Artificial intelligence-driven microsatellite instability profiling reveals distinctive genetic features in patients with lung cancer.

Microsatellite instability (MSI) has emerged as a predictive biomarker for immunotherapy response in various cancers, but its role in non-small cell lung cancer (NSCLC) is not fully understood. The authors used the bioinformatics tool MIAmS to assess microsatellite status from next-generation sequencing (NGS) data using a tailored microsatellite score. Immunohistochemistry (IHC) assays were also performed to evaluate the correspondence between MSI and deficient mismatch repair (dMMR) status. A retrospective analysis of 1547 lung cancer patients was conducted, focusing on those with an MSI phenotype. Clinical characteristics, co-occurring molecular alterations, tumor mutation burden (TMB), and homologous recombination deficiency (HRD) status were evaluated in this subset. Of the 1547 patients analyzed, eight (0.52%) were identified as having MSI through MIAmS, with six (0.39%) of these cases also being dMMR on IHC. All patients with dMMR had an MS score ≥2 and a history of smoking. Most patients showed loss of MLH1 and PMS2 staining on IHC. No correlation was found between MSI status and programmed death-ligand 1 expression, although all MSI patients exhibited high TMB, averaging 21.4 ± 5.6 mutations per megabase. MSI/dMMR in lung cancer is exceedingly rare, affecting less than 1% of cases. NGS-based analysis combined with bioinformatics tools provides a robust method to identify MSI/dMMR patients, potentially guiding immunotherapy decisions. This comprehensive approach integrates molecular genotyping and MSI detection, offering personalized treatment options for lung cancer patients. NGS-based MSI testing is emerging as the preferred method for detecting microsatellite instability in various tumor types, including rare cancers.

Thomas QD ，Vendrell JA ，Khellaf L ，Cavaillon S ，Quantin X ，Solassol J ，Cabello-Aguilar S ... -  《-》

Microsatellite instability and high tumor mutational burden detected by next generation sequencing are concordant with loss of mismatch repair proteins by immunohistochemistry.

Impairment of DNA mismatch repair function in neoplasms can be assessed by DNA-based methods to assess for high microsatellite instability (MSI-High) or immunohistochemical (IHC) analysis to assess for deficiency of mismatch repair proteins (dMMR). Neoplasms with mismatch repair deficiency often have high tumor mutational burden (TMB-High). MSI-High, dMMR, and TMB-High are all histology agnostic biomarkers for potential therapy using immune checkpoint inhibitors (ICI). In this single center, retrospective study, our primary aim was to assess if NGS-based positive TMB/MSI findings are concordant with patient matched concurrent MMR IHC studies. In addition, we determined if positive TMB/MSI findings are attributable to genetic/epigenetic alterations of MMR genes. Finally, we explored potential associations between IHC, TMB and MSI findings and specific tumor types We screened 4,258 patients in our database who had tumor-normal-testing with our institutional high-throughput NGS-based CLIA assay between Apr 1, 2021-August 31, 2022 for TMB and MSI. We identified 65 patients who had neoplasms with documented TMB-High/MSI-High (n = 59) or TMB-High/MSI-Undetermined (n = 6) results as well as concurrent IHC results for MMR proteins [colorectal (n = 25), endometrial (n = 28), prostatic (n = 7), urothelial (n = 3), other (n = 5)]. The concordance between positive NGS TMB/MSI and MMR results was 98 %. Genetic/epigenetic alterations of MMR genes were documented in 78 % of the neoplasms. IHC studies for dMMR proteins revealed loss of MLH1/PMS2 (n = 33), MSH2/MSH6 (n = 14), MLH1/MSH2/PMS2 (n = 1), MLH1 (n = 1), MSH2 (n = 2), MSH6 (n = 6) and PMS2 (n = 6). All six prostatic neoplasms with dMMR had loss of MSH2/MSH6 (p < 0.0001). We conclude that neoplasms with positive results for TMB/MSI are highly concordant with positive dMMR results. Genetic/epigenetic alterations in the MMR genes are an underlying reason for most positive findings. The association of MSH2/MSH6 loss with prostatic neoplasms is of in-terest, but sample size is limited, and further studies are warranted to address this association.

Yang RK ，Alvarez H ，Lucas AS ，Roy-Chowdhuri S ，Rashid A ，Chen H ，Ballester LY ，Sweeney K ，Routbort MJ ，Patel KP ，Luthra R ，Medeiros LJ ，Toruner GA ... -  《Cancer Genetics》

ESMO recommendations on microsatellite instability testing for immunotherapy in cancer, and its relationship with PD-1/PD-L1 expression and tumour mutational burden: a systematic review-based approach.

Cancers with a defective DNA mismatch repair (dMMR) system contain thousands of mutations most frequently located in monomorphic microsatellites and are thereby defined as having microsatellite instability (MSI). Therefore, MSI is a marker of dMMR. MSI/dMMR can be identified using immunohistochemistry to detect loss of MMR proteins and/or molecular tests to show microsatellite alterations. Together with tumour mutational burden (TMB) and PD-1/PD-L1 expression, it plays a role as a predictive biomarker for immunotherapy. To define best practices to implement the detection of dMMR tumours in clinical practice, the ESMO Translational Research and Precision Medicine Working Group launched a collaborative project, based on a systematic review-approach, to generate consensus recommendations on the: (i) definitions related to the concept of MSI/dMMR; (ii) methods of MSI/dMMR testing and (iii) relationships between MSI, TMB and PD-1/PD-L1 expression. The MSI-related definitions, for which a consensus frame-work was used to establish definitions, included: 'microsatellites', 'MSI', 'DNA mismatch repair' and 'features of MSI tumour'. This consensus also provides recommendations on MSI testing; immunohistochemistry for the mismatch repair proteins MLH1, MSH2, MSH6 and PMS2 represents the first action to assess MSI/dMMR (consensus with strong agreement); the second method of MSI/dMMR testing is represented by polymerase chain reaction (PCR)-based assessment of microsatellite alterations using five microsatellite markers including at least BAT-25 and BAT-26 (strong agreement). Next-generation sequencing, coupling MSI and TMB analysis, may represent a decisive tool for selecting patients for immunotherapy, for common or rare cancers not belonging to the spectrum of Lynch syndrome (very strong agreement). The relationships between MSI, TMB and PD-1/PD-L1 expression are complex, and differ according to tumour types. This ESMO initiative is a response to the urgent questions raised by the growing success of immunotherapy and provides also important insights on the relationships between MSI, TMB and PD-1/PD-L1.

