Analysis of Circulating DNA to Assess Prognoses for Metastatic Colorectal Cancer Patients Treated with Regorafenib Dose-Escalation Therapy: A Retrospective, Exploratory Analysis of the RECC Trial.

INTRODUCTION: Regorafenib is a multi-kinase inhibitor approved for patients with metastatic colorectal cancer (mCRC) who were previously treated with standard therapies. A few reports showed the impact of KRAS mutation on therapeutic efficacy of regorafenib. Only one study reported poor prognoses for patients treated with regorafenib who had large amounts of circulating cell-free DNA (cfDNA). In the present study, we evaluated the impact of KRAS mutations in tissue or plasma and amounts of cfDNA on prognoses of mCRC patients treated with regorafenib. METHOD: This is a biomarker investigation of the RECC study, which evaluated efficacy of regorafenib dose-escalation therapy. Plasma samples were obtained just before initiation of treatment with regorafenib. KRAS mutations were evaluated using tissue and plasma samples. cfDNA was extracted from plasma samples and quantified. RESULTS: Forty-five patients were enrolled in this biomarker study. Median progression-free survival (PFS) and overall survival (OS) of patients without KRAS mutations in tissues were 1.9 months (95% confidence interval [CI] 1.7-2.0) and 8.9 months (95% CI: 6.5-11.2), and those of patients with KRAS mutations were 1.4 months (95% CI: 1.3-1.5) and 6.8 months (95% CI: 5.0-8.5). Median PFS and OS of patients with plasma KRAS mutations were 1.9 months (95% CI: 1.8-1.9) and 7.0 months (95% CI: 5.3-8.7), respectively. Median PFS and OS of patients without plasma KRAS mutations were 1.7 months (95% CI: 1.1-2.3) and 8.9 months (95% CI: 6.7-11.2), respectively. Prior to administration of regorafenib, KRAS mutations were detected in 6 of 16 (37.5%) patients who had no tissue KRAS mutations. Median OS of patients with high cfDNA concentration (>median) was significantly poorer than that of patients with low cfDNA. CONCLUSION: KRAS mutations in the tissue or plasma have no impact on efficacy of regorafenib. KRAS emerging mutations were observed in quite a few patients. Large amounts of cfDNA may indicate poorer prognoses for patients receiving late-line regorafenib chemotherapy.

Cadaveric and CT angiography study of vessels around the transverse colon mesentery.

BACKGROUND: Laparoscopic and robotic surgery for transverse colon cancer are difficult due to complex fusion of the foregut and midgut and variation of the vessels of the transverse colon. Although the vessels of the right colon have been investigated, middle colic artery (MCA) variation and the relationship with vessels around the transvers colon are unknown. We investigated variation of the MCA using computed tomography angiography (CTA) and cadaver specimen and the relationship between the superior mesenteric vein (SMV) and MCA using CTA. The classification of vessels around the transverse colon may lead to safer and reliable surgery. METHODS: This study included 505 consecutive patients who underwent CTA in our institution from 2014 to 2020 and 44 cadaver specimens. Vascular anatomical classifications and relationships were analyzed using CT images. RESULTS: The MCA was defined as the arteries arising from the superior mesenteric artery (SMA) that flowed into the transverse colon at the distal ends. The classifications were as follows: type I, branching right and left from common trunk; type II, the right and left branches bifurcated separately from the SMA; and type III, the MCA branched from a vessel other than the SMA. Type II was subclassified into two subtypes, type IIa with one left branch and type IIb with two or more left branches from SMA. In the CTA and cadaver studies, respectively, the classifications were as follows: type I, n = 290 and n = 31; type IIa, n = 211 and n = 13; type IIb, n = 3 and n = 0; and type III, n = 1 and n = 0. We classified the relationship between the MCA and left side of the SMV into three types: type A, a common trunk runs along the left edge of the SMV (n = 173; 59.7%); type B, a right branch of the MCA runs along the left edge of the SMV (n = 116; 40.0%); and type C, the MCA runs dorsal of the SMV (n = 1; 0.3%). CONCLUSIONS: This study revealed that The MCA branching classifications and relationship between the SMV and MCA. Preoperative CT angiography may be able to reliably identify vessel variation, which may be useful in clinical practice.

