Dosimetric analysis of a simplified intensity modulation technique for prone breast radiotherapy

Goodman, Karyn A.; Hong, Linda; Wagman, Raquel; Hunt, Margie A.; McCormick, Beryl

doi:10.1016/j.ijrobp.2004.02.016

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Volume 60, Issue 1 , Pages 95-102, 1 September 2004

Dosimetric analysis of a simplified intensity modulation technique for prone breast radiotherapy

Presented at the 44th Annual Meeting of the American Society for Therapeutic Radiology and Oncology, New Orleans, LA, October 7, 2002.

Karyn A. Goodman, MD
- Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
Linda Hong, PhD
- Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
Raquel Wagman, MD
- Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
Margie A. Hunt, MS
- Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
Beryl McCormick, MD
- Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
- Reprint requests to: Beryl McCormick, M.D., Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, 1275 York Ave., New York, NY 10021, USA. Tel: (212) 639-6828; Fax: (212) 639-2417

Received 22 September 2003; received in revised form 3 February 2004; accepted 9 February 2004.

Abstract

Purpose

Prone-position breast radiotherapy (RT) has been described as an alternative technique to improve dose homogeneity for women with large, pendulous breasts. We report the feasibility and dosimetric analysis of a simplified intensity-modulated RT (IMRT) technique, previously reported for women in the supine treatment position, to plan prone-position RT to the intact breast.

Methods and materials

Twenty patients with clinical Stage TisN0-T1bN1 breast cancer undergoing breast-conserving therapy underwent whole breast RT using a prone position technique. The treatment plans were developed using both conventional tangents and a simplified intensity-modulated tangential beam technique based on optimization of the intensity distributions across the breast. The plans were compared with regard to the dose–volume parameters.

Results

Dose heterogeneity within the breast planning target volume was significantly greater for the conventional tangent plans. Of 20 patients, 16 (80%) received maximal doses of ≥110% using the conventional tangents vs. only 1 (5%) using the IMRT plan. The isodose level encompassing 5% of the planning target volume was reduced from an average of 110% with conventional tangents to 105% with IMRT. The maximal dose within the planning target volume was reduced from an average of 114% with conventional tangents to 107% with IMRT. The greatest improvement was seen in the patients with the most pendulous breasts.

Conclusion

An IMRT planning approach is feasible for prone-position breast RT and improves dose homogeneity, particularly in women with larger, pendulous breasts. Additional follow-up is necessary to determine whether the improvements in dose homogeneity impact acute toxicity and cosmetic outcome in this cohort of women who have historically suffered from poor cosmesis after breast-conserving therapy.

Keywords: Intensity-modulated radiotherapy, Prone breast radiotherapy, Breast cancer