br Table Mean radiation therapy doses
Table 2 Mean radiation therapy doses to coronary arterial structures from left-sided breast cancer radiation therapy regimens used in Sweden (1958-2001) or Denmark (1978-2000)
Radiation therapy regimen*
Mean coronary artery doses (Gy)y
Country
Median
Medial Border
Field arrangementz,x
Usual beam
Dose
Left
Left anterior descending
Right
Circumflex
Year
Main
Whole
Prox
Mid
Dist
Whole
Prox
Mid
Dist
Pd
Whole
Prox
Dist
Tangential
Anterior AR7 or orthovoltage
Anterior megavoltage
Cobalt chain**
Abbreviations: contra Z contralateral; Co60 Z cobalt 60; dist Z distal; IMC Z internal mammary chain; kV Z kilovoltage; lat Z lateral; MeV Z mega electron-volts; MV Z megavoltage;
prox Z proximal; pd Z posterior descending; SCF Z supraclavicular fossa
Bold tangential regimens are wide tangents, others are midline tangents. Bold anterior electron or orthovoltage regimens are oblique electron fields, others include direct fields.
Practical Radiation Oncology: May-June 2019
Practical Radiation Oncology: May-June 2019
Cardiac segment radiation doses breast cancer
165
A
Midline tangents, 8 MV photons
Left
Right
Left anterior
descending coronary
artery: distal
†
B
Wide tangents, 6 MV photons
Left
Right
Left anterior
descending coronary
artery: mid
LV: apex
†
C
Direct electron IMC, 12 MeV electrons
Left
Right
Left anterior
descending coronary
artery: proximal
Fig. 2 Spatial distribution of cardiac dose from breast cancer tangential and direct electron radiation therapy regimens used to treat women with breast cancer in Sweden (1958-2001) or Denmark (1978-2000). Left regimens A-C are illustrated in Fig. 1. y The main circumflex coronary artery has only 2 segments: Proximal and distal. Abbreviations: MV Z megavoltage; MeV Z mega electron-volts.
The mean doses to the coronary artery segments in the left megavoltage tangential radiation therapy varied from 0.4 Gy to 48.0 Gy. For all megavoltage tangents, the LADCA mid- and distal segments received the highest doses of 32.8 Gy (Table 2, Fig. 2). The LADCA proximal received 18.9 Gy from the wide divergent and partially wide megavoltage tangents and 8.6 Gy to 11.0 Gy from the midline megavoltage tangents. The RCA and Cx segments were further from the fields and received 0.4 Gy to 8.2 Gy.
For orthovoltage midline tangents, the prescribed dose was only 10.5 Gy, and all cardiac segments received 9 Gy (Tables 1, 2, E3 and E4). For McWhirter ortho-voltage wide-tangential radiation therapy (36.0 Gy pre-scribed dose), whole LV and LADCA doses were similar to those for megavoltage wide tangents, but the RCA and Cx doses were higher owing to scattered radiation from orthovoltage beams.
Right
“typical CT-scan”
Mid Div.
Mid Blk.
Direct IMC
Direct CW
Mid Div.
Mid Blk.
Direct IMC
Direct CW
Mid Div.
Mid Blk.
Direct IMC
Direct CW
Mid Div.
Mid Blk.
Direct IMC
Direct CW
Wide
Div. Pa. Wide Blk Oblq CW
Wide
Tangents Anterior electrons Tangents Anterior electrons Tangents Anterior electrons Tangents Anterior electrons
Tangents
Anterior
electrons
Tangents
Anterior
electrons
Tangents
Anterior
electrons
Tangents
Anterior
electrons
Mid Div.
Mid Blk.
Direct IMC
Direct CW
Mid Div.
Mid Blk.
Direct IMC
Direct CW
Mid Div.
Mid Blk.
Direct IMC
Direct CW
Mid Div.
Mid Blk.
Direct IMC
Direct CW
Wide Div.
Pa. Wide Blk Oblq CW
Wide Div.
Pa. Wide Blk Oblq CW
Wide Div.
Pa. Wide Blk Oblq CW
Wide Div.
Pa. Wide Blk Oblq CW
Tangents Anterior electrons Tangents Anterior electrons Tangents Anterior electrons Tangents Anterior electrons
Tangents
Anterior electrons
Tangents
Anterior electrons
Tangents
Anterior electrons
Tangents
Anterior electrons
Direct
IMC
Mid
Div.
Mid Blk.
Direct
CW
Mid Div.
Mid Blk.
Direct IMC
Direct CW
Mid
Div.
Mid Blk.
Direct
IMC
Direct
CW
Mid Div.
Mid Blk.
Direct IMC
Direct CW
Wide
Div. Pa. Wide Blk Oblq CW
Wide
Div.
Pa. Wide Blk Oblq CW
Tangents Anterior electrons Tangents Anterior electrons Tangents Anterior electrons Tangents Anterior electrons
Radiation therapy technique
Fig. 3 Patient-to-patient variability in mean radiation dose to the whole heart, and left ventricular and coronary arterial segments in women receiving tangential or anterior electron regimens for breast cancer in Sweden (1958-2001) or Denmark (1978-2000). For further details on regimens 1 through 7, see Table E1. Regimen definitions: Tangents (1) Mid. Div, midline divergent, (50 Gy/25 fractions); (2) Wide Div, wide divergent, medial border 3 cm contralateral, (41 Gy/22 fractions); (3) Mid. Blk, midline, blocked posterior border tapered inferiorly around breast (48 Gy/24 fractions); (4) Pa. Wide Blk., partially wide, medial border 3 cm contralateral, blocked posterior border tapered inferiorly below 5th rib (48 Gy/28 fractions). Anterior electron (5) Direct IMC: direct internal mammary chain (40 Gy/10 fractions); (6) Oblq CW: oblique chest wall (48 Gy/26 fractions); and (7) Direct CW: direct chest wall (52 Gy/24 fractions). Abbreviations: LADCA Z left anterior descending coronary artery; LV Z left ventricle; RCA Z right coronary artery.