Outcomes of definitive carbon-ion radiotherapy for cT1bN0M0 esophageal squamous cell carcinoma.

BACKGROUND: A recent phase I/II study determined the optimal dose of definitive carbon-ion radiotherapy (CIRT) for cT1bN0M0 esophageal cancer. This study aimed to further confirm the efficacy and feasibility of the recommended dose fractionation of CIRT with long-term follow-up results in a larger sample size. METHODS: This single center retrospective study evaluated patients with cT1bN0M0 esophageal squamous cell carcinoma treated with the recommended dose fractionation of 50.4 Gy relative biological effectiveness in 12 fractions, between 2012 and 2022. RESULTS: Thirty-eight patients underwent CIRT at our hospital. Although eight (21.1%) patients were older than 80 years, 15 (39.5%) had high surgical risk, and seven (18.4%) were at high risk for chemotherapy, all patients underwent CIRT as scheduled. Grade 3 esophagitis occurred in eight (21.1%) patients and grade 3 pneumonia in one (2.6%) patient in this study, but no grade 4 adverse events occurred. The only grade 3 late adverse event was pneumonia in one patient (2.6%). The 5-year overall survival rate, local control rate, and disease-free survival rates were 76.6% (95% CI, 90.9-62.4), 74.9% (95% CI, 90.7-59.0), and 66.4% (95% CI, 83.3-49.5), respectively. Additionally, post CIRT recurrence was as follows: seven (18.4%) patients had recurrence in another part of the esophagus, three (7.9%) in the primary site, three (7.9%) in lymph nodes outside the irradiated area, and one (2.6%) patient had liver metastasis. CONCLUSIONS: Our study demonstrates that CIRT using the recommended dose fractionation is feasible and effective for cT1bN0M0 esophageal squamous cell carcinoma.

Prognostic Impact of Hepatic Steatosis Evaluated by CT on Immunotherapy for Gastric Cancer: Associations with Sarcopenia, Systemic Inflammation, and Hormones.

INTRODUCTION: Immune checkpoint inhibitors (ICIs) are expected to improve the prognosis of gastric cancer (GC). Also, hepatic steatosis has been reported to be associated with cancer cachexia and is expected to be a cancer biomarker. The purpose of this study was to evaluate prognostic impact of hepatic steatosis in ICI therapy for GC. METHODS: Unresectable or recurrent GC treated with ICIs was investigated. Using unenhanced CT, the liver-to-spleen CT attenuation ratio (LSR) was calculated as a parameter of hepatic steatosis. LSR was compared with the presence of sarcopenia and inflammatory markers including neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and monocyte-to-lymphocyte ratio (MLR). These parameters were also compared with disease-specific survival (DSS) and progression-free survival (PFS). Associations of LSR with insulin-like growth factor 1 (IGF-1) and growth hormone were also evaluated. RESULTS: A total of 70 patients were investigated. LSR of sarcopenia patients was significantly lower than that of non-sarcopenic ones (p = 0.02). LSR showed significant negative correlations with NLR, PLR, and MLR (p = 0.003, 0.03, 0.01, respectively). Lower LSR was significantly associated with a higher level of serum IGF-1 (p = 0.03). In univariate analysis, LSR was significantly correlated with DSS and PFS (both p < 0.0001), and multivariate analysis demonstrated that LSR was the independent prognostic factor for both DSS and PFS (both p = 0.01). ROC analysis demonstrated that LSR >1.263 was a good predictive marker for favorable DSS (>5.3 months) with an AUC of 0.80. CONCLUSION: Hepatic steatosis can be a promising prognostic biomarker for ICI therapy of GC, associated with sarcopenia and the elevation of inflammatory markers. Our data suggested that GC with steatohepatitis might be less responsive to ICI therapy.

Comparison of estimated treatment effects between randomized controlled trials, case-matched, and cohort studies on laparoscopic versus open distal gastrectomy for advanced gastric cancer: a systematic review and meta-analysis.

