Supine/prone position fixation treatment in cervical cancer radiotherapy.

Objective: This study aimed to determine the correlation between bladder volume changes and set-up accuracy in cervical cancer patients undergoing radiotherapy.

Methods: Forty patients who underwent intensity-modulated radiotherapy were divided into two groups based on their position during treatment: group A (supine) and group B (prone). Correlations between bladder volume changes and set-up accuracy were retrospectively analyzed using archived data and image files.

Results: The rate of bladder volume change in group A (-3.99% [-24.51-31.53]) was significantly higher (Z = -2.724; P = 0.006) than that in group B (-14.95% [-41.63-7.64]). The set-up errors in the X (left-right), Y (cranial-caudal), and Z (anterior-posterior) directions were 0.05 ± 2.25 mm, 0.84 ± 2.63 mm, and 0.41 ± 2.35 mm, respectively, in group A and -0.31 ± 2.22 mm, -0.38 ± 2.88 mm, and 0.78 ± 3.41 mm, respectively, in group B. No significant differences in the X and Z directions were detected between the two groups; however, a significant difference was detected in the Y direction. The set-up error in the X direction was positively correlated with the rate of bladder volume change (r = 0.284; P = 0.010) in group A; no correlations were observed in the X, Y, and Z directions in group B.

Conclusion: Patients in the prone position demonstrated better performance in the Y direction than those in the supine position. The set-up error in the X direction was positively correlated with the rate of bladder volume change among patients in the supine position.