Brent Chesson

Efficacy of low dose radiotherapy for primary orbital marginal zone lymphoma

Abstract Marginal zone lymphoma (MZL) is a radiosensitive tumor, with high local control (LC) rates with moderate dose radiotherapy (RT). This retrospective study, performed at the Peter MacCallum Cancer Centre, evaluated the efficacy and toxicity of patients with orbital MZL treated to 24–25 Gy. Twenty-four patients (27 orbits) were identified, with median follow-up of 41 months. Disease was conjunctival in 16 orbits (59%), lacrimal in seven (26%), in the eyelid in one (4%) and elsewhere in three (11%). All patients attained a complete response. Three patients had treatment failures: one local relapse, one contralateral and one distant relapse. Freedom from local failure, freedom from progression, progression-free survival and overall survival were 100%, 90%, 90% and 100% at 2 years and 92%, 81%, 81% and 100% at 5 years, respectively. Aside from cataractogenesis, there was no significant late toxicity. Our study shows that RT doses of 24–25 Gy provide high rates of LC for orbital MZL with acceptable morbidity.

Implementation of a lung radiosurgery program: Technical considerations and quality assurance in an Australian institution

Introduction: The Peter MacCallum Cancer Centre has established a stereotactic lung radiosurgery program for the treatment of isolated lung metastases. The aim of this study was to critically assess the technical feasibility of performing stereotactic lung radiosurgery in an Australian institution.

Stereotactic Ablative Body Radiotherapy for Inoperable Primary Kidney Cancer: A Prospective Clinical Trial

To assess the feasibility and safety of stereotactic ablative body radiotherapy (SABR) for renal cell carcinoma (RCC) in patients unsuitable for surgery. Secondary objectives were to assess oncological and functional outcomes.

Vacuum immobilisation reduces tumour excursion and minimises intrafraction error in a cohort study of stereotactic ablative body radiotherapy for pulmonary metastases.

The purpose of this study is to assess the impact of a vacuum immobilisation system on reproducibility of patient set‐up, interfraction stability and tumour motion amplitude.

Respiratory-gated (4D) FDG-PET detects tumour and normal lung response after stereotactic radiotherapy for pulmonary metastases.

Abstract Background. Response assessment after stereotactic ablative body radiotherapy (SABR) in lung can be confounded by radiation-induced inflammation, fibrosis and subsequent alteration of tumour motion. The purpose of this prospective pilot study was to evaluate the utility of four-dimensional (4D) FDG-PET/CT for post-SABR tumour and normal lung response assessment in pulmonary oligometastases. Material and methods. Patients enrolled from February 2010 to December 2011 in this prospective ethics approved study had 1–2 pulmonary metastases on staging FDG-PET. Serial contemporaneous 3D and 4D FDG-PET/CT scans were performed at baseline, 14 days and 70 days after a single fraction of 26 Gy SABR. Tumour response was evaluated in 3D and 4D using SUVmax, RECIST and PERCIST criteria. Normal lung radiotoxicity was evaluated using SUVmean within 0–2 Gy, 2–5 Gy, 5–10 Gy, 10–20 Gy and 20 + Gy isodose volumes. Results. In total, 17 patients were enrolled of which seven were ineligible due to interval progression from staging PET to baseline 4D-PET. The mean time between scans was 62 days. At a median follow-up of 16 months, 10 patients with 13 metastases received SABR, with no patient having local progression. The vector of tumour motion was larger in patients with discordant 3D and 4D PET PERCIST response (p < 0.01), with a mean (± SEM) motion of 10.5 mm (± 0.96 mm) versus 6.14 mm (± 0.81 mm) in those patients with concordant 3D and 4D response. Surrounding normal lung FDG uptake at 70 days was strongly correlated to delivered radiation dose (r2 = 0.99, p < 0.01), with significant elevations across all dose levels (p ≤ 0.05), except the < 2 Gy volume (p = 0.30). Conclusions. We demonstrate high rates of interval progression between staging PET scans in patients with oligometastases. We found that tumour response on conventional 3D PET is not concordant with 4D PET for tumours with large motion. Normal lung metabolic uptake is strongly dose dependent after SABR, a novel finding that should be further validated.

