy in late-stage colorectal cancer.

e15576 Background: Colorectal cancer patients with high-level microsatellite instability (MSI-H) benefit more from immune checkpoint inhibitor therapy, but they only account for around 15% of all colorectal cancer patients. The remaining patients are still lack of effective therapeutic biomarkers to predict their prognosis. For patients in late stage without optimal treatment, it is essential to find novel biomarkers which can be used to select appropriate therapies and therefore improve patients’ overall survival. Methods: We used whole-exome sequencing (WES) to analyze 99 colorectal cancer samples. The patients were further classified into different groups based on their microsatellite status (MS), homologous recombination deficiency (HRD) score, as well as other clinical characteristics, which might associate with clinical outcomes. Afterward, survival analysis and stratification analysis were performed to explore the significant prognosis and predictive indicators in each group. Additionally, we assessed somatic genomic lesions, copy number aberrations, and mutational pathway, and analyzed the differential genetic patterns in distinct clinical benefit groups. Results: The multivariate Cox regression analysis proved that HRD score was associated with significant OS (HR 0.19, 95% CI 0.12-0.94, p = 0.002), suggesting HRD are prognostic factors for late stage CRC. Therefore, the patients were classified into two subgroups according to the value of the HRD scores (HRD-high vs HRD-low). For comparison, the prominent difference was observed in the somatic mutations and copy number alterations (SCNAs). Our results showed TP53 (78%) , APC (50%) and KRAS (41%) as the most frequently cancer-related mutations in CRC, consistent with previous studies. In patients with MSS group, the SMAD4 mutation was occurred frequently (p &lt; 0.01), as well as a distinctive pattern of chromosomal amplification in HRD-high group patients. However, in patients with MSI group, none significant mutations were observed in HRD-high and HRD-low groups. Conclusions: We integrated HRD statue as prognosis and predictive factors for late stage CRC as determined using WES sequencing. Moreover, we also provide a comprehensive differential genetic pattern in stratification of CRC patients, as well as underscore an importance of combining strategy for molecular diagnosis of CRC.

Empowering colorectal cancer patients and caregivers through clinical trials education in COLONTOWN.

e24129 Background: Clinical trials are increasingly part of the continuum of care for colorectal cancer patients, particularly those with metastatic disease. Yet most patients have limited knowledge about clinical trials, and many struggle to navigate the myriad barriers to enrollment. To bridge this gap, PALTOWN supports a broad array of activities in its COLONTOWN online community to help patients and caregivers interested in pursuing clinical trials. The function and impact of these activities is examined here. Methods: A comprehensive inventory of all clinical trial-related activity was conducted across three main sources: 1) resources and activity in COLONTOWN’s nine clinical trial-focused groups; 2) clinical trial materials posted in COLONTOWN UNIVERSITY, an online disease education center; and 3) patient feedback on clinical trial programming. Results: The MSS and MSI-High clinical trial groups in COLONTOWN serve more than 2,200 members, and more than 1,000 members are served by mutation- and location-specific trial groups. These groups have helped at least 187 members enroll in a clinical trial between 2019 and 2022. Among 10 trial-related activities, a majority (6/10) focused on sharing biomedical information, including : 1) patient-friendly descriptions of new trials; 2) explanations of trial results; 3) abstracts, articles, and videos from professional outlets such as ASCO Daily Post and OncLive; 4) patient-created resources on clinical trial basics in COLONTOWN UNIVERSITY; 5) “Doc Talks” by prominent CRC oncologists; and 6) patient advocates serving as information liaisons between patients and NCI Task Forces. A smaller number of activities (3/10) focused on psycho-social support from peers, including 1) accounts of patient experiences while seeking and participating in trials; 2) strategy discussions about how and when to pursue trials; and 3) “Alanna Project” database of members on a trial. COLONTOWN’s Clinical Trial Workshop (1/10) offers a novel approach to integrating biomedical education with psycho-social support via a four-week, peer-led clinical trial navigation program. Assessment of the cognitive and behavioral outcomes of the workshop demonstrate improvements in all four dimensions of health literacy: the ability to access, understand, appraise, and apply relevant information in the search for clinical trials. Conclusions: COLONTOWN's clinical trial programming offers comprehensive clinical trial education to patients and caregivers that leads to enrollment in trials. By embedding that education within a supportive community of peers, it enhances patients' capacity to collaborate with health care professionals in making informed decisions about clinical trials.

