Purpose/Objective The proximity or overlap of PTV and OAR poses a major challenge in SBRT of pancreatic cancer (PACA). This international treatment planning benchmark study investigates whether Simultaneously Integrated Boost (SIB) and Protection (SIP) concepts in PACA SBRT can lead to improved and harmonized plan quality. Materials/Methods A multiparametric specification of desired target doses (GTVD50%, GTVD99%, PTVD95%, PTV0.5cc) with two prescription doses of GTVD50%=5×9.2Gy (46Gy) and GTVD50%=8×8.25Gy (66Gy) and OAR limits were distributed with planning CT and contours from 3 PACA patients. In phase 1, plans were ranked using a scoring system for comparison of trade-offs between GTV/PTV and OAR. In phase 2, re-planning was performed for the most challenging case and prescription with dedicated SIB and SIP contours provided for optimization after group discussion. Results For all 3 cases and both phases combined, 292 plans were generated from 42 institutions in 5 countries using commonly available treatment planning systems. The GTVD50% prescription was performed by only 76% and 74% of planners within 2% for 5 and 8 fractions, respectively. The GTVD99% goal was mostly reached, while the balance between OAR and target dose showed initial SIB/SIP-like optimization strategies in about 50% of plans. For plan ranking, 149 and 217 score penalties were given for 5 and 8 fractions, pointing to improvement possibilities. For phase 2, the GTVD50% prescription was performed by 95% of planners within 2% and GTVD99% as well as OAR doses were better harmonized with notable less score penalties. Fourteen of 19 planners improved their plan rank, 9 of them by at least 2 ranks. Conclusion Dedicated SIB/SIP concepts in combination with multiparametric prescriptions and constraints can lead to overall harmonized and high treatment plan quality for PACA SBRT. Standardized SIB/SIP treatment planning in multicenter clinical trials appears feasible after group consensus and training.

PURPOSE:Our purpose was to investigate whether liver stereotactic body radiation therapy treatment planning can be harmonized across different treatment planning systems, delivery techniques, and institutions by using a specific prescription method and to minimize the knowledge gap concerning intersystem and interuser differences. We provide best practice guidelines for all used techniques. METHODS AND MATERIALS:A multiparametric specification of target dose (gross target volume [GTV]D50%, GTVD0.1cc, GTVV90%, planning target volume [PTV]V70%) with a prescription dose of GTVD50% = 3 × 20 Gy and organ-at-risk (OAR) limits were distributed with computed tomography and structure sets from 3 patients with liver metastases. Thirty-five institutions provided 132 treatment plans using different irradiation techniques. These plans were first analyzed for target and OAR doses. Four different renormalization methods were performed (PTVDmin, PTVD98%, PTVD2%, PTVDmax). The resulting 660 treatments plans were evaluated regarding target doses to study the effect of dose renormalization to different prescription methods. A relative scoring system was used for comparisons. RESULTS:GTVD50% prescription can be performed in all systems. Treatment plan harmonization was overall successful, with standard deviations for Dmax, PTVD98%, GTVD98%, and PTVDmean of 1.6, 3.3, 1.9, and 1.5 Gy, respectively. Primary analysis showed 55 major deviations from clinical goals in 132 plans, whereas in only <20% of deviations GTV/PTV dose was traded for meeting OAR limits. GTVD50% prescription produced the smallest deviation from target planning objectives and between techniques, followed by the PTVDmax, PTVD98%, PTVD2%, and PTVDmin prescription. Deviations were significant for all combinations but for the PTVDmax prescription compared with GTVD50% and PTVD98%. Based on the various dose prescription methods, all systems significantly differed from each other, whereas GTVD50% and PTVD98% prescription showed the least difference between the systems. CONCLUSIONS:This study showed the feasibility of harmonizing liver stereotactic body radiation therapy treatment plans across different treatment planning systems and delivery techniques when a sufficient set of clinical goals is given.

PurposeHigh precision radiosurgery demands comprehensive delivery-quality-assurance techniques. The use of a liquid-filled ion-chamber-array for robotic-radiosurgery delivery-quality-assurance was investigated and validated using several test scenarios and routine patient plans.Methods and materialPreliminary evaluation consisted of beam profile validation and analysis of source–detector-distance and beam-incidence-angle response dependence. The delivery-quality-assurance analysis is performed in four steps: (1) Array-to-plan registration, (2) Evaluation with standard Gamma-Index criteria (local-dose-difference ⩽ 2%, distance-to-agreement ⩽ 2 mm, pass-rate ⩾ 90%), (3) Dose profile alignment and dose distribution shift until maximum pass-rate is found, and (4) Final evaluation with 1 mm distance-to-agreement criterion. Test scenarios consisted of intended phantom misalignments, dose miscalibrations, and undelivered Monitor Units. Preliminary method validation was performed on 55 clinical plans in five institutions.ResultsThe 1000SRS profile measurements showed sufficient agreement compared with a microDiamond detector for all collimator sizes. The relative response changes can be up to 2.2% per 10 cm source–detector-distance change, but remains within 1% for the clinically relevant source–detector-distance range. Planned and measured dose under different beam-incidence-angles showed deviations below 1% for angles between 0° and 80°. Small-intended errors were detected by 1 mm distance-to-agreement criterion while 2 mm criteria failed to reveal some of these deviations. All analyzed delivery-quality-assurance clinical patient plans were within our tight tolerance criteria.ConclusionWe demonstrated that a high-resolution liquid-filled ion-chamber-array can be suitable for robotic radiosurgery delivery-quality-assurance and that small errors can be detected with tight distance-to-agreement criterion. Further improvement may come from beam specific correction for incidence angle and source–detector-distance response.

