ACPSEM position paper: pre-treatment patient specific plan checks and quality assurance in radiation oncology.

The Australasian College of Physical Scientists and Engineers in Medicine (ACPSEM) has not previously made recommendations outlining the requirements for physics plan checks in Australia and New Zealand. A recent workforce modelling exercise, undertaken by the ACPSEM, revealed that the workload of a clinical radiation oncology medical physicist can comprise of up to 50% patient specific quality assurance activities. Therefore, in 2022 the ACPSEM Radiation Oncology Specialty Group (ROSG) set up a working group to address this issue. This position paper authored by ROSG endorses the recommendations of the American Association of Physicists in Medicine (AAPM) Task Group 218, 219 and 275 reports with some contextualisation for the Australia and New Zealand settings. A few recommendations from other sources are also endorsed to complete the position.

Universal evaluation of MLC models in treatment planning systems based on a common set of dynamic tests.

PURPOSE: To demonstrate the feasibility of characterising MLCs and MLC models implemented in TPSs using a common set of dynamic beams. MATERIALS AND METHODS: A set of tests containing synchronous (SG) and asynchronous sweeping gaps (aSG) was distributed among twenty-five participating centres. Doses were measured with a Farmer-type ion chamber and computed in TPSs, which provided a dosimetric characterisation of the leaf tip, tongue-and-groove, and MLC transmission of each MLC, as well as an assessment of the MLC model in each TPS. Five MLC types and four TPSs were evaluated, covering the most frequent combinations used in radiotherapy departments. RESULTS: Measured differences within each MLC type were minimal, while large differences were found between MLC models implemented in clinical TPSs. This resulted in some concerning discrepancies, especially for the HD120 and Agility MLCs, for which differences between measured and calculated doses for some MLC-TPS combinations exceeded 10%. These large differences were particularly evident for small gap sizes (5 and 10 mm), as well as for larger gaps in the presence of tongue-and-groove effects. A much better agreement was found for the Millennium120 and Halcyon MLCs, differences being within ± 5% and ± 2.5%, respectively. CONCLUSIONS: The feasibility of using a common set of tests to assess MLC models in TPSs was demonstrated. Measurements within MLC types were very similar, but TPS dose calculations showed large variations. Standardisation of the MLC configuration in TPSs is necessary. The proposed procedure can be readily applied in radiotherapy departments and can be a valuable tool in IMRT and credentialing audits.

The challenge of planning vertebral body SBRT: Optimizing target volume coverage.

Stereotactic ablative body radiotherapy for vertebral metastases has been shown to be safe and effective to achieve tumor and pain control. To raise awareness of and build familiarity with vertebral stereotactic ablative body radiation therapy (SBRT) for a multicenter clinical trial including SBRT to vertebral metastases, Trans Tasman Radiation Oncology Cancer Research performed an international planning challenge. A single vertebral case was selected and the computed tomography image and contours were made available. Participants performed a treatment plan according to the NIVORAD clinical trial protocol and uploaded the treatment plan and dose grid Digital Imaging and Communications in Medicine (DICOM) files. A progressive scoring matrix was applied which gave each plan a score based on target and organ at risk dosimetry. The plans were compared based on achieved score and treatment technique details. A total of 149 plans were submitted from 26 countries; the treatment geometry for four plans was deemed to result in collision with the couch and these were removed from analysis. Only one plan exceeded spinal cord constraints; all other plans met protocol constraints. The largest variation in plan quality was observed with the target coverage; the highest scoring plans were able to achieve higher target coverage whilst respecting adjacent organ at risk (OAR) constraints. Consequently, plan score was correlated with the dose gradient at the target-cord interface. We have conducted a large multicenter, international vertebral SBRT planning challenge. The results showed consistent ability to meet protocol constraints, however a large variation in the ability to cover the target volume was observed.

