Quality and access - Early experience of implementing a virtual stereotactic chart round across a national network.

INTRODUCTION: Stereotactic radiation therapy is a highly specialised technique which requires careful and structured implementation. As part of a national stereotactic programme implementation, protocols were developed and a national stereotactic chart round was formed, which strongly recommended attendance and presentation of all cases before treatment. Herein, we describe our experiences launching a national chart round and its importance in a stereotactic programme. METHOD: Stereotactic chart rounds were held via videoconference between July 2018 and July 2019. Data collected included attendances, patient-related information including, diagnosis, clinical background, treatment intent, prescribed dose and fractionation and technical approach. Consensus recommendations regarding changes to treatment approaches were also recorded. RESULTS: For the 12 months recorded, there were 1126 attendances, from 144 individual attendees, across 21 locations. In total, 285 cases (237 new cases, and 48 re-presentations) were presented by 27 radiation oncologists (ROs) from 13 different locations. From the cases presented, 65 changes were recommended from 53 patients (22.3%), including 27 (11.4%) changes to contours, 18 (7.6%) changes to dose prescription/fractionation, 9 (3.8%) changes to plan dosimetry, 1 (0.4%) changes to treatment technique and 10 (4.2%) recommendations for which stereotactic radiation therapy was not advised. A significant inverse relationship was found between frequency of recommended changes and the individual RO's stereotactic case load (P < 0.002). CONCLUSION: The implementation of a national stereotactic chart held via videoconference has ensured national protocol compliance across the network of locations. Furthermore, the chart rounds have allowed the entire multidisciplinary team to be provided with mentorship and guidance. Increasing number of cases presented was associated with lower rates of recommended changes highlighting the impact of experience and the need for continued mentorship.

A Comparison of Non-coplanar Three-dimensional Conformal Radiation Therapy, Intensity Modulated Radiation Therapy, and Volumetric Modulated Radiation Therapy for the Delivery of Stereotactic Ablative Radiation Therapy to Peripheral Lung Cancer.

AIM: The objective of the study was to compare three noncoplanar delivery techniques (three-dimensional conformal radiation therapy [3DCRT], intensity-modulated radiation therapy [IMRT], and volumetric-modulated arc therapy [VMAT]) for the delivery of lung stereotactic ablative radiation therapy to peripheral lung tumours. METHODS AND MATERIALS: The plans were compared by assessing the planning target volume coverage, doses to organs at risk, high and intermediate dose constraints (D2cm and R50%) and delivery times using analysis of variance for repeated measurements or Friedman's test when appropriate. RESULTS: Mean PTV54 Gy coverage was found to be 95.6%, 95.7%, and 95.6% for the 3DCRT, IMRT, and VMAT techniques, respectively. No deviations to the intermediate dose constraints were found in 65%, 65%, and 85% of the patients for the 3DCRT, IMRT, and VMAT plans, respectively. Mean treatment times (excluding setup and imaging) were 20.0 minutes (±1.67), 25.2 minutes (±2.15), and 11.7 (±2.0) minutes respectively for 3DCRT, IMRT, and VMAT. CONCLUSION: A noncoplanar VMAT technique was found to provide superior intermediate dose sparing with comparable prescription dose coverage when compared with noncoplanar 3DCRT or IMRT. In addition, VMAT was found to reduce the treatment times of stereotactic ablative radiation therapy delivery for peripheral lung tumours.

A comparison of three different VMAT techniques for the delivery of lung stereotactic ablative radiation therapy.

INTRODUCTION: The purpose of this study was to investigate coplanar and non-coplanar volumetric modulated arc therapy (VMAT) delivery techniques for stereotactic ablative radiation therapy (SABR) to the lung. METHODS: For ten patients who had already completed a course of radiation therapy for early stage lung cancer, three new SABR treatment plans were created using (1) a coplanar full arc (FA) technique, (2) a coplanar partial arc technique (PA) and (3) a non-coplanar technique utilising three partial arcs (NCA). These plans were evaluated using planning target volume (PTV) coverage, dose to organs at risk, and high and intermediate dose constraints as incorporated by radiation therapy oncology group (RTOG) 1021. RESULTS: When the FA and PA techniques were compared to the NCA technique, on average the PTV coverage (V 54Gy) was similar (P = 0.15); FA (95.1%), PA (95.11%) and NCA (95.71%). The NCA resulted in a better conformity index (CI) of the prescription dose (0.89) when compared to the FA technique (0.88, P = 0.23) and the PA technique (0.83, P = 0.06). The NCA technique improved the intermediate dose constraints with a statistically significant difference for the D 2cm and R 50% when compared with the FA (P < 0.03 and <0.0001) and PA (P < 0.04 and <0.0001) techniques. The NCA technique reduced the maximum spinal cord dose by 2.72 and 4.2 Gy when compared to the PA and FA techniques respectively. Mean lung doses were 4.09, 4.31 and 3.98 Gy for the FA, PA and NCA techniques respectively. CONCLUSION: The NCA VMAT technique provided the highest compliance to RTOG 1021 when compared to coplanar techniques for lung SABR. However, single FA coplanar VMAT was suitable for 70% of patients when minor deviations to both the intermediate dose and organ at risk (OAR) constraints were accepted.

