Preoperative prediction of perineural invasion of rectal cancer based on a magnetic resonance imaging radiomics model: A dual-center study.

BACKGROUND: Perineural invasion (PNI) has been used as an important pathological indicator and independent prognostic factor for patients with rectal cancer (RC). Preoperative prediction of PNI status is helpful for individualized treatment of RC. Recently, several radiomics studies have been used to predict the PNI status in RC, demonstrating a good predictive effect, but the results lacked generalizability. The preoperative prediction of PNI status is still challenging and needs further study. AIM: To establish and validate an optimal radiomics model for predicting PNI status preoperatively in RC patients. METHODS: This retrospective study enrolled 244 postoperative patients with pathologically confirmed RC from two independent centers. The patients underwent pre-operative high-resolution magnetic resonance imaging (MRI) between May 2019 and August 2022. Quantitative radiomics features were extracted and selected from oblique axial T2-weighted imaging (T2WI) and contrast-enhanced T1WI (T1CE) sequences. The radiomics signatures were constructed using logistic regression analysis and the predictive potential of various sequences was compared (T2WI, T1CE and T2WI + T1CE fusion sequences). A clinical-radiomics (CR) model was established by combining the radiomics features and clinical risk factors. The internal and external validation groups were used to validate the proposed models. The area under the receiver operating characteristic curve (AUC), DeLong test, net reclassification improvement (NRI), integrated discrimination improvement (IDI), calibration curve, and decision curve analysis (DCA) were used to evaluate the model performance. RESULTS: Among the radiomics models, the T2WI + T1CE fusion sequences model showed the best predictive performance, in the training and internal validation groups, the AUCs of the fusion sequence model were 0.839 [95% confidence interval (CI): 0.757-0.921] and 0.787 (95%CI: 0.650-0.923), which were higher than those of the T2WI and T1CE sequence models. The CR model constructed by combining clinical risk factors had the best predictive performance. In the training and internal and external validation groups, the AUCs of the CR model were 0.889 (95%CI: 0.824-0.954), 0.889 (95%CI: 0.803-0.976) and 0.894 (95%CI: 0.814-0.974). Delong test, NRI, and IDI showed that the CR model had significant differences from other models (P < 0.05). Calibration curves demonstrated good agreement, and DCA revealed significant benefits of the CR model. CONCLUSION: The CR model based on preoperative MRI radiomics features and clinical risk factors can preoperatively predict the PNI status of RC noninvasively, which facilitates individualized treatment of RC patients.

[Implementation of fluorescent imaging technology in endovideosurgical treatment of colorectal endometriosis]. / Vnedrenie tekhnologii fluorestsentnoi vizualizatsii v endovideokhirurgicheskoe lechenie kolorektal'nogo endometrioza.

The article includes a clinical case of a patient with deep infiltrating endometriosis with rectum involving and using intraoperative controlled fluorescence in order to increase the radicality of surgery and improve the prognosis of the disease. Surgical excision of the endometrioitic nodules is the only effective way of treating patients with colorectal endometriosis in terms of relieving pain, improving quality of life and restoring reproductive function. The possible types of surgical interventions can be performed: endometrioid lesion shaving, discoid or circular intestinal resection with anastomosis. The extent of the operation is determined by the following morphological parameters: the number of endometrioid infiltrates of the intestinal wall, the size of each of them, the degree of involvement of the intestine circumference, the depth of the intestinal wall lesion, the distance from the level of anus to the endometriotic nodule and lymphatic dissemination.

A current view of mitochondria damage and the diversity of lipopigment inclusions in neuronal ceroid lipofuscinose type 2 from rectal biopsy.

Neuronal ceroid lipofuscinoses (NCLs) are a growing group of neurodegenerative storage diseases, in which specific features are sought to facilitate the creation of a universal diagnostic algorithm in the future. In our ultrastructural studies, the group of NCLs was represented by the CLN2 disease caused by a defect in the TPP1 gene encoding the enzyme tripeptidyl-peptidase 1. A 3.5-year-old girl was affected by this disease. Due to diagnostic difficulties, the spectrum of clinical, enzymatic, and genetic tests was extended to include analysis of the ultrastructure of cells from a rectal biopsy. The aim of our research was to search for pathognomonic features of CLN2 and to analyse the mitochondrial damage accompanying the disease. In the examined cells of the rectal mucosa, as expected, filamentous deposits of the curvilinear profile (CVP) type were found, which dominated quantitatively. Mixed deposits of the CVP/fingerprint profile (FPP) type were observed less frequently in the examined cells. A form of inclusions of unknown origin, not described so far in CLN2 disease, were wads of osmophilic material (WOMs). They occurred alone or co-formed mixed deposits. In addition, atypically damaged mitochondria were observed in muscularis mucosae. Their deformed cristae had contact with inclusions that looked like CVPs. Considering the confirmed role of the c subunit of the mitochondrial ATP synthase in the formation of filamentous lipopigment deposits in the group of NCLs, we suggest the possible significance of other mitochondrial proteins, such as mitochondrial contact site and cristae organizing system (MICOS), in the formation of these deposits. The presence of WOMs in the context of searching for ultrastructural pathognomonic features in CLN2 disease also requires further research.

