HyperArc VMAT stereotactic radiotherapy for locally recurrent previously‐irradiated head and neck cancers: Plan quality, treatment delivery accuracy, and efficiency

Abstract

This paper demonstrates the clinical feasibility and efficacy of Hyper-Arc VMAT treatments for locally recurrent, locally advanced, or previously irradiated head and neck cancers treated with stereotactic radiotherapy (SRT). Materials/Methods: First, an anthropomorphic SRS head phantom from the MD Anderson's IROC credentialing laboratory containing a 1.9 cm diameter spherical target, including in vivo dosimetry system, was imaged, planned, and irradiated (25 Gy in 1 fraction) using HyperArc VMAT with a 6 MV flattening filter free (FFF) beam. Second, RANDO phantom was imaged, planned, and irradiated (35 Gy in 5 fractions) by generating eight HyperArc VMAT plans (4 right, 4 left neck tumors) at different anatomical locations (C1-C4). Average tumor volume was 21.7 cm 3 up to 32.3 cm 3 . Distance to isocenter from the central marker of the Encompass device down to neck was 25.8 cm up to 28.0 cm and 24.3 cm up to 27.1 cm for left-and right-sided neck tumors, respectively, and 9 cm from both lateral markers defined by the patient protection zone. Third, seven recurrent head and neck cancer patients with 80.3 cm 3 tumors on average, and up to 159 cm 3 , were imaged, planned, and treated with 30-40 Gy in 5 fractions with HyperArc SRT. Plan quality, treatment delivery accuracy, and efficiency are reported herein. Results: Phantom irradiation results met all the compliance requirements set forth by the IROC for HyperArc SRS treatment. For end-to-end RANDO phantom tests, a highly conformal target dose distribution with 50% isodose fall-off within 5 mm from the surface of the target was obtained. Average beam modulation factor, beam-on-time, and overall treatment time were 2.9, 2.56 min, and 13.96 min with 99.1% pre-treatment quality assurance pass rate for the 2%/2 mm gamma criteria, respectively. Immediately adjacent critical structures, such as the spinal cord (maximum, 3.9 Gy and 0.35 cm 3 of cord, 3.7 Gy) and skin (maximum, 10.3 Gy and 10 cm 3 of skin, 5.7 Gy), were spared. Similar results were found on the patient's HyperArc VMAT plans including highly conformal target coverage, sharp dose fall-off, and low doses to the adjacent critical organs such as the spinal cord (< 5 Gy). Average perfect pitch couch correction was <1.5 mm and 2 • in each direction. Average beam-on-time was approximately 3.21 min and treatments were completed within 15 min.

Automated Non-coplanar Volumetric Modulated Arc Therapy Planning for Maxillary Sinus Carcinoma

“…For head and neck cancers, HA has been demonstrated to be an effective treatment with a highly conformal dose distribution and excellent OAR sparing. Additionally, radiation therapists did not need to enter the treatment room to rotate the treatment couch even in the noncoplanar beam arrangement (16,25,26).…”

“…A number of investigators have reported that HA plans provided a higher conformity dose for the target and a lower radiation dose for surrounding tissues compared to VMAT plans for patients with brain metastases (14). Recently, HA has been applied to extracranial tumors, such as angiosarcoma of the scalp (15) and head and neck cancers (16,17). Its superior dose distribution could form a new treatment approach.…”

A novel, end‐to‐end framework for avoiding collisions between the patient's body and gantry in proton therapy

“…Avoiding collisions between the patient's body and the gantry during external radiation therapy is important. Newer treatment planning software (TPS) for x‐ray stereotactic radiotherapy can simulate treatment device parameters, such as the gantry and couch angles, while avoiding collisions 1 . This function benefits proton therapy, where a snout is placed close to patients to optimize the therapeutic dose distribution 2 .…”

“…Newer treatment planning software (TPS) for x-ray stereotactic radiotherapy can simulate treatment device parameters, such as the gantry and couch angles, while avoiding collisions. 1 This function benefits proton therapy, where a snout is placed close to patients to optimize the therapeutic dose distribution. 2 Unfortunately, TPSs cannot check the collision outside the computed tomography (CT) imaging range because they only handle F I G U R E 1 Difference between the proposed and the previous method.…”

Dosimetric effects of rotational errors for single isocenter multiple targets in HyperArc plans: A phantom and retrospective imaging analysis study

“…This automated system has made simultaneous treatment of multiple brain tumors more accessible with efficiency gains in both plan preparation and treatment delivery. [1][2][3] However, unlike single isocenter plans with a single target, Single Isocenter Multiple Targets (SIMT) plans are sensitive to rotational set-up errors. [4][5][6][7][8] In their retrospective study using patient data treated with HyperArc, Sagawa et al 9 investigated the dosimetric impact of setup errors on plans with both single and multiple brain metastases.…”