PURPOSE: In actual surgical research, case-matched studies are frequently conducted as an alternative to randomized controlled trials (RCTs). However, it is still unclear what differences there are between RCTs and case-matched studies in upper gastrointestinal surgery, and clarifying them is a very important clinical issue. Thus, the purpose of this study was to investigate estimated treatment effects between RCTs, case-matched studies, and cohort studies regarding laparoscopic distal gastrectomy (LDG) for advanced gastric cancer (AGC). METHODS: We searched the PubMed, Cochrane Central Register of Controlled Trials, and Web of Science databases for studies that compared LDG versus open distal gastrectomy for AGC published from the inception of the databases until July 2021. A meta-analysis was performed using the Review Manager version 5.3 software program from the Cochrane Collaboration, and six short-term outcomes and three long-term outcomes were assessed. RESULTS: Twenty-three studies with 13698 patients were included. There was no difference in estimated treatment effects between RCTs and case-matched studies for all outcomes except for the number of retrieved lymph nodes and postoperative complications. In terms of intraoperative blood loss, postoperative hospital stay, number of retrieved lymph nodes, and recurrence, observational studies tended to overestimate the treatment effects. CONCLUSION: The estimated treatment effects of LDG for AGC in the case-matched study were almost the same as in the RCTs. However, to assess the true magnitude of the treatment effect, the design and actual implementation of the analysis must be critically evaluated.

Biased expression of mutant alleles in cancer-related genes in esophageal squamous cell carcinoma.

BACKGROUND: Recent progress of large-scale international studies has provided comprehensive catalogs of somatic mutations in cancers. Additionally, it has become evident that allelic imbalance in the abundance of somatic mutations between DNA and RNA were pervasive in various types of cancer. However, the allelic imbalance of the abundance of somatic mutations in esophageal squamous cell carcinoma (ESCC) has not been fully analyzed. METHODS: We performed exome sequencing for 25 Japanese patients with ESCC to detect a comprehensive catalog of somatic mutations in ESCC. Additionally, we performed mRNA sequencing to evaluate the allelic imbalance of the identified somatic mutations at the transcriptional level by comparing the mutant allele frequencies between RNA and DNA. RESULTS: The exome sequencing showed that TP53 and ZNF750 were significantly mutated genes. The expression levels of TP53 and ZNF750 were different depending on the mutation status. In almost all the tumors with missense mutations in TP53 and ZNF750, the mutant allele frequencies were higher in the RNA sequencing than those in the exome sequencing, indicating that the mutant alleles were preferentially expressed. By examining the allelic imbalances for all the identified missense mutations, we demonstrated that genes showing preferential expressions of the mutant alleles were involved in the pathways including cell cycle, cell death, and chromatin modification. CONCLUSIONS: The results of this study suggest that the allelic imbalance of the abundance of somatic mutations plays important roles in the initiation and progression of ESCC by modulating cancer-related biological pathways.

Computed tomography-derived biomarker for predicting the treatment response to neoadjuvant chemoradiotherapy of rectal cancer.

BACKGROUND: Malignant tumor essentially implies structural heterogeneity. Analysis of medical imaging can quantify this structural heterogeneity, which can be a new biomarker. This study aimed to evaluate the usefulness of texture analysis of computed tomography (CT) imaging as a biomarker for predicting the therapeutic response of neoadjuvant chemoradiotherapy (nCRT) for locally advanced rectal cancer. METHODS: We enrolled 76 patients with rectal cancer who underwent curative surgery after nCRT. Texture analyses (Fractal analysis and Histogram analysis) were applied to contrast-enhanced CT images, and fractal dimension (FD), skewness, and kurtosis of the tumor were calculated. These CT-derived parameters were compared with the therapeutic response and prognosis. RESULTS: Forty-six of 76 patients were diagnosed as clinical responders after nCRT. Kurtosis was significantly higher in the responders group than in the non-responders group (4.17 ± 4.16 vs. 2.62 ± 3.19, p = 0.04). Nine of 76 patients were diagnosed with pathological complete response (pCR) after surgery. FD of the pCR group was significantly lower than that of the non-pCR group (0.90 ± 0.12 vs. 1.01 ± 0.12, p = 0.009). The area under the receiver-operating characteristics curve of tumor FD for predicting pCR was 0.77, and the optimal cut-off value was 0.84 (accuracy; 93.4%). Furthermore, patients with lower FD tumors tended to show better relapse-free survival and disease-specific survival than those with higher FD tumors (5-year, 80.8 vs. 66.6%, 94.4 vs. 80.2%, respectively), although it was not statistically significant (p = 0.14, 0.11). CONCLUSIONS: CT-derived texture parameters could be potential biomarkers for predicting the therapeutic response of rectal cancer.

