Pathologic Complete Response and Long-Term Survival After Preoperative Chemotherapy for Transverse Colon Cancer With Para-Aortic Lymph Node Metastases.

A 52-year-old male patient was diagnosed with transverse colon cancer and synchronous stage IVA para-aortic lymph node (PALN) metastases (cT3N1bM1a of the lymph node). Six courses of mFOLFOX6 plus bevacizumab were administered as neoadjuvant chemotherapy. Computed tomography showed shrinkage of the primary tumor and PALN metastases. Extended right hemicolectomy, D3 lymph node dissection, and PALN dissection were performed. A pathologic examination indicated that the tumor had completely changed and comprised necrotic tissue with no viable cells. Therefore, it was considered that mFOLFOX6 plus bevacizumab resulted in a pathologic complete response. Postoperatively, six courses of mFOLFOX6 were administered. Six years postoperatively, the patient did not exhibit any signs of recurrence. There have been few reports of pathologic complete response after neoadjuvant therapy and resection for colon cancer with synchronous PALN metastases. This report describes a unique case involving a pathologic complete response with long-term survival after mFOLFOX6 plus bevacizumab and radical resection, including PALN dissection. Preoperative mFOLFOX6 plus bevacizumab followed by radical resection and adjuvant mFOLFOX6 therapy was safe and resulted in a good outcome. This regimen should be considered for advanced colon cancer with PALN metastases.

Effects of neoadjuvant chemotherapy for patients with obstructive colon cancer: A multicenter propensity score-matched analysis (YCOG2101).

Aim: Obstructive colon cancer is locally advanced colon cancer with poor prognosis. However, the effect of neoadjuvant chemotherapy (NAC) on obstructive colon cancer remains unclear. Therefore, this study aimed to investigate the safety and efficacy of NAC in patients with obstructive colon cancer. Methods: From January 2012 to December 2017, we collected patient data for clinical stage II/III obstructive colon cancer at seven Yokohama Clinical Oncology Group (YCOG) institutions. The long-term outcomes of the NAC and non-NAC groups were analyzed retrospectively after adjusting for patients' background characteristics using propensity score matching. Results: Among the 202 eligible patients, propensity score matching extracted 51 patients each for the NAC and non-NAC groups. After matching, the groups showed no marked differences in the background factors. All the patients in the NAC group underwent diverting stoma construction. Nineteen patients (37.3%) experienced grade 3-4 adverse events during NAC. The incidence of postoperative complications was similar between groups. The 5-year progression-free survival rates were 75.8% in the NAC group and 63.0% in the non-NAC group (p = 0.22, log-rank test). The 5-year overall survival rates were 88.5% in the NAC group and 78.8% in the non-NAC group (p = 0.09, log-rank test). Conclusion: Although NAC was feasible for obstructive colon cancer after diverting stoma construction, its effects on long-term outcomes could not be proven.

Multicenter randomized phase II study on S-1 and oxaliplatin therapy as an adjuvant after hepatectomy for colorectal liver metastases (YCOG1001).

