Jung JH, et al. Prog Med Phys. 2015 Mar;26(1):6-11. http://dx.doi.org/10.14316/pmp.2015.26.1.6

Background and Objectives: Intensity-modulated radiation therapy (IMRT) is becoming a more common method of performing whole breast irradiation (WBI) for early breast cancer. This study aimed to examine the incidental dose to the axillary region using tomotherapy, a unique form of IMRT. Patients and Methods: This study included 30 patients with early-stage breast cancer who underwent adjuvant WBI using TomoDirect IMRT. A hypofractionation scheme of 42.4 Gy delivered in 16 fractions was prescribed. The plan comprised of two parallel-opposed beams, along with two additional beams positioned anteriorly at gantry angles of 20° and 40° from the medial beam. The incidental dose received at axillary levels I, II, and III was evaluated using several dose-volume parameters. Results: The study participants had a median age of 51 years, and 60% had left-sided breast cancer. The mean dose of the axilla for levels I, II, and III were 15.5 ± 4.8 Gy, 14.9 ± 4.2 Gy, and 1.5 ± 1.6 Gy, respectively. Adequate coverage of the axilla, defined as V95%[%], was achieved for 4.7 ± 3.9%, 4.8 ± 3.7%, and 0 ± 0% for levels I, II, and III, respectively. The results were compared with those of previously published studies, and the axillary mean dose and V95%[%] of TomoDirect IMRT were low, comparable to other IMRT techniques, and lower than those of traditional tangential therapy. Conclusions: While incidental axillary radiation during WBI has been proposed to assist in regional disease control, the TomoDirect plan was demonstrated to decrease this dose, and a hypofractionation scheme would further lower its biological effectiveness. Future clinical studies should incorporate dosimetrical analysis of incidental axillary dose, in order to facilitate hypofractionated IMRT planning with risk-adjusted axilla coverage in early breast cancer.

Jung JH, et al. Prog Med Phys. 2013 Mar;24(1):54-60. http://dx.doi.org/10.14316/pmp.2013.24.1.54

Background and Objectives: The axillary lateral vessel thoracic junction (ALTJ) is a key lymphatic drainage pathway for the arm and a potential structure to spare during regional nodal irradiation (RNI) to reduce lymphedema risk in breast cancer patients. This study aims to demonstrate the feasibility of ALTJ-sparing radiation therapy (RT) planning using Tomotherapy. Materials and Methods: Ten breast cancer patients who had undergone axillary lymph node dissection and whose dissected axillary levels were excluded from the RNI target volume were included. A TomoDirect intensity-modulated RT plan was generated at a dose of 50 Gy in 25 fractions. The dissected axilla was not designated as an organ at risk (OAR) in the original treatment plan. For this study, the axillary lymph node level I (AXL1) and the ALTJ were delineated retrospectively, with the ALTJ considered an OAR in the newly generated study plan. A total of 20 RT plans (10 per group) were statistically compared using various dose-volume parameters. Results: Compared to the original plans, the study plans with ALTJ as an OAR significantly reduced the incidental dose to both the ALTJ (mean: 41.7 ± 3.4 Gy vs. 27.2 ± 1.3 Gy; p = 0.005) and the AXL1 (mean: 43.9 ± 2.0 Gy vs. 37.7 ± 1.9 Gy; p = 0.005). All other dosimetric parameters (V25Gy, V35Gy, V40Gy, Dmin, Dmax) for the ALTJ were also significantly lower in the study plans. This ALTJ sparing was achieved while maintaining all required dose-volume constraints for target volumes and standard OARs such as the lung and heart. Conclusions: This study demonstrates that simply excluding the dissected axilla from the target volume without designating it as an OAR still results in a substantial incidental dose to this region. Our findings also show the feasibility of using Tomotherapy to selectively spare the axilla, particularly the ALTJ subregion of AXL1, which is critical for lymphedema risk in breast cancer patients.

Background and Objectives: The axillary lateral vessel thoracic junction (ALTJ) is a key lymphatic drainage pathway for the arm and a potential structure to spare during regional nodal irradiation (RNI) to reduce lymphedema risk in breast cancer patients. This study aims to demonstrate the feasibility of ALTJ-sparing radiation therapy (RT) planning using Tomotherapy. Materials and Methods: Ten breast cancer patients who had undergone axillary lymph node dissection and whose dissected axillary levels were excluded from the RNI target volume were included. A TomoDirect intensity-modulated RT plan was generated at a dose of 50 Gy in 25 fractions. The dissected axilla was not designated as an organ at risk (OAR) in the original treatment plan. For this study, the axillary lymph node level I (AXL1) and the ALTJ were delineated retrospectively, with the ALTJ considered an OAR in the newly generated study plan. A total of 20 RT plans (10 per group) were statistically compared using various dose-volume parameters. Results: Compared to the original plans, the study plans with ALTJ as an OAR significantly reduced the incidental dose to both the ALTJ (mean: 41.7 ± 3.4 Gy vs. 27.2 ± 1.3 Gy; p=0.005) and the AXL1 (mean: 43.9 ± 2.0 Gy vs. 37.7 ± 1.9 Gy; p=0.005). All other dosimetric parameters (V25Gy, V35Gy, V40Gy, Dmin, Dmax) for the ALTJ were also significantly lower in the study plans. This ALTJ sparing was achieved while maintaining all required dose-volume constraints for target volumes and standard OARs such as the lung and heart. Conclusions: This study demonstrates that simply excluding the dissected axilla from the target volume without designating it as an OAR still results in a substantial incidental dose to this region. Our findings also show the feasibility of using Tomotherapy to selectively spare the axilla, particularly the ALTJ subregion of AXL1, which is critical for lymphedema risk in breast cancer patients.