Objective:To analyze and compare the interfractional setup errors between two body posi-tioning fixation methods(lithotomy position with carbon fiber full-body fixation frame vs.conventional carbon fiber body fixation frame combined with thermoplastic membrane)in radical radiotherapy for pros-tate cancer,and to calculate the clinical target volume(CTV)to planning target volume(PTV)margin(MPTV)for both methods to optimize immobilization techniques and radiotherapy workflows.Methods:A retrospective analysis was conducted on 37 consecutive patients who underwent radical prostate radio-therapy at Peking University First Hospital between August 2021 and March 2023.The patients were di-vided into two groups based on the immobilization method:Group A(18 patients,450 CBCT image sets)used a carbon fiber whole-body fixator in the lithotomy position,while Group B(19 patients,461 CBCT image sets)used a conventional carbon fiber fixator combined with a thermoplastic mask.All the patients underwent daily cone-beam computed tomography(CBCT)image guidance.Bone registration combined with manual registration was used to obtain the setup error data in the left-right(X),cranio-caudal(Y)and anterior-posterior(Z)directions.The positioning errors of the two groups were compared by using the independent sample t-test,the Mann-Whitney U test and the chi-square test.The average positioning error,systematic positioning error(Σ)and random positioning error(δ)were calculated,and the CTV-PTV extension distance was calculated by using the(MPTV=2.5Σ+0.7δ).Results:The analysis of the setup errors in the three-dimensional direction showed significant differences between the two groups(all P＜0.01).Specifically,the median(quartile)absolute values of the errors in the X,Y,and Z di-rections of group A were[0.40(0.20,0.70)cm,0.50(0.30,0.80)cm,and 0.35(0.20,0.60)cm],respectively.In group B,the corresponding values were significantly reduced to[0.20(0.10,0.40)cm,0.40(0.20,0.70)cm and 0.20(0.10,0.40)cm].The results of Mann-Whitney U test showed that the differences in each direction were highly statistically significant(X:z=-6.86;Y:z=-2.76;Z:z=-5.71).The cumulative distribution ratio of the setup error displacement within 0.5 cm in the X,Y,and Z directions in group A and group B were 297(66.0％)and 408(88.5％)(P＜0.01),250(55.6％)and 285(61.8％)(P=0.055),308(68.4％)and 391(84.8％)(P＜0.01),re-spectively.The CTV-PTV margins in three directions were X 0.66 cm in group A and 0.35 cm in group B;Y0.67 cm and 0.45 cm;Z 0.54 cm and 0.42 cm.Conclusion:Conventional carbon fiber human body fixator combined with thermoplastic film can significantly reduce the setup error.However,the car-bon fiber whole-body fixator in the lithotomy position demonstrated larger setup errors in the X,Y,and Z directions compared with the conventional fixator combined with a thermoplastic mask,indicating the need for further workflow optimization.Given that the lithotomy position is essential for transperineal ultrasound-guided techniques,further research and improvements are required to achieve higher positioning accuracy.

Objective:To explore the optimization potential of clinical target volume (CTV) delineation proposed in the guidelines of the Oncology Group (RTOG), the Francophone Group of Urological Radiotherapy (GFRU), and the European Society for Radiotherapy and Oncology (ESTRO) based on prostate bed local occurrence patterns after radical prostatectomy identified using prostate-specific membrane antigen positron emission tomography (PSMA PET).Methods:A retrospective analysis was conducted on patients with local prostate bed recurrence after radical prostatectomy who underwent PSMA PET at the Department of Nuclear Medicine, Peking University First Hospital from September 2021 to February 2024. The central point of each recurrence was marked. A six-zone method was established based on prostate bed anatomy and the characteristics of cross-sectional imaging. Then, the positional relationships (within or outside) were recorded with respect to recurrences and CTV defined by the RTOG, GFRU, and ESTRO (CTV RTOG, CTV GFRU, and CTV ESTRO), followed the analysis of the recurrence rates and distribution characteristics of various zones. Results:A total of 63 patients with prostate bed recurrence after radical prostatectomy were enrolled in this study, including 97 recurrences. The recurrence rates in the six zones were as follows: 10% of zone 1, 22% of zone 2, 29% of zone 3, 2% of zone 4, 12% of zone 5a, 18% of zone 5b, and 7% of zone 6. Among these zones, zones 2 and 3 showed the highest and second-highest recurrence rates, respectively. CTV GFRU and CTV ESTRO completely covered zones 2 and 3, while CTV RTOG covered zone 2 completely and zone 3 partially. Zone 4, characterized by a low recurrence rate, was not covered by CTV GFRU and CTV ESTRO but was entirely covered by CTV RTOG. Zone 5a, with a recurrence rate of 12%, was completely covered by CTV RTOG but was partially covered by CTV GFRU and CTV ESTRO. The range of 1.3 cm in front of the posterior wall of the bladder covered all recurrences in zone 5a. Conclusions:For CTV delineation of the prostate cancer surgical bed, zone 4, the anterior half of the bladder above the pubic symphysis midpoint, should be contracted due to the low recurrence rate in this zone. In contrast, the anterior boundary above the pubic symphysis midpoint should extend to 1.3 cm in front of the posterior wall of the bladder to completely cover the recurrence zones.