Robotic versus laparoscopic total mesorectal excision with lateral lymph node dissection for advanced rectal cancer: A systematic review and meta-analysis.

INTRODUCTION: Lateral pelvic node dissection (LPND) poses significant technical challenges. Despite the advent of robotic surgery, determining the optimal minimally invasive approach remains a topic of debate. This study aimed to compare postoperative outcomes between robotic total mesorectal excision with LPND (R-LPND) and laparoscopic total mesorectal excision with LPND (L-LPND). METHODS: This meta-analysis was conducted according to the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) 2020 and AMSTAR 2 (Assessing the Methodological Quality of Systematic Reviews) guidelines. Utilizing the RevMan 5.3.5 statistical package from the Cochrane Collaboration, a random-effects model was employed. RESULTS: Six eligible studies involving 652 patients (316 and 336 in the R-LPND and L-LPND groups, respectively) were retrieved. The robotic approach demonstrated favourable outcomes compared with the laparoscopic approach, manifesting in lower morbidity rates, reduced urinary complications, shorter hospital stays, and a higher number of harvested lateral pelvic lymph nodes. However, longer operative time was associated with the robotic approach. No significant differences were observed between the two groups regarding major complications, anastomotic leak, intra-abdominal infection, neurological complications, LPND time, overall recurrence, and local recurrence. CONCLUSIONS: In summary, the robotic approach is a safe and feasible alternative for Total Mesorectal Excision (TME) with LPND in advanced rectal cancer. Notably, it is associated with lower morbidity, particularly a reduction in urinary complications, a shorter hospital stay and increased number of harvested lateral pelvic nodes. The trade-off for these benefits is a longer operative time.

The Enigma That is Rectal Squamous Cell Carcinoma: A Case Series.

INTRODUCTION: Colorectal cancer is the third most common cancer and the third leading cause of cancer deaths in the United States. As rectal squamous cell carcinoma (SCC) is an uncommon colorectal cancer, there is limited data on this clinical entity. We aimed to evaluate the tumor characteristics, treatment, and clinical outcomes of this rare deadly disease. METHODS: Pathological specimens from 2017 to 2022 at a single National Cancer Institute-designated cancer center were screened for all rectal cases with a diagnosis of SCC. All patients with a primary rectal SCC were included. Patients who had extension to the dentate line or evidence of an anal mass, and those who were treated at an outside institution, were excluded. Demographic, treatment, outcome, and surveillance data was extracted. RESULTS: There were 56 specimens identified, nine of which met inclusion criteria. Most patients were White (78%), Hispanic (78%), and female (67%). The average age at diagnosis was 57 y [52-65]. All patients had nodal involvement at the time of clinical staging. All patients were treated with Nigro protocol, with one patient treated with surgery first. The median time of follow-up was 12 mo after initial treatment, 33% had recurrence, with median time to recurrence of 25 mo. Overall, mortality from rectal SCC was 33% at a median time of 37 mo from initial diagnosis. CONCLUSIONS: Rectal SCC is a colorectal cancer that is not fully understood. Our findings showed that treatment mirrors that of anal SCC, with similar rates of survival to both rectal adenocarcinoma and anal SCC.

Are we ready to use new endoscopic scores for ulcerative colitis?

