Partial-volume segmentation for dose optimization in whole-breast radiotherapy: a comparative dosimetric and clinical analysis.
OBJECTIVE
: 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).


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.


CONCLUSIONS
: 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.
Tromm
Elisabeth
E
Department of Radiotherapy and Special Oncology, Hannover Medical School, Hannover, Germany.
Meyer
Andreas
A
Department of Radiotherapy and Special Oncology, Hannover Medical School, Hannover, Germany.
Frühauf
Jörg
J
Department of Radiotherapy and Special Oncology, Hannover Medical School, Hannover, Germany.
Bremer
Michael
M
Department of Radiotherapy and Special Oncology, Hannover Medical School, Hannover, Germany. bremer.michael@mh-hannover.de.|Klinik für Strahlentherapie und spezielle Onkologie, Medizinische Hochschule Hannover, Carl-Neuberg-Straße 1, 30625, Hannover, Germany. bremer.michael@mh-hannover.de.
D001940:Breast / Q000528:radiation effects; D001943:Breast Neoplasms / Q000188:drug therapy / Q000532:radiotherapy* / Q000601:surgery; D017024:Chemotherapy, Adjuvant; D003131:Combined Modality Therapy; D019583:Dose Fractionation, Radiation; D005260:Female; D006801:Humans; D015412:Mastectomy, Segmental; D011855:Radiodermatitis / Q000209:etiology / Q000517:prevention & control; D011874:Radiometry / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D018714:Radiotherapy, Adjuvant; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed