Purpose: The aim of the present work was to explore plan quality and dosimetric accuracy of intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) for lymph node-positive left-sided breast cancer.
Methods: VMAT and IMRT plans were generated with the Pinnacle(3) V9.0 treatment planning system for 10 lymph node-positive left-sided breast cancer patients. VMAT plans were created using a single arc and IMRT was performed with 4 beams using 6, 10, and 15 MV photon energy, respectively. Plans were evaluated both manually and automatically using ArtiView™. Dosimetric plan verification was performed with a 2D ionization chamber array placed in a full scatter phantom.
Results: Photon energy had no significant influence on plan quality for both VMAT and IMRT. Large variability in low doses to the heart was found due to patient anatomy (range V(5 Gy) 26.5-95 %). Slightly more normal tissue dose was found for VMAT (e.g., V(Tissue30%) = 22 %) than in IMRT (V(Tissue30%) = 18 %). The manual and ArtiView™ plan evaluation coincided very accurately for most dose metrics (difference < 1 %). In VMAT, 96.7 % of detector points passed the 3 %/3 mm gamma criterion; marginally better accuracy was found in IMRT (98.3 %).
Conclusion: VMAT for node-positive left-sided breast cancer retains target homogeneity and coverage when compared to IMRT and allows maximum doses to organs at risk to be reduced. ArtiView™ enables fast and accurate plan evaluation.