Significance of target volume delineation of tumor bed according to metal clips or seroma in determing tumor bed position during radiotherapy after breast-conserving surgery for breast cancer / 肿瘤研究与临床

ABSTRACT

Objective:To investigate the differences between the mental clips placed intraoperatively and the tumor bed's target volume delineation of seroma based on CT scanning during radiotherapy for breast cancer patients who received breast-conserving surgery in the persuit of a better solution to determine the tumor bed position.Methods:The clinical data of 13 patients with early breast cancer who received postoperative radiotherapy after breast-conserving surgery at Beijing Shijingshan Hospital and Beijing Shijitan Hospital of Capital Medical University from December 2020 to January 2022 were retrospectively analyzed. They all had surgical clips implanted during the surgery. The following methods were used to delineate the target volume of tumor bed, including gross target volume delineation of tumor bed based on the mental clips (GTVtb-Clip), the tumor bed's gross target volume delineation of seroma based on CT scanning (GTVtb-Seroma), and the combination of both (GTVtb-C+S). The volume, diameter on three coordinate axis, neutral point displacement and conformability of these delineation methods were compared.Results:The volume of GTVtb-Clip, GTVtb-Seroma and GTVtb-C+S was (25±10) cm 3, (38±17) cm 3, (49±20) cm 3, and the differences were statistically significant (all P<0.05). The diameter on X axis was (4.7±1.2) cm, (5.3±1.4) cm, (5.7±1.6) cm, respectively in GTVtb-Clip, GTVtb-Seroma and GTVtb-C+S; the diameter on Y axis was (4.6±1.7) cm, (5.0±1.6) cm, (5.7±1.7) cm, respectively in GTVtb-Clip, GTVtb-Seroma and GTVtb-C+S; the diameter on Z axis was (4.4±1.5) cm, (5.2±1.4) cm, (5.6±1.4) cm in GTVtb-Clip, GTVtb-Seroma and GTVtb-C+S. The differences in the diameter of GTVtb-Clip and GTVtb-C+S on X,Y, Z axis were statistically significant (all P<0.05); the differences in the diameter of GTVtb-Seroma and GTVtb-C+S on X, Z axis were statistically significant (all P<0.05); the difference in the diameter of GTVtb-Clip and GTVtb-Seroma on X axis was statistically significant ( P<0.05) .Neutral point displacement was (5.8±1.6) cm, (5.5±1.9) cm, (6.0±1.7) cm, respectively of GTVtb-Clip, GTVtb-Seroma, GTVtb-C+S, and the difference was not statistically significant ( P>0.05). Conformability of GTVtb-Clip and GTVtb-Seroma, GTVtb-Clip and GTVtb-C+S, GTVtb-Seroma and GTVtb-C+S was 0.412±0.112, 0.525±0.095, 0.774±0.112,respectively, and the differences were statistically significant (all P<0.05). Conclusions:During radiotherapy after breast-conserving surgery for breast cancer, compared with the single method, the combination of GTVtb-Clip and GTVtb-Seroma can better cover the real tumor bed, thus reducing the omission of tumor bed and recurrence rate. CT position should better take place at 4 to 8 weeks for patients receiving radiotherapy after breast-conserving surgery, and target volume of tumor bed will be delineated based on the postoperative changes of both mental clips and seroma.