3D conformal external beam radiotherapy (3D-CRT) for accelerated partial breast irradiation (APBI): What is the correct prescription dose
ABSTRACT This study is an evaluation of the biologic equivalence of the dose prescriptions for brachytherapy and 3-dimensional conformal external beam radiotherapy (3D-CRT) accelerated partial breast irradiation (APBI), using actual patient dose matrix data, and is based on the concept of equivalent uniform biologically effective dose (EUBED). This formalism allows a nonuniform dose distribution to be reduced to an equivalent uniform dose, while also accounting for fraction size.
Five computed tomography scans were selected from a group of patients treated with multicatheter interstitial APBI. Dose matrices for the brachytherapy plans were computed and analyzed with in-house software. For each patient, the EUBED for the brachytherapy dose matrix was generated based on calculations performed at the voxel-level. These EUBED values were then used to calculate the biologically equivalent fraction size for 3D-CRT (eud).
The mean equivalent fraction size (eudmean) and maximum equivalent fraction size (eudmax) were calculated for each patient using 100 different values of the alpha/beta ratio. The eudmean ranged from 3.67 to 3.69 Gy, while the eudmax ranged from 3.79 to 3.82 Gy. For all values of the alpha/beta ratio, the maximum fraction size calculated to deliver a biologically equivalent dose with 3D-CRT was 3.82 Gy, with an equivalent total prescription dose of 38.2 Gy.
Utilizing a wide range of established radiobiological parameters, this study suggests that the maximum fraction size needed to deliver a biologically equivalent dose using 3D-CRT is 3.82 Gy, supporting the continued use of 3.85Gy BID in the current national cooperative trial.
SourceAvailable from: San Gang Wu[Show abstract] [Hide abstract]
ABSTRACT: Purpose Several accelerated partial breast irradiation (APBI) techniques are being investigated in patients with early-stage breast cancer. The present study evaluated the feasibility, early toxicity, initial efficacy, and cosmetic outcomes of accelerated partial breast intensity-modulated radiotherapy (IMRT) for Chinese female patients with early-stage breast cancer after breast-conserving surgery. Methods A total of 38 patients met the inclusion criteria and an accelerated partial breast intensity-modulated radiotherapy (APBI-IMRT) plan was designed for each patient. The prescription dose was 34 Gy in 10 fractions, 3.4 Gy per fraction, twice a day, in intervals of more than 6 hours. Results Of the 38 patients, six patients did not meet the planning criteria. The remaining 32 patients received APBI-IMRT with a mean target volume conformity index of 0.67 and a dose homogeneity index of 1.06. The median follow-up time was 53 months and no local recurrence or distant metastasis was detected. The most common acute toxicities observed within 3 months after radiotherapy were erythema, breast edema, pigmentation, and pain in the irradiated location, among which 43.8%, 12.5%, 31.3%, and 28.1% were grade 1 toxicities, respectively. The most common late toxicities occurring after 3 months until the end of the follow-up period were breast edema, pigmentation, pain in the irradiated location, and subcutaneous fibrosis, among which 6.2%, 28.1%, 21.9%, and 37.5% were grade 1 toxicities, respectively. Thirty-one patients (96.8%) had fine or excellent cosmetic outcomes, and only one patient had a poor cosmetic outcome. Conclusion It is feasible for Chinese females to receive APBI-IMRT after breast conserving surgery. The radiotherapeutic toxicity is acceptable, and both the initial efficacy and cosmetic outcomes are good.Journal of Breast Cancer 09/2014; 17(3):256-264. DOI:10.4048/jbc.2014.17.3.256 · 1.32 Impact Factor
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ABSTRACT: Accelerated partial breast irradiation (APBI) has emerged as an attractive alternative to whole-breast radiotherapy (WBRT) in adjuvant radiotherapy of early stage breast cancers. Localization of the target, the surgical cavity (SC), is of the utmost important since a large dose per fraction is delivered during treatment. Differences in the shape and position of the SC between planning and treatment can result in a geographic miss of the target. Skin markings (SM) placed around the surgical scar potentially can be used to improve localization of the SC during treatment. However, analysis of such movements is complicated by interobserver and intraobserver variations in defining the SC. Thus, this thesis aims to (1) develop a method to construct a representative surgical cavity (RSC), a contour that combines contributions from multiple SC contours; (2) investigate contouring uncertainties and dosimetric coverage of the SC as contoured by multiple oncologists; and (3) use the RSC to quantify differences between the positions of the SMs and SC. Twelve patients underwent four CT scans: one at the time of planning and three during treatment. Three radiation oncologists contoured the SC on each CT scan. Oncologists delineated two additional repeat contours for three patients. Interobserver and intraobserver contour variability was assessed by comparing the SC contours with a RSC. Volume-based and distance-based measurements were performed to assess contour variability. Clinical consequences of variability were assessed using the equivalent uniform dose (EUD) formalism. Correlations between the change in position of the SM centre-of-mass (COM) and RSC COM were quantified. Interobserver volume, COM, and spatial variations of the SC contours were observed to be larger than intraobserver variations. However, dosimetric coverage of the SC was adequate despite these variations. The SM COM was found to be strongly correlated with the RSC COM in the lateral, anterior-posterior, and superior-inferior directions. The average change in the distance between the SM COM and RSC COM during treatment was more than 4 mm in less than 5% of cases, suggesting that planning margins for the SC can potentially be decreased if the SMs are used for patient setup.04/2009, Degree: M.Sc., Supervisor: Vitali Moiseenko
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ABSTRACT: Breast conserving treatment (breast conserving surgery followed by whole breast irradiation) has commonly been used in early breast cancer since many years. New radiation modalities have been recently developed in early breast cancers, particularly accelerated partial breast irradiation. Three-dimensional conformal accelerated partial breast irradiation is the most commonly used modality of radiotherapy. Other techniques are currently being developed, such as intensity-modulated radiotherapy, arctherapy, and tomotherapy. The present article reviews the indications, treatment modalities and side effects of accelerated partial breast irradiation.Cancer/Radiothérapie 10/2012; 16(7):641–649. DOI:10.1016/j.canrad.2012.03.006 · 1.11 Impact Factor