Set-up errors in patients undergoing image guided radiation treatment. Relationship to body mass index and weight loss.
BACKGROUND
The purpose of this study was to quantify the set-up errors of patient positioning during IGRT and to correlate set-up errors to patient-specific factors such as weight, height, BMI, and weight loss.


METHODS
Thirty four consecutively treated head-and-neck cancer patients (H&N) and 20 lung cancer patients were investigated. Patients were positioned using customized immobilization devices consisting of vacuum cushions and thermoplastic shells. Treatment was given on an Elekta Synergy accelerator. Cone-beam acquisitions were obtained according to a standardized Action Limit protocol and compared to pre-treatment CT images. The average 3D deviation from three initial cone beam scans was compared to deviations at the 10th and 20th treatment session and correlated by linear regression analysis to height, weight, and BMI, and in H&N to weight loss as expressed by the relative weight change over time.


RESULTS
The SD of the translational and rotational random set-up errors during the first three sessions for H&N were 0.9 mm (Left-Right), 1.1mm (Anterior-Posterior), 0.7 mm (Cranio-Caudal) and 0.7 degrees (LR-axis), 0.5 degrees (AP-axis), and 0.7 degrees (CC-axis). The equivalent data for lung cancer patients were 1.1 mm (LR), 1.1mm (AP), 1.5 mm (CC) and 0.5 degrees (LR-axis), 0.6 degrees (AP-axis), and 0.4 degrees (CC-axis). The median BMI for H&N and lung was 25.8 (17.6-39.7) and 23.7 (17.4-38.8), respectively. The median weekly weight change for H&N was -0.3% (-2.0 to 1.1%). With H&N and lung cancer analyzed separately, no statistically significant correlation was observed between set-up errors and height, weight, BMI, or weight change during treatment, irrespectively whether the 3D deviations from the initial three cone beam scans or scans from the 10th or 20th treatment sessions were used.


CONCLUSIONS
This IGRT study did not support the hypothesis that set-up errors during radiotherapy are correlated to patient height, weight, BMI, or weight loss.
Johansen
Jørgen
J
Department of Oncology, Odense University Hospital, Odense C, Denmark. j.johansen@dadlnet.dk
Bertelsen
Anders
A
Hansen
Christian Rønn
CR
Westberg
Jonas
J
Hansen
Olfred
O
Brink
Carsten
C
D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D054893:Cone-Beam Computed Tomography; D005260:Female; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D006801:Humans; D007103:Immobilization; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D011881:Radiotherapy, Computer-Assisted; D015431:Weight Loss