Dose Distribution of High Dose-Rate and Low Dose-Rate Prostate Brachytherapy at Different Intervals-Impact of a Hydrogel Spacer and Prostate Volume.

The study aimed to compare the dose distribution in permanent low-dose-rate brachytherapy (LDR-BT) and high-dose-rate brachytherapy (HDR-BT), specifically focusing on the impact of a spacer and prostate volume. The relative dose distribution of 102 LDR-BT patients (prescription dose 145 Gy) at different intervals was compared with the dose distribution of 105 HDR-BT patients (232 HDR-BT fractions with prescription doses of 9 Gy, n = 151, or 11.5 Gy, n = 81). A hydrogel spacer (10 mL) was only injected before HDR-BT. For the analysis of dose coverage outside the prostate, a 5 mm margin was added to the prostate volume (PV+). Prostate V100 and D90 of HDR-BT and LDR-BT at different intervals were comparable. HDR-BT was characterized by a considerably more homogenous dose distribution and lower doses to the urethra. The minimum dose in 90% of PV+ was higher for larger prostates. As a consequence of the hydrogel spacer in HDR-BT patients, the intraoperative dose at the rectum was considerably lower, especially in smaller prostates. However, prostate volume dose coverage was not improved. The dosimetric results well explain clinical differences between these techniques reported in the literature review, specifically comparable tumor control, higher acute urinary toxicity rates in LDR-BT in comparison to HDR-BT, decreased rectal toxicity after spacer placement, and improved tumor control after HDR-BT in larger prostate volumes.

Focal injection of a radiopaque viscous spacer before focal brachytherapy as re-irradiation for locally recurrent prostate cancer.

PURPOSE: Close vicinity of the target volume and a sensitive organ may prevent an effective radiotherapy/brachytherapy. A liquid hydrogel spacer cannot be placed well focally in specific small areas or fatty tissue. The purpose of this study was to report the injection technique and results of a radiopaque viscous hydrogel spacer. METHODS: The radiopaque viscous spacer was applied focally using transrectal ultrasound guidance before focal brachytherapy in re-irradiated areas in two patients. The technical feasibility of the injection between the recurrence and the rectum / bladder, the resulting distance, visibility in different imaging modalities, stability within several months, dose distribution, toxicity and tumor control up to 18 months after treatment was analyzed. RESULTS: After hydrodissection, the needle was moved from the base towards the apex during injection of each syringe, respectively. The viscous spacer could be successfully injected focally and resulted in a planned distancing of the target volume (right lobe and seminal vesicle area) and the rectum of at least 1 cm and additional distancing to the bladder of at least 5 mm. Both brachytherapy treatments were performed without relevant toxicities. The PSA nadirs indicated a satisfactory short-term response to the treatment. CONCLUSIONS: The viscous hydrogel spacer can be injected focally at a specific prostate lobe or seminal vesicles. A viscous spacer remains stable within fatty tissue in any areas that are accessible by an ultrasound guided needle injection to create a distance between the high brachytherapy dose within the target and the organ at risk.

Permanent interstitial brachytherapy for prostate cancer implementing neoadjuvant prostatic artery embolization.

PURPOSE: Indication for permanent interstitial brachytherapy (PIB) can be limited by prostate volume, commonly decreased using neoadjuvant hormonal therapy. Volume changes and initial clinical results focusing on patients treated with prostatic artery embolization (PAE) were evaluated in this study. METHODS AND MATERIALS: A group of 102 consecutive patients were treated with permanent interstitial brachytherapy (PIB), 13 patients received a neoadjuvant PAE (median 12 weeks before PIB) in case of large prostate volume >60 cm³, and moderate to severe urinary problems. RESULTS: Patients after PAE were treated with significantly larger prostate volumes (52 ± 11 cm³ vs. 39 ± 11 cm³; p < 0.01; 66 ± 17 cm³ before PAE), but larger volume reductions to 44 ± 10 cm³ versus 35 ± 10 cm³ was found at day 30 (p < 0.05). International Prostate Symptom Score (IPSS) decreased significantly from 13 ± 5 before PAE to 7 ± 4 after PAE; p < 0.01. Initial PSA and first PSA after PIB were similar for patients with versus without PAE (5.9 ± 2.9 ng/mL vs. 6.2 ± 2.8 ng/mL and 1.5 ± 0.8 ng/mL vs. 1.9 ± 1.5 ng/mL). However, PSA 12 months after PIB was significantly lower after PAE (0.4 ± 0.3 ng/mL vs. 0.8 ± 0.6 ng/mL; p = 0.03). Four patients without prior PAE needed an intervention after urinary retention - transurethral resection of the prostate (TURP) in three cases and PAE in a single case. Urinary incontinence resulted in two cases after TURP. CONCLUSIONS: PAE could be successfully applied to decrease prostate volume and reduce urinary symptoms before PIB or as a treatment for urinary retention after PIB. A significantly lower PSA is promising for improved long-term cancer control.