Ultra-high dose-rate (FLASH) radiotherapy is a new mode of radiotherapy that can control tumors while significantly reducing damage to surrounding normal tissues. Since its official naming in 2014, FLASH radiotherapy research has continued to grow, and in 2019 it entered a period of exponential development. Studies have shown that electrons, photons, and protons can all induce the FLASH effect, but the proton beam can overcome the physical limitations of shallow incident depth and high penetration dose, which is considered to be the most effective solution. This article summarizes previous research results of FLASH proton therapy from the research at the cell, animal and clinical levels, and summarizes the hypothesis of the FLASH effect mechanism, aiming to provide reference for promoting the research and clinical transformation of FLASH proton therapy.

The comprehensive treatment of esophageal cancer has undergone tremendous changes with the advent of the era of targeted and immunotherapy. The optimization of comprehensive treatment strategies will become increasingly precise with the deep research on biomarkers related to the therapeutic effect of esophageal cancer. With the precise implementation of various treatment methods, the therapeutic effect of esophageal cancer is bound to be significantly improved.

Ultra-high dose-rate (FLASH) radiotherapy is a new mode of radiotherapy that can control tumors while significantly reducing damage to surrounding normal tissues. Since its official naming in 2014, FLASH radiotherapy research has continued to grow, and in 2019 it entered a period of exponential development. Studies have shown that electrons, photons, and protons can all induce the FLASH effect, but the proton beam can overcome the physical limitations of shallow incident depth and high penetration dose, which is considered to be the most effective solution. This article summarizes previous research results of FLASH proton therapy from the research at the cell, animal and clinical levels, and summarizes the hypothesis of the FLASH effect mechanism, aiming to provide reference for promoting the research and clinical transformation of FLASH proton therapy.

Patients with oligometastatic prostate cancer based on accurate diagnosis should be given active treatment. We should optimize the benefit through tailored approaches encompassing systemic treatment, local therapy, and metastasis-directed therapy. The optimal combination and duration of systemic treatment are currently undefined. Combining new hormonal agents with androgen deprivation therapy is recommended. Most experts advocate a duration of hormonal therapy ranging from 18 to 36 months. Local therapy for the primary lesion, surgery or radiotherapy, has been clinically validated for its feasibility and effectiveness in oligometastatic prostate cancer patients. Stereotactic ablative radiation therapy for metastatic lesions ensures safe and reliable local control. In summary, maximal eradication of all visible active lesions may confer a survival benefit to these patients. We provide a comprehensive review for the treatment of oligometastatic hormone-sensitive prostate cancer, aiming to contribute insights for clinical diagnosis and treatment.

As a new therapeutic strategy for esophageal cancer, immunotherapy has attracted more and more attention. The completed and ongoing clinical trials of immunotherapy for esophageal cancer confirm the great potential of immune checkpoint inhibitors in esophageal cancer. Future research will focus on the combination of immunotherapy with existing or new therapeutic modalities and the identification of populations likely to benefit from immunotherapy.

Neoadjuvant chemoradiotherapy is the preferred treatment mode for the diagnosis and treatment of locally advanced operable esophageal carcinoma recommended by many guidelines. However, some problems remain to be further explored. In this article, current problems perplexing clinical practice were sorted out, aiming to provide constructive suggestions for the smooth development of neoadjuvant chemoradiotherapy for esophageal carcinoma in the future.

Objective:To compare positional and volumetric differences between the gross target volumes (GTV) delineated on three-dimensional CT (3D-CT) referencing 18F-FDG PET/CT and the GTV on the deformed image derived from 3D-CT and 18F-FDG PET/CT for primary thoracic esophageal cancer (EC). Methods:Seventy-two patients underwent chemoradiotherapy were enrolled. All the patients sequentially underwent 18F-FDG PET/CT scans for diagnosis and 3D-CT scans for simulation. The GTV 3D was delineated on 3D-CT without referencing 18F-FDG PET/CT. The GTV PET-ref was delineated on 3D-CT referencing 18F-FDG PET/CT. The GTV PET-regwas delineated on the deformed image derived from 3D-CT and 18F-FDG PET/CT by MIM deformable registration software. The differences in position, volume, length, conformity index (CI), and degree of inclusion (DI) of target volumes were compared, respectively. Results:The median volume of GTV 3D, GTV PET-ref, GTV PET-reg were 44.90, 40.36 and 41.15 cm 3, respectively. There was no statistical difference between the volumes of any two targets. The mean lengths of GTV 3D, GTV PET-ref, GTV PET-reg were 8.54, 9.29 and 8.38 cm, respectively. The length of GTV PET-ref was longer than that of GTV 3D ( t=2.134, P<0.05). The median DIs of GTV PET-ref, GTV PET-regin GTV 3D were 0.86, 0.82( Z=-2.741, P<0.05), and that of GTV 3D in GTV PET-ref, GTV PET-reg were 0.87, 0.84 ( Z=-1.429, P<0.05). The median CIs of GTV 3D in GTV PET-ref and GTV PET-reg were 0.72, 0.68 ( Z=2.756, P<0.05), and the difference was significant. The CIs of GTV 3D and GTV PET-ref, GTV 3D and GTV PET-reg, GTV PET-ref and GTV PET-reg had significant negative correlation with the distance of target centers. Conclusions:There was no significant difference between GTV contoured on three-dimensional CT (3D-CT) referencing 18F-FDG PET/CT and the GTV on the deformed image derived from 3D-CT and 18F-FDG PET/CT either in volume size or in spatial position. Therefore, it is recommended that radiation oncologists can refer to the recent diagnostic PET/CT when delineating the gross target volume for primary thoracic esophageal cancer.

