Accuracy and reproducibility of the patient’s position is crucial for successful delivery of radiotherapy (RT). Data on palliative patients’ set-up uncertainties are sparse. The aim of this study was to calculate set-up errors observed for palliative patients positioned using one skin mark (Group 1) versus three skin marks (Group 2) and to assess the accuracy of both approaches.

Displacements in the left–right (L–R) and superior–inferior (S–I) directions were retrospectively analysed for 175 sites treated with a course of fractionated palliative RT. Population mean, systematic and random errors were calculated in both directions for patients positioned with one and three skin marks. Frequency of deviations was also examined for both groups.

The population mean, systematic and random errors for Group 1 and 2 for the L–R direction were 0·0, 4·4, 4·8 and 0·4, 3·1 and 3·3 mm, respectively, and in the S–I direction: 0·1, 3·4, 4·2 and 1·2, 2·7 and 3·3 mm, respectively. Frequency of images within the clinical tolerance of 5 mm was 47·1% for Group 1 and 65·9% for Group 2.

Three skin marks are recommended for patients receiving a fractionated course of palliative RT, as it reduces set-up error, reduces the number of gross displacements (>10 mm) and increases the number of displacements within the clinically acceptable tolerance of 5 mm.

Imaging protocols are implemented to identify and minimise set-up errors. A crucial component to the success of these protocols is staff compliance.

This is case report describing a retrospective review of radiation therapists’ compliance to a palliative imaging protocol in a single large institution in one calendar year.

The review showed a non-compliance to protocol for 8% of treatments. The most frequent protocol deviation was a failure to calculate the mean set-up displacement after 2/3 days of consecutive imaging.

Despite the presence of institutional evidence-based palliative imaging protocol unwanted deviations in practice can occur.