Effects of anatomical changes on pencil beam scanning proton plans in locally advanced NSCLC patients

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• 作者：Yenny Z. Szeto ; Marnix G. Witte ; Simon R. van Kranen ; Jan-Jakob Sonke ; José ; Belderbos ; Marcel van Herk ; ^{marcel.vanherk@manchester.ac.uk" class="auth_mail" title="E-mail the corresponding author}
• 关键词：IMPT ; NSCLC ; Interfractional anatomical changes ; Respiratory motion ; Deformable image registration
• 刊名：Radiotherapy and Oncology
• 出版年：2016
• 出版时间：August 2016
• 年：2016
• 卷：120
• 期：2
• 页码：286-292
• 全文大小：705 K

文摘

Daily anatomical variations can cause considerable differences between delivered and planned dose. This study simulates and evaluates these effects in spot-scanning proton therapy for lung cancer patients.

Materials and methods

Robust intensity modulated treatment plans were designed on the mid-position CT scan for sixteen locally advanced lung cancer patients. To estimate dosimetric uncertainty, deformable registration was performed on their daily CBCTs to generate 4DCT equivalent scans for each fraction and to map recomputed dose to a common frame.

Results

Without adaptive planning, eight patients had an undercoverage of the targets of more than 2GyE (maximum of 14.1GyE) on the recalculated treatment dose from the daily anatomy variations including respiration. In organs at risk, a maximum increase of 4.7GyE in the D₁ was found in the mediastinal structures. The effect of respiratory motion alone is smaller: 1.4GyE undercoverage for targets and less than 1GyE for organs at risk.

Conclusions

Daily anatomical variations over the course of treatment can cause considerable dose differences in the robust planned dose distribution. An advanced planning strategy including knowledge of anatomical uncertainties would be recommended to improve plan robustness against interfractional variations. For large anatomical changes, adaptive therapy is mandatory.