From minimally to maximally invasive; VT ablation in the setting of mechanical aortic and mitral valves.

Double mitral and aortic mechanical valves present an access challenge when planning a ventricular tachycardia (VT) ablation. In this case report, we describe a patient who was considered for stereotactic ablative radiotherapy but was unable to proceed due to unfavorable anatomy making them at high risk of fistula formation. The patient went on to have an endocardial VT ablation via mini-thoracotomy and transapical access without complication. This case highlights the need for careful consideration when planning treatment for patients with double mechanical valves.

Systematic endoscopic staging of mediastinum to determine impact on radiotherapy for locally advanced lung cancer (SEISMIC): protocol for a prospective single arm multicentre interventional study.

BACKGROUND: Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) is established as the preferred method of mediastinal lymph node (LN) staging in non-small cell lung cancer (NSCLC). Selective (targeted) LN sampling is most commonly performed however studies in early stage NSCLC and locally advanced NSCLC confirm systematic EBUS-TBNA evaluation improves accuracy of mediastinal staging. This study aims to establish the rate of detection of positron emission tomography (PET)-occult LN metastases following systematic LN staging by EBUS-TBNA, and to determine the utility of systematic mediastinal staging for accurate delineation of radiation treatment fields in patients with locally advanced NSCLC. METHODS: Consecutive patients undergoing EBUS-TBNA for diagnosis/staging of locally advanced NSCLC will be enrolled in this international multi-centre single arm study. Systematic mediastinal LN evaluation will be performed, with all LN exceeding 6 mm to be sampled by TBNA. Where feasible, endoscopic ultrasound staging (EUS-B) may also be performed. Results of minimally invasive staging will be compared to FDG-PET. The primary end-point is proportion of patients in whom systematic LN staging identified PET-occult NSCLC metastases. Secondary outcome measures include (i) rate of nodal upstaging, (ii) false positive rate of PET for mediastinal LN assessment, (iii) analysis of clinicoradiologic risk factors for presence of PET-occult LN metastases, (iv) impact of systematic LN staging in patients with discrepant findings on PET and EBUS-TBNA on target coverage and dose to organs at risk (OAR) in patients undergoing radiotherapy. DISCUSSION: With specificity of PET of 90%, guidelines recommend tissue confirmation of positive mediastinal LN to ensure potentially early stage patients are not erroneously denied potentially curative resection. However, while confirmation of pathologic LN is routinely sought, the exact extent of mediastinal LN involvement in NSCLC in patient with Stage III NSCLC is rarely established. Studies examining systematic LN staging in early stage NSCLC report a significant discordance between PET and EBUS-TBNA. In patients with locally advanced disease this has significant implications for radiation field planning, with risk of geographic miss in the event of PET-occult mediastinal LN metastases. The SEISMIC study will examine both diagnostic outcomes following systematic LN staging with EBUS-TBNA, and impact on radiation treatment planning. TRIAL REGISTRATION: ACTRN12617000333314, ANZCTR, Registered on 3 March 2017.

A survey of compliance with stereotactic ablative body radiotherapy quality recommendations.

INTRODUCTION: Many publications have proposed quality standards for stereotactic ablative body radiotherapy (SABR). However, data on the level of compliance with these guidelines is lacking in the literature. This study aimed to understand how these guidelines are applied in the clinic and to identify barriers to implementing such recommendations. METHODS: Interviews were conducted with multidisciplinary staff at radiation oncology centres across New South Wales formulated around the RANZCR Guidelines for Safe Practice of Stereotactic Body (Ablative) Radiation Therapy. The interview responses were grouped into 20 topics, assessed against the guidelines and thematically analysed. RESULTS: Good compliance with the guidelines was found, with more than 80% of centres achieving satisfactory results in more than half the topics. The areas with the lowest compliance were auditing, risk assessment and reporting recommendations. Barriers to the quality of SABR treatments included limited training opportunities, low patient numbers and a lack of clear requirements on comprehensive auditing and reporting. CONCLUSION: Overall, the centres surveyed reported good compliance with most of the RANZCR SABR guidelines. The tasks with the lowest compliance were those that monitor quality outcomes. Potential strategies for improvement include inclusion in clinical trials and the use of databases which link treatment parameters, dosimetry and outcomes. Further work will focus on the barriers identified in this survey and propose practical solutions to improve compliance in these areas.

