The clinicopathological features and prognosis of tumor MSI in East Asian colorectal cancer patients using NCI panel

Neoadjuvant Immunotherapy for Patients With Microsatellite Instability-High or POLE-Mutated Locally Advanced Colorectal Cancer With Bulky Tumors: New Optimization Strategy

OBJECTIVE

To evaluate the efficacy and safety of neoadjuvant immunotherapy for patients with microsatellite instability-high (MSI-H) or DNA polymerase ε (POLE)-mutated locally advanced colorectal cancer (LACRC) with bulky tumors.  PATIENTS: We retrospectively reviewed 22 consecutive patients with MSI-H or POLE-mutated LACRC with bulky tumors (>8 cm in diameter) who received preoperative programmed death-1 blockade, with or without CapOx chemotherapy.  MAIN OUTCOME MEASURES: Pathological complete response (pCR), clinical complete response (cCR), toxicity, R0 resection rate, and complications were evaluated. Survival outcomes were analyzed using the Kaplan-Meier method. Multiplex immunofluorescence analysis were performed before and after treatment.  RESULTS: The incidence of immune-related adverse events (irAEs) was 36.4% (8/22). Five of 22 patients presented with surgical emergencies, most commonly perforation or obstruction. The 22 patients underwent a median 4 (1-8) cycles. Two patients were evaluated as cCR and underwent a watch and wait strategy. The R0 resection rate was 100.0% (20/20) and pCR rate was 70.0% (14/20). Twelve of 14 cT4b patients (85.7%) avoided multivisceral resection, and 10 of them achieved pCR or cCR. In the two patients with POLE mutations, one each achieved pCR and cCR. No Grade III/IV postoperative complications occurred. The median follow-up was 16.0 months. Two-year event-free and overall survival for the whole cohort was both 100%.  CONCLUSIONS: Preoperative immunotherapy is the optimal option for MSI-H or POLE-mutated LACRC with bulky tumors, especially cT4b. Preoperative immunotherapy in patients with T4b CRC can reduce multivisceral resection and achieve high CR rate.

Clinical performance of the TrueMark™ MSI assay for microsatellite instability detection in a Chinese colorectal cancer cohort

BACKGROUND

Microsatellite instability (MSI) and mismatch repair (MMR) detection is valuable in assessing prognosis and treatment options. However, the conventional detection methods such as immunohistochemistry (IHC) are limited by not fully consistent results as well as a long turnaround time. TrueMark™ MSI Assay is a novel solution for MSI analysis, but lack of research support in the Chinese colorectal cancer (CRC) patients.

MATERIALS AND METHODS

60 dMMR and 60 pMMR CRC samples identified by IHC were collected and their MSI status were detected using TrueMark™ MSI assay with an expanded panel of 13 markers. The overall performance and diagnostic concordance between TrueMark™ MSI test and MMR IHC analysis were assessed and analyzed.

RESULTS

According to the TrueMark™ test, 55 out of the 120 (45.8 %) CRCs were identified as MSI-high (MSI-H) with an instability at ≥ 4/13 markers. Compared with the MMR IHC analysis, an overall percent agreement of 94.2 % and a Kappa of 0.883 were achieved. For the seven inconsistent samples, tumor mutation burden analysis was performed and the results supported the diagnosis by TrueMark™ test. To confirm the robustness of the above findings, a validation was performed in an independent cohort comprising 51 consecutive CRCs. Furthermore, an optimized panel composed of NR-21, NR-24, NR-27, ABI-16, ABI-17 and ABI-20B was developed by multivariate logistic regression model, and showed 100 % agreement with the 13-marker panel for MSI detection in both the derivation and validation sets.

CONCLUSION

TrueMark™ MSI provides a fast, reliable and highly automated solution to MSI detection in Chinese CRC patients, and the new 6-marker panel we established shows promise deserving further evaluation.

Neoadjuvant Immunotherapy Alone for Patients With Locally Advanced and Resectable Metastatic Colorectal Cancer of dMMR/MSI-H Status

BACKGROUND

The use of programmed death-1 blockade has a significant therapeutic effect in patients with mismatch repair-deficient/microsatellite instability-high metastatic colorectal cancer. However, data on preoperative single-agent programmed death-1 blockade are rare.

OBJECTIVE

This study aims to evaluate the effectiveness and safety of preoperative programmed death-1 blockade as a conversion strategy in patients with locally advanced and resectable metastatic mismatch repair-deficient/microsatellite instability-high colorectal cancer.