Objective To compare the dosimetric and delivery efficiency between intensity-modulated radiation therapy (IMRT) plans based on Halcyon and Trilogy accelerator.Methods Clinical data of 12 patients with cervical cancer receiving Trilogy platform-based IMRT were retrospectively analyzed.The target area and organ at risk were introduced into the Eclipse version 15.1 TPS.The Halcyon-based IMRT was re-designed.The dose coverage of target area and organs at risk,monitor unit (MU) efficiency,delivery time and segment area and the differences between the proximal and distal segment area were statistically compared between two IMRT plans.Results The Halcyon treatment platform could meet the clinical objectives.Dose distribution of the target area was similar to that of the Trilogy plan (P＞O.05).The volumes in the bladder and rectum receiving 30 Gy and the volumes in the left femoral head receiving 20 Gy of Halcyon plan and the mean dose (D) of bladder,rectum and left femoral head were significantly lower compared with those of the Trilogy plan (P=0.001-0.043).The MUs of the Halcyon plan was 2 316.7± 209.7,significantly higher than 1 692.5± 259.5 of the Trilogy plan (P=0.000).The delivery time significantly differed between the Halcyon [(3.01±0.28) min] and Trilogy [(12.38± 1.49) min] (P=0.000).The average segment area of Halcyon plan for proximal and distal MLC was (43.7±32.5) cm2 and (28.8±25.4) cm2,the average segment area of Trilogy plan was (25.7±16.8) cm2,the ratio of the proximal and distal segment area was 1.73±0.43,ranging from 0.71 to 6.28.Conclusions Halcyon treatment platform can meet the clinical requirements and reduce the dosage coverage of normal tissues with better delivery efficiency.The ratio of proximal and distal segment areas should be considered during the plan design.

Objective To compare the size of the internal target volume (ITV),biological target volume (BTV) and internal biological target volume (IBTV) based on PET-CT and 4DCT for primary nonsmall cell lung cancer (NSCLC),as well as try to apply IBTV in radiotherapy planning.Methods A total of 15 patients with NSCLC were sequentially scanned by an axial enhanced 3DCT,4DCT and 18F-FDG PET-CT in the thoracic region.The gross target volumes (GTVs) of ten phases of 4DCT images were contoured,and ITV was obtained by fusion of ten GTVs.BTV based on PET-CT images was determined by the SUV 2.0.The IBTV was defined by fusion of ITV and BTV.Planning target volumes (PTVs) based on ITV,BTV,and IBTV (PITV,PBTV,PIBTV) were obtained by ITV,BTV and IBTV with a 10-mm expansion respectively.The metrics of PIBTV,PITV and PBTV were compared,and the planning parameters of target volumes and risk organs were evaluated.Results There was no significant difference between ITV and BTV,but there was significant difference between IBTV and ITV and BTV (F=22.533,P ＜ 0.05).To include more than 95％ volume of IBTV,it is necessary to expand the margin of 9.0(6.0,12.0)mm based on BTV or 10.00(7.0,12.0)mm based on ITV.There was no significant difference between the two groups (P ＞ 0.05).Dice's similarity coefficient of BTV and ITV was 0.72(0.54,0.79).The intensity modulated radiotherapy plan based on PBTV can guarantee 85.6％ (80.5％,91.2％) of PITV to reach the prescription dose,compared with 80.2％ (74.4％,87.6％) of PBTV by the plan from PITV.Additionally,the conformity index and homogeneity index were not ideal.The dosimetric parameters of PITV and PBTV in the PIBTV plan were much better than those in PBTV-and PITV plan.Conclusions The radiotherapy plan based on PET-CT or 4DCT could not guarantee a reasonable dose distribution of PTV expanded from ITV or BTV.Thus,using IBTV for radiotherapy is advised.

Objective To analyze the efficacy of different clinical characteristics and treatment modalities for patients with primary esophageal small cell carcinoma (PESC),and to find out the prognostic factors,and provide reference for clinical treatment decision.Methods Patients with PESC who were treated at Shandong Cancer Hospital Affiliated to Shandong University from January 2008 to May 2017 were retrospectively enrolled.The clinical features were collected.Their disease progression time and survival status were determined by follow-up,and the follow-up ended in October 2017.Data analysis was performed using SPSS 25.0 software,and GraphPad Prism 7.0 was used for mapping.Survival analysis was performed by Kaplan-Meier method,and log-rank test was used to compare the differences in survival curves of each group.Factors with significant differences in univariate analysis were included in the Cox multivariate survival analysis.ROC curve was used to verify the sensitivity and specificity of the model.Results A total of 83 PESC patients with a complete follow-up were included in the study,including 68 males and 15 females.The average age was 61.93 years old (41-82 years old).The median progression-free survival (PFS) was 9.1 months (1.0-60.0 months) and the median overall survival (OS) was 26.1 months (1.8-60.0 months).Cox multivariate survival analysis showed radiotherapy or not (HR=0.321,95％ C I:0.184-0.559,P ＜0.001) and chemotherapy cycles (HR =0.841,95％CI:0.737-0.960,P =0.010) were independent prognostic factors for PFS.The Veterans Administration Lung Study Group (VALSG) staging (HR =3.050,95 ％ CI:1.606-5.794,P =0.001),radiotherapy or not (HR =0.312,95％CI:0.174-0.560,P ＜0.001),and chemotherapy cycle (HR =0.711,95％ CI:0.601-0.842,P ＜0.001) were independent predictors of OS.The ROC curve showed that the sensitivity and specificity of the PFS prediction model were 78.26％ and 73.33％,and the sensitivity and the specificity of the OS prediction model were 80.00％ and 58.49％.Conclusion VALSG staging is an independent predictor of PESC survival.Comprehensive therapy based on radiotherapy and chemotherapy can improve disease control,reduce metastasis,and improve survival.