Objective:To analyze and compare the interfractional setup errors between two body posi-tioning fixation methods(lithotomy position with carbon fiber full-body fixation frame vs.conventional carbon fiber body fixation frame combined with thermoplastic membrane)in radical radiotherapy for pros-tate cancer,and to calculate the clinical target volume(CTV)to planning target volume(PTV)margin(MPTV)for both methods to optimize immobilization techniques and radiotherapy workflows.Methods:A retrospective analysis was conducted on 37 consecutive patients who underwent radical prostate radio-therapy at Peking University First Hospital between August 2021 and March 2023.The patients were di-vided into two groups based on the immobilization method:Group A(18 patients,450 CBCT image sets)used a carbon fiber whole-body fixator in the lithotomy position,while Group B(19 patients,461 CBCT image sets)used a conventional carbon fiber fixator combined with a thermoplastic mask.All the patients underwent daily cone-beam computed tomography(CBCT)image guidance.Bone registration combined with manual registration was used to obtain the setup error data in the left-right(X),cranio-caudal(Y)and anterior-posterior(Z)directions.The positioning errors of the two groups were compared by using the independent sample t-test,the Mann-Whitney U test and the chi-square test.The average positioning error,systematic positioning error(Σ)and random positioning error(δ)were calculated,and the CTV-PTV extension distance was calculated by using the(MPTV=2.5Σ+0.7δ).Results:The analysis of the setup errors in the three-dimensional direction showed significant differences between the two groups(all P＜0.01).Specifically,the median(quartile)absolute values of the errors in the X,Y,and Z di-rections of group A were[0.40(0.20,0.70)cm,0.50(0.30,0.80)cm,and 0.35(0.20,0.60)cm],respectively.In group B,the corresponding values were significantly reduced to[0.20(0.10,0.40)cm,0.40(0.20,0.70)cm and 0.20(0.10,0.40)cm].The results of Mann-Whitney U test showed that the differences in each direction were highly statistically significant(X:z=-6.86;Y:z=-2.76;Z:z=-5.71).The cumulative distribution ratio of the setup error displacement within 0.5 cm in the X,Y,and Z directions in group A and group B were 297(66.0％)and 408(88.5％)(P＜0.01),250(55.6％)and 285(61.8％)(P=0.055),308(68.4％)and 391(84.8％)(P＜0.01),re-spectively.The CTV-PTV margins in three directions were X 0.66 cm in group A and 0.35 cm in group B;Y0.67 cm and 0.45 cm;Z 0.54 cm and 0.42 cm.Conclusion:Conventional carbon fiber human body fixator combined with thermoplastic film can significantly reduce the setup error.However,the car-bon fiber whole-body fixator in the lithotomy position demonstrated larger setup errors in the X,Y,and Z directions compared with the conventional fixator combined with a thermoplastic mask,indicating the need for further workflow optimization.Given that the lithotomy position is essential for transperineal ultrasound-guided techniques,further research and improvements are required to achieve higher positioning accuracy.