DESIGN

This is a retrospective observational study.

SETTINGS

This study was conducted at a high-volume tertiary referral cancer center in China.

PATIENTS

Twenty-four patients of consecutive cases since 2020 to 2022 with mismatch repair-deficient/microsatellite instability-high colorectal cancer who received preoperative single-agent programmed death-1 blockade were retrospectively reviewed. These patients had either bulking tumors scheduled for multivisceral resection, a strong desire for organ preservation, or potentially resectable metastatic lesions.

MAIN OUTCOME MEASURES

Pathological complete response, clinical complete response, toxicity, R0 resection rate, and complications were evaluated.

RESULTS

Patients tolerated preoperative immunotherapy well. The R0 resection rate was 95.2%, and the pathological complete response rate was 47.6%. Three patients (12.5%) were evaluated as having a clinical complete response and then underwent "watch and wait." One-half of the patients with cT4b were spared multivisceral resection, whereas 60% (3/5) achieved pathological complete response. All 3 patients with liver metastases obtained complete response of all liver lesions after programmed death-1 blockade treatment. Grade III postoperative complications occurred in 2 patients.

LIMITATIONS

The limitations of this study are as follows: retrospective study, small sample size, and short follow-up.

CONCLUSIONS

Preoperative anti-programmed death-1 therapy alone as a conversion strategy in initially resected difficult mismatch repair-deficient/microsatellite instability-high colorectal cancer can achieve a high tumor complete response. The use of immunopreoperative therapy in patients with T4b colon cancer or low rectal cancer can reduce multivisceral resection and achieve high organ function preservation. See the Video Abstract .

INMUNOTERAPIA NEOADYUVANTE SOLA PARA PACIENTES CON CNCER COLORRECTAL LOCALMENTE AVANZADO Y METASTSICO RESECABLE CON ESTADO DMMR/MSIH

ANTECEDENTES:El uso del bloqueo de muerte programada-1 tiene un efecto terapéutico significativo en pacientes con cáncer colorrectal metastásico deficiente en reparación de desajustes/inestabilidad de microsatélites-alta (dMMR/MSI-H). Sin embargo, los datos sobre el bloqueo preoperatorio de muerte programada-1 con un solo agente son escasos.OBJETIVO:Este estudio tiene como objetivo evaluar la eficacia y seguridad del bloqueo preoperatorio de muerte programada-1 como estrategia de conversión en pacientes con cáncer colorrectal localmente avanzado y metastásico resecable con dMMR/MSI-H.DISEÑO:Este es un estudio observacional retrospectivo.ESCENARIO:Este estudio se realizó en un centro oncológico terciario de referencia de gran volumen en China.PACIENTES:Se revisaron retrospectivamente veinticuatro pacientes de casos consecutivos desde 2020-2022 con cáncer colorrectal y dMMR/MSI-H que recibieron bloqueo preoperatorio de muerte programada-1 con un solo agente. Estos pacientes tenían un tumor voluminoso programado para resección multivisceral, un fuerte deseo de preservación del órgano o lesiones metastásicas potencialmente resecables.PRINCIPALES MEDIDAS DE RESULTADO:Se evaluaron la respuesta patológica completa, la respuesta clínica completa, la toxicidad, la tasa de resección R0 y las complicaciones.RESULTADOS:Los pacientes toleraron bien la inmunoterapia preoperatoria. La tasa de resección R0 fue del 95,2% y la tasa de respuesta patológica completa fue del 47,6%. Tres pacientes (12,5%) fueron evaluados como respuesta clínica completa y luego sometidos a "observar y esperar". La mitad de los pacientes cT4b se salvaron de la resección multivisceral, mientras que el 60% (3/5) lograron una respuesta patológica completa. Los tres pacientes con metástasis hepáticas obtuvieron respuesta completa de todas las lesiones hepáticas después del tratamiento de bloqueo de muerte programada-1. En dos pacientes se produjeron complicaciones postoperatorias de grado III.LIMITACIONES:Las limitaciones de este estudio son las siguientes: estudio retrospectivo, tamaño de muestra pequeño y seguimiento corto.CONCLUSIONES:La terapia preoperatoria anti muerte programada-1 sola como estrategia de conversión en el cáncer colorrectal inicialmente difícil de resecar con dMMR/MSI-H puede lograr una alta respuesta completa tumoral. El uso de terapia inmunopreoperatoria en pacientes con cáncer de colon T4b o cáncer de recto bajo puede reducir la resección multivisceral y lograr una alta preservación de la función del órgano. (Traducción-Dr. Felipe Bellolio ).