For ulcerative colitis (UC), the variability in inflammatory activity along the colon poses a challenge in management. The focus on achieving endoscopic healing in UC is evident, where the UC Endoscopic Index of Severity and Mayo Endoscopic Subscore are commonly used for evaluation. However, these indices primarily consider the most severely affected region. Liu et al recent study validates the Toronto Inflammatory Bowel Disease Global Endoscopic Reporting (TIGER) score offering a comprehensive assessment of inflammatory activity across diverse segments of the colon and rectum and a reliable index correlating strongly with UC Endoscopic Index of Severity and moderately with Mayo Endoscopic Subscore (MES). Despite recommendation, certain aspects warrant further investigation. Fecal calprotectin, an intermediate target, correlates with TIGER and should be explored. Determining TIGER scores defining endoscopic remission and response, evaluating agreement with histological activity, and assessing inter-endoscopist agreement for TIGER require scrutiny. Exploring the correlation between TIGER and intestinal ultrasound, akin to MES, adds value.

The efficacy and safety of short-course radiotherapy followed by sequential chemotherapy and Cadonilimab for locally advanced rectal cancer: a protocol of a phase II study.

BACKGROUND: For patients with locally advanced rectal cancer (LARC), total neoadjuvant therapy (TNT), namely, intensifying preoperative treatment through the integration of radiotherapy and systemic chemotherapy before surgery, was commonly recommended as the standard treatment. However, the risk of distant metastasis at 3 years remained higher than 20%, and the complete response (CR) rate was less than 30%. Several clinical trials had suggested a higher complete response rate when combining single-agent immunotherapy with short-course radiotherapy (SCRT). The CheckMate 142 study had shown encouraging outcomes of dual immunotherapy and seemingly comparable toxicity for CRC compared with single-agent immunotherapy in historical results. Therefore, dual immunotherapy might be more feasible in conjunction with the TNT paradigm of SCRT. We performed a phase II study to investigate whether the addition of a dual immune checkpoint inhibitor bispecific antibody, Cadonilimab, to SCRT combined with chemotherapy might further increase the clinical benefit and prognosis for LARC patients. METHODS: This single-arm, multicenter, prospective, phase II study included patients with pathologically confirmed cT3-T4N0 or cT2-4N + rectal adenocarcinoma with an ECOG performance score of 0 or 1. Bispecific antibody immunotherapy was added to SCRT combined with chemotherapy. Patients enrolled would be treated with SCRT (25 Gy in five fractions over 1 week) for the pelvic cavity, followed by 4 cycles of CAPOX or 6 cycles of mFOLFOX and Cadonilimab. The primary endpoint was the CR rate, which was the ratio of the pathological CR rate plus the clinical CR rate. The secondary endpoints included local-regional control, distant metastasis, disease-free survival, overall survival, toxicity profile, quality of life and functional outcome of the rectum. To detect an increase in the complete remission rate from 21.8% to 40% with 80% power, 50 patients were needed. DISCUSSION: This study would provide evidence on the efficacy and safety of SCRT plus bispecific antibody immunotherapy combined with chemotherapy as neoadjuvant therapy for patients with LARC, which might be used as a candidate potential therapy in the future. TRIAL REGISTRATION: This phase II trial was prospectively registered at ClinicalTrials.gov, under the identifier NCT05794750.

Fluorescence guidance using near-infrared fluorescent clips in robotic rectal surgery: a case series.

PURPOSE: Tattoo markings are often used as preoperative markers for colorectal cancer. However, scattered ink markings adversely affect tumor site recognition intraoperatively; therefore, interventions for rectal cancer may lead to an inaccurate distal resection margin (DRM) and incomplete total mesorectal excision (TME). This is the first case series of fluorescence-guided robotic rectal surgery in which near-infrared fluorescence clips (NIRFCs) were used to localize rectal cancer lesions. METHODS: We enrolled 20 consecutive patients who underwent robotic surgery for rectal cancer between December 2022 and December 2023 in the current study. The primary endpoints were the rate of intraoperative clip detection and its usefulness for marking the tumor site. Secondary endpoints were oncological assessments, including DRM and the number of lymph nodes. RESULTS: Clip locations were confirmed in 17 of 20 (85%) patients. NIRFCs were not detected in 3 out of 7 patients who underwent preoperative chemoradiation therapy. No adverse events, including bleeding or perforation, were observed at the time of clipping, and no clips were lost. The median DRM was 55 mm (range, 22-86 mm) for rectosigmoid (Rs), 33 mm (range, 16-60 mm) for upper rectum (Ra), and 20 mm (range, 17-30 mm) for low rectum (Rb). The median number of lymph nodes was 13 (range, 10-21). CONCLUSION: The rate of intraoperative clip detection, oncological assessment, including DRM, and the number of lymph nodes indicate that the utility of fluorescence-guided methods with NIRFCs is feasible for rectal cancer.

