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Featured Application: Automatable replanning strategies can improve patient-specific quality assurance outcomes of radiotherapy plans identified at risk by machine learning models without compromising the dosimetric quality. Patient-specific quality assurance (PSQA) procedures ensure the safe delivery of volumetric modulated arc therapy (VMAT) plans. PSQA requires extensive time and resources and may cause treatment delays if replanning is needed due to failures. Recently, our group developed a machine learning (ML) model predicting gamma passing rate (GPR) for VMAT arcs. This study explores automatable replanning strategies for plans identified at risk of failure, aiming to improve deliverability while maintaining dosimetric quality. Between 2022 and 2023, our ML model analyzed 1252 VMAT plans. Ten patients having a predicted GPR (pGPR) <95% were selected. Replanning strategies consisted of limiting monitor units (MUlimit) and employing the aperture shape controller (ASC) tool. Re-optimized plans were compared with the originals in terms of dose volume constraints (DVCs) for the target and organs-at-risk (OARs), and deliverability using the modulation complexity score (MCS), pGPR, and measured GPR (mGPR). Forty-five re-optimizations were performed. Replanning led to an increase in DVCs for OARs and a reduction for the target. Complexity decreased, reflected by the increase in the MCS from 0.17 to 0.21 (MUlimit) and 0.20 (ASC). The deliverability improved, with the pGPR increasing from 93.3% to 94.4% (MUlimit) and 95.1% (ASC), and the mGPR from 99.3% to 99.7% (MUlimit) and 99.8% (ASC). Limiting the MUs or utilizing the ASC reduced the complexity of plans and improved the GPR without compromising the dosimetric quality. These strategies can be used to automate replanning procedures, reduce the workload related to PSQA, and improve patient safety. [ABSTRACT FROM AUTHOR]

Aim: The gold standard of care for pancreatic adenocarcinoma is the integrated treatment of surgery and chemotherapy (ChT), but about 50% of patients present with unresectable disease. Our study evaluated the efficacy in terms of local control, survival and safety of stereotactic body radiation therapy (SBRT) in locally advanced pancreatic cancer (LAPC). Methods: A retrospective study (STEP study) analyzed patients with LAPC treated with a dose of 45 Gy in 6 fractions. Local control (LC), distant progression free survival (DPFS), overall survival (OS) and toxicity were analyzed according to the Kaplan-Meier method. Results: A total of 142 patients were evaluated. Seventy-six patients (53.5%) received induction ChT before SBRT. The median follow-up was 11 months. One-, 2- and 3-year LC rate was 81.9%, 69.1% and 58.5%. Median DPFS was 6.03 months; 1- and 2-year DPFS rate was 19.9% and 4.5%. Median OS was 11.6 months and 1-, 2- and 3-year OS rates were 45.4%, 16.1%, and 9.8%. At univariate analysis, performed by the log-rank test, age < 70 years (p = 0.037), pre-SBRT ChT (p = 0.004) and post-SBRT ChT (p = 0.019) were associated with better OS. No patients experienced G3 toxicity. Conclusion: SBRT represents an effective and safe therapeutic option in the multimodal treatment of patients with LAPC in terms of increased LC. When SBRT was sequentially integrated with ChT, the treatment proved to be promising in terms of OS as well. [ABSTRACT FROM AUTHOR]