Intraoperative rapid immunohistochemistry of microsatellite instability using non-contact alternating current electric field mixing

OBJECTIVES

Tumors caused by failure of the DNA-mismatch repair system generally show microsatellite instability (MSI). High-frequency MSI cancers have been shown to be susceptible to immuno-oncology therapies. The aim of this study was to evaluate the clinical reliability of a rapid immunohistochemistry (IHC) technique for intraoperatively assessing molecular status through detection of tumoral deficiencies in the expression of mismatch repair proteins (dMMR; MLH1, MSH2, MSH6, and PMS2).

METHODS

The rapid IHC method uses non-contact alternating current (AC) mixing to achieve more rapid/stable staining within a minimum of 13 min during surgery. Sixteen formalin-fixed paraffin-embedded (FFPE) tumor samples from 3 dMMR patients with Lynch syndrome and 6 FFPE samples from 6 dMMR-cancer patients were collected to establish an IHC protocol for MMR proteins. Next, 26 surgical patients treated and whose MSI status was determined using PCR-based tests were retrospectively analyzed. The concordance of dMMR diagnoses for thoracic tumors between the conventional (frozen section (FS)- and FFPE-IHCs) and rapid AC-mixing IHC with FSs were compared.

RESULTS

A rapid IHC protocol using primary antibodies against four MMR proteins (mixed 5-10 min) was established (entire process within 40 min). The concordance rate for MMR-IHC between the conventional and rapid IHC was 100%. dMMR diagnoses including an MSI-high pulmonary sarcoma patient entirely matched between FS- and FFPE-IHC.

CONCLUSION

Rapid MMR-IHC could potentially serve as a clinical tool for intraoperative determination of tumor MSI/dMMR status. AC-mixing technology will contribute to improving pathological diagnostic capability through the development of an original and innovative rapid IHC.

Head-to-head comparative study: evaluating three panels for MSI-PCR testing in patients with colorectal and gastric cancer

AIMS

Due to the lack of large clinical cohorts in the Chinese populations with colorectal cancer (CRC) and gastric cancer (GC), there is no consensus among the preferred panel for microsatellite instability (MSI)-PCR testing. This study aims to evaluate a more appropriate panel.

METHODS

We tested the MSI status of 2572 patients with CRC and GC using the NCI panel and 2 mononucleotide panels (5 and 6 mononucleotide panels). Immunohistochemistry (IHC) was employed to perform mismatch repair protein testing in 1976 samples.

RESULTS

We collected 2572 patients with CRC and GC. The National Cancer Institute (NCI) panel failed to detect 13 cases. Of the 2559 cases that received results from all three panels, 2544 showed consistent results. In the remaining 15 cases, 9 showed discrepancies between MSI-H and MSI-L, and 6 showed discrepancies between MSI-L and microsatellite stability (MSS). The misdiagnosis rate of MSI-L was significantly lower in two mononucleotide panels than in the NCI panel (12.5% vs 87.5%, p=0.010) in CRC. In patients with GC, only the NCI panel detected three MSI-L cases, while the results of the two mononucleotide panels were one MSI-H and two MSS. Based on their IHC results, the MSI-L misdiagnosis rate of the NCI panel was 33.3%. Furthermore, compared with two mononucleotide panels, the NCI panel had a much lower rate of all loci instability in CRC (90.8% and 90.3% vs 25.2%) and GC (89.5% and 89.5% vs 12.0%).

CONCLUSION

In Chinese patients with CRC and GC, the five and six mononucleotide panels have advantages for detecting MSI over the NCI panel.

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.

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.

New Perspectives in Colorectal Cancers Treatment, the Role of MicroRNAs

The main epidemiological and clinical data on colorectal cancer, as well as the features of molecular pathology, are discussed in the literature review. Efforts are being putto identify promising targets, particularly small non-coding nucleotide sequences, which can lead to new treatments for this disease. The discovery of significant mutations that contribute to the development of colorectal tumors is a major step in the advancement of molecular oncology, as these mutations give rise to heterogeneous tumors that differ in their origin. These mutations play a significant role in the progression of the disease and are now being targeted for treatment. The prognosis for a disease is influenced by the patient's sensitivity to antitumor therapy. However, new approaches to finding effective targets for antitumor treatments face new fundamental challenges due to clinical issues. These issues include the epigenetic regulation of markers of oncogenesis, which allows for the development of new therapeutic strategies. RNA interference, in particular, has been linked to non-copying RNA sequences such as microRNAs. These microRNAs are associated with certain processes that can influence all aspects of oncogenesis. The diversity of microRNAs allows for a differentiated approach when treating tumors in various locations.

