Analysis of Treatment Response With Proteins Related to Tumor Immunity in Postoperative Irradiated Cervical Cancer Patients.

BACKGROUND/AIM: This study evaluated the association between programmed cell death-ligand 1 (PD-L1) and prognosis in patients with cervical cancer treated with postoperative radiation and the impact of neoadjuvant chemotherapy (NAC) on this association. PATIENTS AND METHODS: Immunohistochemical analysis was performed on biopsy specimens from 42 patients who did not receive NAC and from paired samples before (biopsies) and after (resected tissues) chemotherapy from 46 patients who received NAC to determine the association of PD-L1 with radiotherapy outcomes. RESULTS: In the non-NAC group, patients with ≥10% PD-L1-expressing tumor cells prior to treatment had better recurrence-free survival (RFS) than those with <10% PD-L1-expressing tumor cells (p=0.001). In the NAC group, RFS was significantly lower (p=0.005) in the group with a ≥5% reduction of PD-L1 expression in tumor cells after chemotherapy than in those with <5% reduction. In multivariate analysis, only PD-L1 expression (non-NAC group) and the change in PD-L1 expression (NAC group) were associated with RFS. CONCLUSION: Low PD-L1 expression in a cervical tumor prior to treatment was identified as a risk factor for a poor outcome after postoperative radiotherapy. Furthermore, NAC induces an immunological shift that reduces PD-L1 levels in tumor cells, thereby negatively impacting treatment outcomes.

Identification and Quantification of Radiotherapy-related Protein Expression in Cancer Tissues Using the Qupath Software and Prediction of Treatment Response.

BACKGROUND/AIM: Automated measurement of immunostained samples can enable more convenient and objective prediction of treatment outcome from radiotherapy. We aimed to validate the performance of the QuPath image analysis software in immune cell markers detection by comparing QuPath cell counting results with those of physician manual cell counting. PATIENTS AND METHODS: CD8- and FoxP3-stained cervical, CD8-stained oropharyngeal, and Ku70-stained prostate cancer tumor sections were analyzed in 104 cervical, 92 oropharyngeal, and 58 prostate cancer patients undergoing radiotherapy at our Institution. RESULTS: QuPath and manual counts were highly correlated. When divided into two groups using ROC curves, the agreement between QuPath and manual counts was 89.4% for CD8 and 88.5% for FoxP3 in cervical cancer, 87.0% for CD8 in oropharyngeal cancer and 80.7% for Ku70 in prostate cancer. In cervical cancer, the high CD8 group based on QuPath counts had a better prognosis and the low CD8 group had a significantly worse prognosis [p=0.0003; 5-year overall survival (OS), 65.9% vs. 34.7%]. QuPath counts were more predictive than manual counts. Similar results were observed for FoxP3 in cervical cancer (p=0.002; 5-year OS, 62.1% vs. 33.6%) and CD8 in oropharyngeal cancer (p=0.013; 5-year OS, 80.2% vs. 47.2%). In prostate cancer, high Ku70 group had worse and low group significantly better outcome [p=0.007; 10-year progression-free survival (PFS), 56.0% vs. 93.8%]. CONCLUSION: QuPath showed a strong correlation with manual counting, confirming its utility and accuracy and potential applicability in clinical practice.

Prediction of late adverse events in pelvic cancer patients receiving definitive radiotherapy using radiation-induced gamma-H2AX foci assay.

Radiation can induce DNA double-stranded breaks, which are typically detected by the fluorescence of phosphorylated histone H2AX. In this study, we examined the usefulness of the dynamics of radiation-induced gamma-H2AX foci of peripheral blood lymphocytes (PBLs), as a marker of DNA repair ability, in predicting late adverse events from radiotherapy. A total of 46 patients with cervical, vaginal and anal canal cancers treated with radical radiotherapy between 2014 and 2019 were included in this analysis. Concurrent chemotherapy was administered in 36 cases (78.3%). Peripheral blood was obtained before treatment, and then irradiated ex vivo with 1 Gy X-ray. The ratio of radiation-induced gamma-H2AX foci in PBLs measured at 30 min and at 4 h was defined as the foci decay ratio (FDR). With a median follow-up of 54 months, 9 patients (19.6%) were observed to have late genitourinary or gastrointestinal (GU/GI) toxicity. The FDR ranged from 0.51 to 0.74 (median 0.59), with a significantly higher incidence of Grade 1 or higher late adverse events in the FDR ≥ 0.59 group. In multivariate analysis, FDR ≥ 0.59 and hypertension also emerged as significant factors associated with the development of late toxicities. Overall, our results suggest that measurement of radiation-induced gamma-H2AX foci in PBLs may predict the risk of late GU/GI toxicities from chemoradiotherapy, which can enable tailoring the radiation dose to minimize adverse effects.