Efficacy and safety of regorafenib dose-escalation therapy for Japanese patients with refractory metastatic colorectal cancer (RECC study).

BACKGROUND: Regorafenib significantly improves overall survival in previously treated metastatic colorectal cancer patients. However, various toxicities, such as hand-foot skin reaction (HFSR), fatigue, and liver dysfunction have limited the use of regorafenib. These toxicities appear soon after treatment initiation. The ReDOS study demonstrated the effectiveness of a weekly dose-escalation therapy of regorafenib starting with a lower daily dose; however, its usefulness in Asian subjects is unknown. We conducted a phase II study to evaluate the safety and survival benefit of regorafenib dose-escalation therapy for Japanese patients. METHODS: Patients with sufficient organ function, who had previously received more than two lines of chemotherapy were included. Regorafenib was started at 80 mg/day and escalated to 120 mg/day in Week 2 and 160 mg/day in Week 3, if no severe drug-related toxicities were observed. The primary endpoint was cancer progression-free survival (PFS). Tumor response and progression were assessed radiologically every 8 weeks. This study was registered in the University Hospital Medical Information Network (UMIN#UMIN000028933). RESULTS: 57 patients were enrolled and all started regorafenib at 80 mg/day. 32 patients (56.1%) were subsequently escalated to 120 mg/day and 19 (33.3%) to 160 mg/day. Only 8 patients (14.0%) discontinued treatment because of adverse events. Median PFS was 1.9 months. Median overall survival was 8.9 months, the response rate was 0%, and the disease control rate was 31.6%. The most frequent adverse event greater than grade 3 was hypertension (19.3%), followed by HFSR (14.0%). CONCLUSIONS: Regorafenib dose-escalation therapy is well tolerated with PFS-like regorafenib standard therapy.

Perioperative coagulofibrinolytic responses in colorectal surgery patients without chemical thromboprophylaxis: a retrospective observational study.

PURPOSE: During the perioperative period, coagulofibrinolytic activation occurs, which occasionally results in thromboembolic complications. However, natural perioperative coagulofibrinolytic responses have not been well investigated. The present study examined perioperative coagulofibrinolytic changes and their association with the development of venous thromboembolism (VTE). METHODS: We retrospectively analyzed the changes in coagulofibrinolytic markers for 7 days in 70 patients undergoing elective colorectal surgery. To explore the natural coagulofibrinolytic response, we investigated patients not undergoing perioperative chemical thromboprophylaxis. RESULTS: Coagulation activation occurred from just after surgery to postoperative day (POD) 1, followed by a gradual decrease, but persisted to even POD 7. Fibrinolytic activity showed a tri-phasic response: activation, shutdown and reactivation. Consequently, fibrin/fibrinogen degradation product (FDP) and D-dimer levels continued to increase until POD 7. The development of deep vein thrombosis (DVT) was observed in 11 patients (15.7%). Postoperative sustained hyper-coagulation [soluble fibrin (SF) or thrombin-antithrombin complex (TAT) values on POD 7 > their normal limits] was significantly associated with the development of DVT (SF, p < 0.001; TAT, p = 0.001). CONCLUSION: We found initial coagulation activation and a tri-phasic response of fibrinolytic activity after colorectal surgery. Thus, physicians need to pay attention to these responses when attempting to prevent or treat VTE.

Long-term prognosis of laparoscopic gastrectomy for patients on antithrombotic therapy: a retrospective cohort study.

