Single-isocenter hybrid IMRT plans versus two-isocenter conventional plans and impact of intrafraction motion for the treatment of XXXX with supraclavicular lymph nodes involvement.

@entity1 @entity2194 @entity0 @entity6723 @entity5 @entity2246
UNASSIGNED: The purpose of this study was to compare the single-isocenter, four-field hybrid IMRT with the two-isocenter techniques to treat the whole breast and supraclavicular fields and to investigate the intrafraction motions in both techniques in the superior direction. Fifteen @entity0 @entity1 who underwent lumpectomy and adjuvant radiation to the whole breast and supraclavicular ( @entity6723 ) fossa at our institution were selected for this study. Two planning techniques were compared for the treatment of the breast and @entity6723 lymph nodes. The @entity1 were divided into three subgroups according to the whole breast volume. For the two-isocenter technique, conventional wedged or @entity2194 ( @entity2194 ) were used to match with the same anterior field for the @entity6723 region. For the single-isocenter technique, four-field hybrid IMRT was used for the tangent fields matched with a half blocked anterior field for the @entity6723 region. To simulate the intrafraction uncertainties in the longitudinal direction for both techniques, the treatment isocenters were shifted by 1 mm and 2 mm in the superior direction. The average breast clinical @entity5 volume (CTV) receiving 100% (V100%) of the prescription dose (50 Gy) was 99.3%    0.5% and 96.4%    1.2% for the for two-isocenter and single-isocenter plans (   < 0.05), respectively. The breast CTV receiving 95% of the prescription dose (V95%) was close to 100% in both techniques. The average breast CTV receiving 105% (V105%) of the prescription dose was 32.4%    19.3% and 23.8%    13.3% (   = 0.08). The percentage volume of the breast CTV receiving 110% of the dose was 0.4%    1.2% in the two-isocentric technique vs. 0.1%    0.2% in the single-isocentric technique. The average uniformity index was 0.91    0.02 vs. 0.91    0.01 in both techniques (p = 0.04), but had no clinical impact. The percentage volume of the contralateral breast receiving a dose of 1 Gy was less than 2.3% in small breast @entity1 and insignificant for medium and large breast sizes. The percentage of the total lung volume receiving > 20 Gy (V20Gy) and the heart receiving > 30 Gy (V30Gy) were 13.6% vs. 14.3% (   = 0.03) and 1.25% vs. 1.2% (   = 0.62), respectively. Shifting the treatment isocenter by 1 mm and 2 mm superiorly showed that the average maximum dose to 1 cc of the breast volume was 55.5    1.8 Gy and 58.6    4.3 Gy in the two-isocentric technique vs. 56.4    2.1 Gy and 59.1    5.1 Gy in the single-isocentric technique (   = 0.46, 0.87), respectively. The single-isocenter technique using four-field hybrid IMRT approach resulted in comparable plan quality as the two-isocentric technique. The single-isocenter technique is more sensitive to intra-fraction motion in the superior direction compared to the two-isocentric technique. The advantages of the single-isocenter include elimination of @entity2246 due to couch and collimator rotations and reduction in treatment time. This study supports consideration of a single-isocenter four-field hybrid IMRT technique for @entity1 undergoing breast and supraclavicular nodal irradiation.