Immunohistological evaluation of patients treated with intra-arterial chemoradiotherapy and surgery for oral cancer.

Preoperative intra-arterial chemoradiotherapy (IACRT) can improve the outcome and reduce the extent of surgery in patients with advanced oral cancer. However, the response to this regimen varies among patients, which may be related to the immune status of the tumor. We investigated the effects of proteins involved in tumor immunity on the outcomes of combined IACRT and surgery for oral cancer. We examined CD8 + and FoxP3 + tumor-infiltrating lymphocytes (TILs) and programmed death ligand 1 (PD-L1) expression on immune cells and tumor cells in pretreatment biopsy samples from 69 patients diagnosed with oral cancer treated with IACRT at our institution during 2000-2020. Patients with abundant CD8 + TILs had significantly better 5-year disease-specific survival (DSS) compared to that of patients with less infiltration of these cells (P = 0.016). Patients with higher FoxP3 + T-cells invasion had significantly better DSS compared to that of less FoxP3 (P = 0.005). Patients with high PD-L1 expression in tumor cells and immune cells had significantly better DSS than that of patients with low PD-L1 expression in these cells (P = 0.009 and P = 0.025, respectively). Collectively, these results suggest that the tumor immune microenvironment could affect outcomes of IACRT treatment in oral cancer.

Predictive value of an exosomal microRNA-based signature for tumor immunity in cervical cancer patients treated with chemoradiotherapy.

Resistance of cervical cancer to radiotherapy with concurrent chemotherapy (CCRT) results in a poor prognosis. To identify new biomarkers for predicting the treatment response and prognosis, we explored exosomal microRNA (miRNA) expression signatures associated with the outcome of cervical cancer patients treated with CCRT. Exosomes were isolated from the plasma of 45 patients prior to CCRT during 2014-2020, and miRNA analysis was performed by next-generation sequencing. At a median follow-up of 38 months, 26 patients were recurrence free, 15 patients had died of the disease, and 4 patients received salvage chemotherapy due to distant metastasis. Of the 2522 miRNAs detected, 9 (miR-148a-5p, 1915-3p, 3960, 183-5p, 196b-5p, 200c-3p, 182-5p, 374a-5p, and 431-5p) showed differential expression between the recurrence-free and recurrence groups. Patients were divided into high- and low-risk groups according to the cutoff of the miRNAs-based risk score calculated from respective expression levels. The high-risk group had significantly worse disease-specific survival than the low-risk group (p < 0.001). In addition, miR-374a-5p and miR-431-5p expression showed a weak inverse correlation with tumor-infiltrating CD8+ and FOXP3+ T cells, suggesting a potential inhibitory effect on CCRT by suppressing tumor immunity. This miRNA signature could improve non-invasive monitoring and personalized treatment for cervical cancer.

Combined chemoradiotherapy and programmed cell death-ligand 1 blockade leads to changes in the circulating T-cell receptor repertoire of patients with non-small-cell lung cancer.

Combined chemoradiotherapy (CRT) and programmed cell death-ligand 1 (PD-L1) blockade is a new care standard for unresectable stage III non-small-cell lung cancer (NSCLC). Although this consolidation therapy has improved the overall survival of patients with NSCLC, the synergistic action mechanisms of CRT and immunotherapy on T cells remain unclear. In addition, there is a paucity of reliable biomarkers to predict clinical responses to therapy. In this study, we analyzed T-cell receptor (TCR) sequences in the peripheral blood of five patients with NSCLC. T-cell receptor analysis was undertaken before treatment, after CRT, and after PD-L1 blockade. Notably, we observed the expansion and alteration of the dominant T-cell clonotypes in all cases with a complete response. In contrast, neither expansion nor alteration of the TCR repertoire was observed in cases with progressive disease. T cell expansion was initiated after CRT and was further enhanced after PD-L1 blockade. Our findings suggest the systemic effect of CRT on circulating T cells in addition to the curative effect on limited tumor sites. Dynamic changes in circulating T-cell clonotypes could have a prognostic significance for combined CRT and PD-L1 blockade.

