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Poster display - Cocktail

187 - Breast board comined with a thermoplastic head mask immobilization can improve the reproducibility of the treatment setup for breast cancer patients who received whole breast and supraclavicular nodal region irradiation

Date

24 Nov 2018

Session

Poster display - Cocktail

Presenters

Ming wei Ma

Citation

Annals of Oncology (2018) 29 (suppl_9): ix8-ix12. 10.1093/annonc/mdy427

Authors

M.W. Ma1, S. Wang2, S. Qin2

Author affiliations

  • 1 Radiation Oncology, Peking University First Hospital, 100034 - Beijing/CN
  • 2 Radiation Oncology, Cancer Hospital, Chinese Academy of Medical Sciences, 100034 - Beijing/CN
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Resources

Abstract 187

Background

To quantify the setup errors measured with kV CBCT using breast board with or without a thermoplastic head mask in breast cancer patients who received whole breast and supraclavicular nodal region irradiation.

Methods

30 patients received both whole breast and supraclavicular nodal region irradiation and were treated on Elekta Versa HD linear accelerators (Elekta Oncology Systems, Crawley, UK) between June 2016 and January 2018. The setup error data were retrospectively analyzed. Patients were immobilized in the supine position on a breast board system with both arms raised. In 20 of the patients a thermoplastic head mask was added in order to avoid the neck rotation and the uncertainty of the relative position between neck and the board. The shifts in left-right(X), superior-inferior(Y), anterior-posterior(Z) were recorded by CBCT. Population of the two groups was compared in terms of distribution of the mean shift (systematic error) and their standard deviations (random error) and in terms of Van Herk's setup margin defined as MPTV (2.5Σ) 0.7δ.

Results

Shifts of the breast board only and head mask group in X, Y, Z were 0.212±0.174 vs. 0.272±0.242cm, p = 0.07;0.364±0.246 vs. 0.242±0.171cm, p = 0.001; 0.423±0.302 vs. 0.364±0.269 cm, p = 0.204, respectively. Proportion of the shift less than 5mm in the breast board only group and the head mask group were 91.07% vs. 85.32%, p = 0.294 (67.86% vs. 89.91%, p = 0.001; 67.86% vs. 74.31%, p = 0.381, respectively. The CTV to PTV margin were 0.595, 0.865, 1.139cm in breast board only group and 0.699, 0.647, 0.990 cm in the head mask group.Table: 28P

XYZ
ΣδΣδΣδ
Breast board only group0.2220.0570.3180.1020.4270.102
Head mask group0.2660.0500.2390.0710.3680.101
P0.5030.5960.1560.8020.4420.212

Conclusions

for the alignment and immobilization of patients who received whole breast and supraclavicular nodal region irradiation, using a breast board in combination with a thermoplastic head mask may significantly help to reduce the shift variance in superior-inferior direction compared to using breast board only. The anterior-posterior error is relatively large, other immobilization devices or patient alignment methods are needed to be further explored to improve accuracy.

Editorial acknowledgement

Clinical trial identification

Legal entity responsible for the study

Prof. Shulian Wang.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.

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