Abstract
BackgroundLocalization of the tumor bed of breast cancer is crucial for accurate planning of boost irradiation. Lumpectomy cavity and surgical clips provide localizing information about tumor bed. However, defining the tumor bed is often difficult because of presence of unclear lumpectomy cavity and lack of certain information such as absence of surgical clips. In the present study, we evaluated the feasibility of initial diagnostic PET-CT in localization of the tumor bed using deformable image registration (DIR).MethodsWe selected twenty-five patients who had an initial diagnostic PET-CT performed and underwent breast-conserving surgery with surgical clips in tumor bed. In every individual patient, two target volumes were separately delineated on planning CT; 1) target volume based on surgical clips with a margin of 1 cm (TVclip) and 2) tumor volume based on 90% of maximum SUV on PET-CT registered by DIR (TVPET). The percent of TVPET in TVclip (Vin) was calculated and distance between center points of two volumes (Dcenter) was also measured.ResultsMean Dcenter between two volumes was 1.4 cm (range, 0.33 – 2.53). Mean Vin was 94.8% (range, 60.9-100) and 100% in 18 out of 25 patients. When compared to the center of TVclip, the center of TVPET tended to be located posteriorly (mean 0.3 cm, standard deviation 0.6), laterally (mean 0.3 cm, standard deviation 0.8) and inferiorly (mean 0.4 cm, standard deviation 0.9).ConclusionInitial diagnostic PET-CT can be one of the possible references to localize the tumor bed in breast cancer radiotherapy.
Highlights
Whole breast irradiation after breast conserving surgery is one of the standard treatments for the patients with early-stage breast cancer [1,2]
To investigate the feasibility of diagnostic PET-CT in localization of tumor bed, we delineated and compared two separate target volumes in each patient; 1) target volume based on surgical clips with a margin of 1 cm (TVclip) and 2) target volume based on 90% of maximum SUV on PET-CT registered by deformable image registration (DIR) (TVPET) (Figure 1D)
The percent volume of TVPET included in TVclip (Vin) ranged from 60.9 to 100% and 100% in 18 out of 25 patients
Summary
Whole breast irradiation after breast conserving surgery is one of the standard treatments for the patients with early-stage breast cancer [1,2]. After the whole breast irradiation, additional boost to the tumor bed have demonstrated considerable improvement in local control rate [3,4]. The accuracy of defining the tumor bed has been improved by the use of CT-based simulation, in which lumpectomy cavity and surgical clips provide localizing information [5,6,7]. Based on deformable image registration, we hypothesized that the localization of tumor bed may be feasible using preoperative imaging work-up without requirement of additional study for the sole purpose of radiotherapy planning. Localization of the tumor bed of breast cancer is crucial for accurate planning of boost irradiation. Lumpectomy cavity and surgical clips provide localizing information about tumor bed. We evaluated the feasibility of initial diagnostic PET-CT in localization of the tumor bed using deformable image registration (DIR)
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