PURPOSE: The high recurrence rate of colorectal cancer liver metastasis (CRCLM) after surgery remains a crucial problem. However, adjuvant chemotherapy after hepatectomy for CRCLM has not yet been established. This study evaluated the efficacy of adjuvant therapy with S-1 and oxaliplatin (SOX). METHODS: In a multicenter, randomized, phase II study, patients undergoing curative resection of CRCLM were randomly enrolled in a 1:1 ratio to either the low- or high-dose group. S-1 and oxaliplatin were administered from days 1 to 14 of a 3-week cycle as a 2-h infusion every 3 weeks. The dose of S-1 was fixed at 80 mg/m2. The doses in the low- and high-dose oxaliplatin groups were 100 mg/m2 (low-dose group) and 130 mg/m2 (high-dose group), respectively. This treatment was repeated eight times. The primary endpoint was the rate of discontinuation owing to toxicity. The secondary endpoints were the relapse-free survival (RFS) and frequency of adverse events (AEs). RESULTS: Between August 2010 and March 2015, 44 patients (low-dose group: 31 patients and high-dose group: 13 patients) were enrolled in the study. Of these, one patient was excluded from the efficacy analysis. In the high-dose group, five of nine patients were unable to continue the study due to toxicity in February 2013. At that time, recruitment to the high-dose group was stopped from the protocol. The relative dose intensity (RDI) for S-1 in the low- and high-dose groups were 49.8 and 48.7% (p = 0.712), and that for oxaliplatin was 75.9 and 73.0% (p = 0.528), respectively. The rates of discontinuation due to toxicity were 60 and 53.8% in the low- and high-dose groups, respectively, with no marked difference noted between the groups (p = 0.747). The frequency of grade ≥ 3 common adverse events was neutropenia (23.3%/23.1%), diarrhea (13.3%/15.4%), and peripheral sensory neuropathy (6.7%/7.7%). The disease-free survival (DFS) at 3 years was 52.9% in the low-dose group, which was not significantly different from that in the high-dose group (46.2%; p = 0.705). CONCLUSIONS: SOX regimens as adjuvant therapy after hepatectomy for CRCLM had high rates of discontinuation due to toxicity in both groups. In particular, the RDI of S-1 was < 50%. Therefore, the SOX regimen is not recommended as adjuvant chemotherapy after hepatectomy for CRCLM.

Exploratory randomized phase II trial for optimizing treatment dosage and duration of adjuvant S-1 plus oxaliplatin in patients with stage III colon cancer: YCOG1402 (SOAP trial).

Introduction: Conventionally, the recommended duration of adjuvant chemotherapy of colon cancer had been 6 months. The IDEA Collaboration suggested that shortening capecitabin and oxaliplatin (CAPOX) adjuvant chemotherapy may be possible. S-1 and oxaliplatin (SOX) treatment is standard treatment in metastatic colorectal cancer in Japan. The aim of this study was to optimize treatment dosage and duration of adjuvant SOX in stage III colon cancer. Methods: This trial was as open-label multi-center randomized phase II study. Patients with stage III colon cancer were randomly assigned to 3 months or 6 months of adjuvant SOX treatment in different doses: 130 mg/m2 (3 months) or 100 mg/m2 (6 months) of oxaliplatin. The primary endpoint was 3-year disease-free survival (DFS) and the null hypothesis for the primary endpoint was that the 3-year DFS was ≤72% in each arm and was tested with a one-sided significance level of 10%. Results: Eighty-two patients were assigned to the 6 months arm and 81 to the 3 months arm. The 3-year DFS was 75.0% (80% CI 67.95-80.72, p = 0.282) in the 6 months arm and 76.9% (80% CI 70.1-82.38, p = 0.171) in the 3 months arm. Treatment completion rate and relative dose intensity (RDI) were higher in 3 months than 6 months arm. The adverse events (AE) were similar in both arms. Conclusions: The 3-year DFS was not significantly superior to null hypothesis in both 3 months and 6 months arms for the stage III colon cancer. Primary endpoint was not achieved. The SOX regimen was not feasible in long-term outcomes.

Pancreas-sparing partial duodenectomy as an alternative to emergency pancreaticoduodenectomy for a major duodenal perforation: a case report.

A 71-year-old woman underwent endoscopic submucosal dissection for early duodenal cancer at the second portion of the duodenum and developed acute peritonitis due to delayed duodenal perforation. Emergency laparotomy was performed. A huge perforation formed at the descending duodenum without ampulla involvement. Pancreas-sparing partial duodenectomy (PPD) with gastrojejunostomy was performed (250 min operative time) with 50 mL of intraoperative blood loss. She required intensive care for 3 days and was discharged on postoperative day 21 with no severe complications. Emergency treatment for a major duodenal injury or perforation remains challenging because of high morbidity and mortality. An appropriate treatment should be considered according to the nature of the defect. Although PPD is an acceptable procedure for patients with a duodenal neoplasm, its use in emergency surgery is rarely reported. PPD is more reliable than primary repair or anastomosis using a jejunal wall, and less invasive than pancreaticoduodenectomy, for emergency treatment. We performed PPD in this patient because the duodenal perforation was too large to reconstruct and did not involve the ampulla. PPD can be a safe and feasible alternative surgical procedure to pancreaticoduodenectomy for a major duodenal perforation, especially in patients with a duodenal perforation that does not involve the ampulla.