PURPOSE: Few studies have reported on the interactions between gastrectomy and antithrombotic therapy, especially the long-term prognosis. We aimed to clarify the short- and long-term prognosis of gastrectomy for patients on antithrombotic therapy. METHODS: We reviewed the perioperative data and survival rate of patients who underwent laparoscopic distal gastrectomy (LDG) at our institute between 2010 and 2013. RESULTS: There were 119 patients enrolled in this retrospective study: 31 who were taking antithrombotic drugs (antithrombotic therapy (ATT) group), and 88 who were not (non-ATT group). The mean age was significantly higher in the ATT group than in the non-ATT group. No significant differences were observed in the amount of intraoperative bleeding or blood hemoglobin level after surgery between the groups. Bleeding complications occurred in only one patient from the ATT group, and the postoperative complication rate was comparable between the groups. During follow-up, cerebrovascular or cardiovascular events developed in 19.4% of the ATT group patients and 4.5% of the non-ATT group patients; however, there were no significant differences in the 5-year overall survival rates between the groups (ATT group, 76.9%; non-ATT group, 82.9%). CONCLUSIONS: Antithrombotic therapy did not affect the short-term or long-term prognosis of patients after LDG.

SNX9 determines the surface levels of integrin ß1 in vascular endothelial cells: Implication in poor prognosis of human colorectal cancers overexpressing SNX9.

Angiogenesis, the formation of new blood vessels, is involved in a variety of diseases including the tumor growth. In response to various angiogenic stimulations, a number of proteins on the surface of vascular endothelial cells are activated to coordinate cell proliferation, migration, and spreading processes to form new blood vessels. Plasma membrane localization of these angiogenic proteins, which include vascular endothelial growth factor receptors and integrins, are warranted by intracellular membrane trafficking. Here, by using a siRNA library, we screened for the sorting nexin family that regulates intracellular trafficking and identified sorting nexin 9 (SNX9) as a novel angiogenic factor in human umbilical vein endothelial cells (HUVECs). SNX9 was essential for cell spreading on the Matrigel, and tube formation that mimics in vivo angiogenesis in HUVECs. SNX9 depletion significantly delayed the recycling of integrin ß1, an essential adhesion molecule for angiogenesis, and reduced the surface levels of integrin ß1 in HUVECs. Clinically, we showed that SNX9 protein was highly expressed in tumor endothelial cells of human colorectal cancer tissues. High-level expression of SNX9 messenger RNA significantly correlated with poor prognosis of the patients with colorectal cancer. These results suggest that SNX9 is an angiogenic factor and provide a novel target for the development of new antiangiogenic drugs.

Laparoscopy-assisted distal gastrectomy is feasible also for elderly patients aged 80 years and over: effectiveness and long-term prognosis.

BACKGROUND: Elderly patients usually have concurrent ailments, and the safety and effectiveness of laparoscopy-assisted distal gastrectomy (LADG) for these patients have been controversial. This study aimed to evaluate whether laparoscopy-assisted distal gastrectomy is safe and effective for elderly patients aged 80 years and over, as well as to clarify their long-term prognosis. METHODS: A total of 31 patients aged 80 years and over who underwent LADG in our hospital were retrospectively reviewed. Peri- and postoperative data were compared with those of 38 patients aged 65 years and younger. The median follow-up period of the elderly and younger group was 56.0 and 63.0 months, respectively, and their prognosis was examined. RESULTS: There were significant differences between the two groups in preoperative respiratory and renal functions, hemoglobin, and nutritional index. Significant differences in postoperative complications were seen only in pneumonia and delirium. There were no hospital deaths, but the 3-year and 5-year overall survival rates were significantly lower in the elderly group than in the non-elderly group. However, in the elderly group, only one patient died of gastric cancer recurrence, whereas four died of cardiovascular disease and three died of pneumonia during follow-up. Therefore, the recurrence-free survival rate was not significantly different between the groups. CONCLUSIONS: LADG seems to be safe and effective even for elderly patients, and their prognosis was satisfactory. However, careful monitoring for cardiovascular and pulmonary disease should be observed during the follow-up period.

