In vitro study of radiosensitivity in colorectal cancer cell lines associated with Lynch syndrome.

Introduction: Lynch syndrome patients have an inherited predisposition to cancer due to a deficiency in DNA mismatch repair (MMR) genes which could lead to a higher risk of developing cancer if exposed to ionizing radiation. This pilot study aims to reveal the association between MMR deficiency and radiosensitivity at both a CT relevant low dose (20 mGy) and a therapeutic higher dose (2 Gy). Methods: Human colorectal cancer cell lines with (dMMR) or without MMR deficiency (pMMR) were analyzed before and after exposure to radiation using cellular and cytogenetic analyses i.e., clonogenic assay to determine cell reproductive death; sister chromatid exchange (SCE) assay to detect the exchange of DNA between sister chromatids; γH2AX assay to analyze DNA damage repair; and apoptosis analysis to compare cell death response. The advantages and limitations of these assays were assessed in vitro, and their applicability and feasibility investigated for their potential to be used for further studies using clinical samples. Results: Results from the clonogenic assay indicated that the pMMR cell line (HT29) was significantly more radio-resistant than the dMMR cell lines (HCT116, SW48, and LoVo) after 2 Gy X-irradiation. Both cell type and radiation dose had a significant effect on the yield of SCEs/chromosome. When the yield of SCEs/chromosome for the irradiated samples (2 Gy) was normalized against the controls, no significant difference was observed between the cell lines. For the γH2AX assay, 0, 20 mGy and 2 Gy were examined at post-exposure time points of 30 min (min), 4 and 24 h (h). Statistical analysis revealed that HT29 was only significantly more radio-resistant than the MLH1-deficient cells lines, but not the MSH2-deficient cell line. Apoptosis analysis (4 Gy) revealed that HT29 was significantly more radio-resistant than HCT116 albeit with very few apoptotic cells observed. Discussion: Overall, this study showed radio-resistance of the MMR proficient cell line in some assays, but not in the others. All methods used within this study have been validated; however, due to the limitations associated with cancer cell lines, the next step will be to use these assays in clinical samples in an effort to understand the biological and mechanistic effects of radiation in Lynch patients as well as the health implications.

PIGA mutations and glycosylphosphatidylinositol anchor dysregulation in polyposis-associated duodenal tumorigenesis.

The pathogenesis of duodenal tumours in the inherited tumour syndromes Familial Adenomatous Polyposis (FAP) and MUTYH-associated Polyposis (MAP) is poorly understood. This study aimed to identify genes that are significantly mutated in these tumours and to explore the effects of these mutations. Whole exome and whole transcriptome sequencing identified recurrent somatic coding variants of PIGA in 19/70 (27%) FAP and MAP duodenal adenomas, and further confirmed the established driver roles for APC and KRAS. PIGA catalyses the first step in glycosylphosphatidylinositol (GPI) anchor biosynthesis. Flow cytometry of PIGA-mutant adenoma-derived and CRISPR-edited duodenal organoids confirmed loss of GPI anchors in duodenal epithelial cells and transcriptional profiling of duodenal adenomas revealed transcriptional signatures associated with loss of PIGA. Implications: PIGA somatic mutation in duodenal tumours from patients with FAP and MAP and loss of membrane GPI-anchors may present new opportunities for understanding and intervention in duodenal tumorigenesis.

Treatment of Complex Desmoid Tumors in Familial Adenomatous Polyposis Syndrome by Intestinal Transplantation.