Radiotherapy for HPV-related cancers: prediction of therapeutic effects based on the mechanism of tumor immunity and the application of immunoradiotherapy.

Human papillomavirus (HPV)-related cancer is one of the diseases entities for which the applications of radiotherapy have been increasing. Recently, the process of carcinogenesis from HPV infection and the mechanism of tumor immunity that develops during disease progression have been elucidated. In this review, we will describe the mechanism of tumor immunity and how chemoradiotherapy may overcome and improve the efficacy of tumor immunity. We will also discuss the usefulness of proteins involved with tumor immunity as a predictive marker of radiotherapy response, and present an overview of ongoing clinical trials of combinations of immune checkpoint inhibitors and radiotherapy to demonstrate the promising combination therapy that has been currently emerging.

Prediction of treatment response from the microenvironment of tumor immunity in cervical cancer patients treated with chemoradiotherapy.

To supplement clinical decision-making in the management of cervical cancer, various prognostic factors, including tumor immune microenvironments, were examined in patients with cervical cancer treated with definitive chemoradiotherapy. We retrospectively analyzed the expression of CD8, FoxP3, HLA-1, PD-L1, and XRCC4 in 100 cases of cervical cancer. The observed tumor immune microenvironments were also classified into three types: inflamed, excluded, and cold type. Less FoxP3+ T cells and cold-type tumor were found to be poor prognostic factors in addition to non-SCC, large pre-treatment tumor volume, and three or less cycles of concurrent chemotherapy based on multivariate analysis. Cold-type tumors had significantly worse prognoses than the other two types, whereas inflamed- and excluded-type tumors showed similar 5-year disease-specific survival (P < 0.001; 0% vs. 60.3% vs. 72.3%). Radiotherapy could overcome the inhibitory immune microenvironment that occurs in excluded type. Individualized combination therapy adapted to pre-treatment tumor immunity may be necessary to improve radiotherapy outcomes in cervical cancer.

Association between cancer immunity and treatment results in uterine cervical cancer patients treated with radiotherapy.

OBJECTIVE: To evaluate proteins related to tumor immune response and treatment outcome from radiotherapy for uterine cervical cancer patients. METHODS: We performed a retrospective immunohistochemical staining of 81 patients with uterine cervical cancer who underwent definitive radiotherapy. We examined the expression of programmed death ligand 1, human leukocyte antigen class I, tumor-infiltrating CD8+, and forkhead box P3+ (FoxP3+) T cells in tumor tissues. RESULTS: In biopsy specimen, patients with a higher number of CD8+ T cells and FoxP3+ T cells had a better disease-specific survival than patients with a lower number of CD8+ T cells and FoxP3+ cells (P = 0.018 and P = 0.009). Multivariate analysis showed that equivalent dose in 2 Gy fractions (EQD2) of the minimum dose to 90% of the high-risk clinical target volume, FoxP3+ T cells and expression of human leukocyte antigen class I were significant prognostic factors. When the EQD2 is 70 Gy or more, a higher local control rate is obtained regardless of the number of CD8- or FoxP3-positive cells. When EQD2 is <70 Gy, the number of CD8-positive cells has a significant impact on treatment outcome: the recurrence rate (local recurrence rate + distant metastasis rate) was 46.2% in the group with a CD8 value of 230 or higher, whereas the recurrence rate was 75.7% in the group with a CD8 value of less than 230. CONCLUSION: The combination of CD8 or FoxP3 with EQD2 can be potentially useful to predict the treatment results of radiotherapy for cervical cancer, leading to individualized optimal selection of treatment for cervical cancer.

Evaluation of the urethral α/ß ratio and tissue repair half-time for iodine-125 prostate brachytherapy with or without supplemental external beam radiotherapy.

PURPOSE: To assess the correlation between postimplant dosimetric quantifiers and the genitourinary (GU) toxicity of low-dose rate brachytherapy for prostate cancer. METHODS AND MATERIALS: The minimum urethral dose (UD10, 30, and 90) and the percent volume of the urethra receiving the prescription dose (V100, V150) were calculated from the postimplant dose-volume histograms of 182 patients. We then calculated various urethral biologically equivalent doses (uBEDs) using different values of the α/ß ratio and tissue repair half-time (t1/2) and examined the correlations with GU toxicity. RESULTS: Common dosimetric quantifiers, such as UD90 (brachytherapy) + UD50 (external beam radiotherapy), showed no correlation with Grade ≥ 2 GU toxicity. There was a significant correlation between Grade ≥2 GU toxicity and uBED when the α/ß value was 0.5 or 1 Gy and t1/2 was 0.5-2.5 h. An uBED (α/ß = 1.0, t1/2 = 0.5) had the largest hazard ratio for GU toxicity, and it was also significantly correlated with Grade ≥ 2 GU toxicity according to multivariate analysis. CONCLUSIONS: We observed a significant correlation of uBED with GU toxicity when α/ß was 0.5 or 1.0 Gy and t1/2 was 0.5-2.5 h. As the simple formula we used has not been verified in basic experiments, more data are needed to validate our results.

