Dosimetric comparison of vaginal vault brachytherapy vs applicator-guided stereotactic body radiotherapy with volumetric modulated arc therapy and helical tomotherapy for endometrium cancer patients.

We performed this dosimetric study to compare a nonstandard volumetric modulated arc therapy (VMAT) and helical tomotherapy (HT) techniques with high-dose rate (HDR) brachytherapy (BRT) plan of vaginal vault in patients with postoperative endometrial cancer (EC). Twelve postoperative patients with early stage EC were included in this study. Three plans were performed for each patient; dosimetric and radiobiological comparisons were made using dose-volume histograms and equivalent dose for determining the planning target volume (PTV) coverages in brachytherapy and external beam radiotherapy, and organs-at-risk (OARs) doses between three different delivery techniques. All the plans achieved adequate dose coverage for PTV; however, the VMAT plan yielded better dose conformity, and the HT plan showed better homogeneity for target volume. With respect to the OARs, the bladder D2cc was significantly lower in the BRT plan than in the VMAT and HT plans, with the highest bladder D2cc value being observed in the HT plan. However, no difference was observed in the rectum D2cc of the three plans. Other major advantages of the BRT plan over the VMAT and HT plans were the relatively lower body integral doses and femoral head doses as well as the fact that the integral doses were significantly lower in the BRT plan than in the VMAT and HT plans. This is the first dosimetric comparison of vaginal vault treatment for EC with BRT, VMAT, and HT plans. Our analyses showed the feasibility of stereotactic body radiotherapy technique as an alternative to HDR-BRT for postoperative management of EC patients.

A 10-year experience of linear accelerator-based stereotactic radiosurgery/radiotherapy (SRS/SRT) for paraganglioma: A single institution experience and review of the literature.

OBJECTIVE: Patients with paragangliomas were treated with LINAC-SRS/SRT in this retrospective review to evaluate tumor control, clinical control, and toxicity. METHODS: 16 patients (median age = 65) with paragangliomas were treated with LINAC-SRS/SRT. Patients were treated to a median dose of 25 Gy in 5 Fx and were evaluated for long-term tumor control, symptom control, and toxicity. Median follow-up was 44 months. RESULTS: 16 paragangliomas with a median PTV of 11.7 cc were treated as above. All but 2 lesions were controlled at last follow-up, with a 5-year control rate of 88%. Eighty-one percent of patients reported improved or resolved symptoms after treatment. Toxicities included grade 2 vertigo in 1 patient and grade 3 headache from hydrocephalus requiring ventriculoperitoneal shunt. DISCUSSION: Linear accelerator based SRS/SRT appears to be an effective treatment option for paragangliomas. Recurrences in this cohort occurred 4-5 years after treatment, highlighting the importance of long term follow up.

Optimization of Total Arc Degree for Stereotactic Radiotherapy by Using Integral Biologically Effective Dose and Irradiated Volume / 대한방사선종양학회지

PURPOSE: To find the optimal values of total arc degree to protect the normal brain tissue from high dose radiation in stereotactic radiotherapy planning. METHODS AND MATERIALS: With Xknife-3 planning system & 4 MV linear accelerator, the authors planned under various values of parameters. One isocenter, 12, 20, 30, 40, 50, and 60 mm of collimator diameters, 100degrees, 200degrees, 300degrees, 400degrees, 500degrees, 600degrees of total arc degrees, and 30degrees or 45degrees of arc intervals were used. After the completion of planning, the plans were compared each other using V50 (the volume of normal brain that is delivered high dose radiation) and integral biologically effective dose. RESULTS: At 30degrees of arc interval, the values of V50 had the decreased pattern with the increase of total arc degree in any collimator diameter. At 45degrees arc interval, up to 400degrees of total arc degree, the values of V50 decreased with the increase of total arc degree, but at 500degrees and 600degrees of total arc degrees, the values increased. At 30degreesdegreesof arc interval, integral biologically effective dose showed the decreased pattern with the increase of total arc degree in any collimator diameter. At 45degrees arc interval with less than 40 mm collimator diameter, the integral biologically effective dose decreased with the increase of total arc degree, but with 50 and 60 mm of collimator diameters, up to 400degrees of total arc degree, integral biologically effective dose decreased with the increase of total arc degree, but at 500degrees and 600degrees of total arc degrees, the values increased. CONCLUSION: In the stereotactic radiotherapy planning for brain lesions, planning with 400degrees of total arc degree is optimal. Especially, when the larger collimator more than 50 mm diameter should be used, the uses of 500degrees and 600degrees of total arc degrees make the increase of V50 and integral biologically effective dose. Therefore stereotactic radiotherapy planning using 400degrees of total arc degree can increase the therapeutic ratio and produce the effective outcome in the management of personal and mechanical sources in radiotherapy department.