To determine whether the use of intensity-modulated radiotherapy (IMRT) would lead
to improved dosimetry for the breast and regional nodes.
Ten patients with left-sided breast cancer were selected. The clinical target volume
included left breast and internal mammillary (IM), supraclavicular (SC), and axillary
(AX) nodes. The critical structures included heart, right and left lungs, contralateral
breast, esophagus, thyroid, and humeral head. Conventional and a series of IMRT plans
were generated for comparison.
The average heart D(3) was reduced from 31.4 +/- 18.9 with three-dimensional conformal
radiotherapy (3D-CRT) to 15 +/- 7.2 Gy with 9-field (9-FLD IMRT). The average left
lung D(30) was also decreased from 27.9 +/- 11.5 Gy (3D-CRT) to 12.6 +/- 8.2 Gy (9-FLD
IMRT). The average contralateral breast D(2) was reduced from 4.4 +/- 5.3 Gy (3D-CRT)
to 1.8 +/- 1.2 Gy (4-FLD IMRT). Esophagus D(2) was increased from 9.3 +/- 8.1 Gy (3D-CRT)
to 29.4 +/- 5.4 (9-FLD IMRT); thyroid D(50) was increased from 0.9 +/- 0.6 Gy (3D-CRT)
to 11.9 +/- 6.6 (9-FLD IMRT); humeral head D(2) was increased from 36.1 +/- 13.1 Gy
(3D-CRT) to 39.9 +/- 6.5 (9-FLD IMRT).
The use of IMRT improves breast and regional node coverage while decreasing doses
to the lungs, heart, and contralateral breast when compared with 3D-CRT. Doses to
esophagus, thyroid, and humeral head, however, were increased with IMRT.