[A Case of Unresectable Colorectal Cancer with Complete Remission after Palliative Surgery Due to Continued Pharmacotherapy].

A 50s-year-old man was admitted to our hospital because of abdominal pain and vomitting. CT showed a thickened wall of the sigmoid colon, marked enlargement of the oral side, and a 30 mm tumor on the left lateral section of the liver. We diagnosed colonic obstruction due to sigmoid colon cancer with liver metastasis. We failed to place a colonic stent for decompression, so we performed a colostomy using the cecum. An exploratory laparoscopy was performed instead of curative surgery due to peritoneal disseminations, followed by chemotherapy and molecular targeted therapy. Although primary lesion, liver metastatic lesion and disseminated lesions were reduced by pharmacotherapy the patient developed a grade 2 skin disorder around the colostomy. Therefore, it was determined that molecular targeted therapy could not be continued. The resection of the primary lesion and closure of the colostomy were performed to continue pharmacotherapy. Pharmacotherapy was resumed after operation. The patient is currently getting complete remission, undergoing maintenance therapy with no skin disorders. In this case, surgery was performed as part of the multidisciplinary treatment. It suggested that palliative surgery might be an effective option in multidisciplinary treatment.

[Successful Endoscopic Submucosal Dissection of Early Gastric Cancer after Ulcer Healing Associated with a Malignant Cycle-A Case Report].

A 79-year-old man was detected with anemia on medical examination and underwent gastroscopy at the previous hospital. Gastroscopy revealed a 15-mm ulcerative lesion(Type 0-Ⅱc plus Ⅲ)on the greater curvature of the upper gastric body. Tumor biopsy showed well-differentiated adenocarcinoma. The patient was suspected of deep submucosal invasion due to poor stretching of the gastric wall and the ulcer depth; hence, he was transferred to our hospital for surgery. When gastroscopy was repeated, the ulcer was found to be scarred(Type 0-Ⅱc), thereby indicating the occurrence of intramucosal carcinoma; hence, endoscopic submucosal dissection was performed. The pathological finding showed 10×6 mm, tub1, pT1a, ly0, v0, pUL1, pHM0, pVM0, suggesting a curative resection. Early gastric cancer of the depressed type is known to develop a malignant cycle with repeated improvements and exacerbations of the ulcer. Diagnosing the depth of tumor invasion is particularly difficult when there is an active ulcer. For small lesions with active ulcers, repeating gastroscopy might allow for correct diagnosis and appropriate treatment.

Does thoracoscopic esophagectomy really reduce post-operative pneumonia in all cases?

It has been said that "thoracoscopy suppresses the occurrence of pneumonia in comparison to thoracotomy", but does it reflect real clinical practice? To resolve this clinical question, we compared the results of randomized controlled trials (RCTs) and retrospective cohort studies from limited institutes (CLIs) in which a large number of high-volume centers were the main participants to those of retrospective cohort studies based on nationwide databases (CNDs) in which both high-volume centers and low-volume hospitals participated. A systematic review and meta-analysis were conducted to compare the short-term outcomes of thoracoscopic to open esophagectomy for esophageal cancer in the three above-mentioned research formats. In total, 43 studies with 21,057 patients, which included 1 RCT with 115 patients, 38 CLIs with 6,126 patients and 4 CNDs with 14,816 patients, were selected. Pneumonia was one of the most important complications. Although significant superiority in thoracoscopic esophagectomy was observed in RCTs (p = 0.005) and CLIs (p = 0.003), no such difference was seen in findings using nationwide databases (p = 0.69). In conclusion, unlike RCTs and CLIs, CNDs did not show the superiority of thoracoscopic surgery in terms of post-operative pneumonia. RCTs and CLIs were predominantly performed by high-volume hospitals, while CNDs were often performed by low-volume hospitals. In actual clinical practice including various types of hospitals, the superiority of thoracoscopic over open esophagectomy regarding the incidence of pneumonia may, therefore, decrease.

Development of imaging biomarker for esophageal cancer using intravoxel incoherent motion MRI.