Bei Tumoren im Gastrointestinaltrakt gelingt es im Computertomogramm (CT) für die 3-D-Bestrahlungsplanung häufig nicht, die genaue Ausdehlung des Primärtumors zu verifizieren. Dies erschwert bei der Planung der perkutanen Strahlentherapie die exakte Bestimmung des makroskopischen Tumorvolumens und somit die des Zielvolumens erster Ordnung (ZV 1), in einigen Fällen auch bereits die des Zielvolumens zweiter Ordnung (ZV 2).

Hintergrund: Bei Tumoren im Gastrointestinaltrakt gelingt es im Computertomogramm (CT) für die 3-D-Bestrahlungsplanung häufig nicht, die genaue Ausdehlung des Primärtumors zu verifizieren. Dies erschwert bei der Planung der perkutanen Strahlentherapie die exakte Bestimmung des makroskopischen Tumorvolumens und somit die des Zielvolumens erster Ordnung (ZV 1), in einigen Fällen auch bereits die des Zielvolumens zweiter Ordnung (ZV 2). Patienten und Methode: Elf Patienten mit makroskopischen Tumoren (Rektumkarzinom: n = 5, distales Ösophagus-/Kardiakarzinom: n = 6) vor neoadjuvanter oder definitiver Radiochemotherapie wurden in die Analyse aufgenommen. Unmittelbar vor der 3-D-Bestrahlungsplanung wurden endoskopisch der distale und proximale Tumorrand mit Metallclips versehen, anschließend erfolgten das Planungs-CT und die Definition des Zielvolumens zweiter Ordnung. Für die Planung des Zielvolumens erster Ordnung (Boost) wurde fünf bis sechs Wochen nach der Clipmarkierung ein neues CT durchgeführt. Von zwei unabhängigen Untersuchungen wurde beurteilt, inwiefern die durch Clips definierte Primärtumorausdehnung Einfluss auf die gewählten Planungszielvolumina hatte und ob die Anzahl der Clips zum Zeitpunkt des zweiten Planungs-CT noch ausreichend war, um das Zielvolumen erster Ordnung eindeutig festzulegen. Ergebnisse: Bei allen Patienten gelang es komplikationslos, die Tumorränder durch Clips zu markieren. Der Bestrahlungsbeginn verzögerte sich durch diesen Eingriff nicht. Durch die Clipmarkierungen waren in allen Fällen die Lage und Ausdehnung des Primärtumors im Planungs-CT genau definiert. Bei fünf von elf Patienten veräderten die Clips bereits das Zielvolumen zweiter Ordnung, in sieben von elf Fällen das Boostvolumen (Zielvolumen erster Ordnung). Bei der Simulation der Bestrahlungsfeldpforten ermöglichten die Clips eine bessere Kontrolle beziehungsweise Dokumentation der Planung. In sechs von elf Fällen war auch bei der Ersteinstellung der Boostfelder noch eine ausreichende Anzahl der Clips in situ vorhanden. Bei ausgeprägter Tumorrückbildung nach neoadjuvanter Radiochemotherapie erleichterten die Markierungen in drei Fällen intraoperativ die genaue Bestimmung der Primärtumorregionen. Schlussfolgerung: Bei Patienten mit Tumoren im Gastrointestinaltrakt erleichtert die prätherapeutische Clipmarkierung die Definition der Zielvolumina und erhöht die Präzision der Planung. Die Clips sind auf den Röntgendokumentationsaufnahmen der Bestrahlungsfelder in der Regel gut nachzuvollziehen und tragen so zur Qualitätskontrolle bei. Background: In many cases it is not possible to exactly define the extension of carcinoma of the gastrointestinal tract with the help of computertomography scans made for 3-D-radiation treatment planning. Consequently, the planning of external beam radiotherapy is made more difficult for the gross tumor volume as well as, in some cases, also for the clinical target volume. Patients and Methods: Eleven patients with macroscopic tumors (rectal cancer n = 5, cardiac cancer n = 6) were included. Just before 3-D planning, the oral and aboral border of the tumor was marked endoscopically with hemoclips. Subsequently, CT scans for radiotherapy planning were made and the clinical target volume was defined. Five to 6 weeks thereafter, new CT scans were done to define the gross tumor volume for boost planning. Two investigators independently assesed the influence of the hemoclips on the different planning volumes, and whether the number of clips was sufficient to define the gross tumor volume. Results: In all patients, the implantation of the clips was done without complications. Start of radiotherapy was not delayed. With the help of the clips it was possible to exactly define the position and the extension of the primary tumor. The clinical target volume was modified according to the position of the clips in 5/11 patients; the gross tumor volume was modified in 7/11 patients. The use of the clips made the documentation and verification of the treatment portals by the simulator easier. Moreover, the clips helped the surgeon to define the primary tumor region following marked regression after neoadjuvant therapy in 3 patients. Conclusions: Endoscopic clipping of gastrointestinal tumors helps to define the tumor volumes more precisely in radiation therapy. The clips are easily recognized on the portal films and, thus, contribute to quality control.