Extended panel testing in ovarian cancer reveals BRIP1 as the third most important predisposition gene.

PURPOSE: The prevalence of germline pathogenic variants (PVs) in homologous recombination repair (HRR) and Lynch syndrome (LS) genes in ovarian cancer (OC) is uncertain. METHODS: An observational study reporting the detection rate of germline PVs in HRR and LS genes in all OC cases tested in the North West Genomic Laboratory Hub between September 1996 and May 2024. Effect sizes are reported using odds ratios (ORs) and 95% confidence intervals (95% CI) for unselected cases tested between April 2021 and May 2024 versus 50703 controls from the Breast Cancer Risk after Diagnostic Gene Sequencing study. RESULTS: 2934 women were tested for BRCA1/2 and 433 (14.8%) had a PV. In up to 1572 women tested for PVs in non-BRCA1/2 HRR genes, detection rates were PALB2=0.8%, BRIP1=1.1%, RAD51C=0.4% and RAD51D=0.4%. In 940 unselected cases, BRIP1 (OR=8.7, 95% CI 4.6-15.8) was the third commonest OC predisposition gene followed by RAD51C (OR=8.3, 95% CI 3.1-23.1), RAD51D (OR=6.5, 95% CI 2.1-19.7) and PALB2 (OR=3.9, 95% CI 1.5-10.3). No PVs in LS genes were detected in unselected cases. CONCLUSIONS: Panel testing in OC resulted in a detection rate of 2-3% for germline PVs in non-BRCA1/2 HRR genes, with the largest contributor being BRIP1. Screening for LS in unselected cases of OC is unnecessary.

Approaches for Lynch syndrome screening and characteristics of subtypes with mismatch repair deficiency in patients with colorectal carcinoma.

To evaluate different Lynch syndrome (LS) screening approaches and establish an efficient and sensitive strategy are critical for clinical practice. In total, 583 patients with colorectal carcinoma (CRC) at Fudan University Shanghai Cancer Center were enrolled. Patient samples were examined by immunohistochemistry (IHC) and next-generation sequencing (NGS), and MLH1 promoter hypermethylation (MPH) was detected in MLH1-deficient cases. Germline genetic testing was performed in cases with deleterious variants and large genomic rearrangements (LGRs) of tumor MMR genes were detected in cases with dMMR or MSI-H cases with no MMR germline variants. Our results showed that triage with IHC and followed by BRAF/MLH1 methylation testing (Strategy 1) identified 93.3% (70/75) of LS cases. IHC followed by germline NGS (Strategy 2) or direct tumor NGS (Strategy 3) both identified 98.7% (74/75) of LS cases. The proportion of LGRs in LS cases was 16.0% (12/75), while 84.0% (63/75) showed SNV/Indel. The average cost per patient was ¥6010.81, ¥6058.48, and ¥8029.98 for Strategy 1, Strategy 2 and Strategy 3, respectively. The average time spent on different strategies was 4.74 days (Strategy 1), 4.89 days (Strategy 2), and 14.50 days (Strategy 3) per patient, respectively. LS and Lynch-like syndrome (LLS) were associated with an earlier onset age than MPH. In conclusion, we compared different workflows for LS screening and IHC plus germline NGS is recommended for LS screening when taking sensitivity, time, and cost into account. Moreover, multiplex ligation-dependent probe amplification made up for the shortcoming of NGS and should be incorporated into routine screening.

Constitutional mismatch repair deficiency: a case on a commonly misinterpreted mutation in colon cancer.

It is estimated that 153,020 cases of CRC per year, with an increase in diagnoses in younger patients. We present a case of a female with an early presentation of Lynch Syndrome and CRC, who, on her third malignant presentation, was re-diagnosed as a constitutional mismatch repair deficiency.

Lynch syndrome screening in patients with young-onset extra-colorectal Lynch syndrome-associated cancers.

