Stereotactic radiotherapy (SRT) has the characteristics of large irradiation dose per fraction, few fraction sessions and sharp dose falloff out of the target volume, which is an important method to treat brain metastases. At present, stereotactic radiosurgery (SRS) / SRT technology for brain metastases based on linac is more economical and cost-effective than Gamma Knife and Cyberknife, and has more extensive clinical applications. Based on the published domestic and international standards, this guideline mainly focuses on all aspects involved in the clinical practice of stereotactic radiotherapy technology based on linac, and helps domestic radiotherapy institutions to correctly and safely carry out SRT technology.

Objective:To analyze the safety of reduced clinical target volume (CTV) irradiation of suspicious positive lymph nodes in IIa region in patients with N 0-N 1 nasopharyngeal carcinoma (NPC) and the protective effect of submandibular gland and long-term resting dry mouth, and to explore the diagnostic value of multimodal imaging for suspicious cervical lymph nodes. Methods:Clinical data of T 0-4N 0-1M 0 stage NPC patients admitted to Jiangsu Cancer Hospital from July 2015 to April 2017 were retrospectively analyzed. Clinical, radiation therapy planning, multimodal imaging and other relevant data were collected. All patients were treated with an optimized regimen of IMRT with a prophylactic radiation dose of 50.4 Gy (named as CTV50) for IIa region. Imaging characteristics and treatment response of suspicious lymph nodes were monitored by MRI, MRI-DWI, PET-CT and repeated enhanced positioning CT, etc. The dosimetry of the submandibular gland between optimized and standard dose plans (CTV50 vs. CTV60) was compared by paired t-test. The long-term dry mouth degree of the patients was evaluated using advanced radiation injury from Radiation Therapy Oncology Group (RTOG), Jiangsu Cancer Hospital Multi-dimensional Dry Mouth Evaluation Scale and summated xerostomia inventory (SXI). The difference of dry mouth degree was analyzed by rank-sum test. Results:A total of 106 patients were included in this study, including 149 cervical lymph node negative sides, 73 sides of which had ≤3 recognizable lymph nodes, and 76 of which were>3 in Ⅱa region. Among patients with N 1 stage, 63 patients underwent contralateral single neck area optimization, and 43 patients (N 0 stage and N 1 stage patients with retropharyngeal lymph node metastasis) underwent double-neck area optimization. A total of 109 suspicious lymph nodes with a short diameter of >5 mm were found on the largest cross section, of which 105 had clear portal structure. The ratio of long to short diameter was ≥1.5 in 93 cases, and the maximum standardized uptake value (SUV max) in PET-CT was ≥2.5 in 76 cases. No lymph node recurrence was found in the CTV optimized area. There was no significant difference in the average dose of GTV in tumor target area after optimization ( P>0.05), and the D mean and V 39 Gy in submandibular gland were significantly lower than those in unoptimized plan (both P<0.01). There was no significant difference in long-term dry mouth and resting dry mouth between patients with unilateral and bilateral optimization of submandibular gland (both P>0.05). Conclusions:The optimal program of CTV50 reduction irradiation in Ⅱa area of N 0-N 1 NPC patients is safe and effective. The submandibular gland has obvious dosimetric advantages, and patients have a good subjective response to resting dry mouth. The multimodal imaging tools such as enhanced CT, MRI-DWI and PET-CT should be performed to deliver individual evaluation and treatment for suspicious lymph nodes.

