Application of Stochastic Platform Optimization Algorithm in Volumetric Modulated Arc Therapy for Left-Sided Breast Cancer

Objective To investigate the application of the Stochastic Platform Optimization (SPO) algorithm, based on the United Imaging uTPS radiotherapy planning system, in volumetric modulated arc therapy (VMAT) for post-modified radical mastectomy patients with left-sided breast cancer. Methods Twenty patients with left-sided breast cancer after modified radical mastectomy, admitted to our hospital from January to December 2024, were selected. For each patient, two VMAT plans were designed using United Imaging uTPS: one based on the SPO algorithm and the other on the Fluence Map Optimization (FMO) algorithm. Evaluation indicators included the target Conformity Index (CI), Homogeneity Index (HI), dose parameters for organs at risk (OARs: heart, left anterior descending coronary artery [LAD], bilateral lungs, right breast, spinal cord, esophagus, left humeral head, thyroid, stomach, and liver), monitor units (MU), and plan optimization time. Results The CI and HI for SPO plans were (0.85 ± 0.03) and (0.10 ± 0.02), respectively, showing statistically significant differences compared to FMO plans (CI: 0.81 ± 0.04; HI: 0.12 ± 0.02) (t = -6.95, 6.16, respectively;P< 0.01). Regarding OAR sparing, significant differences were observed in SPO plans compared to FMO plans for the following parameters: heart V5 (29.37%± 5.00% vs. 34.75% ± 5.99%), heart Dmean (6.25Gy ± 0.59 Gy vs. 6.44 ± 0.62 Gy), LAD Dmax (45.01Gy ± 4.91 Gy vs. 47.05Gy ± 5.74 Gy), left lung V20 (22.7% ± 1.95% vs. 23.36% ± 2.13%), left lung V5 (53.64% ± 4.09% vs. 54.72% ± 3.40%), and left lung Dmean (12.75Gy ± 0.91Gy vs. 13.14Gy ± 1.00Gy) (t = 9.16, 4.17, 3.74, 4.32, 3.86, 8.44, respectively; P<0.01). Furthermore, SPO plans showed statistically significant improvements in right breast V5, spinal cord PRV Dmax, left humeral head Dmean, thyroid V30, thyroid Dmean, stomach Dmean, liver V5, and liver Dmean compared to FMO plans (all P<0.05). However, both the monitor units and optimization time were increased in SPO plans compared to FMO plans (P<0.01). Conclusion For left-sided breast cancer VMAT, the SPO algorithm not only improves target coverage quality but also achieves more comprehensive OAR protection. Although SPO plans require increased delivery and optimization time, their overall dosimetric advantages are significant, indicating substantial clinical application value.