Immune checkpoint blockade can promote the tumor?specific cytotoxic T?lymphocyte ( CTL) response. However, only a small proportion of patients have good response to immune checkpoint blockade. It has been reported that radiotherapy combined with immune checkpoint blockade can promote antigen presentation, which further enhances the tumor?specific CTL response;moreover, the combined therapy achieves better treatment outcomes than radiotherapy alone or immune checkpoint blockade alone. The latest study has shown that radiotherapy combined with dual immune checkpoint blockade has better efficacy than radiotherapy combined with CTLA?4 blockade in patients with melanoma. Therefore, radiotherapy combined with immune checkpoint blockade will become a new approach for treating tumor. This paper reviews the research advances in the combined therapy.

Objective To investigate the effects of hippocampal?sparing intensity?modulated radiotherapy ( IMRT) on dose distribution of target volume and organs at risk ( OARs) in locally advanced nasopharyngeal carcinoma. Methods A retrospective dosimetric analysis was performed among 11 patients with locally advanced nasopharyngeal carcinoma. The MONACO ? v5. 10 Treatment Planning System was used to design three treatment plans:routine volumetric modulated arc therapy ( VMAT ) , hippocampal?sparing VMAT, and nine fixed?fields IMRT. The D98%, D50%, D2%, Dmean , conformity index ( CI ) , and homogeneity index (HI) of planning target volume (PTV) and PTVnx as well as dose distribution of the hippocampus and OARs were evaluated. Using single factor analysis of variance,two group comparative was LSD or paired t?test. Results For the above three plans,the D2% values of PTVnx were ,7 513,and 7 462 cGy,respectively (P=0. 016);the D98% values of PTV were 5837,5812,and 5914 cGy,respectively (P=0. 029);the average D2% values of PTV were 7 399,7 380,and 7 333 cGy,respectively ( P=0. 047);the HI values of PTV were 0. 239,0. 241,and 0. 220,respectively (P=0. 016);the V10 values of the brain stem were 97. 2%,88. 1%,and 90. 3%,respectively ( P=0. 001);the V20 values of the brain stem were 74. 2%, 62. 3%,and 67. 1%,respectively ( P=0. 032);the V30 values of the brain stem were 50. 9%,35. 8%,and 45. 5%, respectively ( P= 0. 020 );the V40 values of brain stem were 24. 4%, 14. 4%, and 23. 3%, respectively ( P=0. 018);the Dmean values of hippocampus were 1 518,899,and 896 cGy,respectively ( P=0. 000);the D40% values of hippocampus were 1 379,642,and 639 cGy,respectively ( P=0. 000);the V10 values of the hippocampus were 54. 1%,25. 1%,and 3. 8%,respectively ( P=0. 000);the V20 values of the hippocampus were 26. 2%, 12. 6%, and 12. 0%, respectively ( P=0. 001 ) . Conclusions Hippocampal?sparing VMAT and nine fixed?fields IMRT can significantly reduce the dose to the hippocampus without affecting dose distribution of target volume and OARs. VMAT may be superior to IMRT because VMAT can simultaneously reduce the dose to the brain stem.

Objective To investigate the impact of oral contrast agent for assisting in outlining the small bowel on pelvic volumetric modulated arc therapy (VMAT) dose in patients with cervical cancer.Methods Nine cervical cancer patients for postoperative radiotherapy underwent CT scans,and the target volumes and organs at risk including the small bowel were contoured.The VMAT plan was designed for each case.Then another plan was generated by re-calculating the radiation dose after changing the electron density of the small bowel.The first plan (plan A) was the conventional VMAT plan,and the second one (plan B) specified the electron density of the small bowel.Paired t-test was used to compare the dose distribution between the two plans.Results The Dg8,D5o,conformity index,and homogeneity index of plans A and B were 4 989.1 vs.5 000.1 cGy (P =0.026),5 208.6 vs.5 191.6 cGy (P =0.005),0.766 vs.0.765 (P =0.920),and 0.081 vs.0.074(P =0.055),respectively.The volumes of the small bowel receiving at least 30 Gy for plans A and B were 309.3 vs.314.3 cm3(P =0.207),while bladder V45 of the two plans was 52.4％ vs.51.1％ (P =0.168).To achieve the same prescribed dose,plan A and plan B needed 893.3 MU and 865.8 MU (P =0.093).Conclusions The contrast agent filling the small bowel does not lead to a significant increase in the pelvic VMAT dose in patients with cervical cancer after surgery.

Objective To study the accuracy of SentinelTM system for patient setup using rigid-body phantom.Methods A 002LFC IMRT phantom was placed on Elekta HexaPODTM 6-degree couch using tattoo and the laser in the treatment room.When a well-know shift (3 directions) and rotation (3 positions) was moved,CBCT and SentinelTM system were scanned respectively,and the measuring errors of six dimensions were recorded.The absolute differences between applied and measured errors were compared and paired t-test.Results Total 15 well-know shifts were investigated.The SentinelTM system was very good stability and the largest absolute difference only 0.9 mm (z direction) and 0.2° (arbitrary direction).At the same time,a good conformance between SentinelTM system and CBCT was displayed because the largest absolute difference between applied and measuring error was less than 0.9 mm (z direction) and 0.2° (arbitrary direction).Conclusions SentinelTM system is fast,simple,non-invasive and seems to be reliable in detecting patient setup errors.It maybe hold potential to ensure precise patient positioning with reduced CBCT frequency in tumor locations with fixed relation to surface structures.

