Using the Diaphragm as a Tracking Surrogate in CyberKnife Synchrony Treatment.

BACKGROUND In this study, we assessed the usefulness of diaphragm surrogate tracking in the design of a respiratory model for CyberKnife Synchrony treatment of lung tumors. MATERIAL AND METHODS Twenty-four patients with lung cancer who underwent stereotactic body radiotherapy with CyberKnife between April and November 2019 were enrolled. Simulation plans for each patient were designed using Xsight lung tracking (XLT) and diaphragm tracking (DT) methods, and tumor visualization tests were performed. The offset consistency at each respiratory phase was analyzed. The relative distance along the alignment center of the superior-inferior (SI) axis in the 2 projections (dxAB), uncertainty (%), and average standard error (AvgStdErr)/maximum standard error (MAXStdErr) were also analyzed. RESULTS Bland-Altman analyses revealed that the average differences±standard deviation (SD) between XLT and DT tracking methods were 0.4±2.9 mm, 0.3±4.35 mm, and -1.8±6.8 mm for the SI, left-right (LR), and anterior-posterior (AP) directions, respectively. These results indicated high consistency in the SI and LR directions and poor consistency in the AP direction. Uncertainty differed significantly between XLT and DT (22.813±5.721% vs 9.384±3.799%; t=-5.236; P=0.0008), but we found no significant differences in dxAB, AvgStdErr, or MAXStdErr. CONCLUSIONS In the majority of cases, motion tracking by XLT and DT was consistent and synchronized in the SI directions, but not in the LR and AP directions. With a boundary margin of 0.3±4.35 mm and 1.8±6.8 mm for the LR and AP directions, DT may contribute to better implementation of CyberKnife Synchrony treatment in patients with lung tumors near the diaphragm that cannot be seen in tumor visualization tests.

Long-term Therapeutic Outcome and Prognostic Factors of Patients with Nasopharyngeal Carcinoma Receiving Intensity-modulated Radiotherapy: An Analysis of 608 Patients from Low-endemic Regions of China.

OBJECTIVE: To evaluate the long-term outcome and prognostic factors of patients with nasopharyngeal carcinoma (NPC) from low-endemic regions of China who received definitive intensity-modulated radiation therapy (IMRT). METHODS: The clinical data from 608 patients with newly-diagnosed non-metastatic NPC who have received initial treatment at our cancer center from January, 2008 to December, 2013 were retrospectively reviewed. All patients received definitive IMRT, and 87.7% received platinum-based chemotherapy. RESULTS: The median follow-up duration was 51 months (follow-up rate, 98.5%; range, 10-106 months) for the entire cohort. The 5-year overall survival rate was 79.7%. The 5-year local relapse-free survival rate, regional relapse-free survival rate, distant metastasis-free survival rate and progression-free survival rate were 92.4%, 93.3%, 79.2% and 74.3%, respectively. A total of 153 patients had experienced treatment failure, with distant metastasis as the primary cause in 77.1% (118/153). Patients with T4 or N3 diseases had a significantly poorer prognosis than other subcategories. Stage T4 and N3 were closely associated with distant metastasis, with the metastatic rate of 29.3% and 45.5%, respectively. CONCLUSION: IMRT provides patients with non-metastatic NPC with satisfactory long-term survival. Both T stage and N stage are important prognostic factors for NPC patients. Patients with T4 or N3 diseases have significantly increased distant metastatic rates and poor survival time.

Optimized CyberKnife Lung Treatment: Effect of Fractionated Tracking Volume Change on Tracking Results.

OBJECTIVES: To explore the impact of volume change in the fractionated tracking of stereotactic radiotherapy on the results of synchronous, respiratory tracking algorithm using CyberKnife. METHODS: A total of 38 lung tumor patients receiving stereotactic radiotherapy at our center from March 2018 to October 2019 were counted. Photoshop CS4 image processing software was used to obtain the pixels and the average value of brightness of the tracking volume in the image and calculate the grayscale within the contour of the tracking volume on the real-time X-ray image. At the same time, parameters of the synchronous respiratory tracking algorithm of the fractional CyberKnife were extracted for comparison between the volume of image-guided image tracking and the number of fractions during stereotactic radiotherapy. We also analyzed the relationship between fraction tumor location and characteristics and the calculated results of synchronous respiratory tracking by CyberKnife. RESULTS: There were no significant differences between the first four fractions (p > 0.05) for left lung lesions and no significant differences between the first five fractions for right lung lesions (p ≥ 0.05). For peripheral lung cancer, longer fractional treatment led to greater variation in grayscale (G-A: >4 fractions p < 0.05), while for central lung cancer, longer fractional treatment led to greater variation in parameters of the synchronous respiratory tracking algorithm (Uncertainty A and Uncertainty B: >4 fractions p < 0.05). There was a significant correlation between radiotherapy-graded tumor density and relevant parameters, and the correlation was strong (>0.7, p < 0.05). CONCLUSION: With the increase of treatment fractions, the gray value in the patient tracking volume decreased. Patients of >4 fractions were advised to reevaluate with simulated CT and replan. For tumors with small diameter and low density, the imaging changes of volume should be closely followed during treatment. For left lung and central lung cancer, carefully select the synchronous tracking treatment with 2-view.

[Risk Analysis of Radiotherapy Implementation Process Based on Failure Mode and Effect Analysis].

OBJECTIVE: Providing a risk assessment method for the implementation of radiotherapy to identify possible risks in the implementation of the treatment process, and proposing measures to reduce or prevent these risks. METHODS: A multidisciplinary expert evaluation team was developed and the radiotherapy treatment process flow was drawn. Through the expert team, the failure mode analysis is carried out in each step of the flow chart. The results were summarized and the RPN (risk priority ordinal) score was obtained, and the quantitative evaluation results of the whole process risk were obtained. RESULTS: One hundred and six failure modes were obtained, risk assessment of RPN (20%) high risk failure model are 22 and severity S (≥ 8) high risk failure model are 27. The reasons for the failures were man-made errors or hardware and software failures. CONCLUSIONS: Failure mode and effect analysis can be used to evaluate the risk assessment of radiotherapy, and it provides a new solution for risk control in radiotherapy field.

Optimization of parameters for preparation of docetaxel-loaded PLGA nanoparticles by nanoprecipitation method.

The purpose of this study was to develop docetaxel-poly (lactide-co-glycolide) (PLGA) loaded nanoparticles by using nanoprecipitation method and optimize the relative parameters to obtain nanoparticles with higher encapsulation efficiency and smaller size. The physicochemical characteristics of nanoparticles were studied. The optimized parameters were as follows: the oil phase was mixture of acetone and ethanol, concentration of tocopheryl polyethylene glycol succinate (TPGS) was 0.2%, the ratio of oil phase to water phase was 1:5, and the theoretical drug concentration was 5%. The optimized nanoparticles were spherical with size between 130 and 150 nm. The encapsulation efficiency was (40.83±2.1)%. The in vitro release exhibited biphasic pattern. The results indicate that docetaxel-PLGA nanoparticles were successfully fabricated and may be used as the novel vehicles for docetaxel, which would replace Taxotere® and play great roles in future.