Maartje Nielsen

Prevalence and Prognosis of Lynch Syndrome and Sporadic Mismatch Repair Deficiency in Endometrial Cancer

Abstract Background Standard screening of endometrial cancer (EC) for Lynch syndrome (LS) is gaining traction; however, the prognostic impact of an underlying hereditary etiology is unknown. We established the prevalence, prognosis, and subsequent primary cancer incidence of patients with LS-associated EC in relation to sporadic mismatch repair deficient (MMRd)-EC in the large combined Post Operative Radiation Therapy in Endometrial Carcinoma-1, -2, and -3 trial cohort. Methods After MMR-immunohistochemistry, MLH1-promoter methylation testing, and next-generation sequencing, tumors were classified into 3 groups according to the molecular cause of their MMRd-EC. Kaplan-Meier method, log-rank test, and Cox model were used for survival analysis. Competing risk analysis was used to estimate the subsequent cancer probability. All statistical tests were 2-sided. Results Among the 1336 ECs, 410 (30.7%) were MMRd. A total of 380 (92.7%) were fully triaged: 275 (72.4%) were MLH1-hypermethylated MMRd-ECs; 36 (9.5%) LS MMRd-ECs, and 69 (18.2%) MMRd-ECs due to other causes. Limiting screening of EC patients to 60 years or younger or to 70 years or younger would have resulted in missing 18 (50.0%) and 6 (16.7%) LS diagnoses, respectively. Five-year recurrence-free survival was 91.7% (95% confidence interval [CI] = 83.1% to 100%; hazard ratio = 0.45, 95% CI = 0.16 to 1.24, P = .12) for LS, 95.5% (95% CI = 90.7% to 100%; hazard ratio = 0.17, 95% CI = 0.05 to 0.55, P = .003) for “other” vs 78.6% (95% CI = 73.8% to 83.7%) for MLH1-hypermethylated MMRd-EC. The probability of subsequent LS-associated cancer at 10 years was 11.6% (95% CI = 0.0% to 24.7%), 1.5% (95% CI = 0.0% to 4.3%), and 7.0% (95% CI = 3.0% to 10.9%) within the LS, “other,” and MLH1-hypermethylated MMRd-EC groups, respectively. Conclusions The LS prevalence in the Post Operative Radiation Therapy in Endometrial Carcinoma trial population was 2.8% and among MMRd-ECs was 9.5%. Patients with LS-associated ECs showed a trend towards better recurrence-free survival and higher risk for second cancers compared with patients with MLH1-hypermethylated MMRd-EC.

Discordant Staining Patterns and Microsatellite Results in Tumors of MSH6 Pathogenic Variant Carriers

Diagnosis of Lynch syndrome (LS) caused by a pathogenic germline MSH6 variant may be complicated by discordant immunohistochemistry (IHC) and/or by a microsatellite stable (MSS) phenotype. This study aimed to identify the various causes of the discordant phenotypes of colorectal cancer (CRC) and endometrial cancer (EC) in MSH6-associated LS. Data were collected from Dutch family cancer clinics. Carriers of a (likely) pathogenic MSH6 variant diagnosed with CRC or EC were categorized based on an microsatellite instability (MSI)/IHC test outcome that might fail to result in a diagnosis of LS (eg, retained staining of all 4 mismatch repair proteins, with or without an MSS phenotype, and other staining patterns). When tumor tissue was available, MSI and/or IHC were repeated. Next-generation sequencing (NGS) was performed in cases with discordant staining patterns. Data were obtained from 360 families with 1763 (obligate) carriers. MSH6 variant carriers with CRC or EC (n = 590) were included, consisting of 418 CRCs and 232 ECs. Discordant staining was reported in 77 cases (36% of MSI/IHC results). Twelve patients gave informed consent for further analysis of tumor material. Upon revision, 2 out of 3 MSI/IHC cases were found to be concordant with the MSH6 variant, and NGS showed that 4 discordant IHC results were sporadic rather than LS-associated tumors. In 1 case, somatic events explained the discordant phenotype. The use of reflex IHC mismatch repair testing, the current standard in most Western countries, may lead to the misdiagnosis of germline MSH6 variant carriers. The pathologist should point out that further diagnostics for inheritable colon cancer, including LS, should be considered in case of a strong positive family history. Germline DNA analysis of the mismatch repair genes, preferably as part of a larger gene panel, should therefore be considered in potential LS patients.

Delineating genotype and parent‐of‐origin effect on the phenotype in MSH6‐associated Lynch syndrome

AbstractBackgroundThis study investigates the potential influence of genotype and parent‐of‐origin effects (POE) on the clinical manifestations of Lynch syndrome (LS) within families carrying (likely) disease‐causing MSH6 germline variants.Patients and MethodsA cohort of 1615 MSH6 variant carriers (310 LS families) was analyzed. Participants were categorized based on RNA expression and parental inheritance of the variant. Hazard ratios (HRs) were calculated using weighted Cox regression, considering external information to address ascertainment bias. The findings were cross‐validated using the Prospective Lynch Syndrome Database (PLSD) for endometrial cancer (EC).ResultsNo significant association was observed between genotype and colorectal cancer (CRC) risk (HR = 1.06, 95% confidence interval [CI]: 0.77–1.46). Patients lacking expected RNA expression exhibited a reduced risk of EC (Reference Cohort 1: HR = 0.68, 95% CI: 0.43–1.03; Reference Cohort 2: HR = 0.63, 95% CI: 0.46–0.87). However, these results could not be confirmed in the PLSD. Moreover, no association was found between POE and CRC risk (HR = 0.78, 95% CI: 0.52–1.17) or EC risk (Reference Cohort 1: HR = 0.93, 95% CI: 0.65–1.33; Reference Cohort 2: HR = 0.8, 95% CI: 0.64–1.19).Discussion and ConclusionNo evidence of POE was detected in MSH6 families. While RNA expression may be linked to varying risks of EC, further investigation is required to explore this observation.

Randomized Trial of Radiation Therapy With or Without Chemotherapy for Endometrial Cancer

RATIONALE: Drugs used in chemotherapy, such as cisplatin, paclitaxel, and carboplatin, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Radiation therapy uses high-energy x-rays to kill tumor cells. Giving chemotherapy and radiation therapy after surgery may kill any tumor cells that remain after surgery. It is not yet known whether giving chemotherapy together with radiation therapy is more effective than giving radiation therapy alone in treating endometrial cancer. PURPOSE: This randomized phase III trial is studying chemotherapy and radiation therapy to see how well they work compared with radiation therapy alone in treating patients with high-risk, stage I, stage II, or stage III endometrial cancer.