Objective:To investigate the effects of radiation dose to the host immune system during radiotherapy on disease progression and survival in patients with peripheral early-stage non-small cell lung cancer (ES-NSCLC) receiving stereotactic body radiation therapy (SBRT).Methods:Clinical data of pathologically confirmed ES-NSCLC patients who were treated with SBRT at Tianjin Medical University Cancer Institute and Hospital between January 2007 and December 2020 were retrospectively analyzed. The prognostic significance of the estimated dose of radiation to immune cells (EDRIC) in ES-NSCLC patients undergoing SBRT was cited and validated. EDRIC was calculated using the model developed by Kong et al. and improved by Ladbury et al. Kaplan-Meier method and Cox proportional hazards regression were adopted to estimate cancer-specific survival (CSS), progression-free survival (PFS), local progression-free survival (LPFS), and distant metastasis-free survival (DMFS). Pearson's correlation was used to assess the correlation between variables. Results:The median prescription dose/fraction was 60 Gy/5 fractions (range: 48-60 Gy in 3-10 fractions). The median follow-up time was 52.17 (1.17-154.77) months. The median gross tumor volume (GTV) and EDRIC were 10.98 (0.91-120.34) cm 3 and 2.064 (0.426-6.015) Gy, respectively. Person's correlation analysis showed that GTV was positively correlated with EDRIC ( r=0.712, P<0.001). In multivariate analysis, EDRIC was an important prognostic variable of CSS and DMFS. Higher EDRIC was significantly associated with worse CSS ( HR=1.763, P=0.004) and DMFS ( HR=1.902, P=0.004). Compared to patients with EDRIC ≤ 1.56 Gy, those with EDRIC > 2.64 Gy and EDRIC between <2.06-2.64 Gy exhibited significantly lower CSS ( P<0.001, P=0.049). There were significant differences in DMFS among the groups divided by quartiles of EDRIC (compared to EDRIC ≤1.56 Gy, the P values were <0.001, 0.004, and 0.022 respectively). Conclusions:EDRIC is an important predictor of CSS and DMFS in ES-NSCLC patients treated with SBRT, suggesting that radiation dose to the immune system is a critical determinant of treatment outcomes. EDRIC can be used to quantify the effects of radiation therapy on the host immune system.

Objective:To investigate the influencing factors of pathologic complete response (pCR) after neoadjuvant chemoradiotherapy (NCRT) in patients with locally advanced esophageal squamous cell carcinoma (ESCC), and to compare the clinical prognosis of ESCC patients with and without pCR after NCRT (40 Gy/ 20F).Methods:Among patients enrolled in a prospective clinical study, 87 ESCC patients treated with NCRT followed by surgery in Tianjin Medical University Cancer Institute & Hospital between June 2015 and October 2019 were selected. They were divided into the pCR ( n=35) and non-pCR groups ( n=52). Clinicopathological characteristics were retrospectively analyzed and subsequent follow-up was performed. Clinical prognosis and influencing factors were compared between two groups by using Kaplan-Meier and Cox regression analyses. Results:After NCRT, 40% of the ESCC patients could achieve pCR. Univariate analysis showed that patients in the pCR group had a disease-free survival (DFS) of 39.3 months and an overall survival (OS) of 64.0 months. In comparison, patients in the non-pCR group had a DFS of only 14.1 months and an OS of only 25.2 months. The differences were statistically significant (DFS: P<0.01, OS: P<0.05). Multivariate analysis revealed that whether pCR or not after NCRT, age, number of primary lesions, evaluation results after NCRT and postoperative pathological outcomes were important prognostic factors. The differences were statistically significant between two groups (all P<0.05). Conclusion:pCR after NCRT is significantly correlated with long-time survival of patients with ESCC, and pCR after NCRT has an important value in predicting clinical prognosis for long-term survival of ESCC patients.