Background: Desmoid tumors are fibroblastic lesions which often have an unpredictable and variable clinical course. In the context of familial adenomatous polyposis (FAP), these frequently occur intra-abdominally, especially in the small-bowel mesentery resulting in sepsis, fistulation, and invasion of the abdominal wall and retroperitoneum. In selected cases where other modalities have failed, the most radical option is to perform a total enterectomy and intestinal transplantation (ITx). In this study, we present our center's experience of ITx for desmoid in patients with FAP. Methods: We performed a retrospective review of our prospectively collected database between 2007 and 2022. All patients undergoing ITx for FAP-related desmoid were included. Results: Between October 2007 and September 2023, 144 ITx were performed on 130 patients at our center. Of these, 15 patients (9%) were for desmoid associated with FAP (7 modified multivisceral transplants, 6 isolated ITx, and 2 liver-containing grafts). The median follow-up was 57 mo (8-119); 5-y patient survival was 82%, all with functioning grafts without local desmoid recurrence. These patients presented us with several complex surgical issues, such as loss of abdominal domain, retroperitoneal/abdominal wall involvement, ileoanal pouch-related issues, and the need for foregut resection because of adenomatous disease. Conclusions: ITx is a viable treatment in selected patients with FAP and extensive desmoid disease. The decision to refer for ITx can be challenging, particularly the timing and sequence of treatment (simultaneous versus sequential exenteration). Delays can result in additional disease burden, such as secondary liver disease or invasion of adjacent structures.

Gene-specific ACMG/AMP classification criteria for germline APC variants: Recommendations from the ClinGen InSiGHT Hereditary Colorectal Cancer/Polyposis Variant Curation Expert Panel.

PURPOSE: The Hereditary Colorectal Cancer/Polyposis Variant Curation Expert Panel (VCEP) was established by the International Society for Gastrointestinal Hereditary Tumours and the Clinical Genome Resource, who set out to develop recommendations for the interpretation of germline APC variants underlying Familial Adenomatous Polyposis, the most frequent hereditary polyposis syndrome. METHODS: Through a rigorous process of database analysis, literature review, and expert elicitation, the APC VCEP derived gene-specific modifications to the ACMG/AMP (American College of Medical Genetics and Genomics and Association for Molecular Pathology) variant classification guidelines and validated such criteria through the pilot classification of 58 variants. RESULTS: The APC-specific criteria represented gene- and disease-informed specifications, including a quantitative approach to allele frequency thresholds, a stepwise decision tool for truncating variants, and semiquantitative evaluations of experimental and clinical data. Using the APC-specific criteria, 47% (27/58) of pilot variants were reclassified including 14 previous variants of uncertain significance (VUS). CONCLUSION: The APC-specific ACMG/AMP criteria preserved the classification of well-characterized variants on ClinVar while substantially reducing the number of VUS by 56% (14/25). Moving forward, the APC VCEP will continue to interpret prioritized lists of VUS, the results of which will represent the most authoritative variant classification for widespread clinical use.

The Diagnostic Yield of Genetic Testing in Patients With Multiple Colorectal Adenomas: A Specialist Center Cohort Study.

INTRODUCTION: Adenoma multiplicity is associated with increased colorectal cancer (CRC) risk. The utility of genetic testing in patients with multiple colorectal adenomas (MCRA) remains uncertain. We evaluated the diagnostic yield of mutations in polyposis- and CRC-associated genes in patients with MCRA. METHODS: We performed a cross-sectional review of adult patients with 10-99 cumulative adenomas from the prospective database at the St Mark's Hospital Polyposis Registry and Family Cancer Clinic between 1999 and 2021. Genetic testing was performed for adenomatous polyposis-associated genes, hamartomatous polyposis-associated genes, and nonpolyposis colorectal cancer-associated genes. Clinicopathological outcomes were extracted for multiple logistic regression analysis. RESULTS: Two hundred fifty-nine patients with MCRA (median age 61 [interquartile range 53-69] years) were identified. Sixty-six patients (25.5%) had a pathogenic variant or likely pathogenic variant, with APC and biallelic MUTYH mutations constituting the majority of identified pathogenic variant/likely pathogenic variants. Diagnostic yields were greater than 10% at any adenoma burden. In univariate analysis, higher adenoma burden and younger age were associated with higher yield (both P < 0.0001). In patients with MCRA with 10-19 adenomas without a relevant personal or family history of CRC, the diagnostic yield was nil. In multiple logistic regression analysis, higher adenoma burden, younger age, personal history of CRC, and first-degree familial history of CRC were associated with higher diagnostic yield. DISCUSSION: Diagnostic yield of >10% at any adenoma burden supports current guidance for constitutional genetic testing in patients with MCRA, although the low yield in people older than 60 years with 10-19 adenomas suggests that a stratified approach might be appropriate.