Retrospective DVH analysis of point A based intracavitary brachytherapy for uterine cervical cancer.

Combining external beam radiotherapy (EBRT) with intracavitary brachytherapy (ICBT) is important for definitive treatment of cervical cancer. In cervical cancer patients receiving radiotherapy, we evaluated treatment outcomes in relation to dose-volume histogram parameters, including the computed tomography (CT)-based high-risk clinical target volume (HR-CTV) for ICBT. Between 2010 and 2015, 89 consecutive cervical cancer patients were mostly treated with 40 Gy of EBRT in 20 fractions and 18 Gy of ICBT prescribed to point A in 3 fractions. CT scans were obtained during ICBT. The HR-CTV D90 was calculated and the total doses of ICBT and EBRT were converted to the equivalent dose in 2 Gy fractions (EQD2). When the patients were divided into four groups according to EQD2 of the HR-CTV D90, the 3-year local recurrence-free survival rates were 95.2, 78.4, 52.7 and 42.9% for patients receiving >80 , 70-80 , 60-70 and <60 Gy, respectively. There was a significant negative correlation between EQD2 of the HR-CTV D90 and the HR-CTV volume at first ICBT (r = -0.713). Local recurrence was more frequent when the HR-CTV volume was ≥22 cc and EQD2 of the HR-CTV D90 was <70 Gy. Multivariate analysis showed that EQD2 of the HR-CTV D90 and concurrent chemotherapy (≥4 cycles) were significant determinants of overall survival. HR-CTV D90 was an important prognostic indicator for local recurrence. HR-CTV D90 >70 Gy is required for the better local control, especially in patients with a larger HR-CTV (≥22 cc at initial ICBT).

Association between radiotherapy-induced alteration of programmed death ligand 1 and survival in patients with uterine cervical cancer undergoing preoperative radiotherapy.

PURPOSE: To evaluate radiotherapy-induced changes in the expression of programmed death ligand 1 (PD-L1), programmed death 1 (PD-1), and human leukocyte antigen class I (HLA-1) in patients with uterine cervical cancer, as well as infiltration of CD8+ and Forkhead box P3+ (FoxP3+) T lymphocytes into tumor tissue and the prognostic value of these parameters. MATERIALS AND METHODS: We performed immunohistochemical analysis of pre-radiotherapy biopsies and corresponding post-radiotherapy resected tissues in 104 uterine cervical cancer patients undergoing preoperative chemoradiotherapy or radiotherapy alone. We scored the expression of various proteins to distinguish positive from negative samples. RESULTS: PD-L1-expressing tumor cells (PD-L1 TC) increased significantly after chemoradiotherapy (p = 0.043). CD8+ T cell infiltration (p = 0.002) and FoxP3+ T cell infiltration (p = 0.003) decreased significantly after chemoradiotherapy. Expression of PD­1, PD-L1-expressing immune cells (PD-L1 IC), and HLA­1 did not change after chemoradiotherapy. In biopsy specimens obtained before chemoradiotherapy or radiotherapy, greater infiltration of CD8+ T cells (p = 0.001) and FoxP3+ T cells (p = 0.003) were significant predictors of better overall survival (OS). In surgical specimens obtained after chemoradiotherapy or radiotherapy, greater infiltration of PD-L1 TC was the only significant predictor of better OS (p < 0.001) and was related to a significantly lower probability of out-of-field recurrence (p = 0.005). CONCLUSION: Chemoradiotherapy induced an immunologic shift that increased PD-L1 TC. Chemoradiotherapy has immunological effects that can influence the results of treatment for uterine cervical cancer.

Influence of XRCC4 expression by breast cancer cells on ipsilateral recurrence after breast-conserving therapy.

