KEY POINTS
- This single-institution retrospective study replanned 15 patients previously treated with CyberKnife for left-sided accelerated partial-breast irradiation using noncoplanar volumetric modulated arc therapy and noncoplanar three-dimensional conformal radiotherapy.
- All plans prescribed 30 Gy in 5 fractions and were normalized to comparable target coverage. CyberKnife achieved the best conformity index (0.900 versus 0.832 and 0.576) and steepest dose gradient (2.65 versus 3.22 and 3.52) compared with volumetric modulated arc therapy and three-dimensional conformal radiotherapy.
- Mean heart dose was lowest with CyberKnife at 1.69 Gy, compared with 2.30 Gy for volumetric modulated arc therapy and 1.91 Gy for three-dimensional conformal radiotherapy. Mean left anterior descending coronary artery dose was 1.92 Gy versus 4.00 Gy and 4.50 Gy, respectively.
- CyberKnife also reduced mean ipsilateral lung dose (2.29 Gy versus 3.12 Gy and 2.67 Gy) and produced the smallest low-dose bath; the volume receiving 3 Gy was 1,016 cc, compared with 1,450 cc and 1,395 cc.
- These dosimetric gains came with greater target heterogeneity and substantially higher delivery complexity: mean monitor units were 12,626 with CyberKnife versus 808 with volumetric modulated arc therapy and 732 with three-dimensional conformal radiotherapy.
CLINICAL TAKEAWAY
CyberKnife provided the most conformal dose distribution and lowest cardiac, pulmonary, and low-dose exposure for left-sided accelerated partial-breast irradiation in this planning study. However, the comparison involved only 15 patients, used different dose-calculation algorithms and motion-management approaches across techniques, and reported no clinical outcomes; noncoplanar linac-based plans remain reasonable alternatives where CyberKnife is unavailable.