Evaluation of a standard breast tangent technique: A dose-volume analysis of tangential irradiation using three dimensional tools

Purpose: A thorough dose-volume analysis of a standard tangential radiation technique has not been published. We evaluated the adequacy of a tangentia l radiation technique in delivering dose to the breast and regional lymphat ics, as well as dose delivered to underlying critical structures. Methods a nd Materials: Treatment plans of 25 consecutive women with breast cancer un dergoing lumpectomy and adjuvant-breast radiotherapy were studied, Patients underwent two-dimensional (2D) treatment planning followed by treatment wi th standard breast tangents. These 2D plans were reconstructed without modi fication on our three-dimensional treatment planning system and analyzed wi th regard to dose-volume parameters. Results: Adequate coverage of the brea st (defined as 95% of the target receiving at least 95% of the prescribed d ose) was achieved in 16 of 25 patients, with all patients having at least 8 5% of the breast volume treated to 95% of the prescribed dose. Only 1 patie nt (4%) had adequate coverage of the Level I axilla, and no patient had ade quate coverage of the Level II axilla, Level III axilla, or the internal ma mmary lymph nodes. Conclusion: Three-dimensional treatment planning is supe rior in quantification of the dose received by the breast, regional lymphat ics, and critical structures. The standard breast tangent technique deliver s an adequate dose to the breast but does not therapeutically treat the reg ional lymph nodes in the majority of patients. If coverage of the axilla or internal mammary lymph nodes is desired, alternate beam arrangements or tr eatment fields will be necessary, (C) 2000 Elsevier Science Inc.