BACKGROUND: We examined the expression of nonhomologous end-joining (NHEJ) proteins by breast cancer cells in patients with or without ipsilateral breast tumor recurrence (IBTR) after breast-conserving therapy. We also investigated whether there was a difference of NHEJ-related protein expression by tumor cells between two types of IBTR, i.e., true recurrence (TR) with regrowth from the tumor bed or development of a new primary tumor (NP). PATIENTS AND METHODS: The original cohort comprised 560 breast cancer patients who received breast-conserving therapy between February 1995 and March 2006, including 520 patients without IBTR and 40 patients with IBTR. Propensity score matching was employed to select 40 trios (120 patients) consisting of 1 patient with IBTR and 2 patients without IBTR. Immunohistochemical examination of proteins related to NHEJ was performed in surgical specimens. RESULTS: The 40 patients with IBTR included 22 patients who developed TR and 18 who had NP. The 15-year overall survival rate was 85.9% for patients with NP and 95.5% for those with TR, while it was 96.5% for patients without IBTR. Patients with high XRCC4 expression in tumor cells had significantly higher IBTR rates than those with low XRCC4 expression (P < 0.001). The frequency of TR was significantly higher in patients with high expression of XRCC4 than in those with low XRCC4 expression (p < 0.001). XRCC4 expression by tumor cells was not significantly related to development of NP. CONCLUSION: IBTR due to TR may be related to low radiosensitivity of tumor cells, possibly related to high XRCC4 expression.

Efficacy of combined radiotherapy and anti-programmed death 1 therapy in acral and mucosal melanoma.

Some studies showed that clinical response to immune check point inhibitors is lower in acral and mucosal melanoma than in cutaneous melanoma. Although the synergistic effect of radiotherapy (RT) and ipilimumab has been reported in patients with brain metastasis, the efficacy of combined RT and anti-programmed death 1 (PD-1) therapy for acral and mucosal melanoma is unclear. The present study aimed to evaluate the efficacy of combined RT and anti-PD-1 therapy for acral and mucosal melanoma. We retrospectively analyzed patients with acral or mucosal melanoma who were treated with anti-PD-1 and RT at Sapporo Medical University Hospital. In 10 patients (acral, 3; mucosal, 7), the response rate (RR) and the disease control rate (DCR) were 40% and 60%, respectively. As regards mucosal melanoma, four of the seven patients had achieved complete response + partial response, and three had progressive disease (RR = 57.1%). Meanwhile, two of the three patients with acral melanoma had stable disease and one had progressive disease (RR and DCR were 0% and 66.6%, respectively). Except for the patients treated with palliative RT for bone metastasis in the present study, the RR was 50% (4/8 patients), and the DCR was 75% (6/8 patients). Vitiligo developed after RT in five (50%) patients at a median duration of 2 months after RT. The clinical response and the high occurrence of vitiligo suggest that the combination of RT and anti-PD-1 therapy could be effective in some patients with mucosal melanoma.

Influence of PD-L1 expression in immune cells on the response to radiation therapy in patients with oropharyngeal squamous cell carcinoma.

BACKGROUND AND PURPOSE: To investigate influences of proteins involved with tumor immunity on outcomes of radiotherapy for oropharyngeal squamous cell carcinoma (OPSCC). MATERIAL AND METHODS: We performed immunohistochemical staining to examine expressions of p16 and proteins involved with tumor immunity in 92 OPSCC patients treated with radiotherapy. RESULTS: Patients with abundant infiltrating CD8-positive cells had the significantly better overall survival (OS) rate than patients with fewer CD8-positive cells (p = 0.026). Patients with higher PD-L1 expression in tumor cells (TC 1-3) had a better outcome than those with low PD-L1 expression in tumor cells (TC 0) for both OS (p = 0.019) and progression-free survival (PFS) rate (p = 0.032). Patients with high PD-L1 expression in infiltrating immune cells (IC 3) showed significantly better OS (p = 0.009) and PFS (p = 0.011) than those with low PD-L1 expression (IC 0-2). Patients with p16-negative and IC 3 showed similar OS to patients with p16-positive and IC 0-2. P16-positive tumors had a significantly higher CD8-positive cell infiltration and PD-L1 expression in tumor cells than p16-negative tumors. CONCLUSIONS: In addition to tumor p16 expression, PD-L1 expression in TC and IC can be useful for predicting the response of OPSCC to radiotherapy.

Prediction of acute gastrointestinal and genitourinary radiation toxicity in prostate cancer patients using lymphocyte microRNA.