BACKGROUND: Intravoxel incoherent motion MRI (IVIM-MRI) can quantify micro-perfusion at the capillary level in the tissue. The purpose of this study is to measure tumor perfusion using IVIM-MRI, and evaluate its value as a biomarker to predict prognosis in esophageal squamous cell carcinoma (ESCC) patients. METHODS: 109 ESCC patients (93 men and 16 women; median age: 72) who underwent IVIM-MRI prior to treatment between February 2018 and August 2020 were retrospectively investigated. Both mean apparent diffusion coefficient (ADC) value and mean perfusion-related parameter (PP) value of the primary tumor were measured using three b values of 0, 400, and 1000 s/mm2 based on the IVIM model. We analyzed associations of these parameters with clinical stage and disease-specific survival (DSS). RESULTS: Lower ADC and PP values of the tumor were significantly associated with the higher clinical T stage (p < 0.0001, p < 0.0001, respectively). In Kaplan-Meier analyses, patients with lower PP value tumors (< 18.94, median) had significantly worse DSS (p < 0.0001), while tumor ADC value did not show a significant correlation with DSS. In a multivariate analysis, PP value of the tumor was an independent prognostic factor for DSS (p = 0.0027). CONCLUSIONS: Quantification of tumor perfusion using IVIM-MRI can be a non-invasive prognostic biomarker of ESCC, reflecting clinical stage and survival.

[A Case of Gallbladder Jejunal Anastomosis and Duodenal Jejunal Anastomosis to Maintain QOL for an Elderly Patient with Pancreatic Cancer].

An 87-year-oldwoman was admittedto our hospital with abdominal pain andfever. Computedtomography showeda 25 mm tumor mass in the pancreatic headandshowedd ilatation of the pancreatic duct andcommon bile duct. She was diagnosed with obstructive cholangitis due to pancreatic head cancer. An endoscopic naso-biliary drainage(EUS)tube was inserted, and an endoscopic ultrasound(ENBD)examination was performed. At this time, duodenal perforation occurred, and an emergency operation was performed. During the laparotomy, perforation was found in the anterior wall of the duodenum. The contamination in the abdominal cavity and the degree of tissue damage in the duodenum were mild. Gall bladder jejunal andd uodenal jejunal anastomoses were performedfor biliary bypass andto close the perforation andbypass the gastrointestinal tract, respectively. She hadno postoperative complications andwas discharged 13 days postoperatively. Oral intake was possible after discharge, andthe patient returnedhome without complications. She died 5 months postoperatively. In this case, we performedbile duct andgastrointestinal bypass surgery prophylactically. Although this surgery will not be effective for all patients, we thought that it wouldbe useful for predicting the patient's future condition and for increasing the procedural options, even in case of emergency surgery.

[Long-Term Survival of a Rectal Cancer Patient with Virchow Lymph Node Metastasis, Liver Metastasis, and Para-Aortic Lymph Node Metastasis].

A 67-year-old female was diagnosed with Stage Ⅳ rectal cancer with paraaortic lymph node metastasis. The patient underwent Hartmann's operation with D3 lymph node and paraaortic lymph node dissection. Postoperative chemotherapy with FOLFIRI was then administered for 1 year. However, liver metastasis developed, for which partial hepatectomy was performed. Postoperative chemotherapy with S-1(20 courses)was then administered. Three years and 11 months following the first operation, lymph node metastases developed and resection of lymph nodes(No. 12p, No. 16b1int)was performed. Postoperative chemotherapy with capecitabine(Cape)(8 courses)was then administered. Five years and 7 months following the first operation, Virchow lymph node metastasis developed. Despite chemotherapy with Cape and bevacizumab (Bmab), Virchow lymph node swelling recurred, and resection was performed. Nine years and 4 months following the first operation, lymph node metastases developed, and resection of lymph nodes(Virchow, No. 16b1int)was performed. Postoperative chemotherapy with S-1(8 courses)was then administered. At present, 11 years and 4 months after the first operation, the patient, whose chemotherapy has been discontinued, is alive without recurrence.

[Pulmonary Metastasis Resection Twice after Curative Resection of Esophageal Cancer-A Long-Term Survival Case].

The prognosis of patients with esophageal cancer recurrence is poor, and surgical treatment is rarely performed. Here, we report on a patient with long-term survival who underwent pulmonary metastasis resection twice after curative resection of esophageal cancer. A 62-year-old male underwent curative resection of esophageal cancer after preoperative chemoradiotherapy. The histopathological diagnosis was poorly differentiated squamous cell carcinoma(pT2N1M0, fStage Ⅱ). Five months after the operation, right lung metastasis(right-S2)was detected. Accordingly, pulmonary metastasis resection was performed. Fourteen months after the initial operation, left lung metastases(left-S3/S6)were detected. The patient underwent resection again for the pulmonary metastases. The patient died of pneumonia without recurrence 8 years 3 months after the initial operation. In selected cases, surgical resection seems effective for treating distant esophageal cancer metastasis, suggesting that surgery should be an option in cases of accumulation of numerous distant metastases in esophageal cancer.