BACKGROUND: Lynch syndrome (LS) is a hereditary cancer syndrome caused by pathogenic germline variants in mismatch repair (MMR) genes, which predisposes to various types of cancers showing deficient MMR (dMMR). Identification of LS probands is crucial to reduce cancer-related deaths in affected families. Although universal screening is recommended for colorectal and endometrial cancers, and age-restricted screening is proposed as an alternative, LS screening covering a broader spectrum of cancer types is needed. In the current study, we elucidated the rate of dMMR tumors and evaluated the outcome of LS screening in young-onset extra-colorectal LS-associated cancers. METHODS: Immunohistochemistry for MMR proteins were retrospectively performed in a total of 309 tissue samples of endometrial, non-mucinous ovarian, gastric, urothelial, pancreatic, biliary tract, and adrenal cancers in patients < 50 years of age. Clinicopathological information and the results of genetic testing were obtained from medical charts. RESULTS: There were 24 dMMR tumors (7.8%) including 18 endometrial, three ovarian, two urothelial, and one gastric cancer. Co-occurrence of colorectal cancer and family history of LS-associated cancers was significantly enriched in patients with dMMR tumors. Among the 16 patients with dMMR tumors who were informed of the immunohistochemistry results, five with endometrial and one with urothelial cancer were diagnosed as LS with positive pathogenic variants in MMR genes. CONCLUSIONS: We report the outcome of immunohistochemistry for MMR proteins performed in multiple types of young-onset extra-colorectal LS-associated cancers. Our study demonstrates the feasibility of a comprehensive LS screening program incorporating young-onset patients with various types of extra-colorectal LS-associated cancers.

Progression of fertility-sparing treatment for atypical endometrial hyperplasia in a woman with lynch syndrome: a case report and review of the literature.

Endometrial cancer in Lynch syndrome is characterized by a higher incidence, younger age at onset, and increased recurrence rates compared to sporadic cases, while the safety and efficacy of fertility-sparing treatments remain uncertain. This case report presents the oncology outcome of fertility-preserving treatment in a 39-year-old woman diagnosed with Lynch syndrome and atypical endometrial hyperplasia. Initially, she responded favorably to fertility-preserving treatment but subsequently experienced disease relapse and rapid progression during retreatment. Final pathology revealed endometrial cancer with metastasis to the right ovary, categorized as FIGO 2023 stage IIIA1. This population's unique molecular mechanisms and genetic mutations warrant special consideration when opting for fertility-sparing treatment. We have reviewed and summarized the oncology and pregnancy outcomes among Lynch syndrome and MMR-deficient patients through previous literature. However, no studies have investigated retreatment after recurrence in Lynch syndrome. Our case highlights the potential risks associated with retreatment following relapse. Vigilant monitoring and prompt consideration of surgical intervention are recommended upon disease relapse.

Oncological characteristics, treatments and prognostic outcomes in MMR-deficient colorectal cancer.

Colorectal cancer (CRC) ranks as the third most prevalent cancer globally. It's recognized that the molecular subtype of CRC, characterized by mismatch repair deficiency (dMMR) or microsatellite instability-high (MSI-H), plays a critical role in determining appropriate treatment strategies. This review examines the current molecular classifications, focusing on dMMR/MSI-H CRC and its subtypes: Lynch syndrome (LS), Lynch-like syndrome (LLS), and sporadic cases. Despite advances in understanding of these genetic backgrounds, clinical trials have not conclusively differentiated the efficacy of immune checkpoint inhibitors among these subgroups. Therefore, while this review details the molecular characteristics and their general implications for treatment and prognosis, it also highlights the limitations and the need for more refined clinical studies to ascertain tailored therapeutic strategies for each subtype. Furthermore, this review summarizes completed and ongoing clinical studies, emphasizing the importance of developing treatments aligned more closely with molecular profiles. By discussing these aspects, the review seeks to provide a comprehensive analysis of oncological characteristics, presenting a detailed understanding of their implications for treatment and prognosis in dMMR/MSI-H CRC.

An Unusual Tumor: Squamous Cell Carcinoma of the Colon in Lynch Syndrome.