Dosimetric Consequences of 3D Versus 4D PET/CT for Target Delineation of Lung Stereotactic Radiotherapy

Introduction: Lung tumor delineation is frequently performed using 3D positron emission tomography (PET)/computed tomography (CT), particularly in the radiotherapy treatment planning position, by generating an internal target volume (ITV) from the slow acquisition PET. We investigate the dosimetric consequences of stereotactic ablative body radiotherapy (SABR) planning on 3D PET/CT in comparison with gated (4D) PET/CT. Methods: In a prospective clinical trial, patients with lung metastases were prescribed 26 Gy single-fraction SABR to the covering isodose. Contemporaneous 3D PET/CT and 4D PET/CT was performed in the same patient position. An ITV was generated from each data set, with the planning target volume (PTV) being a 5-mm isotropic expansion. Dosimetric parameters from the SABR plan derived using the 3D volumes were evaluated against the same plan applied to 4D volumes. Results: Ten lung targets were evaluated. All 3D plans were successfully optimized to cover 99% of the PTV by the 26 Gy prescription. In all cases, the calculated dose delivered to the 4D target was less than the expected dose to the PTV based on 3D planning. Coverage of the 4D-PTV by the prescription isodose ranged from 74.48% to 98.58% (mean of 90.05%). The minimum dose to the 4D-ITV derived by the 3D treatment plan (mean = 93.11%) was significantly lower than the expected dose to ITV based on 3D PET/CT calculation (mean = 111.28%), p < 0.01. In all but one case, the planned prescription dose did not cover the 4D-PET/CT derived ITV. Conclusions: Target delineation using 3D PET/CT without additional respiratory compensation techniques results in significant target underdosing in the context of SABR.

Novel 3D conformal technique for treatment of choroidal melanoma with external beam photon radiotherapy.

To report a 3D conformal radiotherapy (3D‐CRT) technique that utilises a specific eye immobilisation and treatment set‐up method as an alternative to stereotactic radiotherapy (SRT), for treatment of juxtapapillary choroidal melanoma (CM) and report early treatment outcomes of this technique.

Analysis of the impact of chest wall constraints on eligibility for a randomized trial of stereotactic body radiotherapy of peripheral stage I non-small cell lung cancer.

Chest wall toxicities are recognized complications of stereotactic radiotherapy (SBRT) in non‐small cell lung cancer. To minimize toxicity, the Trans‐Tasman Radiation Oncology Group (TROG) 09.02 ‘CHISEL’ study protocol excluded patients with tumours within 1 cm of the chest wall. The purpose of this study is to evaluate the implication of chest wall proximity constraints on patient eligibility, toxicity and potential accrual.

WE‐C‐BRA‐02: Patient‐Specific QA Tool for Motion Management in Hypofractionated Lung Radiotherapy

Purpose: As radiotherapy approaches become more complex and individualized, it must be considered to extend patient‐specific QA beyond IMRT. We report on a tool and procedure developed to conduct patient‐specific QA for hypofractionated stereotactic lung treatments accounting for tumor motion. Method and Materials: Patients are immobilised in a BodyFix system and treated based on 4DCT/PET planning. The Varian RPM system is used during planning 4DCT acquisition and/or patient mock‐up to acquire a patient‐specific breathing pattern and used during treatment only to monitor breathing. A Modus Quasar phantom is used to mimic the patient breathing pattern with a customised motor, and a moving cylinder that accommodates ion chambers and radiochromic film. The patients treatment plan is transferred onto the average 4DCT of the moving phantom and point doses per beam and isodose distributions are extracted. The plan is then delivered to the stationary phantom as well as the phantom moving with the patient‐specific breathing pattern, and film (EBT2) and ion chamber (CC13) measurements are conducted. Film is scanned using a flatbed scanner and qualitatively evaluated in Excel against the planned isodose distributions. Three patient plans have been evaluated to date. Results: The agreements between planned and measured stationary doses ranged from 0.2% to 2.0% (3.0% tolerance), and from 0.9% to 2.4% for dynamic doses (5.0% tolerance). Qualitative film analysis found no discernible discrepancies from planned isodose distributions. The QA session demonstrates that the treatment can be delivered as planned and rectifies initial problems that arise during implementation. Conclusion: We have developed a QA tool and procedure that goes beyond conventional patient‐specific QA that accounts for breathing patterns during dosimetry and treatment for hypofractionated stereotactic lungradiotherapy. This procedure is integral in verifying the accuracy of both the planning and delivery of techniques involving high doses in small‐fields and complex beam arrangements.