Objective To analyze the difference of prescription dose between ICRU report 83 and Chinese recommendation in the nasopharyngeal carcinoma (NPC) for intensity modulated radiation therapy (IMRT).Methods Eighty-four NPC were treated using IMRT technology from Jan 1,2010 to Apr 1,2012.All dose volume histogram of the 84 IMRT plan were analyzed retrospectively.The target volumes of planning gross tumor volume of nasopharynx (PGTVnx) or planning clinical target volume and high risk lymphatic drainage (PCTV1) and doses of D100,D98,D95,D50,D2 and D0 were recorded.The mean,standard error,medial,range,coefficient of variation (CV) of PGTVnx,PCTV1,and D100,D98,D95,D50,D2and D0 were calculated,respectively.The homogeneity index (HI) and deviation between D95 and D50 of PGTVnx and PCTV1 were calculated,respectively.The differentiation of grouping results were analyzed with grouped t-test method.Results The HI of PGTVnx and PCTV1 were 0.118 ± 0.045 and 0.272 ± 0.037,respectively.It is the bigger target volume,the worse HI;and the advanced T stage,the worse HI.Either PGTVnx or PCTV1,D95 were less than D50.The average deviation was-5.15％ and-10.97％,and the actual difference value was (382± 180) cGy (P=0.000) and (741± 140) cGy (P=0.000).Conclusions D550,which is the recommendation prescription dose of PTV in ICRU report 83,could evaluate accurately the IMRT plan with combining D98 and D2· When D50 is used to instand of D95,the prescription dose of PGTVnx and PCTV1 should increase 5％ and 11％,respectively.

Objective To analyze the stability and accuracy of the equipment for three-dimensional ultrasound-based image-guided radiation therapy (3DUS-IGRT) in daily practice, and to provide a basis for clinical application of radiotherapy for soft tissue tumors.Methods A specific calibration phantom was used for continuous calibration and quality control of the 3DUS-IGRT equipment in a year.The method for daily quality control of ultrasound-guided equipment was explored, and its stability and accuracy were monitored.Results The phantom position errors in both Sim and Guide stations of the 3DUS-IGRT equipment were within 1 mm.Conclusions The 3DUS-IGRT equipment has a stable performance with the support of a complete set of stringent and accurate calibration and quality control, which provides a new image-guided method for precise radiotherapy for soft tissue tumors.

Objective To investigate the feasibility of prophylactic cranial irradiation with hippocampal avoidance (HA-PCI) in non-small cell lung cancer (NSCLC).Methods The clinical data of 56 patients with brain metastases of NSCLC who were treated from 2011 to 2014 were collected.Brain metastases and the hippocampus were delineated on T1 W1 contrast-enhanced MRI,and the distance between brain metastases and the hippocampus was analyzed;an HA-PCI regimen was also developed,and the distribution of the metastases in planning target volume (PTV) low-dose regions around the hippocampus was analyzed.Results None of the 139 metastases involved the hippocampus.There were 6(4.3％) and 18 (12.9％) metastases within 5 mm and 10 mm,respectively,outside the hippocampus.In the HA-PCI regimen,the D50％ and D2％ of PTV were 25.6 Gy and 27.1 Gy,respectively.Dmean and D2％ for the hippocampus were 7.4 Gy and 9.9 Gy,respectively;D50％ within 0-5.0 mm,5.1-10.0 mm,and 10.1-15.0 mm outside the hippocampus was 10.3 Gy,15.1 Gy,and 20.5 Gy,respectively.Conclusions HA-PCI may be feasible theoretically,but this needs to be confirmed by the intracranial failure pattern in patients with long-term survival.

Objectives:To analyze the risk factors related to infection after posterior lumbar interbody fusion(PLIF)by random forest algorithm and develop a prediction model,providing a certain reference for clinical prevention of surgical site infection(SSI)after PLIF.Methods:A retrospective study was conducted on the masked data of patients hospitalized for PLIF in the spinal surgery department of some third-level grade A hospitals in Beijing municipality and Hebei Province from June 2019 to June 2021 provided by Beijing Zhongwei Cloud Medical Data Analysis and Application Technology Research Institute through data processing and analysis.The classification data were analyzed and compared between SSI group and non-SSI group to obtain variables that significantly impacted the postoperative infection.SPSS Modeler 20 system was used as the tool for model development,and random forest algorithm was applied to analyze,obtaining the patient characteristics of postoperative infection,namely the infection model.Results:A total of 8,764 patients were included in study,and 373 patients were diagnosed with SSI,with an incidence rate of 4.4％(95％CI:2.2％to 6.5％).After statistical analysis,six variables,including obesity,ASA Ⅲ and above,prolonged operative time,chronic heart disease,diabetes and renal dysfunction,were independently associated with SSI.Classification with a random forest model yielded a high accuracy of 90.6％.The characteristics of patients prone to infection after PLIF(two models of infection)was:[(BMI=1)and(SD=1)and(ASA=1)and(RI=1)]or[(BMI=0)and(SD=1)and(DM=1)and(RI=1)].Conclusions:The random forest algorithm applied in this study could obtain an average accuracy of 90.6％,and two infection models were obtained as:(1)Patients with obesity,renal insufficiency,ASA grade Ⅲ or above,and operative time≥3h;(2)Patients who are not obese,but with diabetes,renal insufficiency,and the operative time ≥3h.