Modified Intestinal Derotation Procedure with Reversed Kocherization to Facilitate Mesopancreas Excision During Pancreaticoduodenectomy.

BACKGROUND: Although intestinal derotation procedure has advantages of facilitating mesopancreas excision during pancreaticoduodenectomy, the wide mobilization takes time and risks injuring other organs. This article describes a modified intestinal derotation procedure in pancreaticoduodenectomy and its clinical impact on short-term outcomes. METHODS: The modified procedure comprised the pinpoint mobilization of the proximal jejunum following reversed Kocherization. Among 99 consecutive patients who underwent pancreaticoduodenectomy between 2016 and 2022, the short-term outcomes of pancreaticoduodenectomy with the modified procedure were compared with those of conventional pancreaticoduodenectomy. The feasibility of the modified procedure was investigated based on the vascular anatomy of the mesopancreas. RESULTS: Compared with conventional pancreaticoduodenectomy (n = 55), the modified procedure (n = 44) involved less blood loss and shorter operation time (p < 0.001 and 0.017, respectively). Severe morbidity, clinically relevant postoperative pancreatic fistula, and prolonged hospitalization occurred less often with the modified procedure compared with conventional pancreaticoduodenectomy (p = 0.003, 0.008, and < 0.001, respectively). According to preoperative image findings, most (72%) patients had a single inferior pancreaticoduodenal artery sharing a common trunk with the first jejunal artery. The inferior pancreaticoduodenal vein drained into the jejunal vein in 71% of the patients. The first jejunal vein ran behind the superior mesenteric artery in 77% of the patients. CONCLUSIONS: By combining our modified intestinal derotation procedure with preoperative recognition of the vascular anatomy of mesopancreas, mesopancreas excision during pancreaticoduodenectomy can be performed safely and accurately.

Lengthened Efferent Limb in Braun Enteroenterostomy Reduces Delayed Gastric Emptying After Pancreaticoduodenectomy.

BACKGROUND: Delayed gastric emptying (DGE) is a common complication after pancreaticoduodenectomy (PD), but a method to prevent DGE has not been established. This study aims to demonstrate a novel technique utilizing a lengthened efferent limb in Billroth-II (B-II) reconstruction during PD and to evaluate the impact of the longer efferent limb on DGE occurrence. METHODS: Patients who underwent PD with B-II reconstruction were divided into two groups: PDs with lengthened (50-60 cm) efferent limb (L group) and standard length (0-30 cm) efferent limb (S group). Postoperative outcomes were compared. DGE was defined and graded according to the International Study Group of Pancreatic Surgery criteria. RESULTS: Among 283 consecutive patients who underwent PD from 2002 to 2021, 206 patients were included in this study. Patients who underwent Roux-en-Y reconstruction (n = 77) were excluded. Compared with the S group, the L group included older patients and those who underwent PD after 2016 (p = 0.025, < 0.001, respectively). D2 lymphadenectomy, antecolic route reconstruction, and Braun enteroenterostomy were performed more frequently in the L group (p = 0.040, < 0.001, < 0.001, respectively). The rate of DGE was significantly decreased to 6% in the L group, compared with 16% in the S group (p = 0.027), which might lead to a shorter hospital stay in the L group (p < 0.001). Multivariable analysis identified two factors as independent predictors for DGE: intraabdominal abscess [odds ratio (OR) 5.530, p = 0.008] and standard efferent limb length (OR 2.969, p = 0.047). CONCLUSION: A lengthened efferent limb in Braun enteroenterostomy could reduce DGE after PD.

