Abstract
BackgroundThis prospective study aimed to compare dose volume histograms (DVH) of the breasts and organs at risk (OARs) of whole breast radiotherapy in the supine and prone positions, and frequency and severity of acute and late toxicities were analyzed.MethodsEarly-stage breast cancer patients with large breasts (Japanese bra size C or larger, or the widest measurements of the bust ≥ 95 cm) undergoing partial mastectomy participated in this study. CT-based treatment plans were made in each position, and various dosimetric parameters for the breast and OARs were calculated to compare the supine and prone radiotherapy plans. The actual treatment was delivered in the position regarded as better.ResultsFrom 2009 to 2010, 22 patients were prospectively accrued. Median follow-up period was 58 months. The homogeneity index and lung doses were significantly lower in the prone position (P = 0.008, P < 0.0001 and P < 0.0001, respectively). Cardiac dose showed no significant differences between two positions. By comparing two plans, the prone position was chosen in 77 % of the patients. In the prone position, ≥ grade 2 acute dermatitis were seen in 47 % of patients treated, whereas 20 % of the patients treated in the supine position had grade 2 and no cases of grade 3, although without a statistical significance of the rates of ≥ grade 2 acute dermatitis between the two positions (P = 0.28). The actual dose measurement using a breast phantom revealed significantly higher surface dose of the breast treated in the prone position than that in the supine position.ConclusionsBreast irradiation in the prone position improves PTV homogeneity and lowers doses to the OARs in the Japanese large-breast patients. However meticulous positioning of the breast in the prone board avoiding the bolus effect is necessary to prevent acute dermatitis.
Highlights
This prospective study aimed to compare dose volume histograms (DVH) of the breasts and organs at risk (OARs) of whole breast radiotherapy in the supine and prone positions, and frequency and severity of acute and late toxicities were analyzed
A previous study from our institution reported that the incidence of ≥ grade 2 acute dermatitis for the patients with large-volume breasts treated with whole breast radiotherapy (WBRT) were higher than for the other patients without a statistical significance (15 % vs 7 %, p = 0.214) [5]
Patient characteristics Between September 2009 and May 2010, 22 patients with breast cancer undergoing partial mastectomy were prospectively accrued to this trial (13 right-sided: nine left-sided)
Summary
This prospective study aimed to compare dose volume histograms (DVH) of the breasts and organs at risk (OARs) of whole breast radiotherapy in the supine and prone positions, and frequency and severity of acute and late toxicities were analyzed. A previous study from our institution reported that the incidence of ≥ grade 2 acute dermatitis for the patients with large-volume breasts treated with WBRT were higher than for the other patients without a statistical significance (15 % vs 7 %, p = 0.214) [5]. WBRT in the prone position aims to overcome some of the technical limitations associated with treating large, pendulous breasts and/or large body habitus, and it may reduce radiation doses to the organs at risk (OARs) [6,7,8,9,10,11]
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