Objective:To analyze the incidence and influencing factors of lymphopenia in prostate cancer patients undergoing pelvic radiotherapy.Methods:A retrospective analysis was conducted on 123 prostate cancer patients treated at the Department of Radiation Oncology, Peking University First Hospital, from November 2011 to May 2015. Radiotherapy was administered using conventional fractionated intensity-modulated radiotherapy. Blood routine, including absolute lymphocyte count (ALC), was performed on patients before radiotherapy, weekly during radiotherapy, and at the end of radiotherapy. Severe lymphopenia was defined as an ALC <500 cells/μl. Based on whether the minimum ALC during radiotherapy was lower than 500 cells/μl, the entire cohort and 55 patients (excluding those with undelineated pelvic bone marrow due to radiotherapy planning system issues) with delineated pelvic bone marrow (divided into pelvic bone marrow, iliac bone marrow, and lower pelvic bone marrow) were stratified into a severe lymphopenia group (33 cases and 16 cases, respectively) and a mild lymphopenia group (90 cases and 39 cases, respectively). Differences in clinical factors and dosimetric parameters were compared between the groups using the chi-square test (or Fisher's exact test), t-test, and Wilcoxon rank-sum test. Univariate and multivariate logistic regression analyses were performed to identify the clinical and dosimetric factors influencing severe lymphopenia. Results:All 123 prostate cancer patients experienced lymphopenia during radiotherapy, with a median minimum ALC of 0.6×10 9/L [range: (0.2-2.3)×10 9/L]. Severe lymphopenia occurred in 26.8% (33 cases) of patients. Univariate analysis of the entire cohort showed that pre-radiotherapy baseline ALC, initial neutrophil-to-lymphocyte ratio, prostate-specific antigen value, Gleason score, and pelvic radiotherapy were promoting factors for severe lymphopenia ( P<0.05). Multivariate analysis identified pre-radiotherapy baseline ALC ( OR=0.217, 95% CI: 0.072-0.650, P=0.006) and pelvic radiotherapy ( OR=23.852, 95% CI: 2.834-200.787, P=0.004) as promoting factors for severe lymphopenia. In patients with delineated pelvic bone marrow, univariate analysis showed that pelvic bone marrow V 30 Gy and V 40 Gy, iliac bone marrow V 30 Gy and V 40 Gy, lower pelvic bone marrow V 30 Gy and V 40 Gy were promoting factors for severe lymphopenia during treatment ( P<0.05). Conclusions:Lymphopenia is common in prostate cancer patients undergoing radiotherapy, with a high incidence of severe lymphopenia. Pre-radiotherapy baseline ALC, as well as pelvic, iliac, and lower pelvic bone marrow V 30 Gy and V 40 Gy, are promoting factors for severe lymphopenia during radiotherapy.

Objective:To compare the efficacy and safety of extended-field versus reduced-field radiotherapy in upper tract urothelial carcinoma (UTUC) patients after radical operation.Methods:A retrospective analysis was conducted on the data of 210 UTUC patients who underwent full-length nephrectomy and received postoperative adjuvant radiotherapy in Peking University First Hospital from January 2013 to November 2023, and follow-up continued until June 2024. According to the target area of postoperative radiotherapy, patients were divided into the extended-field radiotherapy group (127 cases) and the reduced-field radiotherapy group (83 cases). The overall survival (OS), distant metastasis free survival (DMFS), local recurrence free survival (LRFS) and adverse reactions were compared. In the same period, 114 patients with recurrent abdominal and pelvic lymph nodes who did not receive adjuvant therapy after surgery for UTUC in our center were prospectively collected, and the coverage of the reduced-field target area was analyzed. Chi square test was used to compare the clinical characteristics, Kaplan-Meier method was used to analyze survival outcomes, log-rank test was used to compare the survival rate, and Cox multivariate regression analysis was performed on the influencing factors of survival.Results:The median follow-up was 24.5 (range: 3-74) months. There were no significant differences between the extended-field and reduced-field radiotherapy groups in terms of 2-year LRFS (93.3% vs. 98.1%, P=0.156), 2-year DMFS (84.8% vs. 91.2%, P=0.176), and 2-year OS (90.4% vs. 90.7%, P=0.707). The most common toxicities of adjuvant radiotherapy were nausea and leukopenia, with significantly higher grade 1-2 incidence in the extended-field group compared to the reduced-field group ( P<0.05). According to the analysis of patients with retroperitoneal lymph node recurrence after surgery, the reduced-field target designed according to the location of the primary tumor can cover more than 90% of the postoperative metastatic lymph node area Multivariate analysis revealed that variant histology ( HR=2.180,95% CI: 1.021-4.658, P=0.044) was an independent predictor of worse DMFS, while variant histology ( HR=3.825,95% CI: 1.514-9.662, P=0.005) and T 3-4 stage ( HR=4.452,95% CI: 1.025-19.339, P=0.046) were independent predictors of poorer OS. Conclusions:Compared with extended-field radiotherapy, reduced-field radiotherapy designed based on primary tumor location significantly reduced treatment-related toxicities without compromising postoperative therapeutic efficacy, and the reduced-field can cover more than 90% of local recurrent lesions.