Relationship between stromal regulatory T cells and the response to neoadjuvant chemotherapy for locally advanced rectal cancer.

BACKGROUND: In addition to the direct power of anticancer drugs, the effectiveness of anticancer therapy depends on the host immune function. The present study investigated whether or not the reduction rate and histological response of preoperative chemotherapy were related to the immune microenvironment surrounding a primary tumor of the rectum. METHODS: Sixty-five patients received preoperative chemotherapy followed by resection from 2012 to 2014; all of these patients were retrospectively analyzed. CD3, CD8, and FoxP3 were immunohistochemically examined as markers for T lymphocytes, cytotoxic T lymphocytes, and regulatory T lymphocytes (Treg), respectively. The correlation between the tumor-infiltrating lymphocyte composition and the tumor reduction rate and histological response to neoadjuvant chemotherapy was investigated. RESULTS: The average tumor reduction rate was 41.5% ± 18.8%. According to RECIST, 47 patients (72.3%) achieved a partial response (PR), and 1 patient (1.5%) achieved a complete response (CR). Eight patients (12.3%) showed a grade 2 histological response, and 2 (3.1%) showed a grade 3 response. A multivariate analysis demonstrated that a low Treg infiltration in stromal cell areas was significantly associated with the achievement of a PR or CR [odds ratio (OR) 7.69; 95% confidence interval (CI) 1.96-33.33; p < 0.01] and a histological grade 2 or 3 response (OR 11.11; 95% CI 1.37-98.04; p = 0.02). CONCLUSION: A low Treg infiltration in the stromal cell areas may be a marker of a good response to neoadjuvant chemotherapy in patients with locally advanced rectal cancer.

Cystic Lesion of Dissected Pararectal Lymph Node in a Female Patient With Rectal Carcinoma: A Rare Pattern of Nodal Metastasis Mimicking a Serous Inclusion Cyst.

Nodal metastatic foci of colorectal carcinoma are usually solid nodules. Serous inclusions are occasionally found in lymph nodes, particularly in female patients, and they occasionally form cysts. An 86-year-old woman was treated with laparoscopic low anterior resection and D3 lymph node dissection for advanced rectal carcinoma. A cyst with serous fluid and no necrotic debris was found within one of the dissected pararectal lymph nodes. Histologically, the cyst was lined by low columnar-to-cuboid epithelium with mild nuclear atypia, mimicking a serous inclusion cyst. Immunohistochemically, the epithelial cells were positive for caudal type homeobox 2 and negative for Wilms' tumor suppressor gene1. Immunohistochemistry for p53 showed a diffuse strong positivity, indicating a mutant TP53 as seen in primary rectal carcinoma. Thus, the nodal cystic lesion was confirmed to be a metastatic lesion. It is important to carefully assess a nodal cystic lesion to confirm whether it is benign or malignant.

Long-term survival after pancreatic metastasis resection from breast cancer: a systematic literature review.

BACKGROUND: Patients with advanced-stage breast cancer often demonstrate pancreatic metastases. However, pancreatic metastases resection from breast cancer has been rarely performed, with only 20 cases having been reported to date. CASE PRESENTATION: A 49-year-old woman presented to our hospital in September 2003 with complaints of uncontrollable oozing from her left breast tumor. Computed tomography revealed a left breast tumor approximately 9.3 cm in diameter as well as heterogeneously enhanced solid mass lesions with necrotic foci in the pancreatic tail and body, up to 6.2 cm, which were radiologically diagnosed as pancreatic metastases from breast cancer. An emergent left simple mastectomy was performed to control bleeding. After epirubicin and cyclophosphamide hydrate treatment failed to improve her condition, the pancreatic metastases responded to weekly paclitaxel treatment, but eventually regrew. The patient underwent distal pancreatectomy with splenectomy, left adrenalectomy, partial stomach resection, and paraaortic lymph nodes excision in December 2004 after no other metastasis was confirmed. Furthermore, she received radiation therapy for left parasternal lymph node metastasis 6 months later. The patient recovered well. Consequently, she has no evidence of disease > 15 years after pancreatectomy. CONCLUSIONS: This is the first reported case of pancreatectomy for pancreatic metastases from breast cancer, which was simultaneously diagnosed. Patients with no metastasis other than resectable pancreatic metastases and breast cancer and who possess some sensitivity for chemotherapy may benefit from pancreatectomy.