Association of mismatch repair deficiency in endometrial cancer with 18F-FDG PET/CT and clinicopathological features and their prognostic value

PURPOSE

Identification of the mismatch repair (MMR) deficiency in endometrial cancer (EC) may aid in the screening of patients who may benefit from immunotherapy. Our goal was to investigate the relationship between MMR status and 18F-FDG PET/CT metabolic parameters and clinicopathological features in patients with EC, as well as to explore their prognostic value.

METHODS

This retrospective study included 106 EC patients who were classified as MMR deficient (dMMR) or MMR proficient (pMMR) group based on MMR protein expression status evaluated by immunohistochemistry. Clinicopathological characteristics and PET metabolic parameters were compared between the dMMR and pMMR groups, and their relationships with MMR status and prognosis were evaluated.

RESULTS

Of 106 EC patients, 30 patients (28.1%) had dMMR, while 76 (71.7%) had pMMR. Compared with the pMMR group, the dMMR group showed a lower prevalence of overweight (BMI ≥ 25) (17.2% vs. 43.9%, P = 0.019) and more lymph vascular space invasion (43.3% vs. 21.1%, P = 0.029). Although no relationship between glucometabolism parameters and MMR status was observed in all enrolled patients, higher SUVmax was observed in the endometrioid type of EC with MMR deficiency (P = 0.047). Additionally, SUVmax related to MMR status was found in EC patients with advanced FIGO stage (P = 0.026) or deep myometrial invasion (P = 0.026). Multivariate Cox regression analysis revealed that lymph node metastasis was independently predictive of PFS, while advanced FIGO stage was an independent predictor of OS. No significant association between MMR status and prognosis was found in EC.

CONCLUSION

Higher SUVmax was associated with MMR deficiency in EC patients with endometrioid type, advanced stage, or deep myometrial invasion, which may be useful for predicting the MMR status and thus aiding in determination of immunotherapy for patients with EC.

A comparison of performance of 6-mononucleotide site panel and NCI panel for microsatellite instability detection in patients with colorectal adenocarcinoma

BACKGROUND

Microsatellite instability (MSI) represents as a molecular hallmark of deficient MMR system at the genomic level. Increasing clinical significance of MSI status highlights the necessity of simple, accurate markers for detection. Although 2B3D NCI panel is the most widely applied, it has been questioned whether the performance of NCI panel is second to none in MSI detection.

METHODS

We evaluated the efficacy of the NCI panel versus a 6-mononucleotide site panel (BAT25, BAT26, NR21, NR24, NR27, and MONO-27) in assessing MSI status of 468 Chinese patients with CRC, and compared MSI test results with the results by immunohistochemistry of four MMR proteins (MLH1, PMS2, MSH2, MSH6) in the present study. Clinicopathological variables were also collected, and their associations with MSI or MMR proteins status were analyzed using either the chi-square test or the Fisher's exact test.

RESULTS

MSI-H/dMMR was significantly associated with right colon involvement, poor differentiation, early stage, mucinous adenocarcinoma, negative lymph node, less neural invasion, and KRAS/NRAS/BRAF wild-type. As to the efficiency of detecting deficient MMR system, both panels had good concordance with MMR proteins expression by IHC, and 6-mononucleotide site panel outperformed NCI panel in sensitivity, specificity, positive predictive value, and negative predictive value numerically despite the lack of statistical significance. The advantage was more obvious in the sensitivity and specificity analyses of each single microsatellite markers from 6-mononucleotide site panel in comparison with NCI panel. Additionally, the rate of MSI-L detected by 6-mononucleotide site panel was much lower than that detected by the NCI panel (0.64% vs. 2.86%, P = 0.0326).

CONCLUSION

6-mononucleotide site panel had a greater ability to help resolve cases of MSI-L into either MSI-H or MSS. We propose that 6-mononucleotide site panel may be potentially more suitable than NCI panel for Chinese CRC population. Large-scale studies are warranted to validate our findings.

Are High Levels of Microsatellite Instability and Microsatellite Stability Identical in DNA Mismatch Repair-Deficient Colorectal Cancer Patients?

