Application of a Radiopaque Viscous Hydrogel Spacer for Prostate Cancer Radiation Therapy: A Prospective Phase 2 Study.

PURPOSE: The aim of this study was to evaluate the application of a radiopaque viscous spacer (RVS) for prostate cancer radiation therapy (RT), including injection procedure, toxicity, treatment planning, image guidance, and imaging results up to 12 months after RT. METHODS AND MATERIALS: RVS (median, 10 mL) was injected between prostate and rectal wall in 30 patients. Cone beam computed tomography (CT) was performed during the course of RT, a magnetic resonance imaging 3 and 12 months after RT. Injection and treatment tolerability were analyzed. The resulting distribution was compared with a control group of 30 patients with an initially fluid spacer. RESULTS: Procedure- or device-related adverse events were not observed. Signs of hydrogel migration were not found in any case. The volume decreased by 25% at 3 months after RT, and small residues were detected at 12 months after RT in 3 cases (10%). The median rectal volume percentage within the 90% isodose was 3.0% (interquartile range, 1.5%-4.5%). Acute and late gastrointestinal toxicities were found in 17% and 3%, respectively (all grade 1). The median distance between prostate and rectum at the base/midplane/apex was greater for RVS in comparison to initially fluid spacer (14/12/11 mm vs 12/10/10 mm, respectively), the gel symmetry (right vs left from midline) was comparable. The application was assessed to be easier to control by the users, and visibility in cone beam CT as good. CONCLUSIONS: The injection of a radiopaque viscous hydrogel spacer resulted in a prostate-rectum distance of >10 mm in most cases. The resulting rectum volume within the high-dose region and RT toxicity were very low. Advantages in comparison to the conventional hydrogel spacer are predominantly an improved placement control during the injection process and good visibility on CT.

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.

Interstitial single fraction brachytherapy for malignant pulmonary tumours.

PURPOSE: Interstitial brachytherapy for pulmonary tumours is an alternative to stereotactic radiotherapy, allowing high conformity despite it being an invasive technique. The aim of the study was the analysis of dose distribution, toxicity and tumour response rates. METHODS: In the years 2014-2019, 27 patients with pulmonary tumours received 36 interstitial brachytherapies with Ir-192: 11 patients with non-small cell lung cancer, 16 patients with pulmonary metastases of other entities. RESULTS: Patients were treated with a median (interquartile range) prescription dose of 20 (20-26) Gy in a single fraction. Mean lung dose to the ipsilateral lung was 2.8 (1.6-4.7) Gy. Maximum doses to the heart, oesophagus, thoracic wall and spinal cord were 2.4 (1.8-4.6) Gy, 2.0 (1.2-6.2) Gy, 12.6 (8.0-18.2) Gy and 1.5 (0.6-3.9) Gy. Median survival after treatment was 15 months, with a 1- and 2­year local control of 84% and 60%. Median overall survival after initial cancer diagnosis was 94 months; 2 years following brachytherapy, 75% of patients with colorectal cancer vs. 37% with other histologies were alive; p = 0.14. In 69% (n = 25), brachytherapy could be performed without acute complications. A self-limiting bleeding occurred in 8% (n = 3), fever in 3% (n = 1), pneumothorax in 17% (n = 6), and pulmonary failure in 3% (n = 1). Patients with > 20 Gy in 95% of planning target volume had higher pneumothorax rates needing intervention (31% vs. 5%, p = 0.04). CONCLUSIONS: Interstitial brachytherapy for pulmonary tumours is a highly conformal therapy with minimal doses to the organs at risk. For the majority of patients, treatment can be performed without relevant complications in a single fraction with a satisfactory local control.

[Dosimetric verification of MammoSite treatment plans using Monte Carlo simulations and measurements with a 2D ionization chamber array]. / Dosimetrische Verifikation von MammoSite-Bestrahlungsplänen mit Monte-Carlo-Simulationen sowie Messungen mit einem 2D-Ionisationskammer-Array.

The surgical removal of a breast tumour is often followed by postoperative irradiation of the surrounding tissue with a radioactive source (brachytherapy). When performing the MammoSite procedure, a spherical silicone balloon is inserted and filled with a NaCl solution. In a period of about five days in several sessions an iridium-192 source with high activity travels through a catheter into the balloon (afterloading) to irradiate the tumour cells remaining in the cavity. In this study, dose distributions of a MammoSite applicator are investigated based on measurements with a 2D detector array, Monte Carlo simulations and calculations with BrachyVision. The focus is set on the 2D detector array and its possible application in the verification process in 3D brachytherapy treatment planning. The measured dose distributions conform well to the doses of BrachyVision with deviations of less than 5% within the clinically relevant field range. The deviations of the measured and calculated distributions from the simulation results are below 3%. The 2D detector array allows a new verification method for MammoSite treatment plans with sufficient accuracy. Future verifications can be performed without additional Monte Carlo simulations.

Treatment Results of MammoSite Catheter in Combination with Whole-breast Irradiation.

AIM: To report the initial outcomes of patients treated with the MammoSite brachytherapy device (MSBT) as a boost followed by external whole-breast irradiation (WBI). PATIENTS AND METHODS: From June 2011 to March 2014, 107 patients (typically with pT1-2, pN0-1, M0 disease) were treated with breast-conserving therapy and adjuvant radiotherapy with MSBT (15 Gy in 2.5-Gy fractions) followed by WBI (median=50.4 Gy). Toxicity was classified according to the Common Terminology Criteria for Adverse Events v3.0. The median follow-up was 21 months. RESULTS: To date, no ipsilateral breast-tumor recurrences have been observed; 102 patients (95%) were alive at last follow-up. Two patients (2%) developed distant metastases. Five patients (5%) died during follow-up, only one as a result of breast cancer. The 2-year disease-free survival was 95±3%. The incidence of asymptomatic and symptomatic seroma in 90 days after MSBT was 28% and 10%, respectively. Infectious mastitis was observed in three patients (3%), who were treated successfully with antibiotics. Only three patients (3%) developed RT-induced dermatitis greater than grade 2 after WBI. CONCLUSION: The boost technique used in this study seems to provide excellent local control with acceptable toxicity, similar to the results observed with other forms of interstitial accelerated partial-breast irradiation as a boost. Long-term follow-up is necessary to refine the patient selection criteria and to assess efficacy and late toxicities.