Search

The aim of the study was to evaluate short-term safety and efficacy of simultaneous modulated accelerated radiation therapy (SMART) delivered via helical tomotherapy in patients with nasopharyngeal carcinoma (NPC).

Background: Using propensity score matching method (PSM) to evaluate the feasibility and clinical outcomes of simultaneous modulated accelerated radiation therapy (SMART) using helical tomotherapy (HT) in patients with nasopharyngeal carcinoma (NPC).Methods: Between August 2007 and January 2016, 381 newly diagnosed NPC patients using HT were enrolled in pre-PSM cohort, including 161 cases in a prospective phase II study (P67.5 study, with a prescription dose of 67.5Gy in 30 fractions to the primary tumour and positive lymph nodes) and 220 cases in a retrospective study (P70 study, with a prescription dose of 70Gy in 33 fractions to the primary tumour and positive lymph nodes). Acute and late toxicities were assessed according to the established RTOG/EORTC criteria and Common Terminology Criteria for Adverse Events (CTCAE) V 3.0. Survival rate were assessed with Kaplan-Meier method, log-rank test and Cox regression.Results: After matching, 148 sub-pairs of 296 patients were generated in post-PSM cohort. The incidence of grade 3-4 leukopenia, thrombocytopenia and anemia in the P67.5 group was significantly higher than in the P70 study, but no significant different was found in other acute toxicities or late toxicities between the two groups. The median follow-up was 33 months in the P67.5 and P70 group, ranging 12-54 months and 6-58 months, respectively. No significant differences in 3-year local-regional recurrence free survival (LRRFS), distant metastasis-free survival (DMFS), disease free survival (DFS) and overall survival (OS) were observed between the 2 groups. Univariate analysis showed that age, T stage, clinical stage were the main factors effecting survival. Cox proportional hazards model showed that 67.5Gy/30F pattern seemed superior in 3-year OS (HR = 0.476, 95% CI: 0.236-0.957).Conclusions: Through increasing fraction dose and shortening treatment time, the P67.5 study achieved excellent short-term outcomes and potential clinical benefits, with acceptable acute and late toxicities.Trial Registration: The trial was registered at Chinese Clinical Trial Registry on 5 July 2014 with a registration code of ChiCTRONC-14,004,895. [ABSTRACT FROM AUTHOR]

The paper introduces a helical tomotherapy (HT) adaptive system in assessment of parotid gland dose variation in head and neck cancer. The system, which helical therapy unit is equipped with, is based on megavoltage computed tomography (MVCT) images to calculate the actual volume and dose of region of interest (ROI). Whether to change plan is judged on the fact for the realization of adaptive radiotherapy. One case of nasopharyngeal carcinoma was as a sample to evaluate parotid gland dose variation during the treatment. On every week and last time, patient was scanned by MVCT before treatment, a total of eight MVCT images. As the treatment progressed, the parotid gland volume was shrinking and the dose was increasing. The parotids volume variation was negatively related with D50 and V1 (both P < 0.05).

Background and Objective: Helical tomotherapy (HT) has shown its dosimetric advantages in the radiotherapy for many cancers. To date, no published studies have performed a dosimetric evaluation of whole pelvic radiotherapy (WPRT) using HT for postoperative endometrial cancer. This study was to compare the dosimetric characteristics of HT and step-and-shoot intensity modulated radiation therapy (SaS-IMRT) for endometrial cancer patients undergoing postoperative WPRT, and to explore whether whole pelvic HT for postoperative endometrial cancer has the advantage of dosimetry., Methods: Ten patients with endometrial cancer undergoing postoperative WPRT were enrolled in this study. SaS-IMRT and HT Plans were developed for each patient. The dose distributions of the targets, organs at risk and normal tissue were analyzed and compared., Results: The mean PTV100 were 95.6% and 95.8% (P=0.72) for the SaS-IMRT and HT plans, respectively. The mean homogeneity indexes were 1.10 and 1. 07 (P=0.00). The mean conformity indexes were both 0.87. The mean doses to rectum and bladder for HT were decreased by 1.3 Gy and 3.0 Gy compared with SaS-IMRT, respectively, while the mean dose to pelvic bones was increased by 1.1 Gy. The volumes of small intestine and colon, pelvic bones receiving moderate and low dose also increased. The V5, V10 and V20 of normal tissue were increased by 13.0%, 18.0%, and 5.0% (P=0.00). The mean dose to normal tissue was increased by 2.5 Gy (P=0.00)., Conclusions: Compared with SaS-IMRT, HT resulted in more homogeneous PTV dose distribution, better sparing of rectum and bladder. The volumes of small intestine and colon, pelvic bones and normal tissue receiving moderate and low dose for HT increased. The clinical significance of the dosimetric differences needs further investigations.

Background & Objective: During the helical tomotherapy process, megavoltage computed tomography (MVCT) images are usually used for guiding the precise setup of patients before/after treatment delivery, which would certainly increase the total dose for patients. This study was to investigate the imaging dose of MVCT using the body and head phantom on a tomotherapy machine., Methods: A set of cylindrical body and head phantoms was adopted for scanning with different pitch values (1.0/2.0/3.0), lengths (4.8/7.2/9.6/12/14.4 cm) and patient setups on the couch of tomotherapy system. The average MVCT imaging doses were measured using A1SL chambers inserted in the phantoms with preset geometry. The dose uniformity was qualitatively analyzed., Results: The MVCT scanning dose for the body phantom was between 0.599 and 2.876 cGy during each treatment delivery, while the dose for the head phantom was between 0.913 and 3.231 cGy. Two major parameters, the assigned pitch numbers and scanning lengths, were the most important impacts to the dose variation. The MVCT dose was inversely proportional to the CT pitch value. With respect to the scanning length, the doses responded differently along the radial direction of the phantoms with different setup criteria., Conclusion: The results may provide a reliable guidance for proper planning design of the scanning region, which is valuable to help minimize the extra doses to patient.