[Successful treatment of chronic empyema by the omentopexy after aggressive nutritional support].

Since general thoracic surgery requires a short fasting period, the number of cases that require nutrition support after surgery is limited and few reports exist about nutrition in general thoracic surgery and chronic empyema. Here we report 2 cases of chronic empyema treated with nutritional support team (NST) followed by omentopexy. For chronic empyema, a long period is required to sterilize the thoracic cavity by closed or open drainage before radical treatment. During this period, improvement of the nutrition status is important to control local infection, and to increase the volume of the omentum or muscle flaps used for filling the empyema space effectively. In our 2 cases, radical surgeries using omental flap were successfully performed after the improvement of general condition by aggressive nutritional support.

[Case of ischemic ileitis complicated by portal venous gas].

A 65-year-old woman was admitted with sudden-onset abdominal pain. Abdominal computed tomography revealed hepatic portal venous gas. Physical and laboratory examination suggested that a conservative approach was appropriate; however, 4 days later, the pain recurred and severe ischemic enteritis was diagnosed. A stenosis was identified 60 cm distal to the start of the ileum, and partial resection of the small intestine was performed. The diagnosis of ischemic enteritis was confirmed. Ischemic enteritis affecting the small intestine is uncommon, and enteritis causing intestinal stenosis with hepatic portal vein gas is even rarer.

A case of robot-assisted resection for cecum cancer with anomalous venous confluence.

There are many reports on the positional relationship between the ileocolic artery and superior mesenteric vein (SMV). However, there have been no reports of anomalous venous confluence in the ileocecal vessel area. A 69-year-old man was diagnosed with cecal cancer on a preoperative examination of a lung tumor. We planned to perform surgery for the cecal cancer. Computed tomography angiography revealed an anomalous vein confluence in the ileocolic region. We performed robot-assisted ileocecal resection. Although the small intestinal vein was misidentified as the SMV at first, we confirmed the misidentification, identified the SMV on the dorsal side of the ileocolic artery, and ligated the ileocolic vessels with precise forceps manipulation during robotic surgery. Especially for cases with vascular anomalies revealed by preoperative computed tomography angiography, robotic surgery may be useful, as flexible forceps manipulation prevents vascular injury.

A case of MCA arising from ICA: a case report.

BACKGROUND: Complete mesocolic excision (CME) and central vascular detachment are very important procedures in surgery for colorectal cancer. Preoperative and intraoperative assessments of the anatomy of major colorectal vessels are necessary to avoid massive bleeding, especially in endoscopic surgery. A case with a rare anomaly in which the middle colic artery (MCA) and ileocolic artery (ICA) had a common trunk is reported. CASE PRESENTATION: The patient was a 73-year-old woman diagnosed with ascending colon cancer on colonoscopy. Preoperative abdominal contrast-enhanced computed tomography confirmed that the MCA and ICA had a common trunk. She underwent laparoscopic ileocecal resection for the ascending colon cancer with D3 lymph node dissection. Intraoperative indocyanine green fluorescence imaging was conducted. After confirming vessel bifurcation, the ICA was dissected at the distal end of the MCA bifurcation. The patient has been followed as an outpatient, with no signs of recurrence as of 2 years postoperatively. CONCLUSION: A case of an ascending colon cancer with a unique vascular bifurcation pattern was presented. Preoperative and intraoperative evaluations of the major colorectal vessels are very important for preventing perioperative and postoperative complications.

Early Laparoscopic Colostomy in Advanced Cancer Patients with Rectovaginal Fistula: Results of Seven Patients.

