Planning the breast tumor bed boost: Changes in the excision cavity volume and surgical scar location after breast-conserving surgery and whole-breast irradiation
- Department of Radiation Oncology, University of Michigan Medical School, Ann Arbor, MI (United States)
- Biostatistics Unit of University of Michigan Comprehensive Cancer Center, Ann Arbor, MI (United States)
Purpose: The aims of this study were to determine the changes in breast and excision cavity volumes after whole-breast irradiation and the adequacy of using the surgical scar to guide boost planning. Methods and Materials: A total of 30 women consecutively treated for 31 breast cancers were included in this study. Simulation CT scans were performed before and after whole-breast irradiation. CT breast volumes were delineated using clinically defined borders. Excision cavity volumes were contoured based on surgical clips, the presence of a hematoma, and/or other surgical changes. Hypothetical electron boost plans were generated using the surgical scar with a 3-cm margin and analyzed for coverage. Results: The mean CT breast volumes were 774 and 761 cc (p = 0.22), and the excision cavity volumes were 32.1 and 25.1 cc (p < 0.0001), before and after 40 Gy (39-42 Gy) of whole-breast irradiation, respectively. The volume reduction in the excision cavity was inversely correlated with time elapsed since surgery (R = 0.46, p < 0.01) and body weight (R = 0.50, p < 0.01). The scar-guided hypothetical plans failed to cover the excision cavity adequately in 62% and 53.8% of cases using the pretreatment and postradiation CTs, respectively. Per the hypothetical plans, the minimum dose to the excision cavity was significantly lower for tumors located in the inner vs. outer quadrants (p = 0.02) and for cavities >20 cc vs. <20 cc (p = 0.01). Conclusions: This study demonstrates a significant reduction in the volume of the excision cavity during whole-breast irradiation. Scar-guided boost plans provide inadequate coverage of the excision cavity in the majority of cases.
- OSTI ID:
- 20850150
- Journal Information:
- International Journal of Radiation Oncology, Biology and Physics, Vol. 66, Issue 3; Conference: 48. annual meeting of the American Society for Therapeutic Radiology and Oncology, Pennsylvania, PA (United States), 5-9 Nov 2006; Other Information: DOI: 10.1016/j.ijrobp.2006.04.042; PII: S0360-3016(06)00692-4; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0360-3016
- Country of Publication:
- United States
- Language:
- English
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