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.

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.

Dose-averaged LET optimized carbon-ion radiotherapy for head and neck cancers.

This feasibility study confirmed the initial safety and efficacy of a novel carbon-ion radiotherapy (CIRT) using linear energy transfer (LET) painting for head and neck cancer. This study is the first step toward establishing CIRT with LET painting in clinical practice and making it a standard practice in the future.

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.

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.

Primary esophageal cancer treated by esophagectomy with distal pancreatectomy: a report of three cases.

Esophagectomy and pancreatectomy are recognized as highly invasive procedures with relatively high complication rates; therefore, careful indication decisions are required. The depth of tumors invading adjacent organs, such as the aorta, vertebral body, and trachea, is defined as T4, and are estimated to have a low survival rate even after treatment. Conversely, pancreatic invasion of esophageal cancer is uncommon and not clearly defined as T4. Thus, it is often difficult to decide on a treatment strategy for locally advanced esophageal cancer. In this study, we describe three cases of esophagectomy with combined resection of the pancreas and spleen for esophageal cancer or esophagogastric junction cancer with invasion of the pancreatic body or tail. To the best of our knowledge, this is the first report of esophagectomy and combined resection of the pancreas and spleen in multiple patients from a single institution.

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.

A case report of duodenal arteriovenous malformation: usefulness of intraoperative indocyanine green angiography for precise identification of the lesion.

BACKGROUND: Arteriovenous malformation (AVM) of the gastrointestinal (GI) tract can cause bleeding. The treatment choice for GI tract AVM is surgical resection of the involved bowel segment with complete resection of the nidus. The AVM formed in the duodenum or pancreatic head could also cause gastrointestinal bleeding, and there are several reports of pancreaticoduodenectomy as its treatment. However, if the area of AVM can be accurately identified during surgery, it may be possible to completely resect the AVM while preserving the organ. We report a case of duodenal AVM in a patient successfully treated with a subtotal stomach-preserving duodenal bulb resection using intraoperative indocyanine green (ICG) angiography technique. CASE PRESENTATION: An 18-year-old man was diagnosed with duodenal AVM after several examinations for anemia and was referred to our hospital for further treatment. Preoperative imaging studies showed that the inflow vessels of this duodenal AVM were the inferior pyloric artery and the superior duodenal artery, and the AVM was localized to the duodenal bulb. Thereafter, stomach-preserving duodenal bulb resection preceded by ligation of the inflow vessels was performed. During the surgery, ICG angiography clearly demonstrated the area, where the nidus was distributed, and a duodenal bulb resection with complete resection of the AVM was successfully performed. There was no recurrence at the 6-month follow-up. CONCLUSIONS: Intraoperative ICG angiography was a useful procedure for precise identification of the AVM of the GI tract.

Preoperative evaluation of vascular anatomy of right colic vessels using enhanced computed tomographic colonography.

PURPOSE: The purpose of this study is to define the blood vessels from a surgical perspective and show the frequency of vascular anatomical anomalies as well as the positional relationship with the surrounding organs, including the number of jejunal veins that cross the dissection area in our series. MATERIALS AND METHODS: From January 2016 to December 2018, 126 patients who received ileocecal resection or right hemicolectomy for colonic cancer in our institution were retrospectively analyzed by preoperative enhanced computed tomographic colonography images that were obtained using an 80-detector row CT scanner and workstation. The ileocolic artery/vein, right colic artery/vein and middle colic artery/vein were defined as the vessels that flow directly from or into the superior mesenteric artery/vein. All colic veins that flowed into the gastro-colic trunk were defined as accessory right colic veins. RESULTS: The accessory right colonic vein existed more than two in 62.6% of cases. In 11 cases (8.9%), the inflow point of the ileocecal vein was on the ventral side of the pancreas. There was one jejunal vein that straddled the dissection area in 31% and two in 6.3%. CONCLUSION: This study elucidated the vascular anatomy and positional relationship with surrounding organs that is required in central vascular ligation during complete mesocolic excision for right sided colon cancer.

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.

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 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.

Magnetic compression anastomosis is effective in treating stenosis after esophageal cancer surgery: a case report.