A novel discriminant formula for the prompt diagnosis of strangulated bowel obstruction.

PURPOSES: The diagnosis of strangulated bowel obstruction (SBO) is sometimes difficult. We attempted to create and verify a discriminant formula for use as a diagnostic aid for the early diagnosis of SBO. METHODS: This retrospective study included 97 patients who underwent an operation for SBO from January 2007 to September 2018. First, a discriminant analysis was performed for 73 patients who underwent an operation from January 2007 to December 2015 in order to obtain a formula. Next, we analyzed 34 patients who underwent an operation from January 2016 to September 2018 to verify the formula. RESULTS: The risk factors for SBO included ascites, signs of preperitoneal irritation, and lactate > 1.16 mmol/L. The discriminant formula is as follows: 1.954 × collection of ascites (1 or 0) + 1.239 × peritoneal irritation sign (1 or 0) + 0.378 × lactate - 2.331 (1: positive, 0: negative). The predictive value was as follows: sensitivity, 87.5%; specificity, 64.7%; and predictive accuracy, 73.5%. In patients who presented within 24 h of the onset, the sensitivity was 92.3%, the specificity was 75.0%, and the predictive accuracy was 85.7%. CONCLUSION: Our discriminant formula seems useful for the rapid diagnosis of SBO.

[A Surgical Case of Desmoid Tumor in the Transverse Mesocolon with Pancreatic Invasion].

A 40-year-old man with no previous history of abdominal surgery or noteworthy family history presented to our hospital because of a palpable abdominal mass. Abdominal CT revealed a 9 cm diameter mass in the mesocolon. The differential diagnosis included desmoid tumor, and right hemicolectomy with partial resection of the pancreas head and duodenum was performed. Pathologically, the tumor cells were negative for S-100, c-kit, CD34, and desmin but partially positive for a-SMA and slightly for b-catenin. From these findings, desmoid tumor of the mesocolon was diagnosed. Invasion of the pancreas was also found. Desmoid tumor is pathologically benign, but because of its malignant-like characteristics, such as direct invasion and local recurrence, it is treated as a malignant tumor. Desmoid tumors are associated with familial adenomatous polyposis coli and Gardner syndrome, or they arise in patients who have a history of laparotomy or antecedent trauma. In this paper, we report a rare case of resected sporadic desmoid tumor in the mesocolon with pancreatic invasion, together with a review of the literature.

Colonic Neurogenic Lesion: An Admixture of Mucosal Neurofibromatous Lesion and Submucosal Ganglioneuromatous Lesion With Transition.

Benign neural tumors or tumor-like lesions are rarely detected in the gastrointestinal tract. In this article, we present the case of a neural lesion of the sigmoid colon, which was incidentally detected in a 68-year-old man treated with laparoscopic low anterior resection for an advanced carcinoma of the rectosigmoid junction. Within the resected specimen, a submucosal tumor-like protruding lesion was found in the sigmoid colon. Histologically, the growth was composed of mucosal neurofibromatous and submucosal ganglioneuromatous lesions, between which there was transition. Immunohistochemical analysis revealed a rupture of the perineurium in the area of transition, along with a proliferation of Schwann cells and supporting cells extending into the deep mucosa. This transition indicated that the mucosal and submucosal lesions comprised a single lesion, and that a diagnosis of neurofibroma or ganglioneuroma would be inadequate in this case. Because we could not classify it as an established single entity, we diagnosed the mass as an unclassifiable colonic neurogenic lesion. In summary, we report the case of an extremely rare occurrence of an unclassifiable colonic neurogenic lesion comprising an admixture of transitioning mucosal neurofibromatous and submucosal ganglioneuromatous lesions.