Purpose

The purpose of the current study was to determine whether there is a difference between high levels of microsatellite instability (MSI-H) and microsatellite stability (MSS) in DNA mismatch repair-deficient (DMMR) colorectal cancer (CRC) patients.

Methods

A total of 452 CRC patients with DMMR from December, 2014, to April, 2021, in our hospital were selected retrospectively. However, only 105 patients underwent Sanger or next-generation-sequencing (NGS) to confirm their microsatellite status. Ultimately, 55 MSI-H patients and 20 MSS patients with intact medical record information were included in this study.

Results

The MSS group was associated with a higher mutation rate in the KRAS gene (P=0.011). Meanwhile, MSI-H was related to colon cancer (P < 0.01). However, no significant differences in other clinical characteristics were observed between the two groups of patients. There was no significant difference between the MSI-H and MSS groups in terms of overall survival (OS) (P=0.398) and disease-free survival (DFS) (P=0.307).

Conclusion

The MSI-H status was associated with colon cancer and a lower mutation rate of the KRAS gene in DMMR patients. In CRC-DMMR patients, the MSS group exhibited better OS and DFS than the MSI-H group, although these differences were not statistically significant. Accordingly, in clinical practice, we should not confuse these two types of patients.

An innovative single-base extension method for synchronous detection of point mutations and MSI status in colorectal cancer

BACKGROUND

An accurate genotyping analysis is one of the critical prerequisites for patients with colorectal cancer receiving matched therapies. Conventional genotyping analysis is currently used to detect either gene mutations or MSI status, delaying the detection of critical tumor biomarkers and thus the optimal time for treatment. An assay that analyzes both biomarkers in a streamlined process is eagerly needed.

METHODS

We developed an assay combining Multiplex PCR Amplification, Single-base Extension and capillary electrophoresis (CE) analysis (MASE-CE) for synchronous detection of KRAS/NRAS/BRAF mutations and MSI status. In a 190 colorectal cancer cohort, we identified seven somatic mutations in KRAS, NRAS and BRAF as well as five MSI loci (D2S123/D5S346/D17S250/BAT-25/BAT-26) simultaneously. KRAS/NRAS/BRAF mutations were detected by NGS and MASE-CE, and MSI status were detected by PCR-CE and MASE-CE methods.

RESULTS

The MASE-CE method showed high consistency with NGS for mutation detection (Kappa value ≥0.8) and PCR-CE (Kappa value = 0.79). In addition, the limits of detection (LOD) of MASE-CE assay for MSI and somatic mutation were 5% and 2%, respectively.

CONCLUSIONS

In somatic mutation detection and MSI detection, the LOD of MASE-CE assay was superior to that of qPCR and NGS. MASE-CE assay is a highly sensitive, time-saving and specimen-saving method, which can greatly avoid the cumbersome testing process and provide clinical decision for doctors in time.

Clinicopathological characteristics of high microsatellite instability/mismatch repair-deficient colorectal cancer: A narrative review

Colorectal cancers (CRCs) with high microsatellite instability (MSI-H) and deficient mismatch repair (dMMR) show molecular and clinicopathological characteristics that differ from those of proficient mismatch repair/microsatellite stable CRCs. Despite the importance of MSI-H/dMMR status in clinical decision making, the testing rates for MSI and MMR in clinical practice remain low, even in high-risk populations. Additionally, the real-world prevalence of MSI-H/dMMR CRC may be lower than that reported in the literature. Insufficient MSI and MMR testing fails to identify patients with MSI-H/dMMR CRC, who could benefit from immunotherapy. In this article, we describe the current knowledge of the clinicopathological features, molecular landscape, and radiomic characteristics of MSI-H/dMMR CRCs. A better understanding of the importance of MMR/MSI status in the clinical characteristics and prognosis of CRC may help increase the rates of MMR/MSI testing and guide the development of more effective therapies based on the unique features of these tumors.

Mismatch Repair and Microsatellite Instability Testing for Immune Checkpoint Inhibitor Therapy: Guideline From the College of American Pathologists in Collaboration With the Association for Molecular Pathology and Fight Colorectal Cancer

CONTEXT.—

The US Food and Drug Administration (FDA) approved immune checkpoint inhibitor therapy for patients with advanced solid tumors that have DNA mismatch repair defects or high levels of microsatellite instability; however, the FDA provided no guidance on which specific clinical assays should be used to determine mismatch repair status.

