Abstract
The purpose was to compare the dosimetric results observed in 201 breast cancer patients submitted to tangential forward intensity‐modulated radiation therapy (IMRT) with those observed in 131 patients treated with a standard wedged 3D technique for postoperative treatment of whole breast, according to breast size and supraclavicular node irradiation. Following dosimetric parameters were used for the comparison: Dmax,Dmin,Dmean,V95% and V107% for the irradiated volume; Dmax,Dmean,V80% and V95% for the ipsilateral lung; Dmax,Dmean,V80% and V95% for the heart. Stratification was made according to breast size and supraclavicular (SCV) nodal irradiation. As respect to irradiated volume, a significant reduction of V107% (mean values: 7.0±6.6 versus 2.4±3.7,p<0.001) and Dmax (mean % values:111.2±2.7 versus 107.7±6.3,p<0.001), and an increase of Dmin (mean % values: 65.0±17.4 versus 74.9±12.9,p<0.001) were observed with forward IMRT. The homogeneity of dose distribution to target volume significantly improved with forward IMRT in all patient groups, irrespective of breast size or supraclavicular nodal irradiation. When patients treated with supraclavicular nodal irradiation were excluded from the analysis, forward IMRT slightly reduced V80% (mean values: 3.7±2.6 versus 3.0±2.4,p=0.03) and V95% (mean values 1.9±1.8 versus 1.2%±1.5;p=0.001) of the ipsilateral lung. The dose to the heart tended to be lower with IMRT but this difference was not statistically significant. Tangential forward IMRT in postoperative treatment of whole breast improved dosimetric parameters in terms of homogeneity of dose distribution to the target in a large sample of patients, independent of breast size or supraclavicular nodal irradiation. Lung irradiation was slightly reduced in patients not undergoing to supraclavicular irradiation.PACS numbers: 87.53.Kn; 87.55.de
Highlights
214 Morganti et al.: Forward planned intensity-modulated radiation therapy (IMRT) in breast carcinoma of care after conservative surgery for early stage breast cancer, as demonstrated by many randomized controlled studies.[1,2,3] In these patients, risks of late complications must be strongly considered due to the long expected disease-free interval
The dose within the planning target volume can vary by as much as 27% in some patients[4] and a significant portion of the breast tissue may receive 110% of the prescription dose, with potential hot spots of up to 120%.(5) This heterogeneity may result in increased normal tissue toxicity and poor cosmetic results.[6,7] In addition, physical compensators were found to increase scatter dose to the contralateral breast.[8]. Irradiation of breast is challenging, because its irregular shape makes it difficult to achieve a homogeneous dose distribution, and because of its proximity to organs at risk (OARs), such as the heart and the lung
Most of published dosimetric comparisons between IMRT and standard techniques were performed in small groups of 5–43 selected patients.[9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28] In particular, many studies included only patients with left-sided breast cancer,(10,11,13-16,19,22,23) with large breasts,(12,18) or with target volume encompassing regional nodes.[11,13,22] In some studies, patients with left-sided breast carcinoma where selected only if a maximum heart distance of at least 1 cm[14,16] or 2 cm[13] was measured
Summary
214 Morganti et al.: Forward planned IMRT in breast carcinoma of care after conservative surgery for early stage breast cancer, as demonstrated by many randomized controlled studies.[1,2,3] In these patients, risks of late complications must be strongly considered due to the long expected disease-free interval. The dose within the planning target volume can vary by as much as 27% in some patients[4] and a significant portion of the breast tissue may receive 110% of the prescription dose, with potential hot spots of up to 120%.(5) This heterogeneity may result in increased normal tissue toxicity and poor cosmetic results.[6,7] In addition, physical compensators were found to increase scatter dose to the contralateral breast.[8] Irradiation of breast is challenging, because its irregular shape makes it difficult to achieve a homogeneous dose distribution, and because of its proximity to organs at risk (OARs), such as the heart and the lung With both the intent of further optimize dose homogeneity through the breast and improve OARs sparing, multileaf collimator (MLC)based intensity-modulated radiation therapy (IMRT) (hereafter shown as IMRT) has been tested in several dosimetric studies,(9-29) with no uniform results. Most of published dosimetric comparisons between IMRT and standard techniques were performed in small groups of 5–43 selected patients.[9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28] In particular, many studies included only patients with left-sided breast cancer,(10,11,13-16,19,22,23) with large breasts,(12,18) or with target volume encompassing regional nodes.[11,13,22] In some studies, patients with left-sided breast carcinoma where selected only if a maximum heart distance of at least 1 cm[14,16] or 2 cm[13] was measured
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