Room: AAPM ePoster Library
Purpose: We hypothesized that VMAT-TBI would be a safe and effective alternative to conventional TBI. Here we present the clinical outcomes from our five-year experience using VMAT-TBI.
Methods: Simulation is performed with the patient immobilized in a custom rotation frame in which head and feet first CT scans are acquired. A typical VMAT-TBI plan consists of 5-7 isocenters. The PTV consists of the body with a 5mm contraction and lungs subtracted. Planning objectives include V90%Rx of 100% and lung dose of 66-75%Rx. A single institution retrospective review was performed for all patients treated with VMAT-TBI. 44 patients were identified who were treated between 2014-20. The mean age was 27.1 years and median KPS was 90. 12 patients received 2-4Gy single-fraction TBI; the remaining received 12-13.2Gy multi-fraction TBI.
Results: Average PTV and lung coverage were 93.9% and 70.6% of the Rx dose, respectively. Typical treatment time ranges from 60-90 minutes. Median follow-up was 14 months. At last follow-up, 35/44 patients (80%) were alive. 2 deaths were due to recurrence. 4 other patients developed recurrence but underwent salvage treatment (total of 6 recurrences; recurrence free survival 85%). Mean overall and progression-free survival were 16.3 and 15.3 months, respectively, for the patients who received transplantation for malignant indications. Diarrhea (89%), mucositis (82%), and fatigue (77%) were the most common acute toxicities. The only grade 3 or higher acute toxicity was mucositis, observed in 71% of all patients and 25% of patients receiving single-fraction TBI. Late Grade 3+ pneumonitis was observed 4 patients (9%); of these cases, only one case (grade 3) was likely related to radiation and 3 cases were multifactorial with concomitant respiratory tract infections.
Conclusion: VMAT-TBI has replaced conventional TBI in our center and has shown to be as safe and effective with improved patient comfort, convenience, and dosimetric accuracy.