The effect of beam arrangements and the impact of non-coplanar beams on the treatment planning of stereotactic ablative radiation therapy for early stage lung cancer.

INTRODUCTION: The aim of this study was to compare various coplanar and non-coplanar 3-dimensional conformal radiation therapy (3DCRT) beam arrangements for the delivery of stereotactic ablative radiation therapy (SABR) to patients with early stage lung cancer, based on the dosimetric criteria from the Radiation Therapy Oncology Group (RTOG) 1021 protocol. METHODS: Ten medically inoperable lung cancer patients eligible for SABR were re-planned using three different coplanar and three different non-coplanar beam arrangements. The plans were compared by assessing planning target volume (PTV) coverage, doses to normal tissues, the high-dose conformity (conformity index) and intermediate dose spillage as defined by the D2cm, (the dose at any point 2 cm away from the PTV), and the R50% (the ratio of the volume of half the prescription dose to the volume of the PTV). RESULTS: Sixty plans in total were assessed. Mean PTV coverage with the prescription isodose was similar between coplanar (95.14%) and non-coplanar (95.26%) techniques (P = 0.47). There was significant difference between all coplanar and all non-coplanar fields for the R50% (P < 0.0001) but none for the D2cm (P = 0.19). The seven and nine field beam arrangements with two non-coplanar fields had less unacceptable protocol deviations (10 and 7) than the seven and nine field plans with only coplanar fields (13 and 8). The 13 field coplanar fields did not improve protocol compliance with eight unacceptable deviations. The 10 field non-coplanar beam arrangement achieved best compliance with the RTOG 1021 dose criteria with only one unacceptable deviation (maximum rib dose). CONCLUSION: A 3DCRT planning technique using 10 fields with ≥6 non-coplanar beams best satisfied high and intermediate dose constraints stipulated in the RTOG 1021 trial. Further investigations are required to determine if minor protocol deviations should be balanced against efficiency with the extended treatment times required to deliver non-coplanar fields and if treatment times can be improved using novel intensity modulated techniques.

Quantifying intra- and inter-fractional motion in breast radiotherapy.

INTRODUCTION: The magnitude of intra- and inter-fractional variation in the set up of breast cancer patients treated with tangential megavoltage photon beams was investigated using an electronic portal imaging device (EPID). METHODS: Daily cine-EPID images were captured during delivery of the tangential fields for ten breast cancer patients treated in the supine position. Measurements collected from each image included the central lung distance (CLD), central flash distance (CFD), superior axial measurement (SAM) and the inferior axial measurement (IAM). The variation of motion within a fraction (intra-fraction) and the variation between fractions (inter-fraction) was analysed to quantify set up variation and motion due to respiration. RESULTS: Altogether 3775 EPID images were collected from 10 patients. The effect of respiratory motion during treatment was <0.1 cm standard deviation (SD) in the anterior-posterior (AP) direction. The inter-fraction movement caused by variations in daily set up was larger at 0.28 cm SD in the AP direction. Superior-inferior (SI) variation was more difficult to summarise and proved unreliable as the measurements were taken to an ambiguous point on the images. It was difficult to discern true SI movement from that implicated by AP movement. CONCLUSION: There is minimal intra-fractional chest wall motion due to respiration during treatment. Inter-fractional variation was larger, however, on average it remained within departmental tolerance (0.5 cm) for set up variations. This review of our current breast technique provides confidence in the feasibility of utilising advanced treatment techniques (field-in-field, intensity modulated radiotherapy or volumetric modulated arc therapy) following a review of the current imaging protocol.

Volumetric modulated arc therapy versus step-and-shoot intensity modulated radiation therapy in the treatment of large nerve perineural spread to the skull base: a comparative dosimetric planning study.

INTRODUCTION: Cutaneous squamous cell carcinoma with large nerve perineural (LNPN) infiltration of the base of skull is a radiotherapeutic challenge given the complex target volumes to nearby organs at risk (OAR). A comparative planning study was undertaken to evaluate dosimetric differences between volumetric modulated arc therapy (VMAT) versus intensity modulated radiation therapy (IMRT) in the treatment of LNPN. METHODS: Five consecutive patients previously treated with IMRT for LNPN were selected. VMAT plans were generated for each case using the same planning target volumes (PTV), dose prescriptions and OAR constraints as IMRT. Comparative parameters used to assess target volume coverage, conformity and homogeneity included V95 of the PTV (volume encompassed by the 95% isodose), conformity index (CI) and homogeneity index (HI). In addition, OAR maximum point doses, V20, V30, non-target tissue (NTT) point max doses, NTT volume above reference dose, monitor units (MU) were compared. RESULTS: IMRT and VMAT plans generated were comparable for CI (P = 0.12) and HI (P = 0.89). VMAT plans achieved better V95 (P = < 0.001) and reduced V20 and V30 by 652 cubic centimetres (cc) (28.5%) and 425.7 cc (29.1%), respectively. VMAT increased MU delivered by 18% without a corresponding increase in NTT dose. CONCLUSION: Compared with IMRT plans for LNPN, VMAT achieved comparable HI and CI.