Objective:To explore the patterns of failure after postoperative intensity-modulated radiotherapy for gastric cancer.Methods:Clinical data of patients diagnosed with gastric cancer or gastroesophageal junction carcinoma with pathological stages T 3-4N 0 or T xN 1-3 admitted to Cancer Hospital of Chinese Academy of Medical Sciences from May 2009 to December 2018 were retrospectively analyzed. All patients received postoperative radiotherapy. During the follow-up, tumor recurrence was confirmed by imaging or endoscopic or pathological data, etc. According to the location of tumor recurrence, recurrence patterns were divided into local, regional and distant recurrence. Differences in recurrence patterns among different groups were compared using t-test and Chi-square test. Patient survival was assessed through Kaplan-Meier method. Results:A total of 76 patients were enrolled, with a median age of 49 years old (27-67 years old), 34 cases (45%) were classified as T 3 stage, 40 cases (53%) of T 4 stage, and 75 cases (99%) of N 1-3 stage, respectively. Seventy-three patients (92%) were classified as stage Ⅲ, and 38 patients (50%) underwent D2 dissection. The median follow-up time was 32.8 months (7.1-138.5 months). The median time of recurrence was 17.6 months (2.9-113.6 months). The median survival time after recurrence was 8.19 months (0.6-91.9 months). There were 13 cases (17%) of local recurrence, 6 cases (8%) of regional recurrence, and 72 cases (95%) of distant metastasis in patients. Peritoneal metastasis (33 cases, 43%) and distant lymph node metastasis (12 cases, 16%) were the main patterns of distant recurrence. Conclusions:By intensity-modulated radiotherapy technology, adjuvant radiotherapy yields favorable local and regional control for gastric cancer. Distant metastasis is still the main pattern of recurrence.

Objective:To assess the efficacy and safety of programmed death-1 (PD-1) inhibitor combined with radiotherapy in advanced and relapsed / refractory extranodal NK/T cell lymphoma (ENKTL).Methods:Clinical data of 26 patients with advanced and recurrent / refractory ENKTL admitted to Sun Yat-sen University Cancer Center from January 2019 to December 2021 were retrospectively analyzed. All patients were treated with the PD-1 inhibitor combined with radiotherapy. The treatment responses, survival rate and and adverse reactions of the regimen were analyzed. The Kaplan-Meier method was used to estimate the 1- and 2-year progression-free survival (PFS) rate and overall survival (OS) rate, and the Cox proportional risk model was used for univariate prognostic factorial analysis for PFS and OS.Results:The median follow-up time of 26 patients was 29 months (10-49 months). The objective response rate (ORR) was 85%. The complete and partial remission rates were 77% and 8%. The median PFS time was 25 months. The 1- and 2- year PFS rates were 73.1% and 53.3%. The 1- and 2- year OS rates were 88.5% and 75.3%. The main adverse reaction was acute mucositis with an incidence rate of 31% (8/26), followed by hematological toxicity. The incidence of immune-related adverse events in lung, liver and thyroid were low. Only 1 patient developed grade 3 acute mucositis, 1 patient developed grade 4 immune pneumonitis, and the remaining patients had grade 1-2 toxicities. All patients showed good tolerance. The univariate analysis showed that elevated lactate dehydrogenase, Epstein-Barr virus DNA positive after treatment, and less than 6 cycles of anti-PD-1 immunotherapy were prognostic factors for poor OS.Conclusion:The regimen of PD-1 inhibitor combined with radiotherapy demonstrates promising efficacy and well tolerance in patients with advanced and relapsed / refractory ENKTL.

Objective:To compare the safety and efficacy of high-dose- rate interstitial brachytherapy and particle implantation radiotherapy in the treatment of lymph nodes with pelvic metastases in the field after external radiotherapy.Methods:Clinical data of 42 patients with residual or newly metastatic pelvic lymph nodes after radiotherapy at Cangzhou Integrated Traditional Chinese and Western Medicine Hospital who met the inclusion criteria from January 2017 to April 2020 were retrospectively analyzed. Among them, 12 patients were male and 30 females, aged 39-82 years, (61.6±9.64) years on average. According to the treatment method, all patients were divided into the high-dose-rate interstitial brachytherapy group ( n=18) and particle implantation radiotherapy group ( n=24). During 3-year follow-up, the local control rate (LCR), incidence of complications and overall survival (OS) were compared between two groups. Age and operation time conforming to normal distribution were analyzed by t-test. The remaining indexes were analyzed by the Chi-square test or Fisher's exact test. The OS and LCR were calculated by Kaplan-Meier method. Results:There was no significant difference in baseline data between two groups (all P>0.05). The operation time in the high-dose- rate interstitial brachytherapy group was longer than that in the particle implantation radiotherapy group [(66.39±11.07) : (45.75±9.19) min, P<0.001]. During subsequent follow-up, there was no significant difference in the LCR between two groups (1-year LCR 88.9% vs. 87.5%, P=0.927; 2-year LCR 72.2% vs. 62.5%, P=0.874). There was no significant difference in the median OS between two groups (31.6 vs. 29.8 months, P=0.798). There was no significant difference in the incidence of early complications between two groups [ (4/18) vs. 5/24 (20.8%), P=1.000]. No late complications observed. Conclusion:High-dose- rate interstitial brachytherapy yields equivalent efficacy and safety to particle implantation radiotherapy in the treatment of lymph nodes with pelvic metastases.