Cold snare polypectomy for duodenal adenomas in familial adenomatous polyposis: a prospective international cohort study.

Background and study aims In patients with familial adenomatous polyposis (FAP), endoscopic resection of duodenal adenomas is commonly performed to prevent cancer and prevent or defer duodenal surgery. However, based on studies using different resection techniques, adverse events (AEs) of polypectomy in the duodenum can be significant. We hypothesized that cold snare polypectomy (CSP) is a safe technique for duodenal adenomas in FAP and evaluated its outcomes in our centers. Patients and methods We performed a prospective international cohort study including FAP patients who underwent CSP for one or more superficial non-ampullary duodenal adenomas of any size between 2020 and 2022. At that time, this technique was common practice in our centers for superficial duodenal adenomas. The primary outcome was the occurrence of intraprocedural and post-procedural AEs. Results In total, 133 CSPs were performed in 39 patients with FAP (1-18 per session). Median adenoma size was 10 mm (interquartile range 8-15 mm), ranging from 5 to 40 mm; 27 adenomas were ≥20 mm (20%). Of the 133 polypectomies, 109 (82%) were performed after submucosal injection. Sixty-one adenomas (46%) were resected en bloc and 72 (54%) piecemeal. Macroscopic radical resection was achieved for 129 polypectomies (97%). Deep mural injury type II occurred in three polyps (2%) with no delayed perforation after prophylactic clipping. There were no clinically significant bleeds, perforations or other post-procedural AEs. Histopathology showed low-grade dysplasia in all 133 adenomas. Conclusions CSP for (multiple) superficial non-ampullary duodenal adenomas in FAP seems feasible and safe. Long-term prospective research is needed to evaluate whether protocolized duodenal polypectomies prevent cancer and surgery.

Germline de novo mutations in families with Mendelian cancer syndromes caused by defects in DNA repair.

DNA repair defects underlie many cancer syndromes. We tested whether de novo germline mutations (DNMs) are increased in families with germline defects in polymerase proofreading or base excision repair. A parent with a single germline POLE or POLD1 mutation, or biallelic MUTYH mutations, had 3-4 fold increased DNMs over sex-matched controls. POLE had the largest effect. The DNMs carried mutational signatures of the appropriate DNA repair deficiency. No DNM increase occurred in offspring of MUTYH heterozygous parents. Parental DNA repair defects caused about 20-150 DNMs per child, additional to the ~60 found in controls, but almost all extra DNMs occurred in non-coding regions. No increase in post-zygotic mutations was detected, excepting a child with bi-allelic MUTYH mutations who was excluded from the main analysis; she had received chemotherapy and may have undergone oligoclonal haematopoiesis. Inherited DNA repair defects associated with base pair-level mutations increase DNMs, but phenotypic consequences appear unlikely.

Personalized endoscopic surveillance and intervention protocols for patients with familial adenomatous polyposis: the European FAP Consortium strategy.