OBJECTIVE.—

To develop an evidence-based guideline to identify the optimal clinical laboratory test to identify defects in DNA mismatch repair in patients with solid tumor malignancies who are being considered for immune checkpoint inhibitor therapy.

DESIGN.—

The College of American Pathologists convened an expert panel to perform a systematic review of the literature and develop recommendations. Using the National Academy of Medicine-endorsed Grading of Recommendations Assessment, Development and Evaluation approach, the recommendations were derived from available evidence, strength of that evidence, open comment feedback, and expert panel consensus. Mismatch repair immunohistochemistry, microsatellite instability derived from both polymerase chain reaction and next-generation sequencing, and tumor mutation burden derived from large panel next-generation sequencing were within scope.

RESULTS.—

Six recommendations and 3 good practice statements were developed. More evidence and evidence of higher quality were identified for colorectal cancer and other cancers of the gastrointestinal (GI) tract than for cancers arising outside the GI tract.

CONCLUSIONS.—

An optimal assay depends on cancer type. For most cancer types outside of the GI tract and the endometrium, there was insufficient published evidence to recommend a specific clinical assay. Absent published evidence, immunohistochemistry is an acceptable approach readily available in most clinical laboratories.

Analysis of KRAS, NRAS, and BRAF Mutations, Microsatellite Instability, and Relevant Prognosis Effects in Patients With Early Colorectal Cancer: A Cohort Study in East Asia

Background

Early colorectal cancer (ECRC) refers to any size of colorectal cancer (CRC) whose depth of invasion is limited to the mucosa and submucosa. About 10% of patients with ECRC die from cancer after surgery. KRAS, NRAS, and BRAF mutations and microsatellite instability (MSI) are considered diagnostic and prognostic markers in CRC. However, their characteristics in ECRC and whether postoperative chemotherapy based on them will benefit ECRC patients or not remain unknown.

Patients and Methods

Patients with ECRC and 298 patients with advanced colorectal cancer (ACRC) were collected in our hospital from January 2013 to December 2015. The Amplification Refractory Mutation System (ARMS)-PCR was used to perform the KRAS, NRAS, and BRAF mutant tests.

Results

In ECRC patients, 43 cases of KRAS mutation were found, accounting for 69.35%. Interestingly, among KRAS mutations, there were 10 KRAS multi-site mutation patients (16.13% in 62 ECRC patients). Moreover, the NRAS mutation rate was 3.23% but no BRAF mutation was found and only 1 case of MSI-High was detected. KRAS mutation was only related to the depth of tumor invasion whereas KRAS multi-site mutations were related to mucus components and tumor size. As far as NRAS is concerned, mutations were associated with elevated CEA, mucus components, and the depth of tumor invasion. Notably, compared with 2.35% KRAS multi-site mutation in ACRC, the rate of KRAS multi-site mutation in ECRC was much higher. Furthermore, Cox regression analysis revealed that KRAS mutation could be an independent prognostic factor of ECRC in patients who have undergone endoscopic resection or surgery.

Conclusion

Patients with ECRC might benefit from KRAS mutation testing but not from postoperative chemotherapy.

The clinicopathological characteristics, prognosis and immune microenvironment mapping in MSI-H/MMR-D endometrial carcinomas

Endometrial cancer had a relatively high prevalence of MMR deficiency. MMR-D/MSI-H endometrial cancer patients are suggested to be potential beneficiaries of PD-1/PD-L1 inhibitor therapy. Here, we explored the prognostic value of MSI subtype in endometrial cancer and its correlation with immune environment. Based on expression and clinical data of 78 POLE, 123 MSI and 299 Other EC samples from the TCGA-UCEC project, we found that the MSI tumors were identified more often in early stage, had a lower age, better patient survival, enriched CD8⁺ T cells, and regulatory T cells and less M2 macrophages and activated dendritic cells than the Other group, and shared a relatively similar expression profile with POLE group by differential analysis. In addition, we established the immune landscape of an MMR-D endometrial cancer tissue using unbiased single-cell RNA-seq analysis of 3371 cells. By immunohistochemistry analysis, we found that the MMR-D tumors showed a higher trend of CD20⁺ B cells infiltration. Our study might expand our understanding of the role of immune subsets in MSI endometrial carcinomas and provide guidance of immunotherapy for endometrial cancer.