[A Case of Colon Metastasis from Invasive Lobular Carcinoma of the Breast].

The patient was a 48-year-old woman. She consulted our hospital with a chief complaint of vomiting. Colonoscopy showed stenosis and edematous mucosa, and biopsy was performed. Histological examination demonstrated the lesion to be colonic metastasis of breast cancer, invasive lobular carcinoma. Although colorectal metastasis of breast cancer has a poor prognosis and chemotherapy is considered as the main treatment modality, hormone therapy is also a treatment option depending on the condition.

[A Case of HER2 Positive Locally Advanced Breast Cancer Successfully Treated with a Combination Therapy of Eribulin, Trastuzumab and Pertuzumab].

The patient was an 82-year-oldwoman. She consultedour hospital with a chief complaint of left breast mass. MRI showed enhancedtumor with skin andextensive pectoral muscle invasion, so it was unresectable. Immunohistopathological analysis revealeda HER2-positive lesion. We administerederibulin, trastuzumab andpertuzumab, after which the tumor became resectable. Histological examination revealedremarkable response. Combination therapy of eribulin, trastuzumab andpertuzumab was well toleratedandconsid eredto be effective.

[A Comparison of the Treatment Methods for Obstructive Colorectal Cancer].

PURPOSE: Emergency surgery for obstructive colorectal cancer is considered to be associated with a high degree of risk, and surgery may after decompression is considered to be safer. In cases of obstructive colorectal cancer, decompression can be achieved with surgery, an ileus tube, or a stent, depending on the disease condition. We herein compare the treatment methods for obstructive colorectal cancer. METHODS: Forty-two patients with obstructive colorectal cancer underwent emergency treatment between January 2012 and December 2016. RESULTS: Among the patients with obstructive colorectal cancer, 18 receiveda stent, 10 receiveda nasal ileus tube, 6 receiveda transanal ileus tube, 5 underwent stoma construction, and 3 underwent emergency surgery without decompression. The stent group showed the highest laparoscopic operation rate. There was no significant difference in the overall survival of the treatment groups. One patient in the stent group developed duplicated cancer. CONCLUSION: Stent placement can be considered to be a viable option in the emergency treatment for obstructive colorectal cancer because laparoscopic surgery anda preoperative examination can be performed.

[Surgical Simulation-CT Colonography for Laparoscopic Assisted Sigmoid Colectomy Preserving the Inferior Mesenteric Artery and Vein].

D2 lymph node dissection in laparoscopic surgery for early colon cancer requires selective vessel dissection, making it technically very difficult. Using surgical simulation-CT colonography (simulation-CTC), we could perform laparoscopic assisted sigmoid colectomy preserving the inferior mesenteric artery (IMA) and vein (IMV) more accurately and safely. The case described here was a type 0-Ip sigmoid colon cancer with a tumor size of 13 mm. Endoscopic mucosal resection was performed to confirm a pathological diagnosis of pT1b (4,000 mm) and v1. Sigmoid colectomy was planned, and simulation-CTC was performed, which demonstrated that the cancer was located in the proximal sigmoid colon and supplied by the first sigmoid colon artery (S1). To maintain the blood flow to the distal sigmoid colon, selective S1 resection preserving the IMA and IMV was planned. At the operation, S1, which branches off from the IMA near the bifurcation of the abdominal aorta, was dissected, and the vein accompanying S1, which branches from the IMV in the same area as S1, was dissected. The operation was performed accurately according to the plan, showing that simulation-CTC can be very useful.

[Heavy ion radiotherapy for recurrence of an esophageal primary malignant melanoma].

A 55-year-old man, with a prior diagnosis of primary malignant melanoma of the esophagus, had undergone esophagectomy 6 years prior. During the postoperative follow-up, a flat tumor with black pigmentation, about 2 cm in diameter, was detected during upper gastrointestinal endoscopy. A pathological examination of the biopsy specimen showed a recurrent malignant melanoma. He underwent heavy ion radiotherapy for the tumor, and it disappeared after 6 months. Subsequently, a mediastinal lymph node metastasis was detected a year after radiotherapy. He received heavy ion radiotherapy for that tumor, and it was reduced in size a year after radiotherapy. At present, the patient is alive, 13 years after the initial radiotherapy. Although malignant melanoma is generally considered to be a radioresistant cancer, heavy ion radiotherapy led to a favorable outcome. This is the first reported case of heavy ion radiotherapy for treating the recurrence of a primary malignant melanoma of the esophagus.