Primary squamous cell carcinoma of the colon and rectum is a rare malignancy. Most of the anatomical sites that are reported to be affected include the esophagus and anal canal. This report highlights the case of a 54-year-old male with a known history of Lynch syndrome and a previous diagnosis of colon cancer who was found to have a recurrence of malignancy affecting this unlikely area. The treatment strategies for this colorectal squamous cell carcinoma have not been thoroughly explored, so this report aims to highlight effective interventions, including surgical resection and neoadjuvant chemotherapy and radiation. There is a poor prognosis associated with this condition, as it does not typically present until the late stages; however, in this particular instance, early detection leads to improved outcomes.

MSH6 germline mutations leading to Lynch syndrome-associated cholangiocarcinoma: a case report.

Lynch syndrome, a hereditary cancer susceptibility syndrome, arises from pathogenic mutations in mismatch repair genes. This syndrome is strongly linked to colorectal and endometrial cancers, as well as an elevated risk for other cancers such as gastric, ovarian, renal pelvis/ureter, and prostate. Notably, Lynch syndrome is rarely associated with cholangiocarcinoma (CCA). In this case study, we present a unique instance of Lynch syndrome-related CCA resulting from a singular MSH6 mutation. Notably, our findings reveal discrepancies between immunohistochemistry (IHC) and microsatellite stability results compared to genetic testing outcomes. This discrepancy underscores the limitations of solely relying on IHC analysis and microsatellite stability testing for the detection of hereditary tumors, emphasizing the crucial role of genetic testing in such cases. This insight enhances our comprehension of the mechanisms involved in cancer development and underscores the significance of thorough analysis integrating immunohistochemistry and genetic testing for diagnosing Lynch syndrome-related cancers.

Universal testing in endometrial cancer in Sweden.

BACKGROUND: The aim of the study was to test a universal screening strategy on endometrial cancer to evaluate its effectiveness to find Lynch Syndrome (LS) cases to two established clinical criteria: Amsterdam II criteria, and the revised Bethesda criteria to select cases for prescreening with immunohistochemistry (IHC). Cases were subsequently screened for germline disease causing variants regarding the DNA mismatch repair (MMR) genes. METHODS: IHC was performed on 221 endometrial cancer (EC) cases, using antibodies against the DNA mismatch repair proteins MLH1, PMS2, MSH2, and MSH6. MMR loss was found in 54 cases, and gene mutation screening was undertaken in 52 of those. RESULTS: In this set of patients, the use of Amsterdam II criteria detected two (0.9%), the Bethesda criteria two (0.9%), and universal testing five (2.3%) cases of LS. The combination of universal testing and family history criteria resulted in detection of five patients (2.3%) with LS. CONCLUSIONS: Based on our results and other similar studies to date we propose a screening protocol for LS on EC tumors with prescreening using IHC for the four MMR proteins on all new EC cases diagnosed before 70 years of age, followed by mutation screening of all tumors with loss of MSH2 and/or MSH6 or only PMS2, plus consideration for mutation screening of all LS genes in cases fulfilling the clinical Amsterdam II criteria regardless of MMR status on IHC.

Lynch syndrome-associated and sporadic microsatellite unstable colorectal cancers: different patterns of clonal evolution yield highly similar tumours.

