Improve dosimetric outcome in stage III non-small-cell lung cancer treatment using spot-scanning proton arc (SPArc) ther
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RESEARCH
Open Access
Improve dosimetric outcome in stage III non-small-cell lung cancer treatment using spot-scanning proton arc (SPArc) therapy Xiaoqiang Li*, Peyman Kabolizadeh, Di Yan, An Qin, Jun Zhou, Ye Hong, Thomas Guerrero, Inga Grills, Craig Stevens and Xuanfeng Ding*
Abstract Background: To evaluate spot-scanning proton arc therapy (SPArc) and multi-field robust optimized intensity modulated proton therapy (RO-IMPT) in treating stage III non-small-cell lung cancer (NSCLC) patients. Methods: Two groups of stage IIIA or IIIB NSCLC patients (group 1: eight patients with tumor motion less than 5 mm; group 2: six patients with tumor motion equal to or more than 5 mm) were re-planned with SPArc and RO-IMPT. Both plans were generated using robust optimization to achieve an optimal coverage with 99% of internal target volume (ITV) receiving 66 Gy (RBE) in 33 fractions. The dosimetric results and plan robustness were compared for both groups. The interplay effect was evaluated based on the ITV coverage by single-fraction 4D dynamic dose. Total delivery time was simulated based on a full gantry rotation with energy-layer-switching-time (ELST) from 0.2 to 4 s. Statistical analysis was also evaluated via Wilcoxon signed rank test. Results: Both SPArc and RO-IMPT plans achieved similar robust target volume coverage for all patients, while SPArc significantly reduced the doses to critical structures as well as the interplay effect. Specifically, compared to RO-IMPT, SPArc reduced the average integral dose by 7.4% (p = 0.001), V20, and mean lung dose by an average of 3.2% (p = 0.001) and 1.6 Gy (RBE) (p = 0.001), the max dose to cord by 4.6 Gy (RBE) (p = 0.04), and the mean dose to heart and esophagus by 0.7 Gy (RBE) (p = 0.01) and 1.7 Gy (RBE) (p = 0.003) respectively. The average total estimated delivery time was 160.1 s, 213.8 s, 303.4 s, 840.8 s based on ELST of 0.2 s, 0.5 s, 1 s, and 4 s for SPArc plans, compared with the respective values of 182.0 s (p = 0.001), 207.9 s (p = 0.22), 250.9 s (p = 0.001), 509.4 s (p = 0.001) for RO-IMPT plans. Hence, SPArc plans could be clinically feasible when using a shorter ELST. Conclusions: This study has indicated that SPArc could further improve the dosimetric results in patients with locally advanced stage NSCLC and potentially be implemented into routine clinical practice. Keywords: Spot scanning, Proton arc therapy, Lung cancer, Robust treatment planning
Background Lung cancer remains the leading cause of cancer deaths for both men and women in the United States [1]. For patients with locally advanced lung cancer, radiotherapy alone or concurrent chemoradiotherapy has been widely used. Many trials have shown the benefits of concurrent chemoradiotherapy to improve the prognosis of patients, in terms of local control and survival [2–6]. However, the * Correspondence: [email protected]; [email protected] Department of Radiation Oncology, Beaumont Health System, Royal Oak, MI, USA
associated toxicities to the surrounding normal tissues can be significant,
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