The set-up markings are created during the simulation session, after the CT simulation is acquired. For the experimental group, patients' markings are tattooed using an electric marking device developed for set-up marking, the Comfort Marker 2.0® (CM), designed by CIVCO medical solutions, using the 0.2mm deep application depth and the brand-included black pigment. After cleaning the excess ink, if the tattooing was considered unsuccessful, the process was repeated. Markings arrangement followed our departmental protocol. No limit on the maximum number of cutaneous reference points is specified.

Comfort is verbally assessed on the 11-point numeric pain scale. As more than one reference point is tattooed, the patients are asked to give an overall score to the procedure.

Effectiveness is assessed by the RTT team that delivered the daily fractions. Skin markings are individually evaluated at several periods, specifically at the first fraction, then every 5 fractions, and one last time in the last fraction of RT. These evaluations are scored on a 4-point graded scale (corresponding to bad, reasonable, good, and excellent).

The RTT that executed the tattooing is asked to score the ease of the process on a three-point scale (easy, medium, and hard).

A photographic assessment is performed. Every set-up marking is individually photographed on one of the last three days of treatment. All photographs are scored by independent observers (both physicians and RTTs) blind to patient identity and treatment allocation, on a five-point scale (corresponding from bad to excellent cosmesis).

A photographic assessment is performed. Every set-up marking is individually photographed a. All photographs are scored by indepe6 months after completion of the RT. All photographs are scored by independent observers(both physicians and RTTs) blind to patient identity and treatment allocation, on a five-point scale (corresponding from bad to excellent fading).