Objective:To evaluate the acute toxicities and related influencing factors of vertebral-body-sparing proton craniospinal irradiation (VBSpCSI) using pencil beam scanning (PBS) technology in pediatric patients, and to assess spinal growth and survival outcomes.Methods:A retrospective analysis was conducted on 70 pediatric patients treated with PBS-based VBSpCSI at Hebei Yizhou Cancer Hospital between January 2020 and December 2022, and continued to follow up until November 2023. Acute toxicities were assessed, and linear regression analysis combined with receiver operating characteristic curve were employed to investigate the dose-effect relationship between vertebral dose and toxicities. Spinal growth after radiotherapy was evaluated by measuring the Cobb angle on follow-up MRI. Overall survival (OS) and progression-free survival (PFS) were estimated using the Kaplan-Meier method.Results:The median age of patients at the time of irradiation was 6 years (range, 2-16 years). Two patients (3%) developed grade ≥3 gastrointestinal toxicities, while 7 patients (10%) experienced grade 1 radiation-induced esophagitis. The nadirs of white blood cell count (WBC), absolute neutrophil count (ANC), and absolute lymphocyte count (ALC) during treatment were significantly negatively correlated with vertebral V 5 Gy ( P=0.009, 0.006, 0.001) and vertebral V 20 Gy ( P=0.007, 0.011, <0.001). When vertebral V 5 Gy<86.5% and vertebral V 20 Gy<73.2%, the incidence of grade ≥3 myelosuppression was significantly reduced ( P<0.001, =0.001). Additionally, younger patient age (in months) and concurrent chemotherapy were also significantly associated with increased acute hematologic toxicity. Among 43 patients with MRI follow-up, no scoliosis, kyphosis, or chronic lumbosacral pain was observed. The 3-year OS and PFS rates were 95.7% and 86.4%, respectively. Conclusions:PBS-based VBSpCSI in pediatric patients demonstrates manageable acute toxicities, with a clear dose-effect relationship between vertebral V 5 Gy , V 20 Gy and hematologic toxicities, and the incidence of non-hematological toxicities remains low. No adverse effects on spinal growth or survival outcomes were observed in the short term.

Objective:To explore the optimization potential of clinical target volume (CTV) delineation proposed in the guidelines of the Oncology Group (RTOG), the Francophone Group of Urological Radiotherapy (GFRU), and the European Society for Radiotherapy and Oncology (ESTRO) based on prostate bed local occurrence patterns after radical prostatectomy identified using prostate-specific membrane antigen positron emission tomography (PSMA PET).Methods:A retrospective analysis was conducted on patients with local prostate bed recurrence after radical prostatectomy who underwent PSMA PET at the Department of Nuclear Medicine, Peking University First Hospital from September 2021 to February 2024. The central point of each recurrence was marked. A six-zone method was established based on prostate bed anatomy and the characteristics of cross-sectional imaging. Then, the positional relationships (within or outside) were recorded with respect to recurrences and CTV defined by the RTOG, GFRU, and ESTRO (CTV RTOG, CTV GFRU, and CTV ESTRO), followed the analysis of the recurrence rates and distribution characteristics of various zones. Results:A total of 63 patients with prostate bed recurrence after radical prostatectomy were enrolled in this study, including 97 recurrences. The recurrence rates in the six zones were as follows: 10% of zone 1, 22% of zone 2, 29% of zone 3, 2% of zone 4, 12% of zone 5a, 18% of zone 5b, and 7% of zone 6. Among these zones, zones 2 and 3 showed the highest and second-highest recurrence rates, respectively. CTV GFRU and CTV ESTRO completely covered zones 2 and 3, while CTV RTOG covered zone 2 completely and zone 3 partially. Zone 4, characterized by a low recurrence rate, was not covered by CTV GFRU and CTV ESTRO but was entirely covered by CTV RTOG. Zone 5a, with a recurrence rate of 12%, was completely covered by CTV RTOG but was partially covered by CTV GFRU and CTV ESTRO. The range of 1.3 cm in front of the posterior wall of the bladder covered all recurrences in zone 5a. Conclusions:For CTV delineation of the prostate cancer surgical bed, zone 4, the anterior half of the bladder above the pubic symphysis midpoint, should be contracted due to the low recurrence rate in this zone. In contrast, the anterior boundary above the pubic symphysis midpoint should extend to 1.3 cm in front of the posterior wall of the bladder to completely cover the recurrence zones.

