Research article
Protocolised way to cope with anatomical changes in head & neck cancer during the course of radiotherapy

https://doi.org/10.1016/j.tipsro.2019.11.001Get rights and content
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Highlights

  • Protocolised evaluation of daily CBCT by RTTs result in re-planning in 10%.

  • Patients treated with chemoradiotherapy have the highest probability of requiring re-planning.

  • Most anatomical changes visible on CBCT were detected in treatment week 2, 3 and 4.

Abstract

Introduction

During a course of radiotherapy for head-and-neck-cancer (HNC), non-rigid anatomical changes can be observed on daily Cone Beam CT (CBCT). To objectify responses to these changes, we use a decision support system (traffic light protocol). Action levels orange and red may lead to re-planning. The purpose of this study was to evaluate how often re-planning was done for non-rigid anatomical changes, which anatomical changes led to re-planning and in which subgroups of patients treatment adaptation was deemed necessary.

Materials and methods

A consecutive series of 388 HNC patients were retrospectively selected using the digital log of CBCT scans. The logs were analyzed for the number of new plans on an original planning CT scan (O-pCT) or a new pCT scan (N-pCT). Reasons for re-planning were categorized into: target volume increase/decrease, body contour decrease/increase and local shift of target volume. Subgroup analysis was performed to investigate relative differences of re-planning between treatment modalities.

Results

For 33 patients the treatment plan was adapted due to anatomical changes, resulting in 37 new plans in total. Re-planning on a N-pCT with complete re-delineation was done 22 times. In fifteen cases a new plan was created after adjustment of contours on the O-pCT. Main reasons for re-planning were target volume increase, body contour decrease and local shifts of target volume. Most re-planning (23%) was seen in patients treated with chemoradiotherapy.

Conclusion

Visual detection of anatomical changes on CBCT during treatment of HNC, results in re-planning in 1 out of 10 patients.

Keywords

Head and neck cancer
Cone beam CT
Image guided radiotherapy
Traffic light protocol
Anatomical changes
Adaptive delivery

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1

Both authors have contributed equally.