Incorporation of immunohistochemistry in the assessment of survival and prognosis of endometrial cancers: Are we ready for the change?

Objectives: The aim of the study was to determine the mismatch repair (MMR) proteins and p53 expression by immunohistochemistry in operable endometrial carcinoma (EC) patients. The study aimed to analyze and correlate clinicopathological factors and survival with MMR and p53 immunohistochemistry markers. Material and Methods: A retrospective cohort study of 115 cases of carcinoma endometrium who underwent primary surgery in our hospital from July 1, 2013, to December 31, 2020, with a minimum follow-up of 1 year. Available tissue blocks were stained for IHC expression of MMR and p53 proteins. Patients were stratified into Type I and Type II on basis of histopathology. Clinicopathological factors, overall survival (OS), and disease-free survival (DFS) were then compared on the basis of MMR deficiency and p53 status. Results: The mean age of study population was 58.9 years with a mean body mass index of 31.61 kg/m2. The mean follow-up was 41.29 months. Ninety-seven patients underwent IHC staining for MMR and p53 proteins. Among these 97 patients, 79 patients belonged to Type I histopathology and 18 patients belonged to Type II histopathology. The 79 patients of Type I histopathology were further divided into MSS or microsatellite stable group and MSI or microsatellite instable group. MMR deficit status was seen in 17 (21.5%) patients and 62 (78.5%) patients were MSS. For the 18 cases of Type II ECs, 5 (27.8%) patients were p53 positive whereas 13 (72.2%) patients were p53 negative. For patients with Type I histopathology; the clinicopathological factors such as stage, age, grade of the tumor, lymph-vascular space involvement, lymph node status, and myometrial invasion were compared between the MSI and MSS groups. Patients with microsatellite instability were more likely to present with a higher grade, a positive lymph node status, and with lymph-vascular space invasion. The OS and DFS are not significantly affected in patients with loss of MMR proteins. Due to a smaller number of cases in p53 group, clinicopathological features and survival could not be compared. Conclusion: Analyzing of immunohistochemistry status for evaluating the microsatellite instability in patients with Type I endometrioid adenocarcinomas is an alternative and efficient tool in predicting the prognosis for these patients. Further studies with more sample size can help us in studying the impact of MSI and p53 on OS and DFS and for guiding in the management of the same.

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.

Spleen and Symptom Responses with Fedratinib (FEDR) in Patients with Myelofibrosis (MF) and Substantial Splenomegaly

Spleen and Symptom Responses with Fedratinib (FEDR) in Patients with Myelofibrosis (MF) and Substantial Splenomegaly

