[Image-guided application of plant pigment patch and laser microdot ablation for surface marking in radiotherapy for...

To validate the non-inferiority of plant-based pigment patches as surface markers for postoperative radiotherapy localization in breast cancer, evaluate their accuracy, durability and safety, and identify the factors influencing pigment fading to determine the patients eligible for these patches.

In this randomized controlled trial, 80 patients receiving their first course of postoperative radiotherapy for breast cancer were randomly assigned in a 1:1 ratio to plant-based pigment patch group (trial group) or conventional laser microdot tattoo group (control group). The primary outcome was 3-dimensional setup error (non-inferiority margin: 0.7 mm). The secondary outcomes included uniaxial errors, re-marking frequency, skin adverse events, patient comfort, and healthcare satisfaction. Linear mixed-effects models and Cox regression were used for data analyses.

The baseline characteristics of the patients were balanced between the two groups. The trial group demonstrated non-inferiority to the control group in setup accuracy (3-dimensional error: 3.12±1.14 mm vs 3.05±0.98 mm; mean difference: 0.07 mm; 95% CI: -0.31 to 0.45; upper limit <0.7 mm). No significant differences were observed in the uniaxial errors. Patient comfort scores were significantly higher in the trial group (4.23±0.65 vs 0.15±0.82, P<0.001). The incidence of skin adverse events was zero in the trial group but 12.5% in the control group (P<0.05). Multivariable Cox regression identified oily skin (HR=2.78, P<0.001), frequent sweating (HR=3.02, P<0.001), frequent washing (HR=1.42, P<0.05), and a high BMI (HR=1.32, P<0.05) as independent risk factors for faster pigment fading, while the use of a protective agent was a protective factor (HR=0.47, P=0.019).

Plant-based pigment patches are non-inferior to conventional laser microdots and offer comparable positioning accuracy with superior comfort and safety.