Small bowel adenocarcinoma (SBA) is a rare malignancy, with lower incidence, later stage at diagnosis, and poor overall prognosis compared to other cancers of the gastrointestinal tract. Owing to the rarity of the disease along with the paucity of high-quality tissue samples and preclinical models, little is known about the molecular alterations characteristic of SBA. This is reflected by the fact that the clinical management of SBA is primarily extrapolated from colorectal cancer (CRC). Recent advances in genomic profiling have highlighted key differences between these tumors, establishing SBA as a molecularly unique intestinal cancer. Moreover, comprehensive molecular analysis has identified a relatively high incidence of potentially targetable genomic alterations in SBA, predictive of response to targeted and immunotherapies. Further advances in our knowledge of the mutational and transcriptomic landscape of SBA, guided by an increased understanding of the molecular drivers of SBA, will provide opportunities to develop novel diagnostic tools and personalized therapeutic strategies.

Colorectal cancer (CRC) is the second leading cause of cancer deaths worldwide. Although the overall incidence of CRC is decreasing, the incidence of young-onset CRC, characterized by a diagnosis of CRC before age 50, is increasing. Outcomes for CRC patients are improving, partly due to comprehensive molecular characterization of tumors and novel therapeutic strategies. Advances in genomic and transcriptomic analyses using blood- and tumor-tissue-based sequencing have facilitated identification of distinct tumor subtypes harboring unique biological characteristics and therapeutic vulnerabilities. These insights have led to the development and incorporation of targeted therapies and immunotherapy in CRC treatment. In this review, we discuss the molecular landscape and key oncogenes/tumor suppressors contributing to CRC tumorigenesis, metastasis, and therapeutic resistance. We also discuss personalized therapeutic strategies for subsets of CRC patients and provide an overview of evolving novel treatments being evaluated in clinical trials.

Oncological outcomes are improving in gastrointestinal cancer with advancements in systemic therapies, and there is notable potential in combining immunotherapy and radiation therapy (RT) to allow for further improvements. Various preclinical and early phase II studies have shown promising synergy with immunotherapy and RT in gastrointestinal cancer. A few recent phase III studies have shown improved survival with the addition of immunotherapy to standard treatment for gastrointestinal cancer. The timing, duration, sequencing, and integration with other anti-cancer treatments are still areas of ongoing research. We have reviewed the published and ongoing studies of the combinations of immunotherapy and RT in gastrointestinal cancers.

Background: Germline pathogenic variants in CHEK2 are associated with a moderate increase in the lifetime risk for breast cancer. Increased risk for other cancers, including non-medullary thyroid cancer (NMTC), has also been suggested. To date, data implicating CHEK2 variants in NMTC predisposition primarily derive from studies within Poland, driven by a splice site variant (c.444+1G>A) that is uncommon in other populations. In contrast, the predominant CHEK2 variants in non-Polish populations are c.1100del and c.470T>C/p.I157T, representing 61.1% and 63.8%, respectively, of all CHEK2 pathogenic variants in two large US-based commercial laboratory datasets. To further delineate the impact of common CHEK2 variants on thyroid cancer, we aimed to investigate the association of three CHEK2 founder variants (c.444+1G>A, c.1100del, and c.470T>C/p.Ile157Thr) on NMTC susceptibility in three groups of unselected NMTC patients. Methods: The presence of three CHEK2 founder variants were assessed within three groups: (1) 1544 NMTC patients (and 1593 controls) from previously published GWAS analyses, (2) 789 NMTC patients with germline exome sequencing (ORIEN Avatar), and (3) 499 NMTC patients with germline sequence data available in The Cancer Genome Atlas (TCGA). A case-control study design was utilized with odds ratios calculated by comparison of all three groups with the OSU GWAS control group. Results: The predominant Polish variant (c.444+1G>A) was present in only one case. The proportion of patients with c.1100del was 0.92% in the GWAS group, 1.65% in the ORIEN Avatar group, and 0.80% in the TCGA group. The odds ratios (with 95% confidence intervals) for NMTC associated with c.1100del were 1.71 (0.73-4.29), 2.64 (0.95-7.63), and 2.5 (0.63-8.46), respectively. The proportion of patients with c.470T>C/p.I157T was 0.91% in the GWAS group, 0.76% in the ORIEN Avatar group, and 0.80% in the TCGA group, respectively. The odds ratios (with 95% confidence intervals) for NMTC associated with c.470T>C/p.I157T were 1.75 (0.74-4.39), 1.52 (0.42-4.96), and 2.31 (0.58-7.90), respectively. Conclusions: Our analyses of unselected patients with NMTC suggest that CHEK2 variants c.1100del and c.470T>C/p.I157T have only a modest impact on thyroid cancer risk. These results provide important information for providers regarding the relatively low magnitude of thyroid cancer risk associated with these CHEK2 variants.

PURPOSE: Germline likely pathogenic and pathogenic variants (LPV/PVs) in POT1 have been associated with an increased risk of various cancers including angiosarcoma, melanoma, glioma, thyroid cancer, and chronic lymphocytic leukemia (CLL). However, to date, most of the published data regarding POT1 PVs involve cohorts of patients selected for specific cancer types, or stem from commercial laboratory cohorts from patients selected for germline clinical testing, which may cause ascertainment biases. The objective was to identify germline POT1 variants in a pan-cancer cohort and describe the associated phenotypes. METHODS: Germline exome data available for 19,315 patients with cancer from the Oncology Research Information Exchange Network (ORIEN) were assessed for POT1 LPV/PV. Data regarding cancer diagnoses were obtained for those with and without POT1 variants. Associations were assessed. RESULTS: POT1 LPV/PVs were identified in 23 patients. The cancer types seen in more than one patient include CLL (n = 7), papillary thyroid cancer (PTC, n = 5), colorectal cancer (n = 3), lung cancer (n = 3), glioblastoma (n = 2), and neuroendocrine tumors (n = 2). Compared with POT1 -negative patients, those with POT1 LPV/PVs were 5.5-fold more likely to be diagnosed with PTC (95% CI, 1.9 to 15.1; P = .004) and 16.6-fold more likely to be diagnosed with CLL (95% CI, 6.4 to 41.9; P < .001). Patients with POT1 LPV/PVs had a younger median age of first cancer diagnosis compared with POT1 -negative patients ( P = .008). CONCLUSION: To our knowledge, this study is the largest investigation of POT1 germline variants in a pan-cancer cohort. We identify and confirm specific associations with CLL and PTC in this cohort. Differences in results between analysis of largely unselected cohorts compared with clinical testing cohorts highlight the need to study gene-cancer associations in more unselected populations.