Abstract 2430: HOXC6 promotes tumorigenesis of right-sided colon cancer

Abstract Colorectal cancer (CRC) is a common malignant tumor of the digestive tract, with high heterogeneity. The significant difference in prognosis and therapeutic response of left and right colon cancer is a hot spot in the field of colorectal cancer (CRC) in recent years. The prognosis and drug response of right-sided colon cancer were significantly worse than that of the left-sided colon cancer. Clinical trials have proved that MSI-H colon cancer is mainly seen in the right-sided colon cancer, and the prognosis is better than that of MSS. Because MSS and MSI-H patients have different molecular characteristics and prognosis, we searched for key genes of RCC and LCC in MSS and MSI-H groups respectively. The difference between the prognosis and the curative effect of the left and right-sided colon cancer is essentially the difference between the molecular pathology and the immune environment. Therefore, the aim of this study is to explore the molecular mechanism related to the prognosis of left and right-sided colon cancer in order to provide a molecular target for accurate treatment of left and right-sided colon cancer. First of all, bioinformatics methods were used to screen the right and left-sided CRC differentially expressed genes in MSS and MSI-H. The expression levels of these key genes in clinical samples and cell lines were detected by RT-qPCR and IHC, and their correlation with survival prognosis was analyzed. Homeobox C6(HOXC6)were selected. First, HOXC6 stable overexpressed and knockout colorectal cancer cell lines were established and its biological function was preliminarily studied, including transwell, wound-healing assay and CCK-8 tests. Finally, the ChIP-seq data were used to analyze the carcinogenic mechanism of HOXC6. Bioinformatics methods were used to screen 30 differentially expressed genes in MSS right and left CRC, of which HOXC6 in the right colon cancer was significantly higher than that in the left-sided colon cancer, which was positively correlated with TNM staging and lymph node metastasis. Kaplan-Meier survival analysis showed that the expression of HOXC6 was negatively correlated with the total survival of CRC patients (p=0.002). RT-qPCR and IHC showed that the expression of HOXC6 in the right-sided colon cancer was higher than that in the left, P&amp;lt;0.05. Functional experiments showed that Hoxc6 promoted the growth, invasion and migration. ChIP-seq data and real-time PCR results showed that SPOCD1 and S100A1 were the target genes of HOXC6. Citation Format: Xin li, Jinhong Xia, Dengbo Ji, Jin Gu. HOXC6 promotes tumorigenesis of right-sided colon cancer [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 2430.

Abstract 2523: Novel genomic characterization in late stage colorectal cancer

Abstract Introduction: Colorectal cancer patients with high-level microsatellite instability benefit more from immune checkpoint inhibitor therapy, but they only account for around 15% of all colorectal cancer patients. The remaining patients are still lack of effective therapeutic biomarkers. For patients in late stage without optimal treatment, it is essential to find novel biomarkers which can be used to select appropriate therapies and therefore improve patients' overall survival. Methods: We used whole-exome sequencing to analyze 114 colorectal cancer samples. The samples included 86 primary late stage tumors and 28 metastatic tumors from liver, lung and other organs. The primary samples were further divided into different groups based on their tumor location (sideness) and microsatellite status (MS) since these indications are of great significance in clinical presentation and treatment. We then assessed somatic genomic lesions, copy number variations, germline gene alterations and mutational signatures in the above three pairs of comparisons respectively (primary vs. metastatic, right- vs. left-sided, MS instable vs. stable). Results: There were significant differences between the analyzed pairs. For the primary and metastatic samples, the most prominent difference was the copy number variation which happened in 25 genes in the metastatic samples and only one gene in the primary samples (gain of IL12) (p = 0.036). For the right- and left-sided comparison, SNP/Indel mutations were the most prominent. They happened more frequently in the right-sided than the left-sided tumors and those are rare genes in colorectal cancer, including BCL11A (p = 0.018), DICER1 (p = 0.038), NR4A3 (p = 0.004), NIN (p = 0.008) and FBXW7 (p = 0.019). For the MSI-MSS comparison, tumor mutation burden (TMB) stands out high in the MSI group compared to the MSS group (p &amp;lt; 0.0001). In addition, dozens of significantly mutated genes were observed in the MSI samples (p &amp;lt; 0.0001), such as KMT2B, ACVR2A, KMT2D, ASXL1, TCF7L2 and etc. However, TP53 occurred mainly in the MSS patients (p = 0.0007). Conclusion: Our study enables a deeper understanding of the genomic characterization of colorectal cancer from an integrated view. Copy number variations, gene mutations, and TMB were found to be the most significant differences between the comparison groups of primary vs. metastatic samples, left vs. right sided samples, and MSI vs. MSS samples respectively. Genomic differences between metastatic and primary samples may be potential therapeutic targets for metastatic colorectal cancer. Citation Format: Jianxia Li, Qianchao Wu, Jianwei Zhang, Huabin Hu, Yue Cai, Jiayu Lin, Jun Liu, Yanhong Deng. Novel genomic characterization in late stage colorectal cancer [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 2523.