Objective:To investigate the dosimetric impact of tumor treating fields (TTF) transducer arrays on concurrent radiotherapy for patients with glioblastoma (GBM).Methods:A strategy was developed to accurately simulate the dosimetric impact of TTF arrays on radiotherapy, including the establishment of accurate auto-segmentation technique for TTF arrays, determination of the relative electron density (RED) of the transducer arrays and validation of the dose calculation accuracy in the treatment planning system (TPS) for TTF arrays. Based on this strategy, the dosimetric impact of TTF arrays on clinical treatment plans of 10 patients with GBM was evaluated. Furthermore, the dosimetric comparison between the clinical plans with different beam energies were investigated when TTF arrays were used. The methods of analysis of variance were paired t-test or Wilcoxon signed-rank test based on whether the differences followed a normal distribution. Results:The auto-segmentation technique for TTF arrays was established by designing a workflow in Mim software and achieved a Dice coefficient of 0.93 and a Jaccard index of 0.87 compared to the standard contours. The RED of TTF arrays was 3.3 which was derived from the comparison between the measured and simulated percentage depth dose (PDD) with and without TTF arrays on phantom. Measured and calculated dose distributions were compared using the 2D gamma analysis. The gamma passing rates on the coronal plane of 4 mm and 5.1 cm depth were 96.64% and 94.55% at the criteria of 3% /3 mm, indicating that the calculation accuracy of algorithm in TPS for TTF arrays could meet clinical requirements. In the clinical treatment plans of patients with GBM, the presence of TTF arrays caused a mean reduction of planning target volume (PTV) dose of approximately 1%, and an increase in scalp dose of approximately 5%, with minimal impact on other organs at risk (OAR). The 10 MV plans resulted in a higher dose of PTV by 0.3% and lower dose of scalp by approximately 3% compared to the 6 MV plans, when considering TTF arrays.Conclusions:The accurate simulation strategy for the dosimetric impact of TTF arrays on radiotherapy established in this study ensures the accuracy and precision of the calculations. In TTF therapy combined with concurrent radiotherapy for GBM, TTF arrays have slight effect on PTV dose, but significantly increase scalp dose. High-energy beam can reduce the impact of TTF arrays.

