Senior Scholars Program

Title

Analysis of axillary coverage during tangential radiation therapy to the breast

UMMS Affiliation

Department of Radiation Oncology

Faculty Advisor

Thomas J. Fitzgerald

Date

1-1-2005

Document Type

Article

Medical Subject Headings

Adult; Aged; Axilla; Breast Neoplasms; Female; Humans; Lymphatic Irradiation; Middle Aged; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted; Retrospective Studies

Disciplines

Neoplasms | Oncology | Radiology

Abstract

PURPOSE: To evaluate the percent of the prescribed radiation dose to the breast delivered to the axillary tissue and to evaluate the volume of the axilla receiving 95% of the prescribed dose with normal and with high tangential fields.

METHODS AND MATERIALS: Computed tomographic scan images with 5-mm sections were retrospectively analyzed for 35 patients who had undergone three-dimensional (3D) planning for whole-breast radiation. The axillary nodal region was identified and divided into Levels I to III and Rotter's nodes (RN). Digitally reconstructed radiographs were created, and two plans were developed: (a) the standard clinical opposed tangential irradiation fields and (b) the high-tangential irradiation fields. Axillary coverage was examined by use of dose-volume histograms (DVH), and the average coverage for the four nodal groups was obtained.

RESULTS: The data show that with the standard tangential irradiation fields, the average dose delivered to Levels I, II, III, and RN is 66% (standard deviation, or SD = 13%), 44% (SD = 18%), 31% (SD = 20%), and 70% (SD = 19%) of the prescribed dose, respectively. The coverage increases to 86% (SD = 9%), 71% (SD = 19%), 73% (SD = 17%), and 94% (SD = 8%) of the prescribed dose, respectively, for Levels I, II, III, and RN when the high tangential irradiation fields are used. 51% of Level I, 26% of Level II, and 15% of Level III receive 95% of the prescribed dose with normal tangents. The volume increases to 79%, 51%, and 49% of Levels I, II, and III, respectively, with high tangents.

CONCLUSION: The tangential fields designed to treat only the breast do not adequately cover the axillary region and, therefore, cannot be relied upon for prophylactic therapy of the axilla. The high tangential irradiation fields increase the dosages received by the axillary region, but the average dosages received by the lower axillary regions are still less than 90% of the prescribed dose.

Rights and Permissions

Citation: Int J Radiat Oncol Biol Phys. 2005 Jan 1;61(1):163-8. Link to article on publisher's site

Related Resources

Link to Article in PubMed

Comments

Medical student Julia Reznik participated in this study as part of the Senior Scholars research program at the University of Massachusetts Medical School.

PubMed ID

15629607