Background and study aims Patients with familial adenomatous polyposis (FAP) undergo colectomy and lifelong endoscopic surveillance to prevent colorectal, duodenal and gastric cancer. Endoscopy has advanced significantly in recent years, including both detection technology as well as treatment options. For the lower gastrointestinal tract, current guidelines do not provide clear recommendations for surveillance intervals. Furthermore, the Spigelman staging system for duodenal polyposis has its limitations. We present a newly developed personalized endoscopic surveillance strategy for the lower and upper gastrointestinal tract, aiming to improve the care for patients with FAP. We aim to inform centers caring for FAP patients and encourage the discussion on optimizing endoscopic surveillance and treatment in this high-risk population. Methods The European FAP Consortium, consisting of endoscopists with expertise in FAP, collaboratively developed new surveillance protocols. The proposed strategy was consensus-based and a result of several consortium meetings, discussing current evidence and limitations of existing systems. This strategy provides clear indications for endoscopic polypectomy in the rectum, pouch, duodenum and stomach and defines new criteria for surveillance intervals. This strategy will be evaluated in a 5-year prospective study in nine FAP expert centers in Europe. Results We present a newly developed personalized endoscopic surveillance and endoscopic treatment strategy for patients with FAP aiming to prevent cancer, optimize endoscopic resources and limit the number of surgical interventions. Following this new strategy, prospectively collected data in a large cohort of patients will inform us on the efficacy and safety of the proposed approaches.

Position statement of the International Society for Gastrointestinal Hereditary Tumours (InSiGHT) on APC I1307K and cancer risk.

While constitutional pathogenic variants in the APC gene cause familial adenomatous polyposis, APC c.3920T>A; p.Ile1307Lys (I1307K) has been associated with a moderate increased risk of colorectal cancer (CRC), particularly in individuals of Ashkenazi Jewish descent. However, published data include relatively small sample sizes, generating inconclusive results regarding cancer risk, particularly in non-Ashkenazi populations. This has led to different country/continental-specific guidelines regarding genetic testing, clinical management and surveillance recommendations for I1307K. A multidisciplinary international expert group endorsed by the International Society for Gastrointestinal Hereditary Tumours (InSiGHT), has generated a position statement on the APC I1307K allele and its association with cancer predisposition. Based on a systematic review and meta-analysis of the evidence published, the aim of this document is to summarise the prevalence of the APC I1307K allele and analysed the evidence of the associated cancer risk in different populations. Here we provide recommendations on the laboratory classification of the variant, define the role of predictive testing for I1307K, suggest recommendations for cancer screening in I1307K heterozygous and homozygous individuals and identify knowledge gaps to be addressed in future research studies. Briefly, I1307K, classified as pathogenic, low penetrance, is a risk factor for CRC in individuals of Ashkenazi Jewish origin and should be tested in this population, offering carriers specific clinical surveillance. There is not enough evidence to support an increased risk of cancer in other populations/subpopulations. Therefore, until/unless future evidence indicates otherwise, individuals of non-Ashkenazi Jewish descent harbouring I1307K should be enrolled in national CRC screening programmes for average-risk individuals.

Biology of Precancers and Opportunities for Cancer Interception: Lesson from Colorectal Cancer Susceptibility Syndromes.

Hereditary gastrointestinal cancer is associated with molecular and neoplastic precursors which have revealed much about sporadic carcinogenesis. Therefore, an appreciation of constitutional and somatic events linked to these syndromes have provided a useful model for the development of risk models and preventative strategies. In this review, we focus of two of the best characterized syndromes, Lynch syndrome (LS) and familial adenomatous polyposis (FAP). Our understanding of the neoplasia-immune interaction in LS has contributed to the development of immune mediated therapies including cancer preventing vaccines and immunotherapy for cancer precursors. Chemoprevention in LS with aspirin and nonsteroidal anti-inflammatory drugs has also translated into clinical cancer, however the efficacy of such agents in FAP remains elusive when cancer is applied as an endpoint in trials rather than the use of 'indirect' endpoints such as polyp burden, and requires further elucidation of biological mechanisms in FAP. Finally, we review controversies in gastrointestinal surveillance for LS and FAP, including limitations and opportunities of upper and lower gastrointestinal endoscopy in the prevention and early detection of cancer.

Long-term outcomes of pouch surveillance and risk of neoplasia in familial adenomatous polyposis.