Luchini C ，Bibeau F ，Ligtenberg MJL ，Singh N ，Nottegar A ，Bosse T ，Miller R ，Riaz N ，Douillard JY ，Andre F ，Scarpa A ... -  《-》

Performance of Next-Generation Sequencing for the Detection of Microsatellite Instability in Colorectal Cancer With Deficient DNA Mismatch Repair.

Next-generation sequencing (NGS) was recently approved by the United States Food and Drug Administration to detect microsatellite instability (MSI) arising from defective mismatch repair (dMMR) in patients with metastatic colorectal cancer (mCRC) before treatment with immune checkpoint inhibitors (ICI). In this study, we aimed to evaluate and improve the performance of NGS to identify MSI in CRC, especially dMMR mCRC treated with ICI. CRC samples used in this post hoc study were reassessed centrally for MSI and dMMR status using the reference methods of pentaplex polymerase chain reaction and immunohistochemistry. Whole-exome sequencing (WES) was used to evaluate MSISensor, the Food and Drug Administration-approved and NGS-based method for assessment of MSI. This was performed in (1) a prospective, multicenter cohort of 102 patients with mCRC (C1; 25 dMMR/MSI, 24 treated with ICI) from clinical trials NCT02840604 and NCT033501260, (2) an independent retrospective, multicenter cohort of 113 patients (C2; 25 mCRC, 88 non-mCRC, all dMMR/MSI untreated with ICI), and (3) a publicly available series of 118 patients with CRC from The Cancer Genome Atlas (C3; 51 dMMR/MSI). A new NGS-based algorithm, namely MSICare, was developed. Its performance for assessment of MSI was compared with MSISensor in C1, C2, and C3 at the exome level or after downsampling sequencing data to the MSK-IMPACT gene panel. MSICare was validated in an additional retrospective, multicenter cohort (C4) of 152 patients with new CRC (137 dMMR/MSI) enriched in tumors deficient in MSH6 (n = 35) and PMS2 (n = 9) after targeted sequencing of samples with an optimized set of microsatellite markers (MSIDIAG). At the exome level, MSISensor was highly specific but failed to diagnose MSI in 16% of MSI/dMMR mCRC from C1 (4 of 25; sensitivity, 84%; 95% confidence interval [CI], 63.9%-95.5%), 32% of mCRC (8 of 25; sensitivity, 68%; 95% CI, 46.5%-85.1%), and 9.1% of non-mCRC from C2 (8 of 88; sensitivity, 90.9%; 95% CI, 82.9%-96%), and 9.8% of CRC from C3 (5 of 51; sensitivity, 90.2%; 95% CI, 78.6%-96.7%). Misdiagnosis included 4 mCRCs treated with ICI, of which 3 showed an overall response rate without progression at this date. At the exome level, reevaluation of the MSI genomic signal using MSICare detected 100% of cases with true MSI status among C1 and C2. Further validation of MSICare was obtained in CRC tumors from C3, with 96.1% concordance for MSI status. Whereas misdiagnosis with MSISensor even increased when analyzing downsampled WES data from C1 and C2 with microsatellite markers restricted to the MSK-IMPACT gene panel (sensitivity, 72.5%; 95% CI, 64.2%-79.7%), particularly in the MSH6-deficient setting, MSICare sensitivity and specificity remained optimal (100%). Similar results were obtained with MSICare after targeted NGS of tumors from C4 with the optimized microsatellite panel MSIDIAG (sensitivity, 99.3%; 95% CI, 96%-100%; specificity, 100%). In contrast to MSISensor, the new MSICare test we propose performs at least as efficiently as the reference method, MSI polymerase chain reaction, to detect MSI in CRC regardless of the defective MMR protein under both WES and targeted NGS conditions. We suggest MSICare may rapidly become a reference method for NGS-based testing of MSI in CRC, especially in mCRC, where accurate MSI status is required before the prescription of ICI.

Ratovomanana T ，Cohen R ，Svrcek M ，Renaud F ，Cervera P ，Siret A ，Letourneur Q ，Buhard O ，Bourgoin P ，Guillerm E ，Dorard C ，Nicolle R ，Ayadi M ，Touat M ，Bielle F ，Sanson M ，Le Rouzic P ，Buisine MP ，Piessen G ，Collura A ，Fléjou JF ，de Reyniès A ，Coulet F ，Ghiringhelli F ，André T ，Jonchère V ，Duval A ... -  《-》

[Comprehensive assessment of mismatch repair and microsatellite instability status in molecular classification of endometrial carcinoma].

Liu Y ，Wang YX ，Sun XJ ，Ting X ，Wu R ，Liu XD ，Liu CR ... -  《-》