Objective:To evaluate the feasibility of using MRI-only simulation images for dose calculation of both photon and proton radiotherapy for nasopharyngeal carcinoma cases.Methods:T 1-weighted MRI images and CT images of 100 patients with nasopharyngeal carcinoma treated with radiotherapy in Cancer Hospital of Chinese Academy of Medical Sciences from January 2020 to December 2021 were retrospectively analyzed. MRI images were converted to generate pseudo-CT images by using deep learning network models. The training set, validation set and test set included 70 cases, 10 cases and 20 cases, respectively. Convolutional neural network (CNN) and cycle-consistent generative adversarial neural network (CycleGAN) were exploited. Quantitative assessment of image quality was conducted by using mean absolute error (MAE) and structural similarity (SSIM), etc. Dose assessment was performed by using 3D-gamma pass rate and dose-volume histogram (DVH). The quality of pseudo-CT images generated was statistically analyzed by Wilcoxon signed-rank test. Results:The MAE of the CNN and CycleGAN was (91.99±19.98) HU and (108.30±20.54) HU, and the SSIM was 0.97±0.01 and 0.96±0.01, respectively. In terms of dosimetry, the accuracy of pseudo-CT for photon dose calculation was higher than that of the proton plan. For CNN, the gamma pass rate (3 mm/3%) of the photon radiotherapy plan was 99.90%±0.13%. For CycleGAN, the value was 99.87%±0.34%. The gamma pass rates of proton radiotherapy plans were 98.65%±0.64% (CNN, 3 mm/3%) and 97.69%±0.86% (CycleGAN, 3 mm/3%). For DVH, the dose calculation accuracy in the photon plan of pseudo-CT was better than that of the proton plan.Conclusions:The deep learning-based model generated accurate pseudo-CT images from MR images. Most dosimetric differences were within clinically acceptable criteria for photon and proton radiotherapy, demonstrating the feasibility of an MRI-only workflow for radiotherapy of nasopharyngeal cancer. However, compared with the raw CT images, the error of the CT value in the nasal cavity of the pseudo-CT images was relatively large and special attention should be paid during clinical application.

Objective:To investigate the effect and mechanism of long non-coding RNA (lncRNA) taurine upregulated gene 1 (TUG1) on the radiosensitivity of cervical cancer cells by regulating autophagy.Methods:The radioresistant cervical cancer cell lines HeLa/IR and SiHa/IR were constructed. The radiosensitivity of HeLa/IR and SiHa/IR cells was evaluated by colony formation assay. Real-time reverse transcription PCR (RT-qPCR) was used to detect the expression of lncRNA TUG1 in each group. Western blot was used to detect the expression of autophagy proteins including Beclin1, microtubule-associated protein1 light chain 3 (LC3)Ⅱ/LC3Ⅰ and p62 in each group. NC-siRNA, TUG1-siRNA, TUG1-siRNA combined with rapamycin (an autophagy activator) were transfected into HeLa/IR and SiHa/IR cells, which were named as NC-siRNA group, TUG1-siRNA group and TUG1-siRNA+rapamycin group, respectively. RT-qPCR was used to evaluate the transfection efficiency of lncRNA TUG1. Western blot was used to assess the effect of lncRNA TUG1 silencing on autophagy protein expression. Flow cytometry was employed to evaluate the effect of lncRNA TUG1 silencing on the proliferation and apoptosis of HeLa/IR and SiHa/IR cells, respectively. The differences between two groups were analyzed by t-test, and the comparison among multiple groups was conducted by one-way analysis of variance. Results:Compared with HeLa and SiHa cells, the survival fractions of HeLa/IR and SiHa/IR cells was significantly increased, the expression of lncRNA TUG1 in cells was significantly increased, the expression levels of autophagy proteins Beclin1 and LC3Ⅱ/LC3Ⅰ were significantly increased, and the expression of p62 protein was significantly decreased, and the differences were statistically significant (all P<0. 05). Compared with the NC-siRNA group, the expression of lncRNA TUG1 and cell viability in HeLa/IR and SiHa/IR cells in the TUG1-siRNA group were significantly decreased, the apoptosis rate was significantly increased, the expression levels of Beclin1 and LC3Ⅱ/LC3Ⅰ proteins were significantly decreased, and the expression of p62 protein was significantly increased, and the differences were statistically significant (all P<0. 05). Compared with the TUG1-siRNA group, the expression levels of Beclin1 and LC3Ⅱ/LC3Ⅰ proteins in HeLa/IR cells in the TUG1-siRNA+rapamycin group were significantly increased, the expression of p62 protein was significantly decreased, the cell viability was significantly decreased, and the apoptosis rate was significantly increased, and the differences were statistically significant (all P<0.05). Conclusion:Silencing lncRNA TUG1 can enhance the radiosensitivity of cervical cancer cells by regulating autophagy.