Purpose: To evaluate the feasibility of using helical tomotherapy for locally advanced left-sided breast cancer.
Methods and materials: Treatment plans were generated for 10 left-sided breast cancer patients with positive lymph nodes comparing a multiport breast (three-dimensional) technique with the tomotherapy treatment planning system. The planning target volumes, including the chest wall/breast, supraclavicular, axillary, and internal mammary lymph nodes, were contoured. The treatment plans were generated on the tomotherapy treatment planning system to deliver 50.4 Gy to the planning target volume. To spare the contralateral tissues, directional blocking was applied to the right breast and right lung. The optimization goals were to protect the lungs, heart, and right breast.
Results: The tomotherapy plans increased the minimal dose to the planning target volume (minimal dose received by 99% of target volume = 46.2 +/- 1.3 Gy vs. 27.9 +/- 17.1 Gy) while improving the dose homogeneity (dose difference between the minimal dose received by 5% and 95% of the planning target volume = 7.5 +/- 1.8 Gy vs. 37.5 +/- 26.9 Gy). The mean percentage of the left lung volume receiving >or=20 Gy in the tomotherapy plans decreased from 32.6% +/- 4.1% to 17.6% +/- 3.5%, while restricting the right-lung mean dose to <5 Gy. However, the mean percentage of volume receiving >or=5 Gy for the total lung increased from 25.2% +/- 4.2% for the three-dimensional technique to 46.9% +/- 8.4% for the tomotherapy plan. The mean volume receiving >or=35 Gy for the heart decreased from 5.6% +/- 4.8% to 2.2% +/- 1.5% in the tomotherapy plans. However, the mean heart dose for tomotherapy delivery increased from 7.5 +/- 3.4 Gy to 12.2 +/- 1.8 Gy.
Conclusion: The tomotherapy plans provided better dose conformity and homogeneity than did the three-dimensional plans for treatment of left-sided breast tumors with regional lymph node involvement, while allowing greater sparing of the heart and left lung from doses associated with increased complications.