Tattoo-less Chest Wall Irradiation (VMAT) using Surface Imaging
PO-1300
Abstract
Tattoo-less Chest Wall Irradiation (VMAT) using Surface Imaging
Authors: Boris Mueller1, Yulin Song2, Wang Chia-Ko3, Hao-Yun Hsu4, Xingchen Zhai3, Paul Tamas5, Simon Powell5, Beryl McCormick5, Atif Khan5, Linda Hong3, Laura Cervino-Arriba3, Bo Zhao3, Lior Braunstein5
1MSKCC, Radiation Oncology, New York, USA; 2MSKCC, Medical Physics, New York, USA; 3MSKCC, Medical Physics, NYC, USA; 4Columbia University, Medical Physics, NYC, USA; 5MSKCC, Radiation Oncology, NYC, USA
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Purpose or Objective
Skin tattoos represent the standard for surface alignment and setup of breast cancer radiotherapy yet contribute to adverse cosmesis and patient dissatisfaction. With the advent of contemporary surface imaging technology, we evaluated setup accuracy, time, and dosimetry between “tattoo-less” and traditional tattoo-based setup techniques.
Material and Methods
Patients receiving chest wall radiation for breast cancer underwent traditional tattoo-based setup (TTB), alternating daily with a tattoo-less setup via surface imaging using AlignRT (ART). Following initial setup, position was verified by daily kV imaging, with matching on the chest wall bony anatomy representing ground truth. Translational shifts (TS) and rotational shifts (RS) were ascertained as were setup time and total in-room time. Delivered dosimetry was calculated using the reverse isocenter shift technique. Statistical analyses used the Wilcoxon Signed Rank test and Pitman-Morgan variance test.
Results
A total of 39 breast cancer patients requiring chest wall and regional nodal irradiation were analyzed, For tattoo-less setup via ART, the median absolute TS in the vertical dimension was 0.28cm (range: 0.14 - 0.48), whereas for TTB it was 0.34cm (0.15 – 0.52) (p = 0.038). Analysis based on 95% CI. In the lateral dimension, ART TS was 0.24cm (0.10 - 0.40), vs 0.29 (0.13 – 0.46) for TTB (p = 0.007). In the longitudinal dimension, ART TS was 0.26cm (0.13- 0.44) vs 0.34cm (0.14 – 0.59), for TTB-based setup (p<0.001). Variance testing revealed increased precision with ART in the vertical (p < 0.001) and longitudinal (p < 0.001) axes.
The median absolute RS for ART was 0.80° rotation (range:0.40-1.50), 0.60° roll (0.20-1.20), 0.50° pitch (0.10-1.00). The corresponding median RS for TTB was 1.00° (0.40-1.70), 0.60° (0.20-1.20), and 0.50° (0.10-1.00). For rotational shifts, ART was statistically significantly more accurate than TTB (p = 0.023). ART setup was otherwise not statistically different from TTB in terms of roll and pitch (p=0.558, 0.929, respectively). ART showed no difference in precision versus TTB in terms of RS, pitch, and roll (p=0.181, p=0.544, p=0.858).
The median total in-room time for ART was 18.77 min (range: 16.04-20.77) and 18.70 min (17.58-20.67) for TTB (p=0.38). The median setup time was 12.75 min (11.43-14.80) for ART and 13.78 min (12.42-15.09) for TTB (p=0.054). There was no significant difference between the AlignRT method and the tattoo-based method for both setup time and in-room time.
Conclusion
These results suggest that a tattoo-less setup approach with AlignRT (ART) may be sufficiently accurate to supplant surface tattoos for patients receiving chest wall breast radiation. Further analyses with larger cohorts will determine whether tattoo-based (TTB) approaches can be replaced by surface imaging.