Is intraoperative real-time dosimetry in prostate seed brachytherapy predictive of biochemical outcome?

Abstract

PurposeTo analyze intraoperative (IO) dosimetry using transrectal ultrasound (TRUS), performed before and after prostate low-dose-rate brachytherapy (LDR-BT), and compare it to dosimetry performed 30 days following the LDR-BT implant (Day 30).Material and methodsA total of 236 patients underwent prostate LDR-BT using 125I that was performed with a three-dimensional TRUS-guided interactive inverse preplanning system (preimplant dosimetry). After the implant procedure, the TRUS was repeated in the operating room, and the dosimetry was recalculated (postimplant dosimetry) and compared to dosimetry on Day 30 computed tomography (CT) scans. Area under curve (AUC) statistics was used for models predictive of dosimetric parameters at Day 30.ResultsThe median follow-up for patients without BF was 96 months, the 5-year and 8-year biochemical recurrence (BR)-free rate was 96% and 90%, respectively. The postimplant median D90 was 3.8 Gy lower (interquartile range [IQR], 12.4-0.9), and the V100 only 1% less (IQR, 2.9-0.2%) than the preimplant dosimetry. When comparing the postimplant and the Day 30 dosimetries, the postimplant median D90 was 9.6 Gy higher (IQR [–] 9.5-30.3 Gy), and the V100 was 3.2% greater (0.2-8.9%) than Day 30 postimplant dosimetry. The variables that best predicted the D90 of Day 30 was the postimplant D90 (AUC = 0.62, p = 0.038). None of the analyzed values for IO or Day 30 dosimetry showed any predictive value for BR.ConclusionsAlthough improving the IO preimplant and postimplant dosimetry improved dosimetry on Day 30, the BR-free rate was not dependent on any dosimetric parameter. Unpredictable factors such as intraprostatic seed migration and IO factors, prevented the accurate prediction of Day 30 dosimetry.

Acute and late toxicities in localized prostate cancer patients treated with low-dose 125I brachytherapy (110 Gy) in combination with external beam radiation therapy versus brachytherapy alone (160 Gy)

“…Higher dose can deliver to prostate with lower exposure to organs at risks; 2. The treatment time became remarkably shorter than EBRT because usually the insertion was completed within one day [ 14 , 19 , 27 ]. In comparison with EBRT, LDR-BT can deliver a higher dose with lower exposure to organs at risk.…”

Plan reproducibility of intraoperatively custom-built linked seeds compared to loose seeds for prostate brachytherapy

“…To date, many studies compared stranded seeds to loose seeds [ 9 , 13 , 14 , 19 , 20 , 21 ], but few studies have compared the implant quality of linked seeds with that of loose seeds for prostate brachytherapy [ 17 , 22 , 23 , 24 , 25 ]; however, until now, there have been no reports about the plan reproducibility of linked seeds. Generally, intraoperative dosimetry based on ultrasound would not predict biochemical outcome [ 26 ]. Post-operative D 90 is an important dosimetric parameter for biochemical freedom from failure [ 27 ].…”

Phase II study of intraoperative dosimetry for prostate brachytherapy using registered ultrasound and fluoroscopy

“…Recently, Taussky et al reported that intraoperative USD was predictive of Day 30 dosimetry but with low predictive power due to intraprostatic seed migration and other intraoperative factors that are unpredictable in USD, and biochemical recurrence-free rate was not dependent on any intraoperative USD dosimetry parameters (22). A few groups combined intraoperative CT with TRUS and performed intraoperative adaptive plan modification similarly as our approach, demonstrating improved prostate dose coverage and correlation with Day 30 (15, 23, 24) and Day 0 (15) dosimetry.…”

“…Although prior studies indicated some correlation between intraoperative USD and postoperative CT or CT/MRI dosimetry, there exists significant disparity between them (10, 16–18), suggesting that current USD approach needs improvement to achieve optimal implant distribution (19–22). Recently, Taussky et al reported that intraoperative USD was predictive of Day 30 dosimetry but with low predictive power due to intraprostatic seed migration and other intraoperative factors that are unpredictable in USD, and biochemical recurrence-free rate was not dependent on any intraoperative USD dosimetry parameters (22). A few groups combined intraoperative CT with TRUS and performed intraoperative adaptive plan modification similarly as our approach, demonstrating improved prostate dose coverage and correlation with Day 30 (15, 23, 24) and Day 0 (15) dosimetry.…”