BACKGROUND: Long-term pouch surveillance outcomes for familial adenomatous polyposis (FAP) are unknown. We aimed to quantify surveillance outcomes and to determine which of selected possible predictive factors are associated with pouch dysplasia. METHODS: Retrospective analysis of collected data on 249 patients was performed, analyzing potential risk factors for the development of adenomas or advanced lesions ( ≥ 10 mm/high grade dysplasia (HGD)/cancer) in the pouch body and cuff using Cox proportional hazards models. Kaplan-Meier analyses included landmark time-point analyses at 10 years after surgery to predict the future risk of advanced lesions. RESULTS: Of 249 patients, 76 % developed at least one pouch body adenoma, with 16 % developing an advanced pouch body lesion; 18 % developed an advanced cuff lesion. Kaplan-Meier analysis showed a 10-year lag before most advanced lesions developed; cumulative incidence of 2.8 % and 6.4 % at 10 years in the pouch body and cuff, respectively. Landmark analysis suggested the presence of adenomas prior to the 10-year point was associated with subsequent development of advanced lesions in the pouch body (hazard ratio [HR] 4.8, 95 %CI 1.6-14.1; P = 0.004) and cuff (HR 6.8, 95 %CI 2.5-18.3; P < 0.001). There were two HGD and four cancer cases in the cuff and one pouch body cancer; all cases of cancer/HGD that had prior surveillance were preceded by ≥ 10-mm adenomas. CONCLUSIONS: Pouch adenoma progression is slow and most advanced lesions occur after 10 years. HGD and cancer were rare events. Pouch phenotype in the first decade is associated with the future risk of developing advanced lesions and may guide personalized surveillance beyond 10 years.

Potential risks associated with the use of ionizing radiation for imaging and treatment of colorectal cancer in Lynch syndrome patients.

The aim of this review is to investigate the literature pertaining to the potential risks of low-dose ionizing radiation to Lynch syndrome patients by use of computed tomography (CT), either diagnostic CT colonography (CTC), standard staging CT or CT surveillance. Furthermore, this review explores the potential risks of using radiotherapy for treatment of rectal cancer in these patients. No data or longitudinal observational studies of the impact of radiation exposure on humans with Lynch syndrome were identified. Limited experimental studies utilizing cell lines and primary cells exposed to both low and high radiation doses have been carried out to help determine radio-sensitivity associated with DNA mismatch repair gene deficiency, the defining feature of Lynch syndrome. On balance, these studies suggest that mismatch repair deficient cells may be relatively radio-resistant (particularly for low dose rate exposures) with higher mutation rates, albeit no firm conclusions can be drawn. Mouse model studies, though, showed an increased risk of developing colorectal tumors in mismatch repair deficient mice exposed to radiation doses around 2 Gy. With appropriate ethical approval, further studies investigating radiation risks associated with CT imaging and radiotherapy relevant doses using cells/tissues derived from confirmed Lynch patients or genetically modified animal models are urgently required for future clinical guidance.

Delphi Initiative for Early-Onset Colorectal Cancer (DIRECt) International Management Guidelines.

BACKGROUND & AIMS: Patients with early-onset colorectal cancer (eoCRC) are managed according to guidelines that are not age-specific. A multidisciplinary international group (DIRECt), composed of 69 experts, was convened to develop the first evidence-based consensus recommendations for eoCRC. METHODS: After reviewing the published literature, a Delphi methodology was used to draft and respond to clinically relevant questions. Each statement underwent 3 rounds of voting and reached a consensus level of agreement of ≥80%. RESULTS: The DIRECt group produced 31 statements in 7 areas of interest: diagnosis, risk factors, genetics, pathology-oncology, endoscopy, therapy, and supportive care. There was strong consensus that all individuals younger than 50 should undergo CRC risk stratification and prompt symptom assessment. All newly diagnosed eoCRC patients should receive germline genetic testing, ideally before surgery. On the basis of current evidence, endoscopic, surgical, and oncologic treatment of eoCRC should not differ from later-onset CRC, except for individuals with pathogenic or likely pathogenic germline variants. The evidence on chemotherapy is not sufficient to recommend changes to established therapeutic protocols. Fertility preservation and sexual health are important to address in eoCRC survivors. The DIRECt group highlighted areas with knowledge gaps that should be prioritized in future research efforts, including age at first screening for the general population, use of fecal immunochemical tests, chemotherapy, endoscopic therapy, and post-treatment surveillance for eoCRC patients. CONCLUSIONS: The DIRECt group produced the first consensus recommendations on eoCRC. All statements should be considered together with the accompanying comments and literature reviews. We highlighted areas where research should be prioritized. These guidelines represent a useful tool for clinicians caring for patients with eoCRC.

