Germline Cancer Testing in Unselected Patients with Gastric and Esophageal Cancers: A Multi-center Prospective Study.

BACKGROUND AND AIMS: To determine prevalence and clinical utility of pathogenic germline variants (PGV) in gastric and esophageal cancer patients using universal genetic testing approach. METHODS: We undertook a prospective study of germline sequencing using an > 80 gene next-generation sequencing platform among patients with gastric and esophageal cancers receiving care at Mayo Clinic Cancer Center between April 1, 2018, and March 31, 2020. Patients were not selected based on cancer stage, family history of cancer, ethnicity, or age. Family cascade testing was offered at no cost. RESULTS: A total of 96 patients were evaluated. Median age was 66 years, 80.2% were male, 89.6% were white. Nearly 39% of the cohort had esophageal cancer, 35.4% gastric cancer and 26% gastroesophageal junction cancers. Approximately half (52%) of the patients had metastatic disease. Pathogenic germline variants (PGV) were detected in 15.6% (n = 15) patients. The prevalence of PGV was 10.8% in esophageal cancer, 17.6% in gastric cancer and 20% in gastroesophageal cancer. Eighty percent of patients with a positive result would not have been detected by screening with standard guidelines for genetic testing. Most PGV detected included genes with high and moderate penetrance related to DNA damage response including BRCA1, BRCA2, PALB2 and ATM. CONCLUSIONS: Universal multi-gene panel testing in gastric and esophageal cancers was associated with detection of heritable mutations in 15% of patients. The majority of PGV would not be detected with current screening guidelines and are related to DNA damage response.

Gastrointestinal Polyposis in Cowden Syndrome.

GOALS: To further characterize the gastrointestinal manifestations of Cowden syndrome in clinically well-annotated patients to improve the diagnosis of this syndrome. BACKGROUND: The gastrointestinal manifestations of Cowden Syndrome, an important heritable and multiorgan cancer syndrome, are not well defined. Proper diagnosis is essential for effective cancer surveillance and prevention in these patients. STUDY: Cowden patients with gastrointestinal polyps were selected for medical record and pathologic slide review. RESULTS: Of 19 total patients, genetic testing revealed pathogenic PTEN mutations in 12. Pan-colonic (11-patients, 58%) and pan-gastrointestinal (8-patients, 42%) polyp distributions were common. Inflammatory (juvenile) polyps were the most common of the hamartomatous polyp (18 patients, 95%), along with expansive lymphoid follicle polyps (12 patients, 63%), ganglioneuromatous polyps (10 patients, 53%), and intramucosal lipomas (5 patients, 26%). The findings of 2 or more hamartomatous polyp types per patient emerged as a newly described and highly prevalent (79%) feature of Cowden syndrome. Ganglioneuromatous polyps, rare in the general population, and intramucosal lipomas, which may be unique to Cowden syndrome, should both prompt further evaluation. Colonic adenomas and adenocarcinomas were common; 10 patients (53%) had single and 3 (16%) had ≥3 adenomas, whereas 2 (11%) had colonic adenocarcinoma, strengthening the emerging association of colorectal cancer with Cowden syndrome. CONCLUSIONS: The clinical phenotypes and gastrointestinal manifestations in Cowden syndrome are quite variable but this series adds the following new considerations for this syndromic diagnosis: multiple gastrointestinal hamartomas, especially 2 or more hamartoma types, and any intramucosal lipomas or ganglioneuromas. These features should warrant consideration of Cowden syndrome.

Cigarette smoking and colorectal cancer risk by KRAS mutation status among older women.

OBJECTIVES: Existing data support a modest association between cigarette smoking and incident colorectal cancer (CRC) overall. In this study, we evaluated associations between cigarette smoking and CRC risk stratified by KRAS mutation status, using data and tissue resources from the Iowa Women's Health Study (IWHS). METHODS: The IWHS is a population-based cohort study of cancer incidence among 41,836 randomly selected Iowa women, ages 55-69 years of age at enrollment (1986). Exposure data, including cigarette smoking, were obtained by self-report at baseline. Incident CRCs (n=1,233) were ascertained by annual linkage with the Iowa Cancer Registry. Archived tissue specimens from CRC cases recorded through 2002 were recently requested for molecular epidemiology investigations. Tumor KRAS mutation status was determined by direct sequencing of exon 2, with informative results in 507/555 (91%) available CRC cases (342 mutation negative and 165 mutation positive). Multivariate Cox regression models were fit to estimate relative risks (RRs) and 95% confidence intervals (CIs) for associations between cigarette smoking variables and KRAS-defined CRC subtypes. RESULTS: Multiple smoking variables were associated with increased risk for KRAS mutation-negative tumors, including age at initiation (P=0.02), average number of cigarettes per day (P=0.01), cumulative pack-years (P=0.05), and induction period (P=0.04), with the highest point estimate observed for women who smoked ≥40 cigarettes per day on average (RR=2.38; 95% CI=1.25-4.51; compared with never smokers). Further consideration of CRC subsite suggested that cigarette smoking may be a stronger risk factor for KRAS mutation-negative tumors located in the proximal colon than in the distal colorectum. None of the smoking variables were significantly associated with KRAS mutation-positive CRCs (overall or stratified by anatomic subsite). CONCLUSIONS: Data from this prospective study of older women demonstrate differential associations between cigarette smoking and CRC subtypes defined by KRAS mutation status, and are consistent with the hypothesis that smoking adversely affects the serrated pathway of colorectal carcinogenesis.

Familial colorectal cancer risk by subsite of primary cancer: a population-based study in Utah.

BACKGROUND: Familial occurrence is common in colorectal cancer (CRC), but whether this increased familial risk differs by colonic subsite of the index patients CRC is not well understood. AIM: To quantify the risk of CRC in first-degree (FDR), second-degree (SDR) and first cousin (FC) relatives of individuals with CRC, stratified by subsite in the colorectum and age at diagnosis. METHODS: Colorectal cancers diagnosed between 1980 and 2010 were identified from the Utah Cancer Registry and linked to pedigrees from the Utah Population Database. Age and gender-matched CRC-free controls were selected to form the comparison group for determining CRC risk in relatives using Cox regression analysis. RESULTS: Of the 18,208 index patients diagnosed with CRC, 6584 (36.2%) were located in the proximal colon, 5986 (32.9%) in the distal colon and 5638 (31%) in the rectum. The elevated risk of CRC in relatives was similar in analysis stratified for CRC colorectal subsites in the index cases. FDR had similarly elevated risk of all site CRC, whether the index patient had cancer in the proximal colon [hazards ratio (HR): 1.85; 95% CI: 1.70-2.02], distal colon (HR: 1.90; 95% CI: 1.73-2.08) or rectum (HR: 1.83; 95% CI: 1.66-2.02) compared to relatives of controls. This risk was consistently greater for FDR when cases developed CRC below the age of 60 years. CONCLUSIONS: Relatives of CRC patients have a similarly elevated risk of CRC regardless of colonic tumour subsite in the index patient, and it is greatest for relatives of younger age index cases.