BACKGROUND: To search for novel biomarkers that can predict acute radiation toxicity, we conducted microRNA expression analysis of peripheral blood lymphocytes (PBLs). METHODS: The discovery cohort was 69 patients with localized adenocarcinoma of the prostate who received intensity-modulated radiation therapy between October 2007 and October 2010. The validation cohort was 72 patients treated with low-dose-rate brachytherapy between May 2008 and March 2014. After13 microRNAs were selected by TaqMan® Array analysis in a preliminary experiment, expression of these microRNAs in all samples was analyzed by RT-PCR. RESULTS: In the discovery cohort, the average prostate volume, the rectal volume receiving 70 Gy, and expression of miR-410 and miR-221 were significant risk factors for Grade 1-2 gastrointestinal toxicity. Receiver operating characteristic analysis showed that the area under the curve (AUC) was 0.807. The maximum dose to the urinary bladder, prostate volume, pretreatment urinary function score, and miR-99a and miR-221 expression were risk factors for Grade 2 genitourinary toxicity. The corresponding AUC was 0.796. In the validation cohort, reproducibility of these markers was confirmed for gastrointestinal toxicity, but not for genitourinary toxicity. CONCLUSION: Combining radiation dose parameters with microRNA expression in PBLs may be useful for predicting acute gastrointestinal toxicity of radiation therapy, thus contributing to personalized treatment of prostate cancer.

Expression of Ku70 predicts results of radiotherapy in prostate cancer.

BACKGROUND AND PURPOSE: Therapeutic strategy for prostate cancer is decided according to T stage, Gleason score, and prostate-specific antigen (PSA) level. These clinical factors are not accurate enough to predict individual risk of local failure of prostate cancer after radiotherapy. Parameters involved with radiosensitivity are required to improve the predictive capability for local relapse. PATIENTS AND METHODS: We analyzed 58 patients with localized adenocarcinoma of the prostate between August 2007 and October 2010 treated with 76 Gy of intensity-modulated radiotherapy (IMRT) as a discovery cohort and 42 patients between March 2001 and May 2007 treated with three-dimensional conformal radiotherapy (3D-CRT) as a validation cohort. Immunohistochemical examination for proteins involved in nonhomologous end-joining was performed using biopsy specimens. RESULTS: Ku70 expression was not correlated with various clinical parameters, such as the Gleason score and D'amico risk classification, indicating that Ku70 expression was an independent prognostic factor. The predictive value for PSA relapse was markedly improved after the combination of Gleason score and Ku70 expression, as compared with Gleason score alone. In patients treated with radiotherapy and androgen deprivation therapy (ADT), no relapses were observed in patients with Gleason score ≤7 or low Ku70 expression. In contrast, patients with Gleason score ≥8 and high Ku70 expression had high PSA relapse rates. In the validation cohort, similar results were obtained. CONCLUSION: Treatment with 76 Gy and ADT can be effective for patients with Gleason score ≤7 or low Ku70 expression, but is not enough for patients with Gleason score ≥8 and high Ku70 expression and, thus, require other treatment approaches.

Influence of XRCC4 expression in esophageal cancer cells on the response to radiotherapy.

DNA double-strand break (DSB) is one of the most serious forms of damage induced by ionizing irradiation and is mainly repaired by the non-homologous end joining (NHEJ) repair. Immunohistochemical analysis of proteins involved in NHEJ, such as XRCC4 (X-ray repair cross-complementing protein 4), Ku86 and DNA-PKcs (DNA-dependent protein kinase, catalytic subunits), may be useful for predicting tumor radiosensitivity. We examined 92 patients with esophageal squamous cell carcinoma (ECSS) who were treated by radiotherapy between 1999 and 2008. Immunohistochemical examination of tumor tissue for Ki-67 and DSB-related proteins, including XRCC4, Ku86, and DNA-PKcs, was performed using pretreatment biopsy specimens. Low expression of XRCC4 was detected in 31 of 92 examined samples (33.7 %). The 5-year overall survival (OS) rate was 67.7 % in the low expression group and 31.0 % in the high expression group (P = 0.00). Multivariate analysis confirmed that advanced T-stage (HR 3.24, P = 0.01), radiation dose less than 66 Gy (HR 2.23, P = 0.02), absence of systemic chemotherapy (HR 2.59, P = 0.05), and high expression of XRCC4 (HR 12.0, P = 0.02) were independent prognostic factors for predicting poor OS. Other DSB-related proteins and Ki-67 were not predictive factors. XRCC4 expression might have an influence on results of radiotherapy for patients with ESCC.