Australasian Gastrointestinal Trials Group (AGITG) and Trans-Tasman Radiation Oncology Group (TROG) Guidelines for Pancreatic Stereotactic Body Radiation Therapy (SBRT).

PURPOSE: Nonrandomized data exploring pancreas stereotactic body radiation therapy (SBRT) has demonstrated excellent local control rates and low toxicity. Before commencing a randomized trial investigating pancreas SBRT, standardization of prescription dose, dose constraints, simulation technique, and clinical target volume delineation are required. METHODS AND MATERIALS: Specialists in radiation oncology, medical oncology, hepatobiliary surgery, and gastroenterology attended 2 consecutive Australasian Gastrointestinal Trials Group workshops in 2017 and 2018. Sample cases were discussed during workshop contact with specifically invited international speakers highly experienced in pancreas SBRT. Furthermore, sample cases were contoured and planned between workshop contact to finalize dose constraints and clinical target volume delineation. RESULTS: Over 2 separate workshops, consensus was reached on dose and simulation technique. The working group recommended a dose prescription of 40 Gy in 5 fractions. Treatment delivery during end-expiratory breath hold with triple-phase contrast enhanced computed tomography was recommended. In addition, dose constraints, stepwise contouring guidelines, and an anatomic atlas for pancreatic SBRT were developed. CONCLUSIONS: Pancreas SBRT is emerging as a promising treatment modality requiring prospective evaluation in randomized studies. This work attempts to standardize dose, simulation technique, and volume delineation to support the delivery of high quality SBRT in a multicenter study.

Comparison of treatment techniques for reduction in the submandibular gland dose: A retrospective study.

INTRODUCTION: Recent studies have suggested reducing the dose submandibular glands receive when patients undergo head and neck radiotherapy can play a crucial role in preventing xerostomia. However, they are traditionally not spared due to concern that target coverage may be compromised. We investigated the possibility of sparing the contralateral submandibular gland (cSM) by utilising modern planning techniques. METHODS: 10 head and neck patients previously treated with conformal therapy at our centre were retrospectively planned using intensity modulated radiation therapy (IMRT), and volumetric modulated arc therapy (VMAT). Each patient was prescribed 70 Gy in 35 fractions to the primary volume, with 56 Gy delivered to the elective nodal areas. The primary objective was to spare the cSM gland using appropriate dose constraints. RESULTS: Mean dose to the cSM gland was reduced to an acceptable dose level (39 Gy) for all patients replanned using an IMRT or VMAT technique, without compromising planned target volume (PTV) coverage or other critical structures. VMAT was able to reduce the mean dose to 31.5 ± 5.5 Gy compared to 34.5 ± 4.8 Gy of IMRT and offered improved plan conformity. CONCLUSION: Sparing the cSM gland is possible using IMRT and VMAT planning, whilst preserving coverage on the elective PTV. This has produced a change in protocol in our department, more focus placed on sparing the SM glands. VMAT is a viable alternative method of delivering treatment and will be utilised when required.

External evaluation of the Radiation Therapy Oncology Group brachial plexus contouring protocol: several issues identified.

INTRODUCTION: The aims of the study were to evaluate interobserver variability in contouring the brachial plexus (BP) using the Radiation Therapy Oncology Group (RTOG)-approved protocol and to analyse BP dosimetries. METHODS: Seven outliners independently contoured the BPs of 15 consecutive patients. Interobserver variability was reviewed qualitatively (visually by using planning axial computed-tomography images and anteroposterior digitally reconstructed radiographs) and quantitatively (by volumetric and statistical analyses). Dose-volume histograms of BPs were calculated and compared. RESULTS: We found significant interobserver variability among outliners in both qualitative and quantitative analyses. These were most pronounced for the T1 nerve roots on visual inspection and for the BP volume on statistical analysis. The BP volumes were smaller than those described in the RTOG atlas paper, with a mean volume of 20.8 cc (range 11-40.7 cc) compared with 33 ± 4 cc (25.1-39.4 cc). The average values of mean dose, maximum dose, V60Gy, V66Gy and V70Gy for patients treated with conventional radiotherapy and IMRT were 42.2 Gy versus 44.8 Gy, 64.5 Gy versus 68.5 Gy, 6.1% versus 7.6%, 2.9% versus 2.4% and 0.6% versus 0.3%, respectively. CONCLUSION: This is the first independent external evaluation of the published protocol. We have identified several issues, including significant interobserver variation. Although radiation oncologists should contour BPs to avoid dose dumping, especially when using IMRT, the RTOG atlas should be used with caution. Because BPs are largely radiologically occult on CT, we propose the term brachial-plexus regions (BPRs) to represent regions where BPs are likely to be present. Consequently, BPRs should in principle be contoured generously.

