Background: Given the differences in embryonic origin, vascular and nervous supplies, microbiotic burden, and main physiological functions of left and right colons, tumor location is increasingly suggested to dictate tumor behavior affecting pathology, progression and prognosis. Right-sided colon cancers arise in the cecum, ascending colon, hepatic flexure and/or transverse colon, while left-sided colon cancers arise in the splenic flexure, descending, and/or sigmoid colon. In contrast to prior reports, we attempt to delineate programs of tumorigenesis independently for each side. Methods: Four hundred and eleven samples were extracted from The Cancer Genome Atlas-COAD cohort, based on a conservative sample inclusion criterion. Each side was independently analyzed with respect to their respective normal tissue, at the level of transcription, post-transcription, miRNA control and methylation in both a stage specific and stage-agnostic manner. Results: Our results indicate a suppression of enzymes involved in various stages of carcinogen breakdown including CYP2C8, CYP4F12, GSTA1, and UGT1A within right colon tumors. This implies its reduced capacity to detoxify carcinogens, contributing to a genotoxic tumor environment, and subsequently a more aggressive phenotype. Additionally, we highlight a crucial nexus between calcium homeostasis (sensing, mobilization and absorption) and immune/GPCR signaling within left-sided tumors, possibly contributing to its reduced proliferative and metastatic potential. Interestingly, two genes SLC6A4 and HOXB13 show opposing regulatory trends within right and left tumors. Post-transcriptional regulation mediated by both RNA-binding proteins (e.g. NKRF (in left) and MSI2 (in right)) and miRNAs (e.g. miR-29a (in left); miR-155, miR181-d, miR-576 and miR23a (in right)) appear to exhibit side-specificity in control of their target transcripts and is pronounced in right colon tumors. Additionally, methylation results depict location-specific differences, with increased hypomethylation in open seas within left tumors, and increased hypermethylation of CpG islands within right tumors. Conclusions: Differences in molecular mechanisms captured here highlight distinctions in tumorigenesis and progression between left and right colon tumors, which will serve as the basis for future studies, influencing the efficacies of existing and future diagnostic, prognostic and therapeutic interventions.

Ulcerative colitis (UC) is an inflammatory condition that generally affects the rectum and extends proximally into the colon in a continuous, distal-to-proximal pattern. Surgical resection (total proctocolectomy) is the only cure for UC and is often necessary in managing complicated or refractory disease. However, recent advances in biologically targeted therapies have resulted in improved disease control, and surgery is required in only a fraction of cases. This ever-increasing array of options for medical management has added complexity to surgical decision-making. In some circumstances, the added time required to ensure failure of medical therapy can delay colectomy in patients who will ultimately need it. Indeed, many patients with severe disease undergo trials of multiple medical therapies prior to considering surgery. In severe cases of UC, continued medical management has been associated with a delay to surgical intervention and higher rates of morbidity and mortality. Biomarkers represent a burgeoning field of research, particularly in inflammatory bowel disease and cancer. This review seeks to highlight the different possible settings for surgery in UC and the role various biomarkers might play in each.

Recommendations for elective colectomies after recovery from uncomplicated acute diverticulitis should be individualized. The kinds of associated risk factors that should be considered for this approach remain undetermined. The aim of this study was to identify the risk factors associated with postoperative outcomes in patients with diverticular disease after receiving an elective colectomy. This is a retrospective study using the multi-institutional, nationally validated database of the American College of Surgeons-National Surgical Quality Improvement Program (ACS-NSQIP). The patients who were diagnosed with diverticular disease and received an elective colectomy were included in our risk factor analyses. Postoperative mortality, morbidity, and overall complications were measured. Univariate and multivariate analyses were used to demonstrate the risk factors. We analyzed 30,468 patients with diverticular disease, 67% of whom received an elective colectomy. The rate of 30-day mortality was 0.2%, and superficial surgical site infection was the most common postoperative morbidity (7.2%) in the elective colectomies. The independent risk factors associated with overall complications were age ≥ 75, BMI ≥ 30, smoking status, dyspnea, hypertension, current kidney dialysis, chronic steroid use, ASA III, and open colectomy. In laparoscopic colectomy, 67.5% of the elective colectomies, the associated risk factors associated with overall complications still included age ≥ 75, smoking, hypertension, chronic steroid use, and ASA III. Identification of patient-specific risk factors may inform the decision-making process for elective colectomy and reduce the postoperative complications after mitigation of those risk factors.

