Partial-Volume Segmentation for Dose Optimization in Whole-Breast Radiotherapy

Abstract

Purpose: To analyze the dosimetric and clinical benefit of a forward planned technique to optimize dose distribution in whole-breast irradation (WBI) using additional partial-volume segments (PVSeg). Patients and Methods: In two separate treatment periods, 265 breast cancer patients received tangential-field WBI and were retrospectively analyzed. Between 02/2004 and 03/2006, 96 patients were treated with one to two additional low-weighted PVSeg to reduce dose peaks within the target volume. 169 patients treated between 01/2000 and 12/2001 before implementation of this PVSeg technique served as comparison group. Total dose was 50-50.4 Gy (single dose, 1.8-2 Gy). The planning target volume (PTV) receiving at least 95%, 105% and 110% of the reference dose (V 95-110% ) and frequency of moist skin desquamation during radiotherapy were compared uni-and multivariately with patient-and treatment-related variables. Results: The mean PTV was 1,144 ml (range, 235-2,365 ml). Moist skin desquamations developed in 16 patients (17%) with PVSeg compared to 30 patients (18%) without PVSeg (p = 0.482). In breast volumes > 1,100 ml, the corresponding figures were 19% versus 29% (p = 0.133). V 105% was significantly reduced by the use of PVSeg (82 ± 51 ml vs. 143 ± 129 ml; p < 0.0001). In univariate analysis, the following variables had significant influence on the development of moist skin desquamation: V 95% (p < 0.0001), V 105% (p < 0.001), V 110% (p = 0.012) adjuvant chemotherapy (p = 0.02), and single dose (p = 0.009). In multivariate analysis, only V 95% (p = 0.002) remained significant. Conclusion: The use of PVSeg in WBI reduced dose peaks within the PTV while breast volumes > 1,100 ml benefited most. V 95% was strongly correlated to the risk of developing moist skin desquamations. Partialvolumensegmentierung zurOptimierung der Dosisverteilung bei Ganzbrustbestrahlung. Eine vergleichende dosimetrische und klinische Analyse Ziel: Untersuchung des Nutzens einer einfachen vorwärts geplanten Bestrahlungstechnik mit Partialvolumensegmenten (PVSeg) bei der Ganzbrustbestrahlung. Patienten und Methodik: Es wurden 265 Brustkrebspatientinnen aus zwei Behandlungszeiträumen analysiert, die nach brusterhaltender Therapie eine Ganzbrustbestrahlung mit tangentialen Feldern erhielten. Von 02/2004 bis 03/2006 erhielten 96 Patientinnen ein bis zwei zusätzliche, niedriggewichtete PVSeg zur Reduzierung von Dosisspitzen im Zielvolumen. Als Vergleich dienten 169 Patientinnen im Zeitraum von 01/2000 bis 12/2001 vor Einführung der PVSeg-Technik. Die Gesamtdosis betrug 50-50,4 Gy (Einzeldosis: 1,8-2 Gy). Das Planungszielvolumen (PTV), welches mindestens 95%, 105% und 110% der Referenzdosis (V 95-110% ) erhielt, und die Häufigkeit feuchter Epitheliolysen während der Bestrahlung wurden mittels uni-und multivariater Analyse mit Patienten-und Behandlungsparametern verglichen. Ergebnisse: Das mittlere PTV betrug 1 144 ml (Streubreite: 235-2 365 ml). Feuchte Epitheliolysen traten bei 16 Patientinnen (17%) mit PVSeg versus 30 Patientinnen (18%) ohne PVSeg ...

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