Carbon-Ion Radiation Therapy for Unresectable Locally Recurrent Colorectal Cancer: A Promising Curative Treatment for Both Radiation Therapy: Naïve Cases and Reirradiation Cases.

PURPOSE: It is difficult to effectively cure patients with unresectable locally recurrent colorectal cancers (LRCRCs) using conventional chemotherapy or chemoradiation therapy. Furthermore, treatment options vary depending on the patient's history of radiation therapy. Carbon-ion radiation therapy (CIRT) is a potentially curative treatment for these patients. Here, we compare the treatment outcomes of radiation therapy-naïve cases (nRT) and re-irradiation cases (reRT). METHODS AND MATERIALS: Patients with LRCRC treated with CIRT at QST Hospital between 2003 and 2019 were eligible. CIRT was administered daily 4 d/wk for 16 fractions. The total irradiated dose was set at 73.6 Gy (relative biologic effectiveness-weighted dose [RBE]) for nRT and 70.4 Gy (RBE) for reRT patients. RESULTS: We included 390 nRT cases and 83 reRT cases. The median follow-up period from the initiation of CIRT was 48 (5-208) months. The 3-year overall survival (OS) rates for nRT and reRT were 73% (95% CI, 68%-77%) and 76% (65%-84%), respectively. The 5-year OS rates were 50% (45%-55%) and 50% (38%-61%), respectively. These rates did not differ significantly (P = .55). The 3-year local control (LC) rates for nRT (73.6 Gy) and reRT (70.4 Gy) cases were 80% (75%-84%) and 80% (68%-88%), respectively. The 5-year LC rates were 72% (67%-78%) and 69% (55%-81%), respectively, without a significant difference (P = .56). CONCLUSIONS: Our results suggest that CIRT for LRCRC is a very effective and promising treatment for both nRT and reRT cases.

Reduced Risk of Severe Radiation-Induced Lymphopenia in Carbon Ion Radiation Therapy for Locally Advanced Pancreatic Cancer: A Comparative Analysis of Carbon Versus Photon Therapy.

PURPOSE: Radiation-induced lymphopenia (RIL) is associated with poor prognosis in patients with locally advanced pancreatic cancers. However, there are no reports comparing the effects of carbon ion radiation therapy (CIRT) and photon beam radiation therapy (RT) on the development of RIL. Differences in RIL after CIRT or photon beam RT and predictive factors for RIL in patients with locally advanced pancreatic cancer were investigated. MATERIALS AND METHODS: This retrospective study cohort included 834 patients who received concurrent chemoradiotherapy (CCRT) in 2 separate institutions: 337 and 497 in the CIRT and photon beam RT groups, respectively. Severe RIL was defined as an absolute lymphocyte count (ALC) <0.5 × 109 cells/L. A 1:1 propensity score-matching analysis was performed between the CIRT and photon beam RT groups. Patients were categorized into 3 groups according to the development of recovery from severe RIL: no severe RIL (Group A), recovery from severe RIL (Group B), and no recovery from severe RIL (Group C). Logistic regression analysis was performed to identify the predictive value of severe RIL. The prognostic factors of overall survival (OS) were determined using Cox regression analysis. RESULTS: After propensity score matching, the baseline ALC and planning target volume of the CIRT and photon beam RT groups were comparable. During CCRT, the ALC of the entire cohort decreased and was significantly lower in the photon beam RT group than in the CIRT group (P < .001). Multivariate logistic regression analysis showed that CIRT reduced severe RIL more than photon beam RT. After adjusting for other factors, the RT modality and RIL were significantly associated with OS. Photon beam RT showed a significantly worse OS than CIRT, and Group C showed a significantly worse OS than Group A. CONCLUSIONS: CIRT seems to reduce the development of severe RIL. The RT modality and development/recovery from severe RIL were associated with OS in patients who received CCRT for locally advanced pancreatic cancer. The reduction of severe RIL through optimized RT may be essential for improving treatment outcomes.