Measurement of mean cardiac dose for various breast irradiation techniques and corresponding risk of major cardiovascular event.
After breast conserving surgery, early stage breast cancer patients are currently treated with a wide range of radiation techniques including whole breast irradiation (WBI), accelerated partial breast irradiation (APBI) using high-dose rate (HDR) brachytherapy, or 3D-conformal radiotherapy (3D-CRT). This study compares the mean heart's doses for a left breast irradiated with different breast techniques. An anthropomorphic Rando phantom was modified with gelatin-based breast of different sizes and tumors located medially or laterally. The breasts were treated with WBI, 3D-CRT, or HDR APBI. The heart's mean doses were measured with Gafchromic films and controlled with optically stimulated luminescent dosimeters. Following the model reported by Darby (1), major cardiac were estimated assuming a linear risk increase with the mean dose to the heart of 7.4% per gray. WBI lead to the highest mean heart dose (2.99 Gy) compared to 3D-CRT APBI (0.51 Gy), multicatheter (1.58 Gy), and balloon HDR (2.17 Gy) for a medially located tumor. This translated into long-term coronary event increases of 22, 3.8, 11.7, and 16% respectively. The sensitivity analysis showed that the tumor location had almost no effect on the mean heart dose for 3D-CRT APBI and a minimal impact for HDR APBI. In case of WBI large breast size and set-up errors lead to sharp increases of the mean heart dose. Its value reached 10.79 Gy for women with large breast and a set-up error of 1.5 cm. Such a high value could increase the risk of having long-term coronary events by 80%. Comparison among different irradiation techniques demonstrates that 3D-CRT APBI appears to be the safest one with less probability of having cardiovascular events in the future. A sensitivity analysis showed that WBI is the most challenging technique for patients with large breasts or when significant set-up errors are anticipated. In those cases, additional heart shielding techniques are required.
Radiotherapy Unit, School of Medicine, Pontificia Universidad Católica de Chile , Santiago , Chile ; Department of Radiation Oncology, Sunnybrook Odette Cancer Centre , Toronto, ON , Canada ; Department of Radiation Oncology, University of Toronto , Toronto, ON , Canada.
Tomas Rodrigo
TR
Merino Lara
Department of Radiation Oncology, Sunnybrook Odette Cancer Centre , Toronto, ON , Canada ; Department of Radiation Oncology, University of Toronto , Toronto, ON , Canada.
Emmanuelle
E
Fleury
Department of Radiation Oncology, Sunnybrook Odette Cancer Centre , Toronto, ON , Canada ; Department of Radiation Oncology, University of Toronto , Toronto, ON , Canada.
Shahram
S
Mashouf
Department of Radiation Oncology, Sunnybrook Odette Cancer Centre , Toronto, ON , Canada ; Department of Radiation Oncology, University of Toronto , Toronto, ON , Canada.
Joelle
J
Helou
Department of Radiation Oncology, Sunnybrook Odette Cancer Centre , Toronto, ON , Canada ; Department of Radiation Oncology, University of Toronto , Toronto, ON , Canada.
Claire
C
McCann
Department of Radiation Oncology, Sunnybrook Odette Cancer Centre , Toronto, ON , Canada ; Department of Radiation Oncology, University of Toronto , Toronto, ON , Canada.
Mark
M
Ruschin
Department of Radiation Oncology, Sunnybrook Odette Cancer Centre , Toronto, ON , Canada ; Department of Radiation Oncology, University of Toronto , Toronto, ON , Canada.
Anthony
A
Kim
Department of Radiation Oncology, Sunnybrook Odette Cancer Centre , Toronto, ON , Canada ; Department of Radiation Oncology, University of Toronto , Toronto, ON , Canada.
Nadiya
N
Makhani
Department of Radiation Oncology, Sunnybrook Odette Cancer Centre , Toronto, ON , Canada ; Department of Radiation Oncology, University of Toronto , Toronto, ON , Canada.
Ananth
A
Ravi
Department of Radiation Oncology, University of Toronto , Toronto, ON , Canada ; Department of Radiation Oncology, Erasmus MC , Rotterdam , Netherlands.
Jean-Philippe
JP
Pignol
brachytherapy; breast neoplasms; heart diseases; radiation dosage; radiotherapy