To investigate the plan quality between two treatment planning systems (TPSs) for volumetric modulated arc therapy (VMAT).

VMAT plans based on Varian Eclipse and Philips Pinnacle TPS were designed for 10 cervical cancer patients (2, 3 Arcs) and 10 prostate cancer patients (1, 2 Arcs). The delivery system of VMAT was Varian Clinac^®iX machine, and RapidArc was used. The treatment plan quality between the two TPSs was evaluated based on dose distribution, delivery efficiency, and parameter settings. The differences between the two TPSs were compared using paired t-test.

For cervical cancer patients, the 2-Arc VMAT plans based on the Pinnacle was slightly better than those based on the Eclipse in terms of the conformal index (CI) of planning target volume (PTV), rectum V₃₀ and V₄₀, and bladder V₃₀ and V₄₀, and the homogeneity index (HI) of PTV and PTV₁ as well as CI of PTV₁ in the Eclips were slightly better than those in the Pinnacle(P<0.05)Pinnacle were slightly worse than those in the Eclipse (P>0.05). The number of monitor units with 2-Arcs and 3-Arcs plans of the Eclipse was significantly smaller than those in the Pinnacle (P<0.05). For prostate cancer patients, The 1-arc VMAT plans of the Pinnacle TPS were slightly superior to those of the Eclipse TPS in terms of the HI of PTV, rectumV₃₀ and V₄₀, and bladderV₃₀ and V₄₀, but the former was slight inferior to the latter in terms of the CI of PTV (P<0.05). The number of monitor units of 1-arc and 2-Arcs plans showed no significant difference between the two TPSs (P>0.05).

For patients with cervical cancer and prostate cancer, the VMAT plans based on Varian Eclipse and Philips Pinnacle TPS can achieve a clinically acceptable dose distribution and show a little difference in the treatment plan quality. However, we will still need more cases to further study and determine the performance characteristics of the commercial TPSs for optimizing VMAT.

Cervical cancer/radiotherapy; Prostate cancer/radiotherapy; Volumetric modulated arc treatment; Plan quality