Microsatellite unstable colorectal cancer (MSI-CRC) can arise through germline mutations in mismatch repair (MMR) genes in individuals with Lynch syndrome (LS), or sporadically through promoter methylation of the MMR gene MLH1. Despite the different origins of hereditary and sporadic MSI tumours, their genomic features have not been extensively compared. A prominent feature of MMR-deficient genomes is the occurrence of many indels in short repeat sequences, an understudied mutation type due to the technical challenges of variant calling in these regions. In this study, we performed whole genome sequencing and RNA-sequencing on 29 sporadic and 14 hereditary MSI-CRCs. We compared the tumour groups by analysing genome-wide mutation densities, microsatellite repeat indels, recurrent protein-coding variants, signatures of single base, doublet base, and indel mutations, and changes in gene expression. We show that the mutational landscapes of hereditary and sporadic MSI-CRCs, including mutational signatures and mutation densities genome-wide and in microsatellites, are highly similar. Only a low number of differentially expressed genes were found, enriched to interferon-γ regulated immune response pathways. Analysis of the variance in allelic fractions of somatic variants in each tumour group revealed higher clonal heterogeneity in sporadic MSI-CRCs. Our results suggest that the differing molecular origins of MMR deficiency in hereditary and sporadic MSI-CRCs do not result in substantial differences in the mutational landscapes of these tumours. The divergent patterns of clonal evolution between the tumour groups may have clinical implications, as high clonal heterogeneity has been associated with decreased tumour immunosurveillance and reduced responsiveness to immunotherapy.

Complications of colonoscopy surveillance of patients with Lynch syndrome - 33 years of follow up.

BACKGROUND AND STUDY AIMS: Lynch syndrome (LS) is a hereditary autosomal dominant condition, with an increased lifetime risk of developing malignancies including colorectal cancer (CRC). Current guidelines differ in recommended colonoscopy-surveillance intervals from 1 to 2 years. Although colonoscopy is considered a safe procedure, there are risks of severe adverse events (SAEs), such as perforation and bleeding, as well as adverse events (AEs), such as abdominal discomfort and post-colonoscopy gastrointestinal infections. Colonoscopy-related bleeding and perforation rates have been reported 0.17% and 0.11%, respectively. However, there are insufficient data regarding complications of colonoscopy-surveillance for LS patients. This study aims to investigate the risk of AEs among LS patients during colonoscopy in the Stockholm region. PATIENTS AND METHODS: This retrospective cohort study includes 351 LS patients undergoing endoscopic surveillance at the Karolinska University Hospital, August 1989 - April 2021. Data from endoscopic surveillance colonoscopies were extracted from patients' medical records. RESULTS: Of 1873 endoscopies in 351 LS patients, 12 complications (AEs) were documented within 30 days (0.64%) and with a total of 3 bleedings (SAEs, 0.16%). No perforations were identified. CONCLUSION: Colonoscopy surveillance for LS patients shows a comparatively low risk of AEs per-examination. Colonoscopy complications per-patient, including both SAEs and AEs, show a significantly higher risk. Colonoscopy complications only including SAEs, show a comparatively low risk. Understanding the lifetime risk of surveillance-related colonoscopy complications is important when designing targeted surveillance programmes.

Effect of genetic profiling on surgical decisions at hereditary colorectal cancer syndromes.

Hereditary colorectal cancer syndromes, such as Lynch syndrome and familial adenomatous polyposis (FAP), present significant clinical challenges due to the heightened cancer risks associated with these genetic conditions. This review explores genetic profiling impact on surgical decisions for hereditary colorectal cancer (HCRC), assessing options, timing, and outcomes. Genotypes of different HCRCs are discussed, revealing a connection between genetic profiles, disease severity, and outcomes. For Lynch syndrome, mutations in the MLH1, MSH2, MSH6, and PMS2 genes guide the choice of surgery. Subtotal colectomy is recommended for patients with mutations in MLH1 and MSH2, while segmental colectomy is preferred for those with MSH6 and PMS2 mutations. In cases of metachronous colon cancer after segmental colectomy, subtotal colectomy with ileorectal anastomosis is advised for all mutations. Surgical strategies for primary rectal cancer include anterior resection or abdominoperineal resection (APR), irrespective of the specific mutation. For rectal cancer occurring after a previous segmental colectomy, proctocolectomy with ileal pouch-anal anastomosis (IPAA) or APR with a permanent ileostomy is recommended. In FAP, surgical decisions are based on genotype-phenotype correlations. The risk of desmoid tumors post-surgery supports a single-stage approach, particularly for certain APC gene variants. Juvenile Polyposis Syndrome (JPS) surgical decisions involve genetic testing, polyp characteristics with attention to vascular lesions in SMAD4 mutation carriers. However, genetic profiling does not directly dictate the specific surgical approach for JPS. In conclusion this review highlights the critical role of personalized surgical plans based on genetic profiles to optimize patient outcomes and reduce cancer risk. Further research is needed to refine these strategies and enhance clinical guidelines.