NeoAdjuvant pembrolizumab and STEreotactic radiotherapy prior to nephrectomy for renal cell carcinoma (NAPSTER): A phase II randomised clinical trial.

Background: Surgery remains the standard of care for localised renal cell carcinoma (RCC). Nevertheless, nearly 50% of patients with high-risk disease experience relapse after surgery, with distant sites being common. Considering improved outcomes in terms of disease-free survival with adjuvant immunotherapy with pembrolizumab, we hypothesise that neoadjuvant SABR with or without the addition of pembrolizumab before nephrectomy will lead to improved disease outcomes by evoking better immune response in the presence of an extensive reserve of tumor-associated antigens. Methods and analysis: This prospective, open-label, phase II, randomised, non-comparative, clinical trial will investigate the use of neoadjuvant stereotactic ablative body radiotherapy (SABR) with or without pembrolizumab prior to nephrectomy. The trial will be conducted at two centres in Australia that are well established for delivering SABR to primary RCC patients. Twenty-six patients with biopsy-proven clear cell RCC will be recruited over two years. Patients will be randomised to either SABR or SABR/pembrolizumab. Patients in both arms will undergo surgery at 9 weeks after completion of experimental treatment. The primary objectives are to describe major pathological response and changes in tumour-responsive T-cells from baseline pre-treatment biopsy in each arm. Patients will be followed for sixty days post-surgery. Outcomes and significance: We hypothesize that SABR alone or SABR plus pembrolizumab will induce significant tumor-specific immune response and major pathological response. In that case, either one or both arms could justifiably be used as a neoadjuvant treatment approach in future randomized trials in the high-risk patient population.

A study into the relationship between the measured penumbra and effective source size in the modeling of the Pinnacle RTPS.

The effect of detector size in the broadening of the penumbra on the model in the Pinnacle RTPS is investigated. A second order polynomial was devised to correlate the source size parameter with the RTPS-calculated penumbra. The optimal source size parameter was calculated for penumbra measurements based on the diamond detector and a standard ionization chamber (IC). This work was done for Jaw fields, MLC fields with a leaf end radius of 8 cm, and MLC fields with a leaf end radius of 12 cm. The optimum source size of the 8 cm MLC fields matched the jaw fields, and an average (based on field sizes studied) of 1.1 mm for the diamond detector data and 2.4 mm for the ionization chamber was established. The effect of this overestimation of the source size parameter based on detector-induced penumbra broadening was considered for a clinical IMRT prostate plan by using two models (diamond and IC). There were differences in the DVH of the PTV and of OARs but these effects were of negligible clinical significance. Dose difference distributions showed dose difference areas to be in penumbra regions of the segments, with larger dose differences where penumbras intersected and/or there was a significant weighting on the segment. Gamma analysis was also performed between the two plans, and was found to increase the amount of fail rates significantly for both 2%/2 mm and 3%/3 mm criteria. This decreases the sensitivity of IMRT QA in the detection of systematic errors.

Quality assurance of an image guided intracranial stereotactic positioning system for radiosurgery treatment with helical tomotherapy.

The aim of this work was to determine the accuracy and precision of stereotactic localization and treatment delivery using a helical tomotherapy based stereotactic radiosurgery (SRS) system. A tomotherapy specific radiosurgery workflow was designed that exploits the system's on board megavotage CT (MVCT) imaging system so that it not only provides a pre-treatment volumetric verification image that can be used for stereotactic localization, eliminating the need for a patient-frame based coordinate system, but also supplies the treatment planning image. Using an imaging guidance based intracranial stereotactic positioning system, a head ring and tabletop docking device are used only for fixation, while image guidance is used for localization. Due to the unconventional workflow, a methodology for determining the localization accuracy was developed and results were compared to other linear accelerator based radiosurgery systems. In this work, the localization error using volumetric localization was found to be 0.45 mm +/- 0.17 mm, indicating a localization precision of 0.3 mm within a 95% confidence interval. In addition, procedures for testing the delivery accuracy of the Tomotherapy system are described. Results show that the accuracy of the delivery can be verified to within +/-1 voxel dimension. These results are well within conventional SRS tolerances and compare favorably to other linear accelerator based techniques.