Session Item

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.

Patients receiving accelerated partial breast irradiation (APBI) 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 surgical clips 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.

A total of 43 APBI patients were analyzed for this study. For tattoo-less setup via ART, the median absolute TS were 0.31cm vertical (range: 0.08-0.82), 0.23cm lateral (0.05-0.86), and 0.26cm longitudinal (0.02-0.72). For TTB setup, the corresponding median TS were 0.34cm (0.05-1.98), 0.31cm (0.09-1.84), and 0.34cm (0.08-1.25). The median magnitude shifts were 0.59 (0.30-1.31) for ART and 0.80 (0.27-2.13) for TTB. ART was not statistically distinguishable from TTB in terms of TS (p=0.154, 0.059, 0.021, respectively) and was superior to TTB for magnitude shift (p<0.001). Variance testing of each TS variable also showed an advantage of ART over TTB (p≤0.001, 0.001, 0.005, respectively).

The median absolute RS for ART was 0.64° rotation (range:0.00-1.90), 0.65° roll (0.05-2.90), 0.30° pitch (0.00-1.50). The corresponding median RS for TTB were 0.80° (0.00-2.50), 0.64° (0.00-3.00), and 0.46° (0.00-2.90). ART setup was not statistically different from TTB in terms of RS (p=0.868, 0.236, 0.079, respectively). ART showed lower variance than TTB in terms of pitch (p=0.009).

The median total in-room time was 15.42 minutes (range: 9.80-37.00) for ART and 17.25 minutes (9.50-46.00) for TTB (p=0.008). The median setup time was 11.12 minutes (5.58-31.54) for ART and 13.00 minutes (5.66-42.90) for TTB (p=0.001). Moreover, ART had a narrower distribution of setup time with fewer lengthy outliers vs TTB.

These results suggest that a tattoo-less setup approach with AlignRT (ART) may be sufficiently accurate to supplant surface tattoos for patients receiving APBI. Further analyses with larger cohorts will determine whether tattoo-based (TTB) approaches can be replaced by surface imaging.