Minimal residual disease monitoring via ctDNA: a case report of Lynch syndrome with synchronous colorectal cancer and review of literature.

Background: The investigation of circulating tumor DNA (ctDNA) as a substitute for minimal residual disease (MRD) has been a central focus in various clinical trials, with findings highlighting its effectiveness as a sensitive marker for detecting recurrence. In 2018, a joint review by the American Society of Clinical Oncology and the College of American Pathologists acknowledged a lack of current evidence guiding clinical decisions regarding ctDNA. Nevertheless, there are a multitude of ongoing studies exploring the future applications of ctDNA and its role in clinical decision making for select patient populations. Case Description: The case presented involves a patient with Lynch syndrome who developed synchronous left-sided colorectal cancers (CRC). Each primary malignancy exhibited a distinct mutational profile, introducing complexity to the personalized tumor-informed assays used for quantifying ctDNA levels. Initial ctDNA levels were negative until the assay was calibrated to the transverse colon primary tumor. Unfortunately, surveillance imaging showed radiographic recurrence coinciding with positive ctDNA findings. Treatment with the anti-PD-1 inhibitor pembrolizumab was initiated, resulting in the clearance of ctDNA after just four cycles. As of now, there is no radiographic or biologic evidence indicating disease recurrence. Conclusions: This case study sheds light on the evolving landscape and current limitations of ctDNA as a surrogate for MRD. We describe a patient with synchronous CRC who had radiographic recurrence and a negative MRD assay. Current tumor-informed assays are limited in their capacity to detect a single tumor, and by nature can miss both synchronous and metachronous malignancies. Assays tailored to multiple tumors or utilizing tumor agnostic methods should be a part of clinical decision making in this patient population.

Mismatch Repair (MMR) Gene Mutation Carriers Have Favorable Outcome in Colorectal and Endometrial Cancer: A Prospective Cohort Study.

Germline (Lynch syndrome, LS) and somatic deficiencies of mismatch repair proteins (MMRd) are linked to colorectal and endometrial cancer; however, their prognostic impact in Asian populations remains unclear. This prospective cohort study aimed to determine the prevalence and outcome of germline and somatic MMRd in cancer patients suspected of LS. Patients with colorectal or endometrial cancer suspected of LS were enrolled and underwent gene sequencing for germline MMRd (gMMRd) and immunohistochemistry staining of MMR proteins in a subset of the pathological samples (pMMRd). Among the 451 enrolled patients, 36 patients were gMMRd (+). Compared with gMMRd (-) patients, the 10-year relapse-free survival in gMMRd (+) patients was significantly higher (100% vs. 77.9%; p = 0.006), whereas the 10-year overall survival was similar (100% vs. 90.9%; p = 0.12). Among the 102 gMMRd (-) patients with available pMMR status, 13.7% were pMMRd (+). The 5-year relapse-free survival was 62.9% in gMMRd (-) pMMRd (+) patients and 35.0% in gMMRd (-) pMMRd (-) patients, both lower than gMMRd (+) patients (100%; p < 0.001). This study showed that having LS confers a favorable outcome in colorectal and endometrial cancer patients and highlights the importance of germline genetic testing following the detection of somatic MMRd.

Dual primary gastric and colorectal cancer: The known hereditary causes and underlying mechanisms.