Background: Hypo-fractionation can be an effective strategy to lower costs and save time, increasing patient access to advanced radiation therapy. To demonstrate this potential in practice within the context of temporal evolution, a twenty-year analysis of a representative radiation therapy facility from 2003 to 2022 was conducted. This analysis utilized comprehensive data to quantitatively evaluate the connections between advanced clinical protocols and technological improvements. The findings provide valuable insights to the management team, helping them ensure the delivery of high-quality treatments in a sustainable manner. Methods: Several parameters related to treatment technique, patient positioning, dose prescription, fractionation, equipment technology content, machine workload and throughput, therapy times and patients access counts were extracted from departmental database and analyzed on a yearly basis by means of linear regression. Results: Patients increased by 121 ± 6 new per year (NPY). Since 2010, the incidence of hypo-fractionation protocols grew thanks to increasing Linac technology. In seven years, both the average number of fractions and daily machine workload decreased by −0.84 ± 0.12 fractions/year and −1.61 ± 0.35 patients/year, respectively. The implementation of advanced dose delivery techniques, image guidance and high dose rate beams for high fraction doses, currently systematically used, has increased the complexity and reduced daily treatment throughput since 2010 from 40 to 32 patients per 8 h work shift (WS8). Thanks to hypo-fractionation, such an efficiency drop did not affect NPY, estimating 693 ± 28 NPY/WS8, regardless of the evaluation time. Each newly installed machine was shown to add 540 NPY, while absorbing 0.78 ± 0.04 WS8. The COVID-19 pandemic brought an overall reduction of 3.7% of patients and a reduction of 0.8 fractions/patient, to mitigate patient crowding in the department. Conclusions: The evolution of therapy protocols towards hypo-fractionation was supported by the use of proper technology. The characteristics of this process were quantified considering time progression and organizational aspects. This strategy optimized resources while enabling broader access to advanced radiation therapy. To truly value the benefit of hypo-fractionation, a reimbursement policy should focus on the patient rather than individual treatment fractionation. [ABSTRACT FROM AUTHOR]

Purpose and objective: Commissioning measurements are time-consuming and require high precision in execution. Reference Beam Models (RBM) consist of predefined Pencil Beam and Monte Carlo dose profiles that may dramatically reduce the number of measurements necessary to commission a beam. The purpose of this work was to evaluate the accuracy and robustness of using the RBMs offered by BrainLab®(Munich, Germany) with the treatment planning system (TPS) Elements® for multiple brain metastases. Materials and method: The 6MV and 10MVFFF beams of a TrueBeamSTX Linac were considered. The Linac was equipped with a HD120 MultiLeafCollimator (MLC) whose central leaves have a width of 2.5mm at isocenter. A Beamscan water tank (PTW, Freiburg, Germany) was used with a SSD=900. Absolute dose was measured at isocenter with a Farmer-type calibrated ion chamber for a 10x10cm2 field. Profiles and PDDs were measured for 4 different MLC-defined square fields ranging from 5x5 to 220x220mm2. Output Factors were measured for the same fields and in the same set-up. A PTW MicroDiamond detector and a 0.125cc PTW Semiflex 3D ion chamber were used for all measurements. A comparison between these measurements and calculations performed in a virtual water phantom with MC-Elements and Acuros algorithms were performed. Once the TPS was configured, some “simple” plans (i.e. without MLC) and 5 patients were planned with the Multiple Brain Metastases module and delivered. The dose distribution was verified with three different methods. The 2D fluence distribution was evaluated with Portal Dosimetry. The log-file reconstructed 3D dose distribution was evaluated with an indipendent algorithm (M3D, Mobius). The measured 3D dose distribution was evaluated with the octavius detector. Results: The total time required for the commissioning measurements was less than 6 hours. The best agreement between measured and modeled values both for OFs and profiles was obtained selecting a spot size of 0.4mm and 0.Xmm for 6MV and 10MVFFF beams respectively (figure 1). Calculated OFs were within 1.6% for all field sizes except for the 5x5mm were it was 4.8% (figure 2). The 3%-3mm 3DGamma >96.3% (96.3%-99.8%) for the “simple” plans. Gamma values for the 5 clinical plans were 99.5%-100% for Portal Dosimetry, 99.8%-100% for the M3D calculation and 97.3%-99.1% for the Octavius4D measurements. Conclusion: Machine commissioning times are dramatically reduced and compatible with clinical practice. The configuration and selection of the RBM is simple and intuitive. Good agreement between measured and calculated dose distributions was observed down to very small field sizes. [ABSTRACT FROM AUTHOR]