Efficacy and safety of enoxaparin for preventing venous thromboembolic events after laparoscopic colorectal cancer surgery: a randomized-controlled trial (YCOG 1404).

PURPOSE: We conducted a prospective study to evaluate the efficacy and safety of postoperative enoxaparin for the prevention of venous thromboembolism (VTE) after laparoscopic surgery for colorectal cancer (LAC) in Japanese patients. METHODS: The subjects of this multicenter, open-label randomized-controlled trial were 121 patients who underwent LAC between September 2015 and May 2017. The patients were randomly allocated to receive intermittent pneumatic compression (IPC) with enoxaparin (20 mg, twice daily), started 24-36 h after surgery and continued until discharge (Enoxaparin group; n = 61), or IPC alone (IPC group; n = 60). The primary endpoint was the incidence of VTE on day 28 after surgery. The safety outcome was the incidence of any bleeding during treatment and follow-up. RESULTS: The incidence of VTE on day 28 after surgery was 12.3% (7/57 patients) in the enoxaparin group and 11.9% (7/59 patients) in the IPC group ((p = 1.00). One of the 57 patients (1.8%) in the enoxaparin group and none in the IPC group experienced a bleeding event. CONCLUSIONS: It may be unnecessary to give enoxaparin to all Japanese patients for the prevention of VTE after LAC. The UMIN Clinical Trials Registry number was UMIN000018633.

Risk factors for incisional surgical site infection after elective laparoscopic colorectal surgery.

BACKGROUND: Surgical site infection (SSI) is a common morbidity in patients undergoing colorectal surgery, and the focus of previous studies has primarily been on incisional SSI. Most reports thus far have focused on open surgery rather than on laparoscopic colorectal surgery (Lap CR). Therefore, the aim of the present study was to identify the risk factors for incisional SSI in patients undergoing elective Lap CR. METHODS: This retrospective study was conducted to evaluate the occurrence and risk factors of incisional SSI for elective Lap CR. From January 2008 to June 2018, 1825 consecutive patients with a preoperative diagnosis of colorectal cancer who underwent Lap CR were analyzed at a single institution. RESULTS: Incidence of incisional SSI was 3.3%. Postoperative hospital stay (days) was significantly longer in the incisional SSI group than in the non-incisional SSI group (8 [6-12] vs 10 [8-19], P < 0.001). Incisional SSI were significantly associated with five operative factors: blood loss (g) (P < 0.014), midline wound length (mm) (P = 0.038), suture materials (P = 0.014), suture technique (interrupted vs continuous mass closure, P = 0.003), and organ/space SSI (P = 0.041). Multivariate analysis showed that continuous mass closure (odds ratio 0.290; 95% confidence interval 0.101-0.831, P = 0.021) was the only factor independently associated with the incidence of incisional SSI. CONCLUSIONS: Incidence of incisional SSI was comparable to that in previous reports. Continuous mass closure decreased the risk of incisional SSI in elective Lap CR.

Randomized phase II trial of the prophylactic use of celecoxib for the prevention of oxaliplatin-related peripheral vascular pain in Capeox (YCOG1205).