Altered Mucosal Immune-Microbiota Interactions in Familial Adenomatous Polyposis.

INTRODUCTION: Familial adenomatous polyposis (FAP) is a condition caused by a constitutional pathogenic variant of the adenomatous polyposis coli gene that results in intestinal adenoma formation and colorectal cancer, necessitating pre-emptive colectomy. We sought to examine interaction between the mucosal immune system and commensal bacteria in FAP to test for immune dysfunction that might accelerate tumorigenesis. METHODS: Colonic biopsies were obtained from macroscopically normal mucosal tissue from 14 healthy donors and 13 patients with FAP during endoscopy or from surgical specimens. Intraepithelial and lamina propria lymphocytes were phenotyped. Intraepithelial microbes were labeled with anti-IgA/IgG and analyzed by flow cytometry. RESULTS: Proportions of resident memory CD103-expressing CD8 + and γδ T-cell receptor + intraepithelial lymphocytes were dramatically reduced in both the left and right colon of patients with FAP compared with healthy controls. In lamina propria, T cells expressed less CD103, and CD4 + CD103 + cells expressed less CD73 ectonucleotidase. IgA coating of epithelia-associated bacteria, IgA + peripheral B cells, and CD4 T-cell memory responses to commensal bacteria were increased in FAP. DISCUSSION: Loss of resident memory T cells and γδ T cells in mucosal tissue of patients with FAP accompanies intestinal microbial dysbiosis previously reported in this precancerous state and suggests impaired cellular immunity and tumor surveillance. This may lead to barrier dysfunction, possible loss of regulatory T-cell function, and excess IgA antibody secretion. Our data are the first to implicate mucosal immune dysfunction as a contributing factor in this genetically driven disease and identify potentially critical pathways in the etiology of CRC.

Fluctuating methylation clocks for cell lineage tracing at high temporal resolution in human tissues.

Molecular clocks that record cell ancestry mutate too slowly to measure the short-timescale dynamics of cell renewal in adult tissues. Here, we show that fluctuating DNA methylation marks can be used as clocks in cells where ongoing methylation and demethylation cause repeated 'flip-flops' between methylated and unmethylated states. We identify endogenous fluctuating CpG (fCpG) sites using standard methylation arrays and develop a mathematical model to quantitatively measure human adult stem cell dynamics from these data. Small intestinal crypts were inferred to contain slightly more stem cells than the colon, with slower stem cell replacement in the small intestine. Germline APC mutation increased the number of replacements per crypt. In blood, we measured rapid expansion of acute leukemia and slower growth of chronic disease. Thus, the patterns of human somatic cell birth and death are measurable with fluctuating methylation clocks (FMCs).

Attenuated Familial Adenomatous Polyposis: A Phenotypic Diagnosis but Obsolete Term?