Objective:To analyze the incidence and influencing factors of lymphopenia in prostate cancer patients undergoing pelvic radiotherapy.Methods:A retrospective analysis was conducted on 123 prostate cancer patients treated at the Department of Radiation Oncology, Peking University First Hospital, from November 2011 to May 2015. Radiotherapy was administered using conventional fractionated intensity-modulated radiotherapy. Blood routine, including absolute lymphocyte count (ALC), was performed on patients before radiotherapy, weekly during radiotherapy, and at the end of radiotherapy. Severe lymphopenia was defined as an ALC <500 cells/μl. Based on whether the minimum ALC during radiotherapy was lower than 500 cells/μl, the entire cohort and 55 patients (excluding those with undelineated pelvic bone marrow due to radiotherapy planning system issues) with delineated pelvic bone marrow (divided into pelvic bone marrow, iliac bone marrow, and lower pelvic bone marrow) were stratified into a severe lymphopenia group (33 cases and 16 cases, respectively) and a mild lymphopenia group (90 cases and 39 cases, respectively). Differences in clinical factors and dosimetric parameters were compared between the groups using the chi-square test (or Fisher's exact test), t-test, and Wilcoxon rank-sum test. Univariate and multivariate logistic regression analyses were performed to identify the clinical and dosimetric factors influencing severe lymphopenia. Results:All 123 prostate cancer patients experienced lymphopenia during radiotherapy, with a median minimum ALC of 0.6×10 9/L [range: (0.2-2.3)×10 9/L]. Severe lymphopenia occurred in 26.8% (33 cases) of patients. Univariate analysis of the entire cohort showed that pre-radiotherapy baseline ALC, initial neutrophil-to-lymphocyte ratio, prostate-specific antigen value, Gleason score, and pelvic radiotherapy were promoting factors for severe lymphopenia ( P<0.05). Multivariate analysis identified pre-radiotherapy baseline ALC ( OR=0.217, 95% CI: 0.072-0.650, P=0.006) and pelvic radiotherapy ( OR=23.852, 95% CI: 2.834-200.787, P=0.004) as promoting factors for severe lymphopenia. In patients with delineated pelvic bone marrow, univariate analysis showed that pelvic bone marrow V 30 Gy and V 40 Gy, iliac bone marrow V 30 Gy and V 40 Gy, lower pelvic bone marrow V 30 Gy and V 40 Gy were promoting factors for severe lymphopenia during treatment ( P<0.05). Conclusions:Lymphopenia is common in prostate cancer patients undergoing radiotherapy, with a high incidence of severe lymphopenia. Pre-radiotherapy baseline ALC, as well as pelvic, iliac, and lower pelvic bone marrow V 30 Gy and V 40 Gy, are promoting factors for severe lymphopenia during radiotherapy.

