Axxent Electronic Brachytherapy Research Articles

Measurement of dose enhancement factor for Xoft Axxent electronic brachytherapy device using nanoparticle-embedded alginate film and radiochromic film.

Inw nanoparticles-aided radiotherapy, the radiation sensitivity of tumor is increased with the infusion of nanoparticles in tumor. This therapeutic modality is capable of delivering enhanced dose to tumor, without exceeding the normal tissue tolerance dose. Further, the quantification of the enhanced dose using suitable dosimeter is important. The present study is aimed at measuring the dose enhancement factors (DEFs) using the combination of nanoparticles-embedded alginate (Alg) film and unlaminated Gafchromic EBT3 film. Gold nanoparticles (AuNPs)- and silver nanoparticles (AgNPs)-embedded Alg polymer films were synthesized and characterized using standard techniques. Further, a customized version of the Gafchromic EBT3 film, i.e., unlaminated EBT3 film, was specially fabricated. The DEFs were measured using Xoft Axxent electronic brachytherapy device. The surface plasmon resonance (SPR) and particle size of AuNPs were found to be 550 and 15 ± 2 nm, respectively. In the case of AgNPs, the SPR and particle size were recorded as 400 and 13 ± 2 nm, respectively. The DEFs measured, using unlaminated EBT3 film, for Xoft Axxent electronic brachytherapy using AuNPs and AgNPs were 1.35 ± 0.02 and 1.20 ± 0.01, respectively. The increase in dose enhancement during nanoparticles-aided electronic brachytherapy can be attributed to dominance of photoelectric effect, due to the presence of low-energy X-rays. The investigation indicates that the Xoft Axxent electronic brachytherapy device is suitable for nanoparticles-aided brachytherapy.

Single institute experience of intraoperative radiation therapy in early-stage breast cancer.

Intraoperative radiation therapy (IORT) is an alternative to whole breast irradiation in selected early-stage breast cancer patients. In this single institute analysis, we report the preliminary results of IORT given by Axxent Electronic Brachytherapy (eBT) system.Patients treated with lumpectomy and eBT within a minimum follow-up period of 12 months were analyzed. Eligible criteria include being over the age of 45, having unifocal invasive ductal carcinoma (IDC) or ductal carcinoma in situ <3 cm in diameter, not exhibiting lymph node involvement on preoperative images, and negative sentinel lymph node biopsy. The eBT was given by preloaded radiation plans to deliver a single fraction of 20 Gray (Gy) right after lumpectomy.From January 2016 to April 2019, a total of 103 patients were collected. There were 78 patients with IDC and 25 with ductal carcinoma in situ. At a mean follow-up time of 31.1 months (range, 14.5–54.0 months), the local control rate was 98.1%. Two IDC patients had tumor recurrences (1 local and 1 regional failure). Post-IORT radiotherapy was given to 4 patients. There were no cancer related deaths, no distant metastases, and treatment side effects greater than grade 3 documented.We report the largest single institute analysis using the eBT system in Taiwan. The low recurrence and complication rates at a 31.1 month follow-up time support the use of the eBT system in selected early-stage breast cancer patients.

Abstract PS14-24: Multi-center trial in the treatment of ductal carcinoma in situ of breast using intra-operative electronic brachytherapy technique, results

Abstract Purpose: To report on the technique of intra-operative electronic brachytherapy, local control, side effects and complications after a single fraction of 2000 cGy at the time of partial mastectomy. Material &amp; Methods: 1200 patients with early stage invasive ductal carcinoma and carcinoma in situ were enrolled in the Multi-Center Trial. 246 (20.5%) patients among these 1200 patients had carcinoma in situ and were treated by a single fraction of 2000 cGy dose by intra-operative irradiation to the lumpectomy cavity using Xoft system of electronic brachytherapy at the time of partial mastectomy. 80% of the patients were Caucasian, 7% African American, 7% Hispanic and 6% others. Estrogen receptor was positive in 211 patients, negative in 28 patients and unknown/not assessed in 7 patients. Progesterone receptor was positive in 190 patients, negative in 45 patients and unknown/not assessed in 11 patients. All patients were BRCA negative. 34 (14%) patients had low grade tumors, 109 (44%) intermediate grade tumors, and 103 (42%) high grade tumors. Seroma occurred in 9.8%, induration in 7.6%, and significant fibrosis in 3.5% of the patients. 2/246 (1%) developed ipsilateral recurrence and one patient developed a gastrointestinal cancer. 118 (48%) patients had characteristics of ASTRO criteria being suitable, 108 (44%) cautionary and 20 (8%) unsuitable. Conclusion: The relatively early 2.3 year results of a single fraction of 2000 cGy by IORT to the lumpectomy cavity at the time of partial mastectomy using Xoft Axxent electronic brachytherapy in the treatment of carcinoma in situ of the breast is safe and associated with low morbidity and local recurrence with good to excellent cosmesis in 80% of the patients. Citation Format: Alam M.Nisar Syed. Multi-center trial in the treatment of ductal carcinoma in situ of breast using intra-operative electronic brachytherapy technique, results [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS14-24.