BACKGROUND: Attenuated familial adenomatous polyposis is characterised by low number (≤100) and delayed development of colorectal adenomas. Various definitions have been used, and genotype-phenotype correlations have been suggested. OBJECTIVE: We aimed to evaluate phenotypic and genotypic correlation in patients with presumed attenuated familial adenomatous polyposis and assess familial variability. DESIGN: This is a retrospective study. SETTINGS: This study was conducted at a tertiary polyposis registry. PATIENTS: Individuals with attenuated familial adenomatous polyposis were identified. Phenotypic group was defined as 100 or fewer adenomas at age 25 years and genotypic group was defined as a variant in the adenomatous polyposis coli region associated with attenuated familial adenomatous polyposis. Pathology polyp count was used for patients who had undergone surgery and endoscopic polyp count for those with intact colon. MAIN OUTCOME MEASURES: We evaluated phenotypic and genotypic correlation in patients with presumed attenuated familial adenomatous polyposis and familial variability. RESULTS: A total of 69 patients were identified in the phenotypic group, of whom 54 (78%) had a pathogenic variant in the attenuated regions of the adenomatous polyposis coli gene. Forty-eight (70%) had intact colon (median age at last colonoscopy 43 [25-73] years; median endoscopic polyp count 20 [0-100]) and 21 (30%) had undergone colectomy (median age at surgery 45 [25-54] years; median pathology polyp count 43 [3-100]). Eighty-three patients were identified in the genotypic group of which 54 (65%) had attenuated phenotype. Inter- and intrafamilial variability were observed. LIMITATIONS: This study was limited by its retrospective nature and single-center experience. CONCLUSION: Phenotype in familial adenomatous polyposis lies on a spectrum and is determined in part by genotype and age at adenoma count. Diagnosis of attenuated familial adenomatous polyposis should be based on phenotype; genotype is not a reliable indicator. Management should be personalized according to the phenotype of each individual. See Video Abstract at http://links.lww.com/DCR/B775. POLIPOSIS ADENOMATOSA FAMILIAR ATENUADA UN DIAGNSTICO FENOTPICO PERO TRMINO OBSOLETO: ANTECEDENTES:La poliposis adenomatosa familiar atenuada se caracteriza por un número bajo (≤100) y desarrollo retardado de adenomas colorrectales. Se han utilizado varias definiciones y se han sugerido correlaciones genotipo-fenotipo.OBJETIVO:Nuestro objetivo es evaluar la correlación fenotípica y genotípica en pacientes con presunta poliposis adenomatosa familiar atenuada y evaluar la variabilidad familiar.DISEÑO:Este es un estudio retrospectivo.AJUSTE:Este estudio se realizó en un registro terciario de poliposis.PACIENTES:Se identificaron individuos con poliposis adenomatosa familiar atenuada. El grupo fenotípico se definió como ≤100 adenomas a la edad de 25 años y el grupo genotípico se definió como una variante en la región de poliposis coli adenomatosa asociada con poliposis adenomatosa familiar atenuada. Se utilizó el recuento de pólipos en patología para los pacientes que se habían sometido a cirugía y el recuento de pólipos endoscópico para los que tenían el colon intacto.PRINCIPALES MEDIDAS DE RESULTADO:Evaluamos la correlación fenotípica y genotípica en pacientes con presunta poliposis adenomatosa familiar atenuada y variabilidad familiar.RESULTADOS:Un total de 69 pacientes se identificaron en el grupo fenotípico de los cuales 54 (78%) tenían una variante patogénica en las regiones atenuadas del gen de la poliposis coli adenomatosa. Cuarenta y ocho (70%) tenían colon intacto (edad media en la última colonoscopia 43 [25-73] años; mediana del recuento de pólipos endoscópicos 20 [0-100]) y 21 (30%) se habían sometido a colectomía (edad edia en el momento de la cirugía 45 [25-54] años; mediana del recuento de pólipos patológicos 43 [3-100]). Se identificaron 83 pacientes en el grupo genotípico de los cuales 54 (65%) tenían fenotipo atenuado. Se observó variabilidad inter e intrafamiliar.LIMITACIONES:Este estudio estuvo limitado por su naturaleza retrospectiva y la experiencia de un solo centro.CONCLUSIÓNES:El fenotipo en la poliposis adenomatosa familiar se encuentra en un espectro, determinado en parte por el genotipo y la edad en el momento del recuento de adenomas. El diagnóstico de poliposis adenomatosa familiar atenuada debe basarse en el fenotipo; el genotipo no es un indicador confiable. El manejo debe personalizarse según el fenotipo de cada individuo. Consulte Video Resumen en http://links.lww.com/DCR/B775.