Objective:To compare the efficacy and safety of extended-field versus reduced-field radiotherapy in upper tract urothelial carcinoma (UTUC) patients after radical operation.Methods:A retrospective analysis was conducted on the data of 210 UTUC patients who underwent full-length nephrectomy and received postoperative adjuvant radiotherapy in Peking University First Hospital from January 2013 to November 2023, and follow-up continued until June 2024. According to the target area of postoperative radiotherapy, patients were divided into the extended-field radiotherapy group (127 cases) and the reduced-field radiotherapy group (83 cases). The overall survival (OS), distant metastasis free survival (DMFS), local recurrence free survival (LRFS) and adverse reactions were compared. In the same period, 114 patients with recurrent abdominal and pelvic lymph nodes who did not receive adjuvant therapy after surgery for UTUC in our center were prospectively collected, and the coverage of the reduced-field target area was analyzed. Chi square test was used to compare the clinical characteristics, Kaplan-Meier method was used to analyze survival outcomes, log-rank test was used to compare the survival rate, and Cox multivariate regression analysis was performed on the influencing factors of survival.Results:The median follow-up was 24.5 (range: 3-74) months. There were no significant differences between the extended-field and reduced-field radiotherapy groups in terms of 2-year LRFS (93.3% vs. 98.1%, P=0.156), 2-year DMFS (84.8% vs. 91.2%, P=0.176), and 2-year OS (90.4% vs. 90.7%, P=0.707). The most common toxicities of adjuvant radiotherapy were nausea and leukopenia, with significantly higher grade 1-2 incidence in the extended-field group compared to the reduced-field group ( P<0.05). According to the analysis of patients with retroperitoneal lymph node recurrence after surgery, the reduced-field target designed according to the location of the primary tumor can cover more than 90% of the postoperative metastatic lymph node area Multivariate analysis revealed that variant histology ( HR=2.180,95% CI: 1.021-4.658, P=0.044) was an independent predictor of worse DMFS, while variant histology ( HR=3.825,95% CI: 1.514-9.662, P=0.005) and T 3-4 stage ( HR=4.452,95% CI: 1.025-19.339, P=0.046) were independent predictors of poorer OS. Conclusions:Compared with extended-field radiotherapy, reduced-field radiotherapy designed based on primary tumor location significantly reduced treatment-related toxicities without compromising postoperative therapeutic efficacy, and the reduced-field can cover more than 90% of local recurrent lesions.

Objective:To evaluate the acute toxicities and related influencing factors of vertebral-body-sparing proton craniospinal irradiation (VBSpCSI) using pencil beam scanning (PBS) technology in pediatric patients, and to assess spinal growth and survival outcomes.Methods:A retrospective analysis was conducted on 70 pediatric patients treated with PBS-based VBSpCSI at Hebei Yizhou Cancer Hospital between January 2020 and December 2022, and continued to follow up until November 2023. Acute toxicities were assessed, and linear regression analysis combined with receiver operating characteristic curve were employed to investigate the dose-effect relationship between vertebral dose and toxicities. Spinal growth after radiotherapy was evaluated by measuring the Cobb angle on follow-up MRI. Overall survival (OS) and progression-free survival (PFS) were estimated using the Kaplan-Meier method.Results:The median age of patients at the time of irradiation was 6 years (range, 2-16 years). Two patients (3%) developed grade ≥3 gastrointestinal toxicities, while 7 patients (10%) experienced grade 1 radiation-induced esophagitis. The nadirs of white blood cell count (WBC), absolute neutrophil count (ANC), and absolute lymphocyte count (ALC) during treatment were significantly negatively correlated with vertebral V 5 Gy ( P=0.009, 0.006, 0.001) and vertebral V 20 Gy ( P=0.007, 0.011, <0.001). When vertebral V 5 Gy<86.5% and vertebral V 20 Gy<73.2%, the incidence of grade ≥3 myelosuppression was significantly reduced ( P<0.001, =0.001). Additionally, younger patient age (in months) and concurrent chemotherapy were also significantly associated with increased acute hematologic toxicity. Among 43 patients with MRI follow-up, no scoliosis, kyphosis, or chronic lumbosacral pain was observed. The 3-year OS and PFS rates were 95.7% and 86.4%, respectively. Conclusions:PBS-based VBSpCSI in pediatric patients demonstrates manageable acute toxicities, with a clear dose-effect relationship between vertebral V 5 Gy , V 20 Gy and hematologic toxicities, and the incidence of non-hematological toxicities remains low. No adverse effects on spinal growth or survival outcomes were observed in the short term.