Intra-operative radiation therapy as salvage treatment option for recurrent glioblastoma multiforme.

2535 Background: Glioblastoma multiforme (GBM) is an extremely aggressive cerebral tumor with poor prognosis. The majority of patients relapse after the initial surgery plus adjuvant radiation and chemotherapy. In case of recurrence there is no established standard therapy. The optimal techniques for salvage re-irradiation are unclear, so that procedure poses a challenge. In contrast to traditional external beam radiotherapy (EBRT) intra-operative radiotherapy (IORT) may improve patient’s outcome at the cost of minimal side effects and short treatment duration. Methods: A total of 30 patients were treated with recurrent GBM between August 2016 and June 2019. All patients underwent maximal safe resection; patients were divided into IORT and EBRT groups. 15 patients were included in each group with similar clinical characteristics. All patients in IORT group underwent maximal safe microsurgical resection with subsequent intraoperative balloon electronic brachytherapy (IBEB) and no further adjuvant treatment. IBEB was performed using Axxent electronic brachytherapy device (Xoft Electronic Brachytherapy (eBx) System, USA. Patients in EBRT group underwent same surgery followed by external beam radiotherapy. Contrast-enhanced brain MRI with perfusion was performed within 24 hours of surgery +/- brain PET-CT with 18-FDOPA and then every 3 months. Both groups were also assigned to subgroups (≤ 2.5cm3 and &gt; 2.5cm3) based on post-operative contrast-enhancing volume (POCEV). Median overall survival (OS) since diagnosis and local progression-free survival (locPFS) following the second surgery were analyzed. Possible toxicities and prognostic factors were also evaluated. Results: Median OS was 27 months in IORT group and 21 months in EBRT group. The locPFS range between 3.5 to 39 months in IORT group and only 2 to 10 months in group with EBRT. Kaplan-Meier OS curves in patients with POCEV ≤ 2.5cm3 showed more favorable outcomes for patients in the IORT group (p &lt; 0.05). In patients with POCEV &gt; 2.5cm3 the median OS was 17 months in IORT group and 13.5 months in EBRT group. Conclusions: IORT of recurrent GBM is feasible and provides encouraging local progression-free and overall survival; no high-grade radiation induced toxicities occur and further studies to establish this method are mandatory. The toxicity profile of additional IBEB was manageable. Maximal safe microsurgical resection is the most important prognostic factor and could determine the effectiveness of post-surgical IBEB.

Postoperative endometrial cancer treatments with electronic brachytherapy source

AbstractPurposeThis study is a dosimetric and acute toxicity comparison of endometrial cancer patients treated with either Axxent (Xoft, Inc., San José, CA, USA) electronic and interstitial brachytherapy versus interstitial high dose rate brachytherapy (HDRBT).Materials and MethodsBetween 2015 and 2017, 94 patients with postoperative endometrial cancer were treated in our centre with the Axxent electronic brachytherapy (eBT) system. The V150 and V200 are evaluated prospectively for each plan. The mean age of patients was 65.9 years (age range 33–84 years), with different tumour staging. Of the 94 patients, 37 received exclusive adjuvant brachytherapy (25 Gy in five sessions); the remaining patients received external beam radiotherapy (EBRT) with a regimen of 23 sessions of 2 Gy each to the entire pelvis, followed by eBT (15 Gy in three sessions). Additionally, the absorbed doses received by the organs at risk (OAR), urinary bladder, rectum and sigmoid colon were compared with HDRBT plans, evaluating D2cc, V50% and V35%. Median follow-up was done for each of the 94 patients to assess the toxicity of the treatment: vaginal mucosa toxicity, rectal and urinary toxicity; and results are presented for acute toxicity, toxicity at 1 month after the end of treatment and follow-up after 12 months for a portion of patients according to the Radiation Therapy Oncology Group (RTOG) toxicity criteria.ResultsThe doses in OAR for eBT plans were lower than that for HDRBT plans, both Ir-192 and Co-60 plans, whose doses were similar. The dose in bladder with eBT was 63.8% of the prescribed dose for D2cc versus 70.1% for HDRBT Ir-192, for V50% was 7.2% versus 12.7% and for V35% was 15.2% versus 28.2%. In rectum the D2cc was 61.2% versus 68.4%, for V50% was 7.9% versus 14.3% and for V35% was 16.7% versus 32%. Results demonstrated lower doses to OAR in all eBT plans. Acute toxicity in eBT was very low in cases of mucositis, with only one case of toxicity greater than grade 1, rectal toxicity and urinary toxicity; results at 1 month are equally good, toxicity symptoms disappeared and no relapses have occurred to date.ConclusionsThe results of treatment with the Axxent eBT unit for 94 patients are very good, as no recurrence has been observed and the toxicity of the treatment is very low. The increase in V150 and V200 has not produced an increase in vaginal mucosa toxicity, and the doses in the OAR are lower than in the plans implemented for HDRBT with Ir-192 or Co-60. eBT is a good alternative to treat endometrial cancer in centres without conventional HDR availability. To date, there are limited published studies reporting on outcomes from patients treated with eBT.