In this editorial, I commented on the paper by Lin et al, published in this issue of the World Journal of Gastrointestinal Oncology. The work aimed at analysing the clinicopathologic characteristics and prognosis of synchronous and metachronous cancers in patients with dual primary gastric and colorectal cancer (CRC). The authors concluded the necessity for regular surveillance for metachronous cancer during postoperative follow-up and reported the prognosis is influenced by the gastric cancer (GC) stage rather than the CRC stage. Although surveillance was recommended in the conclusion, the authors did not explore this area in their study and did not include tests used for such surveillance. This editorial focuses on the most characterized gastrointestinal cancer susceptibility syndromes concerning dual gastric and CRCs. These include hereditary diffuse GC, familial adenomatous polyposis, hereditary nonpolyposis colon cancer, Lynch syndrome, and three major hamartomatous polyposis syndromes associated with CRC and GC, namely Peutz-Jeghers syndrome, juvenile polyposis syndrome, and PTEN hamartoma syndrome. Careful assessment of these syndromes/conditions, including inheritance, risk of gastric and colorectal or other cancer development, genetic mutations and recommended genetic investigations, is crucial for optimum management of these patients.

Universal screening for Lynch syndrome in endometrial cancer diagnoses in Auckland, New Zealand: The initial experience.

BACKGROUND: Universal mismatch repair immunohistochemistry (MMR IHC) tumour testing in endometrial cancer (EC) for Lynch syndrome (LS) was introduced in Auckland, New Zealand, in January 2017. Identifying patients with LS allows them and their families to access risk reduction strategies. Universal MMR IHC testing aids in the molecular classification of EC and has prognostic and therapeutic implications. AIM: We aimed to determine the incidence of LS in women with EC in Auckland, New Zealand, following the introduction of MMR testing and the impact of universal screening on local genetic services. MATERIALS AND METHODS: This is a retrospective clinicopathological evaluation of women with a new EC diagnosis referred to the Auckland Gynaecological Oncology Unit from 1/1/17 to 31/12/18. Patient data were extracted from the Gynaecological Oncology Unit database and electronic records, and analysed using descriptive statistics. RESULTS: During the study period, 409 patients were diagnosed with EC, with an over-representation of Pacific Islanders (32.5%). Of these, 82.6% underwent MMR IHC testing, 20% were MMR-deficient (MMRd), and 71% had somatic hypermethylation. The Pacific Islander population had a 64% (odds ratio 0.36, P = 0.005) reduction in the odds of having MMRd tumours compared with Europeans. Of the patients who underwent MMR IHC testing, 5.5% were referred to a genetic clinic for germline testing. LS was confirmed in eight patients (2.3%). CONCLUSION: LS was diagnosed in 2.3% of patients. There was an over-representation of Pacific Islanders in the EC group but not among those diagnosed with LS.

Real-world genetic testing outcomes of pan-cancer testing for mismatch repair deficiency.

BACKGROUND: In 2017, the Food and Drug Administration approved pembrolizumab for treatment of any mismatch repair-deficient (dMMR) tumor making MMR immunohistochemistry (IHC) testing beneficial for all tumor types. For the first time, MMR IHC was not performed exclusively to screen for Lynch syndrome (LS). METHODS: In this study, all MMR IHC reports issued between 2017 and 2021 at an academic hospital were reviewed and completion of genetic testing was determined through chart review. Colorectal cancers (CRCs), endometrial cancers (ECs), and noncancerous lesions were excluded. RESULTS: Between 2017 and 2021, MMR IHC was completed in 1939 patients with a malignancy other than CRC or EC. Absent or weak staining for at least one MMR protein was detected in 115 (5.9%) patients and 59 (51%) of those completed germline genetic testing. Overall, the identification rate of LS in this cohort was 0.72%, which is similar to the rate in our previously reported CRC and EC universal screening cohort. A diagnosis of LS was most commonly made in patients with dMMR brain (18.75%) and small intestinal cancers (10.20%). Five additional patients were found to carry a pathogenic variant in a non-LS gene. CONCLUSIONS: Pan-cancer MMR testing for pembrolizumab consideration can identify LS cases at a rate similar to universal CRC and EC screening programs. A persistent challenge is subsequent uptake of genetic testing. MMR testing should be prioritized in brain and small intestinal tumors, and multigene panel testing is recommended in patients with dMMR, as unexpected pathogenic variants in non-LS genes were found as frequently as LS gene variants.