BACKGROUND: Esophagostomy is important in the treatment of esophageal cancer. However, esophagectomy has a higher risk of postoperative complications. Treatment for complications is often difficult, and in some cases, oral intake is no longer possible. Recently, magnetic compression anastomosis (MCA) was developed; it is a relatively safe method of anastomosis that does not require surgery in patients with stricture, obstruction, or dehiscence of the anastomosis after surgery. CASE PRESENTATION: The patient was a 76-year-old Japanese man. He underwent esophagectomy with a three-field dissection for esophageal cancer. A cervical esophagostomy and chest drainage were performed for necrosis of the gastric tube. Following infection control, colon interposition was performed. However, after the operation, the colon necrotized and formed an abscess. Drainage controlled the infection, but the colon was completely obstructed. The patient was referred to our hospital to restore oral ingestion. Contrast studies showed that the length of the occlusion was 10 mm. The reconstruction was examined; reanastomosis by surgery was judged to be a high risk, so the strategy of anastomosis by MCA was adopted. In the operation, the anterior chest was opened to expose the colon, and a magnet was inserted directly into the blind end of the colon. The magnet was guided to the blind end of the esophagus using an oral endoscope. Two weeks after MCA, a contrast study confirmed the passage of the contrast agent from the esophagus to the colon. The patient eventually took 18 bougies after the MCA. However, since then, he has not needed a bougie. As of 1 year and 8 months after the MCA, the patient is living at home with oral intake restored. CONCLUSIONS: MCA is an effective and safe treatment for complete stenosis after esophageal cancer surgery.

Crohn's Disease Presenting as Granulomatous Appendicitis.

Granulomatous appendicitis is uncommon. It can be caused by infectious or systemic disorders, such as Crohn's disease (CD) and sarcoidosis. It is therefore essential to investigate systematic causes of granulomatous appendicitis after surgery by appropriate examinations. It is also rare for acute appendiceal inflammation to develop due to active CD. We herein report a case of CD presenting as granulomatous appendicitis. The patient was a 28-year-old man who arrived at the emergency room with right lower abdominal pain. Computed tomography showed a low-density lesion with a clear boundary and a small high-density spot in its center behind the cecum. Acute appendicitis with abscess formation was suspected and conservative treatment was started. After 3 consecutive days of conservative treatment there was no improvement in his condition. We therefore performed open appendectomy. Histopathological examination showed numerous noncaseous epithelioid granulomas in the wall of the appendix. Specific staining revealed no evidence of acid-fast bacilli or fungi. During follow-up after discharge, colonoscopy demonstrated erosion from the cecum to the transverse colon. A colon biopsy showed severe inflammation with cryptitis, Paneth cells, and a granulomatous lesion. The patient was therefore diagnosed with CD and treatment with mesalazine was started. Careful examination is necessary to diagnose and properly treat patients with granulomatous inflammation of the appendix.

Fra­1 enhances the radioresistance of colon cancer cells to X­ray or C­ion radiation.

Fos­related antigen 1 (Fra­1) has roles in a variety of cell functions, including cell proliferation, differentiation, transformation, and invasiveness, and it is upregulated in various cancers. We investigated the role of Fra­1 in cellular radioresistance using cells of two human colorectal cancer cell lines, SW620 and SW480. We found that SW620 cells are more sensitive than SW480 cells at doses greater than 6 Gy for X­ray or 3 Gy for carbon­ion (C­ion) radiation. Fra­1 expression tended to be decreased by the radiation in a dose­dependent manner in both cell lines; of note, a greater reduction of Fra­1 expression was observed in SW620 cells, especially at 6 Gy of X­ray or 3 Gy of C­ion irradiation, than in SW480 cells, indicating a possible association between Fra­1 downregulation and cellular radiosensitivity. Knockdown of Fra­1 in SW480 cells significantly increased the radiosensitivity to X­ray or C­ion radiation. On the other hand, overexpression of Fra­1 in SW620 cells significantly enhanced the radioresistance to C­ion radiation, suggesting a role of Fra­1 in radioresistance. Furthermore, we found that downregulation of Fra­1 protein in irradiated SW620 cells was regulated via protein degradation through a proteasome­dependent pathway. Overall, our results indicate a role of Fra­1 in radioresistance to both X­ray and C­ion radiation for colorectal cancer cell lines.