PURPOSE: Capeox is widely used as an adjuvant chemotherapy regimen of colorectal cancer that does not require central vein catheter insertion. However, oxaliplatin-related vascular pain with peripheral administration is a major adverse event. We assessed the preventive effect of Celecoxib on oxaliplatin-related vascular pain. METHODS: A multicenter study of the Yokohama Clinical Oncology Group (YCOG) in Japan. This study was an open label, randomized non-comparative phase II study between Capeox without Celecoxib (C+ Group) and with it (C- group). The primary endpoint was the appearance frequency of grade ≥ 2 vascular pain according to the Verbal Rating Scale (VRS). RESULTS: Between October 2012 and February 2014, 81 patients were recruited to this study and randomly divided into 2 groups: 38 patients in the C- group and 39 patients in the C+ group. Four cases were excluded at the analysis stage because they had not received the allocated intervention. The rate of grade ≥ 2 vascular pain was 55.3% in the C- group and 53.8% in the C+ group (p = 1.000). CONCLUSIONS: Celecoxib was unable to prevent oxaliplatin-related vascular pain in this study. However, it may be able to decrease the vascular pain that patients already have.

Tumor-targeting Salmonella typhimurium A1-R overcomes partial carboplatinum-resistance of a cancer of unknown primary (CUP).

Cancer of unknown primary (CUP) is metastatic disease without a known primary and therefore very difficult to identify effective therapy. Previously, we demonstrated partial efficacy of Salmonella typhimurium A1-R (S. typhimurium A1-R) alone and carboplatinum alone (CAR) on a CUP patient tumor in the patient-derived xenograft (PDOX) model. The aim of the present study was to investigate the efficacy of S. typhimurium A1-R combined with CAR on the CUP PDOX model. The CUP tumors were implanted orthotopically into the left supraclavicular fossa of nude mice to match the site from which they were resected from the patient. CUP PDOX models were divided randomly into the following 4 groups after the tumor volume reached 100 mm3: G1: untreated group; G2: CAR (30 mg/kg, i.p., weekly, 2 weeks); G3: S. typhimurium A1-R (5x107 CFU/body, i.v., weekly, 2 weeks).; G4: S. typhimurium A1-R combined with CAR (S. typhimurium A1-R; 5x107 CFU/body, i.v., weekly, 2 weeks; CAR, 30 mg/kg, i.p., weekly, 2 weeks). Each group comprised 7 mice. All mice were sacrificed on day 15. Tumor volume and body weight were measured twice a week. S. typhimurium A1-R and CAR moderately inhibited tumor growth compared to the untreated group on day 15 (P < 0.001 and P < 0.001, respectively). S. typhimurium A1-R combined with CAR inhibited the tumor growth significantly more compared to S. typhimurium A1-R monotherapy or CAR monotherapy on day 15 (P = 0.004 and P = 0.001, respectively). The present report demonstrates that S. typhimurium A1-R can increase the efficacy of a standard drug used for CUP in a PDOX model.

Tumor-targeting Salmonella typhimurium A1-R suppressed an imatinib-resistant gastrointestinal stromal tumor with c-kit exon 11 and 17 mutations.

Gastrointestinal stromal tumor (GIST) is a refractory disease in need of novel efficacious therapy. The aim of our study was to evaluate the effectiveness of tumor-targeting Salmonella typhimurium A1-R (S. typhimurium A1-R) using on a patient derived orthotopic xenograft (PDOX) model of imatinib-resistant GIST. The GIST was obtained from a patient with regional recurrence, and implanted in the anterior gastric wall of nude mice. The GIST PDOX mice were randomized into 3 groups of 6 mice each when the tumor volume reached 60 mm3: G1, control group; G2, imatinib group (oral administration [p.o.], daily, for 3 weeks); G3, S. typhimurium A1-R group (intravenous [i.v.] injection, weekly, for 3 weeks). All mice from each group were sacrificed on day 22. Relative tumor volume was estimated by laparotomy on day 0 and day 22. Body weight of the mouse was evaluated 2 times per week. We found that S. typhimurium A1-R significantly reduced tumor growth in contrast to the untreated group (P = 0.001). In addition, we found that S. typhimurium A1-R was more effective compared to imatinib (P = 0.013). Furthermore, Imatinib was not significantly effective compared to the control group (P = 0.462). These results indicate that S. typhimurium A1-R may be new effective therapy for imatinib-resistant GIST and therefore a good candidate for clinical development of this disease.