Endoscopic ultrasonography-related diagnostic accuracy and clinical significance on small rectal neuroendocrine neoplasms.

This research aimed to examine the diagnostic accuracy and clinical significance of endoscopic ultrasonography (EUS) in the context of small rectal neuroendocrine neoplasms (NENs). A total of 108 patients with rectal subepithelial lesions (SELs) with a diameter of < 20 mm were included in the analysis. The diagnosis and depth assessment of EUS was compared to the histology findings. The prevalence of NENs in rectal SELs was 78.7% (85/108). The sensitivity of EUS in detecting rectal NENs was 98.9% (84/85), while the specificity was 52.2% (12/23). Overall, the diagnostic accuracy of EUS in identifying rectal NENs was 88.9% (96/108). The overall accuracy rate for EUS in assessing the depth of invasion in rectal NENs was 92.9% (78/84). Therefore, EUS demonstrates reasonable diagnostic accuracy in detecting small rectal NENs, with good sensitivity but inferior specificity. EUS may also assist physicians in assessing the depth of invasion in small rectal NENs before endoscopic excision.

Influence of neoadjuvant treatment strategy on perioperative outcomes in locally advanced rectal cancer.

AIM: Neoadjuvant chemoradiotherapy (nCRT) in locally advanced rectal cancer facilitates tumour downstaging and complete pathological response (pCR). The goal of neoadjuvant systemic chemotherapy (total neoadjuvant chemotherapy, TNT) is to further improve local and systemic control. While some patients forgo surgery, total mesorectal excision (TME) remains the standard of care. While TNT appears to be noninferior to nCRT with respect to short-term oncological outcomes few data exist on perioperative outcomes. Perioperative morbidity including anastomotic leaks is associated with a negative effect on oncological outcomes, probably due to a delay in proceeding to adjuvant therapy. Thus, we aimed to compare conversion rates, rates of sphincter-preserving surgery and anastomosis formation rates in patients undergoing rectal resection after either TNT or standard nCRT. METHODS: An institutional colorectal oncology database was searched from January 2018 to July 2023. Inclusion criteria comprised patients with histologically confirmed rectal cancer who had undergone neoadjuvant therapy and TME. Exclusion criteria comprised patients with a noncolorectal primary, those operated on emergently or who had local excision only. Outcomes evaluated included rates of conversion to open, sphincter-preserving surgery, anastomosis formation and anastomotic leak. RESULTS: A total of 119 patients were eligible for inclusion (60 with standard nCRT, 59 with TNT). There were no differences in rates of sphincter preservation or primary anastomosis formation between the groups. However, a significant increase in conversion to open (p = 0.03) and anastomotic leak (p = 0.03) was observed in the TNT cohort. CONCLUSION: In this series TNT appears to be associated with higher rates of conversion to open surgery and higher anastomotic leak rates. While larger studies will be required to confirm these findings, these factors should be considered alongside oncological benefits when selecting treatment strategies.

Emodin ameliorates acute radiation proctitis in mice by regulating AKT/MAPK/NF-κB/VEGF pathways.

BACKGROUND: Emodin, a natural anthraquinone derivative isolated from the roots of Rheum officinale Baill, has many pharmacological effects including anti-inflammatory, antioxidant, antiviral, antibacterial and anti-cancer. However, little is known about the effect of emodin on acute radiation proctitis (ARP). The present study was conducted to determine its effects and elucidate its mechanisms involving AKT/MAPK/NF-κB/VEGF pathways in ARP mice. METHODS: Total 60 C57BL/6 mice were divided randomly into control group, ARP group, AKT inhibitor MK-2206 group, and different doses of emodin groups. ARP mice were induced by 27 Gy of 6 MV X-ray pelvic local irradiation. MK-2206 was given orally for 2 weeks on alternate days. Emodin was administered daily by oral gavage for 2 weeks. Subsequently, all mice were sacrificed on day 15. The rectal tissues were obtained for further tests. The general signs score and the pathological grade were used to evaluate the severity of ARP. The expression of NF-κB, VEGF and AQP1 were determined by immunohistochemistry and western blot. The expression of p-AKT, p-ERK, p-JNK, p-p38, Bcl-2 and Bax were assessed using western blot. RESULTS: The worse general signs and damaged tissue structure of ARP mice were profoundly ameliorated by emodin. The expression of p-AKT, p-ERK, NF-κB, VEGF and AQP1 were significantly increased, resulting in the inflammation-induced angiogenesis in ARP mice. However, the expression of p-JNK and p-p38 were decreased, leading to the reduction of apoptosis in ARP mice. Excitedly, emodin reversed these changes, not only inhibited inflammation-induced angiogenesis, but also promoted apoptosis. Notably, the effects of emodin were similar to that of AKT inhibitor MK-2206, suggesting the involvement of AKT signaling in the effect of emodin. CONCLUSION: These results suggest that emodin attenuates ARP in mice, and the underlying mechanism might involve inhibition of the AKT/ERK/NF-κB/VEGF pathways and the induction of apoptosis mediated by JNK and p38.

