S.F. Petit

Fully automated VMAT treatment planning for advanced-stage NSCLC patients

PurposeTo develop axa0fully automated procedure for multicriterial volumetric modulated arc therapy (VMAT) treatment planning (autoVMAT) for stagexa0III/IV non-small cell lung cancer (NSCLC) patients treated with curative intent.Materials and methodsAfter configuring the developed autoVMAT system for NSCLC, autoVMAT plans were compared with manually generated clinically delivered intensity-modulated radiotherapy (IMRT) plans for 41xa0patients. AutoVMAT plans were also compared to manually generated VMAT plans in the absence of time pressure. For 16xa0patients with reduced planning target volume (PTV) dose prescription in the clinical IMRT plan (to avoid violation of organs at risk tolerances), the potential for dose escalation with autoVMAT was explored.ResultsTwo physicians evaluated 35/41xa0autoVMAT plans (85%) as clinically acceptable. Compared to the manually generated IMRT plans, autoVMAT plans showed statistically significant improved PTV coverage (V95% increased by 1.1%xa0± 1.1%), higher dose conformity (R50 reduced by 12.2%xa0± 12.7%), and reduced mean lung, heart, and esophagus doses (reductions of 0.9u2009Gyxa0± 1.0u2009Gy, 1.5u2009Gyxa0± 1.8u2009Gy, 3.6u2009Gyxa0± 2.8u2009Gy, respectively, all pxa0< 0.001). To render the six remaining autoVMAT plans clinically acceptable, axa0dosimetrist needed less than 10u2009min hands-on time for fine-tuning. AutoVMAT plans were also considered equivalent or better than manually optimized VMAT plans. For 6/16xa0patients, autoVMAT allowed tumor dose escalation of 5–10u2009Gy.ConclusionClinically deliverable, high-quality autoVMAT plans can be generated fully automatically for the vast majority of advanced-stage NSCLC patients. For axa0subset of patients, autoVMAT allowed for tumor dose escalation.ZusammenfassungZielsetzungEntwicklung einer vollautomatisierten, auf multiplen Kriterien basierenden volumenmodulierten Arc-Therapie-(VMAT-)Behandlungsplanung (autoVMAT) für kurativ behandelte Patienten mit nicht-kleinzelligem Bronchialkarzinom (NSCLC) im Stadiumxa0III/IV.Material und MethodenNach Konfiguration unseres autoVMAT-Systems für NSCLC wurde für 41xa0Patienten der autoVMAT-Plan mit dem manuell erzeugten, klinisch applizierten intensitätsmodulierten Strahlentherapieplan (IMRT) verglichen. AutoVMAT-Pläne wurden ferner mit manuellen und ohne Zeitdruck erstellten VMAT-Plänen verglichen. Für 16xa0Patienten mit reduzierter Dosisverordnung des Planungszielvolumens (PTV) im klinischen IMRT-Plan (zur Vermeidung einer Verletzung von Toleranzdosen für Risikoorgane) wurde das Potenzial für eine Dosiseskalation mit autoVMAT untersucht.ErgebnisseZwei Ärzte bewerteten 35 von 41xa0autoVMAT-Plänen (85u2009%) als klinisch akzeptabel. Verglichen mit den manuell erzeugten IMRT-Plänen zeigten autoVMAT-Pläne eine statistisch signifikant bessere PTV-Abdeckung (V95% erhöht um 1,1u2009%xa0± 1,1u2009%), eine höhere Dosiskonformität (R50 verringert um 12,2u2009%xa0± 12,7u2009%) und eine geringere durchschnittliche Dosis in Lunge, Herz und Oesophagus (verringert um je 0,9u2009Gyxa0± 1,0u2009Gy, 1,5u2009Gyxa0± 1,8u2009Gy, 3,6u2009Gyxa0± 2,8u2009Gy; alle pxa0< 0,001). Um die restlichen 6xa0autoVMAT-Pläne aus klinischer Sicht akzeptabel zu machen, benötigte ein Dosimetrist zur Feinabstimmung jeweils weniger als 10u2009min. AutoVMAT-Pläne wurden verglichen zu manuell optimierten VMAT-Plänen als gleichwertig oder sogar besser erachtet. Für 6 von 16xa0Patienten ermöglichte autoVMAT eine Dosiseskalation im Tumor um 5–10u2009Gy.SchlussfolgerungFür die große Mehrheit von Patienten mit fortgeschrittenem NSCLC konnte ein klinisch applizierbarer, hochqualitativer autoVMAT-Plan vollautomatisch erstellt werden. Für eine Subgruppe ermöglichte autoVMAT eine Dosiseskalation im Tumor.

An individualized strategy to estimate the effect of deformable registration uncertainty on accumulated dose in the upper abdomen

In the abdomen, it is challenging to assess the accuracy of deformable image registration (DIR) for individual patients, due to the lack of clear anatomical landmarks, which can hamper clinical applications that require high accuracy DIR, such as adaptive radiotherapy. In this study, we propose and evaluate a methodology for estimating the impact of uncertainties in DIR on calculated accumulated dose in the upper abdomen, in order to aid decision making in adaptive treatment approaches. Sixteen liver metastasis patients treated with SBRT were evaluated. Each patient had one planning and three daily treatment CT-scans. Each daily CT scan was deformably registered 132 times to the planning CT-scan, using a wide range of parameter settings for the registration algorithm. A subset of realistic registrations was then objectively selected based on distances between mapped and target contours. The underlying 3D transformations of these registrations were used to assess the corresponding uncertainties in voxel positions, and delivered dose, with a focus on accumulated maximum doses in the hollow OARs, i.e. esophagus, stomach, and duodenum. The number of realistic registrations varied from 5 to 109, depending on the patient, emphasizing the need for individualized registration parameters. Considering for all patients the realistic registrations, the 99th percentile of the voxel position uncertainties was 5.6u2009u2009±u2009u20093.3u2009mm. This translated into a variation (difference between 1st and 99th percentile) in accumulated D max in hollow OARs of up to 3.3 Gy. For one patient a violation of the accumulated stomach dose outside the uncertainty band was detected. The observed variation in accumulated doses in the OARs related to registration uncertainty, emphasizes the need to investigate the impact of this uncertainty for any DIR algorithm prior to clinical use for dose accumulation. The proposed method for assessing on an individual patient basis the impact of uncertainties in DIR on accumulated dose is in principle applicable for all DIR algorithms allowing variation in registration parameters.

OC-0266: Automated treatment plan generation for advanced stage NSCLC patients

Material and Methods: Based on treatment plans of 7 previously treated patients, the clinical protocol, and physician’s treatment goals and priorities, our in-house developed system for fully automated, multi-criterial plan generation was configured to generate VMAT plans for advanced stage NSCLC patients without human interaction. For 41 independent patients, treated between January and August 2015, automatic plan generation was then compared with manual plan generation, as performed in clinical routine. Differences in PTV coverage, dose conformality R50 (the ratio between the total volume receiving at least 50% of the prescribed dose and the PTV volume) and sparing of organs at risk were quantified, and their statistical significance was assessed using a Wilcoxon test.