[Impact of skin build-up region on evaluation of irradiation plan of radiotherapy for early stage breast cancer].
OBJECTIVE
Intensity-modulated radiation therapy (IMRT) can improve the dose distribution in the breast irradiation for early stage breast cancer, but the definition and delineation for clinical target volume (CTV) are uncertain. This study was to investigate the impact of skin build-up region on evaluation of IMRT plan for early stage breast cancer by analyzing dose-volume histograms (DVHs).


METHODS
CTVs for 22 patients with early stage breast cancer were delineated on transversal CT images, which included the skin build-up region. The CTVs were contracted and modified to exclude 0.5 cm outer skin surface to form new target volumes (CTV1s). All plans were tailored by using step-and-shoot IMRT techniques. DVHs and dose distributions of these plans were evaluated.


RESULTS
The percentage volume receiving more than 95% of the prescription dose (V95) for CTV was significantly lower than that for CTV1 [(89.6+/-3.2)% vs. (96.5+/-2.0)%, P<0.001]. The homogeneity index of the dose distribution within targets (D99-01) for CTV was significantly higher than that for CTV1 [(14.0+/-2.4) Gy vs. (7.3+/-1.6) Gy, P<0.001].


CONCLUSIONS
The surface effect of skin build-up region is important and must be considered in IMRT for breast cancer. It is better to use the CTV excluding surface and build-up region to evaluate such plans.
Fu
Yu-Chuan
YC
Department of Radiation Oncology, West China Hospital, Sichuan University, Chengdu, Sichuan, 610041, P. R. China.
Wang
Shi-Chao
SC
Xie
Li
L
D001943:Breast Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D009367:Neoplasm Staging; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*