Cost-effective screening using a two-antibody panel for detecting mismatch repair deficiency in sporadic colorectal cancer

BACKGROUND

The microsatellite instability (MSI) test and immunohistochemistry (IHC) are widely used to screen DNA mismatch repair (MMR) deficiency in sporadic colorectal cancer (CRC). For IHC, a two-antibody panel of MLH1 and MSH2 or four-antibody panel of MLH1, MSH2, PMS2, and MSH6 are used. In general, MSI is known as a more accurate screening test than IHC.

AIM

To compare two- and four-antibody panels of IHC in terms of accuracy and cost benefit on the basis of MSI testing for detecting MMR deficiency.

METHODS

We retrospectively analyzed patients with CRC who underwent curative surgery between 2015 and 2017 at a tertiary referral center. Both IHC with four antibodies and MSI tests were routinely performed. The sensitivity and specificity of a four- and two types of two-antibody panels (PMS2/MSH6 and MLH1/MSH2) were compared on the basis of MSI testing for detecting MMR deficiency.

RESULTS

High-frequency MSI was found in 5.5% (n = 193) of the patients (n = 3486). The sensitivities of the four- and two types of two-antibody panels were 97.4%, 92.2%, and 87.6%, respectively. The specificities of the three types of panels did not differ significantly (99.6% for the four-antibody and PMS2/MSH6 panels, 99.7% for the MLH1/MSH2 panel). Based on Cohen's kappa statistic (κ), four- and two-antibody panels were in almost perfect agreement with the MSI test (κ > 0.9). The costs of the MSI test and the four- and two-antibody panels of IHC were approximately $200, $160, and $80, respectively.

CONCLUSION

Considering the cost of the four-antibody panel IHC compared to that of the two-antibody panel IHC, a two-antibody panel of PMS2/MSH6 might be the best choice in terms of balancing cost-effectiveness and accuracy.

Biomarkers in Immunotherapy-Based Precision Treatments of Digestive System Tumors

Immunotherapy, represented by immune checkpoint inhibitors (mainly referring to programmed death-1 (PD-1)/programmed death-ligand 1 (PD-L1) blockades), derives durable remission and survival benefits for multiple tumor types including digestive system tumors [gastric cancer (GC), colorectal cancer (CRC), and hepatocellular carcinoma (HCC)], particularly those with metastatic or recurrent lesions. Even so, not all patients would respond well to anti-programmed death-1/programmed death-ligand 1 agents (anti-PD-1/PD-L1) in gastrointestinal malignancies, suggesting the need for biomarkers to identify the responders and non-responders, as well as to predict the clinical outcomes. PD-L1expression has increasingly emerged as a potential biomarker when predicting the immunotherapy-based efficacy; but regrettably, PD-L1 alone is not sufficient to differentiate patients. Other molecules, such as tumor mutational burden (TMB), microsatellite instability (MSI), and circulating tumor DNA (ctDNA) as well, are involved in further explorations. Overall, there are not still no perfect or well-established biomarkers in immunotherapy for digestive system tumors at present as a result of the inherent limitations, especially for HCC. Standardizing and harmonizing the assessments of existing biomarkers, and meanwhile, switching to other novel biomarkers are presumably wise and feasible.

Incidence and detection of high microsatellite instability in colorectal cancer in a Chinese population: a meta-analysis

Background

The 4 most common types of DNA mutations in tumors are single-nucleotide variations, insertion-deletion, fusion, and copy number variations. This is followed by microsatellite instability (MSI), which is known to trigger the development of MSI-high (MSI-H) cancer and is responsible for 300,000 new cases of cancer per year in China. We aim to conduct a meta-analysis based on a comparison between the positive rates of the National Cancer Institute (NCI) panel (also known as 2B3D NCI panel) and mononucleotide panels for the diagnosis of MSI in the Chinese population.

Methods

In the present meta-analysis, we searched the PubMed, Embase, Web of Science, CNKI, Wanfang, CQVIP, and CBM databases. MSI diagnosis studies by PCR and capillary electrophoresis were included to compare the incidence of MSI-H in colorectal cancer obtained from panels with different microsatellite markers. Egger's bias test was used to assess risk of bias.