Total neoadjuvant therapy (TNT) is the recommended treatment for locally advanced rectal cancer. The optimal sequence of TNT is debated: induction (chemotherapy first) or consolidation (chemoradiation first)? We aim to evaluate the practice patterns and clinical outcomes of total neoadjuvant therapy with either induction or consolidation regiments in the United States for patients with locally advanced rectal cancer. Methods: This is a retrospective analysis of the National Cancer Database for patients with clinical stage II or stage III rectal cancer, diagnosed between 2006 and 2017, who underwent total neoadjuvant therapy followed by surgery. Results: From 2006 to 2017, we identified 8999 patients and found that the utilization of induction chemotherapy increased from 2.0% to 35.0%. TNT resulted in pathologic downstaging 46.7% of the time and a pathologic complete response 11.6% of the time. Induction chemotherapy lead to higher pathologic downstaging (58% vs. 44.7%, p < 0.001) and pathologic complete responses (16.8% vs. 10.7%, p < 0.001). Similar trends held true in a multivariate analysis and subset analysis of stage II and III disease. Conclusions: These findings suggest that induction chemotherapy may be preferred over consolidation chemotherapy when downstaging prior to oncologic resection is desired. The optimal treatment plan for total neoadjuvant therapy is multi-factorial and requires further elucidation.

The Interval Between Neoadjuvant Therapy and Surgery in the Treatment of Locally Advanced Rectal Cancer (CRONOS) study¹ is a large multi-institutional retrospective analysis across several large hospitals in Spain. The authors should be commended on their effort and collaboration to bring together investigators across several large institutions and an impressive database of over 1500 patients. The timing of surgery after neoadjuvant chemoradiation is an area of significant debate and the authors have provided very good insights to support reasoning for expected delay after radiation to allow maximum treatment effect prior to surgery with the possible adverse effect of a more technically challenging operation.

Background: Recent investigations have suggested that-sidedness is associated with the prognosis of colon cancer patients. However, the role of sidedness in surgical outcome is unclear. In this study, we tried to demonstrate the real role of sidedness in postoperative results for colon cancer patients receiving surgical intervention. Methods: This is a propensity score matching study using the database of the American College of Surgeons-National Surgical Quality Improvement Program (ACS-NSQIP) from 2009 to 2013. Sidedness groups including right-sided and left-sided colon cancer were created according to the associated diagnosis and procedure codes. Postoperative 30-day mortality, morbidity, overall complications, and total length of hospital stay were analyzed after performing propensity score matching. Results: Out of a total of 24,436 colon cancer patients who received associated operations, 15,945 patients had right-sided cancer and 8941 patients had left-sided cancer. Right-sided colon cancer patients were accompanied by more preoperative comorbidities including old age, female sex, hypertension, dyspnea, anemia, hypoalbuminemia, and a high American Society of Anesthesiologists grade (SMD > 0.1). Postoperative mortality, morbidities including re-intubation, bleeding, urinary tract infection and deep vein thrombosis, postoperative overall complications, and total length of hospital stay were significantly associated with right-sided cancer (p < 0.05). After 1:1 propensity score matching, postoperative mortality was not significantly different between right-sided cancer (2.3%) and left-sided cancer (2.4%) patients. The patients with left-sided colon cancer had significantly more postoperative morbidities, more overall complications, and longer total length of hospital stay. Conclusions: Poor clinical characteristics and postoperative outcomes were noted in right-sided cancer patients. After propensity score matching, left-sided cancer patients had worse postoperative outcomes than those with right-sided cancer.