A rectovaginal fistula (RVF) is an abnormal tract between the rectum and vagina, which requires surgical intervention in many cases. Although there are many different therapeutic approaches for RVF depending on the patient's' condition, there are no established guidelines for the care of RVF. This study aimed to evaluate the results of laparoscopic colostomy in advanced cancer patients with RVF, and the safety and efficacy of this surgery. In this study, seven female advanced cancer patients with RVF were hospitalized and successfully treated with laparoscopic colostomy from 2015 to 2018 at our university hospital. Their data were retrospectively evaluated from their medical records. The early use of diverting stomas facilitated timely resumption of cancer treatment and enabled early treatment with chemotherapy or radiotherapy. Although vaginal stool leakage affected three patients, all patients recovered, experiencing neither pain nor infection during their cancer treatment. While colostomy was physically and mentally taxing for the patients, it improved the infection and pain caused by the RVF. We conclude that the early use of diverting stomas had two effects: a significant improvement in infection management and facilitation of the rapid resumption of cancer treatment.

Duration of antimicrobial therapy after video-assisted thoracoscopic surgery for thoracic empyema and complicated parapneumonic effusion: A single-center study.

BACKGROUND: There are no evidence-based reports on the proper duration of antimicrobial therapy following video-assisted thoracoscopic surgery debridement (VATS-D) in thoracic empyema (TE) or complicated parapneumonic effusion (PPE). This study aimed to investigate the optimal duration of antimicrobial therapy after VATS-D. METHODS: Between January 2011 and December 2019, 33 patients corresponding to American College of Chest Physicians (ACCP) category 3 or 4 undergoing VATS-D were included. The times until the body temperature (BT) was confirmed to be less than 37.5 °C and 37.0 °C, white blood cell count (WBC) less than 10,000/µl, segmented neutrophils (seg) less than 80%, and C-reactive protein (CRP) level less than 25% of the preoperative value were retrospectively analyzed. RESULTS: The median time from the onset of TE/PPE to surgery was 13 days. The median durations of preoperative and postoperative antibiotic use were five and seven days, respectively. Major complications occurred in four cases (three and one cases of respiratory failure and cerebral infarction, respectively). The median postoperative hospital stay was 14 days. Recurrence or progression to chronic empyema was seen in four cases. The median numbers of days until the conditions were met were three days for BT < 37.5 °C, six days for BT < 37.0 °C, four days for WBC<10,000, seven days for seg<80% and seven days for CRP<25%. CONCLUSIONS: The proper duration of antimicrobial therapy after VATS-D for TE/PPE is approximately three to seven days. Urgent VATS-D may shorten the total antibiotic usage.

Imaging Classification of Constipation.

Objectives: The diagnosis of patients with chronic constipation is very complicated. This study aimed to develop a simple imaging classification for the diagnosis of chronic constipation by abdominal computed tomography (CT). Methods: Sixty-two patients who underwent abdominal CT in our hospital between January and June 2022 were enrolled. The CT values of the stool in the rectum and cecum were measured in patients with chronic constipation (C group) and in those without (non-C group). Results: A strong correlation was observed between the Bristol Stool Form Scale (BSFS) and the CT value of rectal stool. Furthermore, the rectal stool CT value was significantly higher in patients with chronic constipation than in those without. The CT value of cecal stool did not differ between the two groups. The cecal stool CT value was significantly higher in patients with severe constipation (BSFS 1) than in those with BSFS 2-6. A cutoff CT value of 100 was selected as the optimal value for indicating chronic constipation. Conclusions: Abdominal CT was useful in the diagnosis of chronic constipation. If the patient had constipation, the optimal cutoff CT value was 100.

Efficacy of Coagulofibrinolytic Markers for Postoperative Prediction of Venous Thromboembolism in Colorectal Surgery Patients: A Retrospective Observational Study.

