Brigitte Zurl

A comprehensive evaluation of the current national and regional radiotherapy capacity in Austria with an estimation of demands for 2020 and 2030 was performed by the Austrian Society for Radiation Oncology, Radiobiology and Medical Radiophysics (ÖGRO).

E16038 Background: Febrile neutropenia (FN) is a serious complication of chemotherapy (CTX). Here, we aim to characterize the clinical course of FN in patients (pts) with testicular germ cell tumors (TGCT). Methods: 413 TGCT patients who underwent at least one cycle of CTX in adjuvant or curative intent were studied within this single-center observational cohort study. Baseline characteristics of the subpopulation with FN are reported in Table 1. Results: During a total number of 1,196 CTX cycles in 413 patients, we observed 70 episodes of febrile neutropenia (16.9%). 55 (79%) of these episodes occurred during the 1^stcycle of CTX. The median time between CTX start and FN onset was 14 days [IQR: 12-15, range: 7-18]. One (1%) FN episode was fatal, and 56 patients (80%) had to be hospitalized. Median time in hospital was 7 days [IQR: 6-8, range: 3-12], and the median number of days with an absolute neutrophil count below 0.5G/L was 2 [IQR: 2-3, range: 1-7]. Twelve (20%) FN episodes occurred in the 60 pts who received primary G-CSF support. There was very little treatment delay due to FN (median: 0 days [IQR: 0-0, range: 0-7]. 3 patients (4%) developed a second FN episodes. Conclusions: This study supports prior reports that FN is a relatively frequent complication of CTX in TGCT. However, the case-fatality-rate of FN in TGCT appears to be very low. [Table: see text]

Zusammenfassung Hintergrund Bestimmung von Dosisunsicherheiten in der Bestrahlungsplanung durch Schwankungen der Hounsfield-Einheiten (HU) bei Verwendung unterschiedlicher CT-Protokolle. Patienten und Methoden Anhand unterschiedlicher klinisch verwendeter CT-Scan-Protokolle wurden Konversionstabellen zur Dosisberechnung erstellt und im Phantom getestet. Unter Zuhilfenahme dieser Tabellen wurden 28 reale Bestrahlungspläne nachgerechnet, nachdem bei diesen Patienten irrtümlich ein ungeeignetes Scan-Protokoll verwendet worden war. Ergebnisse Unterschiedliche CT-Einstellungsparameter zeigten für Dichten < 1,1 g/cm³ HU-Schwankungen bis zu 2,6 %, bei Dichten > 1,1 g/cm³ jedoch Abweichungen bis zu 25,6 %. Die größten Schwankungen traten bei Änderung der Röhrenspannung auf. Untersuchungen am virtuellen Wasserphantom mit Schichten unterschiedlicher Dicke und Dichte zeigten einen sägezahnartigen Anstieg der Dosisänderungen von 0,3%, 0,6% und 1,5 % bei Schichtstärken von 1, 3 und 7 cm. Bei Verwendung eines „Beam-hardening“-Filters resultierte bei einer Dichteänderung von 5 % eine Referenzdosisänderung von 0,6 %. Die Rekalkulation von 28 Patienten mit Bestrahlungen im Schädelbereich zeigte bei Verwendung der korrekten Konversionstabelle eine Überdosierung im Knochenbereich von 1,3 ± 0,4 % und im Bereich der Gehirnmasse von 0,7 ± 0,1 %. Im Mittel wurde somit zusätzlich eine Monitoreinheit (Spanne 0–3 MU) pro 100 MU verabreicht. Schlussfolgerung Die Verwendung verschiedener CT-Scan-Protokolle führt zu HU-Abweichungen von bis zu 20 %. Dies kann einen mittleren systematischen Dosisfehler von 1,5 % verursachen. Spezifische Konversionstabellen und automatische CT-Protokollerkennung könnten Dosisungenauigkeiten dieser Art reduzieren.

Purpose: Comparison of the amount of irradiated lung tissue volume and mass in patients with breast cancer treated with an optimized tangential-field technique with and without a deep inspiration breath-hold (DIBH) technique and its impact on the normal-tissue complication probability (NTCP). Material and Methods: Computed tomography datasets of 60 patients in normal breathing (NB) and subsequently in DIBH were compared. With a Real-Time Position Management Respiratory Gating System (RPM), anteroposterior movement of the chest wall was monitored and a lower and upper threshold were defined. Ipsilateral lung and a restricted tangential region of the lung were delineated and the mean and maximum doses calculated. Irradiated lung tissue mass was computed based on density values. NTCP for lung was calculated using a modified Lyman-Kutcher-Burman (LKB) model. Results: Mean dose to the ipsilateral lung in DIBH versus NB was significantly reduced by 15%. Mean lung mass calculation in the restricted area receiving ≤ 20 Gy (M₂₀) was reduced by 17% in DIBH but associated with an increase in volume. NTCP showed an improvement in DIBH of 20%. The correlation of individual breathing amplitude with NTCP proved to be independent. Conclusion: The delineation of a restricted area provides the lung mass calculation in patients treated with tangential fields. DIBH reduces ipsilateral lung dose by inflation so that less tissue remains in the irradiated region and its efficiency is supported by a decrease of NTCP.