External validation of the lumbosacral plexus-contouring protocol developed by Yi et al. (IJROBP 2012; 84: 376-82) for pelvic malignancies.

PURPOSE: To evaluate interobserver variability in contouring lumbosacral plexuses (LSP) using the protocol developed by Yi et al. (IJROBP 2012; 84: 376-82) and to review LSP dosimetries for conventional radiotherapy and intensity-modulated radiotherapy (IMRT) for pelvic cancers. METHODS AND MATERIALS: Using the above-mentioned protocol, seven outliners independently contoured LSPs of 10 consecutive patients (five patients treated with conventional radiotherapy and five with IMRT). Interobserver variability was reviewed visually by using planning axial CT images and anteroposterior digitally reconstructed radiographs. Dosimetries of LSPs were also calculated and compared. RESULTS: There was a notable learning curve for each outliner; duration to outline the first patient was 45-185 minutes, versus 15-50 minutes after six patients. We found significant interobserver variability among outliners below the level of the S2 nerve roots. The LSP volumes (mean volume range of 40.9-58.4 cc) were smaller than those described in the atlas paper (71-138 cc). The mean values of mean dose, maximum dose, V40 Gy, V50 Gy and V55 Gy, respectively, for patients treated with conventional radiotherapy versus those treated with IMRT were 35.5 Gy versus 33.6 Gy, 52.2 Gy versus 52.2 Gy, 61.3% versus 54.4%, 14.9% versus 18.8% and 0% versus 2.5%. CONCLUSION: We conclude that the protocol developed by Yi et al. is a useful set of guidelines but suggest that additional at-risk components of the LSP also be contoured. We recommend that radiation oncologists practise 'nerve-sparing' radiotherapy by contouring LSPs, especially when using IMRT. We propose the term 'lumbosacral plexus regions' (LSPRs) to highlight the fact that LSPs are not always radiologically visible, only the regions where they are likely to be present.

ACPSEM ROSG Oncology-PACS and OIS working group recommendations for quality assurance.

The Australasian College of Physical Scientists and Engineers in Medicine (ACPSEM) Radiation Oncology Specialty Group (ROSG) formed a series of working groups in 2011 to develop position papers for guidance of radiation oncology medical physics practice within the Australasian setting. These position papers are intended to provide guidance for safe work practices and a suitable level of quality control without detailed work instructions. It is the responsibility of the medical physicist to ensure that locally available equipment and procedures are sufficiently sensitive to establish compliance to these position papers. The recommendations are endorsed by the ROSG, have been subject to independent expert reviews. For the Australian audience, these recommendations should be read in conjunction with the Tripartite Radiation Oncology Practice Standards [1, 2]. This publication presents the recommendations of the ACPSEM OPACS and OIS Working Group (OISWG) and has been developed in alignment with other international associations. However, these recommendations should be read in conjunction with relevant national, state or territory legislation and local requirements, which take precedence over the ACPSEM position papers. It is hoped that the users of this and other ACPSEM position papers will contribute to the development of future versions through the Radiation Oncology Specialty Group of the ACPSEM.