Objectives: A low rate of the incidence of venous thromboembolism (VTE) after surgeries that are preoperatively classified as having high risk of VTE has been reported in recent years. We seek to identify the optimal cases to receive perioperative pharmacologic thromboprophylaxis. In this study, we evaluated the incidence rate of VTE among patients undergoing colorectal surgery who did not receive perioperative pharmacologic thromboprophylaxis, and the ability of coagulofibrinolytic markers to predict the postoperative development of VTE. Methods: We retrospectively analyzed the rate of postoperative development of VTE in 70 patients undergoing elective colorectal surgery without perioperative pharmacologic thromboprophylaxis and the ability of coagulofibrinolytic markers to predict the development of VTE. Results: The incidence of VTE was observed in 11 patients (15.7%); all cases were asymptomatic and distal-type deep vein thrombosis (DVT). Comparisons of time course changes in perioperative coagulofibrinolytic markers between patients with and without DVT revealed significant differences in soluble fibrin (SF), thrombin-antithrombin complex (TAT), fibrin/fibrinogen degradation product (FDP) and D-dimer. Dynamic postoperative physiological coagulofibrinolytic responses were shown, but all four markers at each postoperative point demonstrated moderate accuracy (median area under the curve [AUC]: 0.788, median sensitivity: 0.865, median specificity: 0.644) for predicting the development of DVT. Conclusions: The incidence of postoperative VTE was low in patients with colorectal surgery even in those who did not receive perioperative pharmacologic thromboprophylaxis. SF, TAT, FDP and D-dimer were useful for predicting the development of DVT when we set cut-off values taking the physiological perioperative coagulofibrinolytic responses into consideration.

Do postoperative infectious complications really affect long-term survival in colorectal cancer surgery? A multicenter retrospective cohort study.

Aim: To investigate the impact of postoperative infection (PI), surgical site infection, and remote infection (RI), on long-term outcomes in patients with colorectal cancer (CRC). Methods: The Japan Society for Surgical Infection conducted a multicenter retrospective cohort study involving 1817 curative stage I/II/III CRC patients from April 2013 to March 2015. Patients were divided into the No-PI group and the PI group. We examined the association between PI and oncological outcomes for cancer-specific survival (CSS) and overall survival (OS) using Cox proportional hazards models and propensity score matching. Results: Two hundred and ninety-nine patients (16.5%) had PIs. The 5-year CSS and OS rates in the No-PI and PI groups were 92.8% and 87.6%, and 87.4% and 83.8%, respectively. Both the Cox proportional hazards models and propensity score matching demonstrated a significantly worse prognosis in the PI group than that in the No-PI group for CSS (hazard ratio: 1.60; 95% confidence interval: 1.10-2.34; P = .015 and P = .031, respectively) but not for OS. RI and the PI severity were not associated with oncological outcomes. The presence of PI abolished the survival benefit of adjuvant chemotherapy. Conclusions: These results suggest that PI after curative CRC surgery is associated with impaired oncological outcomes. This survival disadvantage of PI was primarily derived from surgical site infection, not RI, and PI induced lower efficacy of adjuvant chemotherapy. Strategies to prevent PI and implement appropriate postoperative treatment may improve the quality of care and oncological outcomes in patients undergoing curative CRC surgery.

Appropriate Antibiotic Selection during the in-hospital Waiting Period for Surgery for Appendicitis.

Objectives: Acute appendicitis is a common disease that often requires emergency surgery. However, recently, not all cases are treated as an urgent operation, but surgery may be delayed to when medical resources are abundant to perform the operation safely. In such cases, preoperative antibiotics are administered during the waiting period. Though the choice is empiric, an appropriate choice is needed to avoid emergency surgery. Guidelines for the choice of antibiotics recognized as international standards cannot be applied in Asia due to the high rate of extended-spectrum ß-lactamase (ESBL) producers or fluoroquinolone-resistant Escherichia coli. The purpose of this study was to determine the optimal antibiotic during the in-hospital waiting period for patients with appendicitis scheduled for surgery. Methods: Bacterial culture results and antibiotic susceptibility were retrospectively examined in 106 cases who underwent surgery for appendicitis. Results: Bacterial cultures were positive in 53 cases (50%). Twenty-six strains of E. coli were identified. Of these, four (15%) were ESBL producers, and seven (27%) were fluoroquinolone resistant. Twenty-two strains of anaerobic bacteria were identified. Carbapenems and tazobactam/piperacillin were effective for all. The rates of susceptibility to clindamycin (CLDM) and cefmetazole (CMZ) were 59% and 82%, respectively. Conclusions: In Japan, from the point of view of reducing carbapenem use, CMZ must be considered a first-choice drug during the in-hospital waiting period for appendectomy.