Prevalence and prognosis of microsatellite instability in oesogastric adenocarcinoma, NORDICAP 16-01

BackgroundThe prevalence and prognosis association of microsatellite instability (MSI) in oesogastric junction and gastric adenocarcinoma (OGC) have been reported with conflicting results. MethodsPatients with OGC from 2010 to 2015 were enrolled in this retrospective multicenter study. MSI was determined by genotyping. MLH1 promoter methylation and BRAFV600E mutation were screened in the MSI tumors. ResultsAmong 315 tumors analyzed, 39 (12.4%) were of the MSI phenotype. Compared to MSS tumors, MSI tumors were more frequent in patients >70 years (17% vs 9%, p=0.048) and in gastric antral primary (20% versus 5% in junction tumor and 12% in fundus tumor. Among 29 MSI tumors analyzed, 28 had a loss of MLH1 protein expression and 27 had MLH1 promotor hypermethylation. None had a BRAF V600E mutation. The 4-year cumulative incidence of recurrence for patients with resected tumor was significantly lower in dMMR tumors versus pMMR tumors (17% versus 47%, p=0.01). For the patients with unresectable tumor the median overall survival was 11 months in MSS group and 14 months in MSI group (p=0.24). ConclusionMSI prevalence in OGC was 12.4%, associated with antral localization and advanced age. Patients with MSI tumors had a lower cumulative incidence of recurrence after surgery. MSI phenotype was mainly associated with loss of MLH1 protein expression, MLH1 promotor hypermethylation and had no BRAFV600E mutation.

Sexual Difference Matters: Females with High Microsatellite Instability Show Increased Survival after Neoadjuvant Chemotherapy in Gastric Cancer.

Simple SummaryHere we report a sex- and age-specific analysis of 717 patients with gastric/gastro-esophageal adenocarcinomas treated with or without neoadjuvant chemotherapy (CTx) regarding overall survival (OS) and response to CTx. The analysis was also performed in molecular subtypes determined previously. Females demonstrated a significantly increased OS particularly in the group of patients treated with neoadjuvant CTx. Specifically in this patient group and taken into account the molecular subtypes, females with high microsatellite instability (MSI-H) showed the best survival followed by the male MSI-H, the female microsatellite stable (MSS) group and the male MSS group. Thus, we show an effect of sex on OS in gastric/gastro-esophageal cancer in particular for patients treated with neoadjuvant CTx. The superior survival of women with MSI-H tumors among the CTx patients implies that the combined consideration of these factors could contribute to an individualized treatment of the patients.We aimed to investigate patients with gastric/gastro-esophageal adenocarcinomas for sex- and age-specific differences regarding overall survival (OS) and response to neoadjuvant chemotherapy (CTx) under consideration of tumor specific molecular subtypes. Overall, 717 patients were analyzed, including 426 patients treated with and 291 treated without neoadjuvant CTx. Microsatellite instability (MSI) and Epstein-Barr virus positivity (EBV+) were determined previously. Females demonstrated a significantly increased OS (p = 0.035), particularly in the subgroup treated with CTx (p = 0.054). No significant differences regarding age were found. In the molecular subgroups, no sex-related differences were observed in the non-CTx group. However in the CTx group, females with MSI-high (H) tumors showed the best OS (p = 0.043), followed by the male MSI-H (p = 0.198) and female MSS (p = 0.114) compared to the male MSS group as reference. The interaction between sex and MSI in this patient group was noticeable (p = 0.053) and was included as a relevant factor in multivariable analyses. In conclusion, our results show an effect of sex on OS in gastric/gastro-esophageal cancer specifically for patients treated with neoadjuvant CTx. The superior survival of women with MSI-H tumors after neoadjuvant CTx implies that combined consideration of these factors could contribute to an individualized treatment of the patients.