Assessment of Daily Replanning and Geometrical Variation of High-dose-rate Brachytherapy for the Prostate

Abstract

Background: The present study aimed to estimate geometric changes in applicators and prostate over 3 days in patients with high-dose-rate brachytherapy (HDR-BT) and to assess the need for daily replanning.

Patients and methods: This study retrospectively investigated 18 patients who underwent HDR-BT as monotherapy from February 2016 to October 2018.

Results: Without replanning, the planning target volume coverage significantly worsened on day 2 (p<0.001) and day 3 (p=0.003). The minimum dose distributed to the highest irradiated rectal volume of 5 cc became significantly higher on day 2 (p=0.02), and the maximum dose distributed to the urethra became significantly higher on day 2 (p=0.01).

Conclusion: Conformal, high-dose delivery of HDR-BT is impaired without replanning not only on the second day but also on the third day. Daily replanning is required for achieving accuracy of HDR-BT.

Keywords: HDR-BT; Prostate cancer; brachytherapy; daily replanning.