The arrival time of indocyanine green in tissues can be a quantitative index because of its correlation with tissue oxygen saturation: A clinical pilot study.

Indocyanine green (ICG) fluorescence angiography has recently been reported useful as a method for predicting intestinal blood flow and may reduce anastomotic leakage. However, the quantification method for ICG fluorescence angiography has not been established. We usually measure the tissue oxygen saturation (StO2 ) in the intestinal tract via near-infrared spectroscopy, as it is able to measure the oxygen concentration accurately and immediately shows objective data. In this study, we propose that the time to reach the anastomotic site after intravenous ICG injection is an effective parameter for quantifying ICG fluorescence angiography from the comparison to the data of StO2 in the intestinal tract.

Tumor Screening, Incidence, and Treatment for Patients with Severe Motor and Intellectual Disabilities.

BACKGROUND: The increasing age of patients with severe motor and intellectual disabilities (SMID) has become a serious concern. Few studies have investigated tumor treatment in this population. METHODS: Tumor treatments for 12 SMID patients were examined. RESULTS: Blood tests and ultrasonography were useful for screening. With regard to treatment, surgery for SMID patients was performed in the same manner as for patients without SMID, and the results were generally satisfactory, without major complications. Typically, cancer was diagnosed at an advanced stage, and many metachronous double cancers were observed. CONCLUSIONS: Treatment yielded satisfactory results for patients with SMID and their families. Future studies should examine the clinical significance of screening and tumor operative method for patients with SMID.

A Trial Protocol of Precision Medicine for Patients with RAS Wild Metastatic Colorectal Cancer Using Liquid Biopsy (RAS-liquid Study): A Prospective, Multicenter Observational Study.

BACKGROUND: Anti-epidermal growth factor receptor (EGFR) therapy has been identified to prolong the survival of metastatic colorectal cancer (mCRC) patients without RAS mutations. However, its efficacy is not always consistent for these patients. Genomic profiles of primary tumors and metastases are not always concordant; thus, chemotherapeutic agents can alter the tumor molecular profile. This molecular heterogeneity may explain resistance to anti-EGFR therapy. Liquid biopsy using circulating tumor DNA (ctDNA) is a novel, non-invasive diagnostic tool that can accommodate this molecular heterogeneity, providing a comprehensive, real-time view of the molecular landscape. In this study, we evaluated the predictive value of genomic mutations in ctDNA for primary and acquired resistance to anti-EGFR therapy. METHODS/DESIGN: This study is a prospective, multicenter, observational study of mCRC patients with wild-type tissue RAS treated with cytotoxic agents and anti-EGFR antibodies as first-line therapy. Genomic mutations, including RAS, BRAF, PIK3CA, and EGFR in ctDNA, are assessed via Droplet Digital PCR before starting chemotherapy and every 3 months thereafter until disease progression. The target sample size is estimated to be 100. The primary endpoint is the response rate in patients without RAS mutation in their blood sample before starting chemotherapy. DISCUSSION: This study will clarify the predictive value of baseline RAS mutation in ctDNA for responses to anti-EGFR therapy; the frequency of emerging RAS, BRAF, PIK3CA, and EGFR mutations in ctDNA; and the association with secondary resistance to anti-EGFR therapy in first-line therapy for wild-type tissue RAS mCRC patients.