Cardiac dose evaluation for 3Dimensional conformal partial breast irradiation compared with whole breast irradiation

To compare the radiation dose to normal cardiac tissue for 3Dimensional (3D) conformal external beam partial breast irradiation (PBI) and standard whole breast irradiation (WBI), and examine the effect of tumor bed location. For 14 patients with left breast tumors randomized on the National Surgical Adjuvant Breast and Bowel Project B-39 protocol, computer-generated radiotherapy treatment plans were devised for WBI and PBI. Tumor bed location was designated according to whether more than 50 % of the excision cavity was medial or lateral to the nipple line. The volume of heart receiving doses of 2.5, 5, 10, and 20 Gy was calculated for all PBI and WBI plans. Dose to 5 % of the heart volume (D5) and mean heart dose were also calculated. The biologically-equivalent dose (BED) was calculated to account for the different fractionation used in PBI and WBI. Of the 14 patients, 8 had lateral tumor beds, and 6 had medial tumor beds. The volumes of heart receiving 2.5, 5, 10, and 20 Gy were significantly lower for lateral PBI compared with WBI. For medial PBI, significant cardiac sparing wa