Results

Seventeen articles were included, which used the Newcastle-Ottawa Scale (NOS) scale for quality evaluation. The NOS scores of the included documents were ≥7 points, and the quality of the documents met the requirements. The incidence of MSI-H detected by the 2B3D NCI panel was 13.5% [95% confidence interval (CI): 10.8-16.4, I²=52.321%, P=0.026, n=10 studies including 2,681 participants], the incidence of MSI-H detected by the mononucleotide panels was 10.6% (95% CI: 7.1-14.7, I²=81.147%, P=0.000, n=7 studies including 3,249 participants). This indicates that, in the Chinese population, the 2B3D NCI panel can detect 27.4% more MSI-H cancers than the mononucleotide panels, 54.7% more MSI-H cancers than the panel of 6 mononucleotides, and its sensitivity is comparable to that of Promega.

Conclusions

The findings of the meta-analysis demonstrated that, using the 2B3D NCI panel for MSI detection can avoid the underestimation of the incidence MSI-H in colorectal cancer and can be considered the most suitable panel for MSI detection in the Chinese population. The inclusion of only published data might be a potential source of publication bias.

Implication of Microsatellite Instability in Chinese Cohort of Human Cancers

Background

Microsatellite instability (MSI) has been a hot topic in cancer research. Determining MSI status greatly aids tumor prognosis and treatment plans. However, MSI data for Asian cancer patients with prognostic information are scarce. Here, our aim was to clarify MSI status and its prognostic value in a large Chinese cohort with different tumors.

Patients and Methods

Tissue samples from 600 Chinese cases, including 150 endometrial cancers, 150 colorectal cancers, 150 liver cancers and 150 gastric cancers, were used for IHC and MSI examinations. Two mononucleotide and three dinucleotide markers were used to analyze MSI status.

Results

In total,17.3% (26/150) of endometrial cancer patients showed positive MSI,10.0% (15/150) in colorectal cancer, 2.7% (4/150) in liver cancer, and 2.7% (4/150) in gastric cancer. Tumor location (P < 0.001 for colorectal cancer) and clinical stage (P =0.038 for gastric cancer) showed significant correlations with MSI status in gastrointestinal carcinogenesis. The mismatch repair (MMR) deficiency was observed in 20 colorectal cases (13.3%) and was significantly more frequent in the MSI-positive group (P < 0.001). Interestingly, the prevalence of MSI-H was mostly occurred in early-stage tumors, and none was in late stage (stage IV). Meanwhile, low clinicopathological stage had significant correlation with longer survival in multiple cancers here.

Conclusion

The incidence of microsatellite instability varies among different cancer types. And the prevalence of MSI-H mostly occurred early clinicopathological stage. In addition, our study provided a large Asian cohort screened by five loci PCR method and significantly increased knowledge on the prognostic significance of MSI in Asia.

The Better Survival of MSI Subtype Is Associated With the Oxidative Stress Related Pathways in Gastric Cancer

Background: Gastric cancer (GC) is the third leading fatal cancer in the world and its incidence ranked second among all malignant tumors in China. The molecular classification of GC, proposed by the The Cancer Genome Atlas (TCGA), was added to the updated edition (2019) of WHO classification for digestive system tumor. Although MSI and EBV subtypes appeared as ever-increasingly significant roles in immune checkpoint inhibitor therapy, the underlying mechanisms are still unclear.

Methods: We systematically summarized the relationship between EBV, d-MMR/MSI-H subtypes and clinicopathological parameters in 271 GC cases. Furthermore, GSE62254/ACRG and TCGA-STAD datasets, originated from Gene Expression Omnibus (GEO) and TCGA respectively, were analyzed to figure out the prognosis related molecular characteristics by bioinformatics methods.

Results: Patients with MSI subtype had better prognosis than the MSS subtype (P = 0.013) and considered as an independent biomarker by the univariate analysis (P = 0.017) and multivariate analysis (P = 0.050). While there was no significant difference between EBV positive and negative tissues (P = 0.533). The positive prognostic value conferred by MSI in different cohorts was revalidated via the clinical analysis of GSE62254/ACRG and TCGA-STAD datasets regardless of race. Then key gene module that tightly associated with better status and longer OS time for MSI cases was obtained from weighted gene co-expression network analysis(WGCNA). NUBP2 and ENDOG were screened from the gene cluster and oxidative phosphorylation, reactive oxygen species(ROS) and glutathione metabolism were analyzed to be the differential pathways in their highly expressed groups.

Conclusions: Our results manifested the significant prognostic value of MSI in Chinese GC cohort and comparisons with other populations. More opportunities to induce apoptosis of cancer cells, led by the unbalance between antioxidant system and ROS accumulation, lay foundations for unveiling the better prognosis in MSI phenotype through the bioinformatics analysis.