Regular endoscopic surveillance and polypectomy is effective in managing rectal adenoma progression following colectomy and ileorectal anastomosis in patients with familial adenomatous polyposis.

AIM: Total colectomy with ileorectal anastomosis (TC-IRA) is a surgical option for patients with familial adenomatous polyposis (FAP). Regular endoscopic surveillance of the rectum is recommended to prevent rectal cancer. We aimed to document polyp progression in the rectum following TC-IRA and evaluate the role of polypectomy during surveillance. METHOD: Patients with FAP who underwent TC-IRA between 1990 and 2017 were identified. Demographic, endoscopic and genetic data were retrieved. Cumulative rectal adenoma (polyp) counts were obtained, whilst accounting for any polypectomies during the study period. The rate of polyp progression and factors influencing secondary proctectomy were evaluated. RESULTS: One hundred and ninety-nine patients fulfilled our inclusion criteria, of which 44% were male. The median age at colectomy was 19 (range 11-70) years and median preoperative rectal polyp count was 7 (range 0-50). All patients had an APC pathogenic variant, of which 151 (79%) were 5' of the mutation cluster region (MCR), 19 (10%) in the MCR, six (3%) were 3' of the MCR and 15 (8%) had a gross deletion. After a median follow-up of 8.6 (range1-27) years and a median of 11 (range 2-37) flexible sigmoidoscopies per patient, the median rate of polyp progression was 5.5 polyps/year (range 0-70.2). There was no evidence of polyp regression. Eight (4%) patients underwent secondary proctectomy for neoplasia, of which one (0.5%) had rectal adenocarcinoma. A total of 13,527 polyps were removed, a median of 35 polyps/patient (range 0-829). The rate of polyp progression was not significantly associated with genotypic or phenotypic factors. CONCLUSION: Progression of rectal adenoma burden following TC-IRA appears to be slow and dependent on the length of follow-up. In the modern era of stringent endoscopic surveillance and therapeutic procedures such as cold snare polypectomy, the rate of secondary proctectomy and the risk of rectal cancer after TC-IRA are very low. These findings are important when counselling patients with regard to the choice of surgery for FAP and implementing endoscopic surveillance.

The clinical features of polymerase proof-reading associated polyposis (PPAP) and recommendations for patient management.

Pathogenic germline exonuclease domain (ED) variants of POLE and POLD1 cause the Mendelian dominant condition polymerase proof-reading associated polyposis (PPAP). We aimed to describe the clinical features of all PPAP patients with probably pathogenic variants. We identified patients with a variants mapping to the EDs of POLE or POLD1 from cancer genetics clinics, a colorectal cancer (CRC) clinical trial, and systematic review of the literature. We used multiple evidence sources to separate ED variants into those with strong evidence of pathogenicity and those of uncertain importance. We performed quantitative analysis of the risk of CRC, colorectal adenomas, endometrial cancer or any cancer in the former group. 132 individuals carried a probably pathogenic ED variant (105 POLE, 27 POLD1). The earliest malignancy was colorectal cancer at 14. The most common tumour types were colorectal, followed by endometrial in POLD1 heterozygotes and duodenal in POLE heterozygotes. POLD1-mutant cases were at a significantly higher risk of endometrial cancer than POLE heterozygotes. Five individuals with a POLE pathogenic variant, but none with a POLD1 pathogenic variant, developed ovarian cancer. Nine patients with POLE pathogenic variants and one with a POLD1 pathogenic variant developed brain tumours. Our data provide important evidence for PPAP management. Colonoscopic surveillance is recommended from age 14 and upper-gastrointestinal surveillance from age 25. The management of other tumour risks remains uncertain, but surveillance should be considered. In the absence of strong genotype-phenotype associations, these recommendations should apply to all PPAP patients.