Tata Memorial Centre Evidence Based Management of Colorectal cancer.

ABSTRACT: This review article examines the evidence-based management of colorectal cancers, focusing on topics characterized by ongoing debates and evolving evidence. To contribute to the scientific discourse, we intentionally exclude subjects with established guidelines, concentrating instead on areas where the current understanding is dynamic. Our analysis encompasses a thorough exploration of critical themes, including the evidence surrounding complete mesocolic excision and D3 lymphadenectomy in colon cancers. Additionally, we delve into the evolving landscape of perioperative chemotherapy in both colon and rectal cancers, considering its nuanced role in the context of contemporary treatment strategies. Advancements in surgical techniques are a pivotal aspect of our discussion, with an emphasis on the utilization of minimally invasive approaches such as laparoscopy and robotic surgery in both colon and rectal cancers, including advanced rectal cases. Moving beyond conventional radical procedures, we scrutinize the feasibility and implications of endoscopic resections for small tumors, explore the paradigm of organ preservation in locally advanced rectal cancers, and assess the utility of total neoadjuvant therapy in the current treatment landscape. Our final segment reviews pivotal trials that have significantly influenced the management of colorectal liver and peritoneal metastasis.

[A Case of Pathologically Complete Response after Preoperative Chemotherapy in a Locally Advanced Rectal Cancer].

The case is a 78-year-old male. The chief complaint was melena and weight loss. After careful examination, the patient was diagnosed with advanced rectal cancer, and 3 courses of capecitabine plus oxaliplatin therapy were performed as preoperative chemotherapy. He underwent robot-assisted laparoscopic rectal resection, D3 lymphadenectomy, lateral lymphadenectomy, and temporary colostomy, and was discharged on hospital day 15. Postoperative pathological diagnosis showed only ulcerative lesions in the rectum, and malignant cells could not be confirmed. After postoperative adjuvant chemotherapy, the patient is alive without recurrence on an outpatient basis. There are many reports that it is slightly lower than radiotherapy. Therefore, it is important to select a more appropriate preoperative treatment, and the concentration of future cases is recognized.

Recurrence and Carcinogenetic Rates of Colorectal Polyps.

AIM: to determin the recurrence rate of benign recto-colonic polyps in a 5-year interval, and compare the development rate of intrapolypoid carcinomatous lesions in polypectomized versus nonpolypectomized subjects. MATERIAL AND METHOD: a group of 77 patients diagnosed with recto-colonic polypoid lesions during the period 2014-2019 underwent colonoscopy at the time of study initiation and then annually during a five-year interval. Results: The recurrence rate of polyps increased annually from 5 to 12.5%; the highest rate was noted in the last two years. The five-year cumulative risk of neoplastic lesions was 73% in patients without polypectomy and 20% among those with endoscopic resection (p 0.05). Comparing the recurrence rate of benign lesions (60%) in patients without neoplastic findings with the recurrence rate of adenomas in patients with benign lesions (40%), a higher risk of recurrence was found in the first category, and seemed to be influenced by the personal history of pre-existing adenomatous lesions. CONCLUSION: an increased risk of colorectal polyps recurrence was reported during five year follow up; moreover, during the first three years an increased risk of malignant transformation was observed among cases in which endoscopic resection was not feasible when compared to those in which complete excision was feasible.

Technical Considerations in Surgical Resection of Desmoplastic Small Round Cell Tumors.

Abdominal metastatic disease is a nearly universal feature of Desmoplastic Small Round Cell Tumor. The presence of this large tumor burden can be dissuasive to surgeons. Aggressive attempts at resection of all of the dozens to hundreds of nodules in the abdomen are often fraught with difficulty. This author has operated on over 200 patients with Desmoplastic Small Round Cell Tumor and offers technical considerations that aid in complete removal of all intraabdominal tumors (sarcomatosis) with an organ sparing approach. The most challenging portion of the operation is resection of the pelvic tumor in the pouch of Douglas without removing either the bladder or the rectum. These tumors are almost always large and adherent to the bladder and rectum. The desired result should be a partial peritonectomy without any evidence of gross, visible disease.

