One Minute Poster Pitches Archive

UK & Ireland Prostate Brachytherapy Conference 2024

Abstract number 13 

Possibility of salvage re-irradiation of perineal prostate cancer nodule following prostate low dose rate brachytherapy (LDR-BT). 

Mark Long
Royal Surrey County Hospital 

Purpose: To address the technical challenges of retreatment of prostate/pelvic relapse following previous radiotherapy (including brachytherapy). A specific case study demonstrating this process is highlighted: SABR following prostate LDR-BT for a 62-year-old gentleman who was originally treated in 2016 with LDR-BT, 145Gy to whole prostate using I-125 seeds. 

Methods: The patient was offered salvage SABR 30Gy in 5 fractions on alternate days. Radiobiological calculations were used to derive bespoke planning aims for the urethral planning organ-at-risk volume (PRV) in the region of treatment overlap near the I-125 seeds. 

Due to the time since the previous treatment a tissue recovery factor of 20% was used, and alpha/beta ratio of 3 was taken for the urethral tissue. The planning CT was acquired with an indwelling catheter to maximise accuracy of daily image guided radiotherapy (IGRT) thus limiting urethral dose and ensuring cumulative dose estimates remain accurate through the course of treatment. 

Results: A clinically acceptable plan was generated that met the required constraints to maximise dose to the surrounding target and minimise potential urethral complications. The high dose region was highly conformal around the PRV whilst maintaining high dose SABR coverage to the remaining target with maximum doses of >125% achieved, even in this unusual case of re-irradiation following permanent brachytherapy implant. 

Conclusions: At 3 months post-SABR, the patient experienced no acute toxicity and his PSA has reduced from 7.4 to 5.7 microg/L. The importance of a multi-disciplinary approach was highlighted and the possibility of salvage radiotherapy to the prostate after brachytherapy remains a suitable option.