Clinical utility of a new immobilization method in image-guided intensity-modulated radiotherapy for breast cancer patients after radical mastectomy

Article type: Research Article

Authors: Dong, Fangfen^{a; b; c; d; 1} | Weng, Xing^{b; c; d; 1} | Deng, Xianzhi^a | Yang, Yong^{a; b; c; d} | Xu, Benhua^{a; b; c; d; 2; *} | Li, Xiaobo^{a; b; c; d; e; 2; *}

Affiliations: [a] College of Medical Technology and Engineering, Fujian Medical University, Fuzhou, China | [b] Department of Radiation Oncology, Fujian Medical University Union Hospital, Fuzhou, China | [c] Fujian Key Laboratory of Intelligent Imaging and Precision Radiotherapy for Tumors (Fujian Medical University), Fuzhou, China | [d] Clinical Research Center for Radiology and Radiotherapy of Fujian Province (Digestive, Hematological and Breast Malignancies), Fuzhou, China | [e] Department of Engineering Physics, Tsinghua University, Beijing, China

Correspondence: [*] Corresponding authors: Xiaobo Li and Benhua Xu, Department of Radiation Oncology, Fujian Medical University Union Hospital, Fuzhou, China. E-mails: [email protected] (Xiaobo Li) and E-mail: [email protected] (Benhua Xu).

Note: [1] These authors have contributed equally to this work and share first authorship.

Note: [2] These authors have contributed equally to this work.

Abstract: OBJECTIVE:To investigate clinical utility of a new immobilization method in image-guided intensity-modulated radiotherapy (IMRT) for breast cancer patients after radical mastectomy. MATERIALS AND METHODS:Forty patients with breast cancer who underwent radical mastectomy and postoperative IMRT were prospectively enrolled. The patients were randomly and equally divided into two groups using both a carbon-fiber support board and a hollowed-out cervicothoracic thermoplastic mask (Group A) and using only the board (Group B). An iSCOUT image-guided system was used for acquiring and correcting pretreatment setup errors for each treatment fraction. Initial setup errors and residual errors were obtained by aligning iSCOUT images with digitally reconstructed radiograph (DRR) images generated from planning CT. Totally 600 initial and residual errors were compared and analyzed between two groups, and the planning target volume (PTV) margins before and after the image-guided correction were calculated. RESULTS:The initial setup errors of Group A and Group B were (3.14±3.07), (2.21±1.92), (2.45±1.92) mm and (3.14±2.97), (2.94±3.35), (2.80±2.47) mm in the left-right (LAT), superior-inferior (LONG), anterior-posterior (VERT) directions, respectively. The initial errors in Group A were smaller than those in Group B in the LONG direction (P < 0.05). No significant difference was found in the distribution of three initial error ranges (≤3 mm, 3–5 mm and > 5 mm) in each of the three translational directions for the two groups (P > 0.05). The residual errors of Group A and Group B were (1.74±1.03), (1.62±0.92), (1.66±0.91) mm and (1.70±0.97), (1.68±1.18), (1.58±0.98) mm in the three translational directions, respectively. No significant difference was found in the residual errors between two groups (P > 0.05). With the image-guided correction, PTV margins were reduced from 8.01, 5.44, 5.45 mm to 3.54, 2.99, 2.89 mm in three translational directions of Group A, respectively, and from 8.14, 10.89, 6.29 mm to 2.67, 3.64, 2.74 mm in those of Group B, respectively. CONCLUSION:The use of hollowed-out cervicothoracic thermoplastic masks combined with a carbon-fiber support board showed better inter-fraction immobilization than the single use of the board in reducing longitudinal setup errors for breast cancer patients after radical mastectomy during IMRT treatment course, which has potential to reduce setup errors and improve the pretreatment immobilization accuracy for breast cancer IMRT after radical mastectomy.

Keywords: Immobilization device, breast cancer, intensity-modulated radiotherapy (IMRT), radical mastectomy, setup errors

DOI: 10.3233/XST-221127

Journal: Journal of X-Ray Science and Technology, vol. 30, no. 4, pp. 641-655, 2022