Lynch Syndrome and Thyroid Nodules: A Single Center Experience.

BACKGROUND: Lynch syndrome (LS) is a genetic disease with increased risk of colorectal cancer and other malignancies. There are few reported cases of thyroid cancer in LS patients. The aim of this study is to investigate the presence of thyroid nodules in LS patients and to explore their association with the genetic features of the disease. METHODS: A retrospective and descriptive analysis was conducted to include all LS patients followed at the CEMAD (Centro Malattie Apparato Digerente) of Fondazione Policlinico Universitario A. Gemelli IRCCS. The characteristics of LS disease, gene mutations, and previous history of thyroid disease were evaluated. Majority of patients underwent thyroid ultrasound (US), and nodule cytology was performed when needed. RESULTS: Of a total of 139 patients with LS, 110 patients were included in the study. A total of 103 patients (74%) underwent thyroid ultrasound examinations, and 7 patients (5%) had a previous history of thyroid disease (cancer or multinodular goiter). The mean age was 51.9 years. Thyroid nodules were found in 62 patients (60%) who underwent US, and 9 of them (14%) had suspicious features of malignancy, inducing a fine-needle aspiration biopsy. A cytologic analysis classified 7 of 9 cases (78%) as TIR2 and 2 (22%) as TIR3a. Between patients with nodular thyroid disease (single nodule, multinodular goiter, and cancer), most of them (25 patients, 36% of total) were carriers of the MSH6 mutation, while 22 (32%), 17 (24%), and 5 (7%) had MSH2, MLH1, and PMS2 mutations, respectively. CONCLUSIONS: A high prevalence of thyroid nodules was found in patients with LS, especially in MSH6-carrying patients. Performing at least one thyroid ultrasound examination is suggested for the detection of nodular thyroid disease in LS patients. Systematic investigations are needed to estimate their prevalence, features, and risk of malignant transformation.

Performance evaluation of predictive models for detecting MMR gene mutations associated with Lynch syndrome in cancer patients in a Chinese cohort in Taiwan.

Identifying Lynch syndrome significantly impacts cancer risk management, treatment, and prognosis. Validation of mutation risk predictive models for mismatch repair (MMR) genes is crucial for guiding genetic counseling and testing, particularly in the understudied Asian population. We evaluated the performance of four MMR mutation risk predictive models in a Chinese cohort of 604 patients with colorectal cancer (CRC), endometrial cancer (EC), or ovarian cancer (OC) in Taiwan. All patients underwent germline genetic testing and 36 (6.0%) carried a mutation in the MMR genes (MLH1, MSH2, MSH6, and PMS2). All models demonstrated good performance, with area under the receiver operating characteristic curves comparable to Western cohorts: PREMM5 0.80 (95% confidence interval [CI], 0.73-0.88), MMRPro 0.88 (95% CI, 0.82-0.94), MMRPredict 0.82 (95% CI, 0.74-0.90), and Myriad 0.76 (95% CI, 0.67-0.84). Notably, MMRPro exhibited exceptional performance across all subgroups regardless of family history (FH+ 0.88, FH- 0.83), cancer type (CRC 0.84, EC 0.85, OC 1.00), or sex (male 0.83, female 0.90). PREMM5 and MMRPredict had good accuracy in the FH+ subgroup (0.85 and 0.82, respectively) and in CRC patients (0.76 and 0.82, respectively). Using the ratio of observed and predicted mutation rates, MMRPro and PREMM5 had good overall fit, while MMRPredict and Myriad overestimated mutation rates. Risk threshold settings in different models led to different positive predictive values. We suggest a lower threshold (5%) for recommending genetic testing when using MMRPro, and a higher threshold (20%) when using PREMM5 and MMRPredict. Our findings have important implications for personalized mutation risk assessment and counseling on genetic testing.