Multimodality Imaging to Direct Management of Primary and Recurrent Rectal Adenocarcinoma Beyond the Total Mesorectal Excision Plane.

Rectal tumors extending beyond the total mesorectal excision (TME) plane (beyond-TME) require particular multidisciplinary expertise and oncologic considerations when planning treatment. Imaging is used at all stages of the pathway, such as local tumor staging/restaging, creating an imaging-based "roadmap" to plan surgery for optimal tumor clearance, identifying treatment-related complications, which may be suitable for radiology-guided intervention, and to detect recurrent or metastatic disease, which may be suitable for radiology-guided ablative therapies. Beyond-TME and exenterative surgery have gained acceptance as potentially curative procedures for advanced tumors. Understanding the role, techniques, and pitfalls of current imaging techniques is important for both radiologists involved in the treatment of these patients and general radiologists who may encounter patients undergoing surveillance or patients presenting with surgical complications or intercurrent abdominal pathology. This review aims to outline the current and emerging roles of imaging in patients with beyond-TME and recurrent rectal malignancy, focusing on practical tips for image interpretation and surgical planning in the beyond-TME setting. Keywords: Abdomen/GI, Rectum, Oncology © RSNA, 2024.

Differences in Mucosal Permeability Among Patients With Ulcerative Colitis Classified Based on the Colonic Location and Disease Activity.

INTRODUCTION: Factors affecting mucosal permeability (MP) in ulcerative colitis (UC) are largely unknown. We aimed to investigate the difference in MP among patients with UC classified according to the colonic locations and to evaluate the correlations between local MP and endoscopic or histological activity of UC. METHODS: The transepithelial electrical resistance (TER), which is inversely proportional to permeability, of tissue samples from the mucosa of the ascending colon, descending colon, and rectum of patients with UC and healthy individuals (HIs) was measured by using the Ussing chamber. TERs were compared between patients with UC and HIs and evaluated according to colonic locations and disease activity of UC. RESULTS: Thirty-eight patients with UC and 12 HIs were included in this study. Both in HIs and patients with UC, MP tends to be higher in the anal side. TER in the ascending colon was significantly lower in patients with UC than in HIs (45.3 ± 9.0 Ω × cm 2 vs 53.5 ± 9.7 Ω × cm 2 , P = 0.01). The increased permeability in UC was observed also in the descending colon, only when the inflammation involved the location. A significant correlation between TER and endoscopic activity was found in the rectum only ( r = -0.49, P = 0.002). There were no significant correlations between TERs and UC histology. DISCUSSION: The MP in the colon differs according to the colonic location. The ascending colon among patients with UC showed disease-specific changes in MP, whereas the MP is increased in proportion to the endoscopic activity in the rectum.

Tumor location matters, next generation sequencing mutation profiling of left-sided, rectal, and right-sided colorectal tumors in 552 patients.

Despite the introduction of new molecular classifications, advanced colorectal cancer (CRC) is treated with chemotherapy supplemented with anti-EGFR and anti-VEGF targeted therapy. In this study, 552 CRC cases with different primary tumor locations (250 left side, 190 rectum, and 112 right side) were retrospectively analyzed by next generation sequencing for mutations in 50 genes. The most frequently mutated genes were TP53 in left-sided tumors compared to right-sided tumors and BRAF in right-sided tumors compared to left-sided tumors. Mutations in KRAS, NRAS, and BRAF were not detected in 45% of patients with left-sided tumors and in 28.6% of patients with right-sided tumors. Liver metastases were more common in patients with left-sided tumors. Tumors on the right side were larger at diagnosis and had a higher grade (G3) than tumors on the left. Rectal tumors exhibit distinctive biological characteristics when compared to left-sided tumors, including a higher absence rate of KRAS, NRAS, and BRAF mutations (47.4% in rectal versus 42.8% in left-sided tumors). These rectal tumors are also unique in their primary metastasis site, which is predominantly the lungs, and they have varying mutation rates, particularly in genes such as BRAF, FBXW7, and TP53, that distinguish them from tumors found in other locations. Primary tumor location has implications for the potential treatment of CRC with anti-EGFR therapy.