Dosimetric effects of saline- versus water-filled balloon applicators for IORT using the model S700 electronic brachytherapy source

PurposeThe Xoft Axxent Electronic Brachytherapy System (Xoft, Inc., San Jose, CA) is a viable option for intraoperative radiation therapy (IORT) treatment of early-stage breast cancer. The low-energy (50-kVp) X-ray source simplifies shielding and increases relative biological effectiveness but increases dose distribution sensitivity to medium composition. Treatment planning systems typically assume homogenous water for brachytherapy dose calculations, including precalculated atlas plans for Xoft IORT. However, Xoft recommends saline for balloon applicator filling. This study investigates dosimetric differences due to increased effective atomic number (Zeff) for saline (Zeff = 7.56) versus water (Zeff = 7.42). MethodsBalloon applicator diameters range from 3 to 6 cm. Monte Carlo N-Particle software is used to calculate dose at the surface (Ds) of and 1 cm away (D1cm) from the water-/saline-filled balloon applicator using a single dwell at the applicator center as a simple estimation of the dosimetry and multiple dwells simulating the clinical dose distributions for the atlas plans. ResultsSingle-dwell plans show a 4.4–6.1% decrease in Ds for the 3- to 6-cm diameter applicators due to the saline. Multidwell plans show similar results: 4.9% and 6.4% Ds decrease, for 4-cm and 6-cm diameter applicators, respectively. For the single-dwell plans, D1cm decreases 3.6–5.2% for the 3- to 6-cm diameter applicators. For the multidwell plans, D1cm decreases 3.3% and 5.3% for the 4-cm and 6-cm applicators, respectively. ConclusionsThe dosimetric effect introduced by saline versus water filling for Xoft balloon applicator–based IORT treatments is ∼5%. Users should be aware of this in the context of both treatment planning and patient outcome studies.

Physics aspects of the Papillon technique—Five decades later

PurposeThe Papillon technique using 50-kVp soft X-rays to treat rectal adenocarcinomas was developed and clinically implemented in the 1960s. We describe differences between accurate dosimetry and clinical implementation of this technique that is extending from its very inception to date. Methods and MaterialsA renaissance of the Papillon technique occurred with two recently introduced 50-kVp systems: Papillon+ by Ariane and a custom-made rectal applicator (consisting of a surface applicator inserted into a proctoscope) by iCAD's Xoft Axxent Electronic Brachytherapy (eBT) System (iCad, Inc., Sunnyvale, CA). In contrast to the initial design, we investigated the impact of introducing a plastic lid, which would provide more reproducible and more accurate dose delivery across the rectal adenocarcinoma patient population. We use both parallel-plate chamber and radiochromic film dosimeters to determine differences in basic dosimetry characteristics (beam half-value layers, outputs, percent depth doses, and profiles) between the Xoft Electronic Brachytherapy rectal applicator system with and without the plastic lid in place. ResultsCompared to the open-cone applicator, the proposed applicator with the plastic lid produces a slightly harder (more penetrating) beam quality (half-value layer of 1.4 vs. 1.3-mm Al), but with reduced output (by 33%), and a slightly broader beam with flatness not worse than 3% and symmetry not worse than 2%. ConclusionsIn addition to characterizing beam properties modified by the possible introduction of the plastic cap, we also pointed out and addressed misconceptions in the use of radiochromic films for dose measurements at low-energy photon beams.

Acute and Chronic Complications in Breast Cancer Patients Treated with Intraoperative Radiation Therapy.

Intraoperative radiation therapy (IORT) permits the delivery of radiation therapy directly to the tumor bed at the time of surgery. Minimal data are available about the complications associated with this modality of treatment using the Xoft(®) Axxent Electronic Brachytherapy (Axxent) System. A total of 702 patients who received IORT using the Xoft(®) Axxent System at Hoag Memorial Hospital Presbyterian between June 2010-February 2016 were accrued in an IORT data registry study. The prospective and retrospective protocols were approved by the institutional review board and met the guidelines of their responsible governmental agency. Data were collected at 1week, 1month, 3months, 6months, 1year, and thereafter yearly. Acute complications were defined as those occurring within the first month. Chronic complications were those that persisted beyond 6months. Acute complications were observed in 21% of patients and included hematomas that required drainage, seromas requiring drainage more than 3 times, infections treated with antibiotics or surgery, necrosis requiring surgery, and erythema. Chronic complications were observed in 13% of patients and included seromas, fibrosis, and hyperpigmentation. The majority of acute and chronic problems from IORT were mild. If grade I erythema, fibrosis, and hyperpigmentation were removed, only 32 of 702 (4.6%) had significant complications. Our complication rates were comparable to those of the TARGIT trial. IORT is a modality that safely delivers radiation therapy to patients diagnosed with breast cancer. This technique allows women who cannot (or decline to) undergo whole breast radiation to consider breast-conserving therapy rather than mastectomy.

SU‐F‐T‐45: Dosimetric Effects of Saline Filled Balloons During IORT Using Xoft Electronic Brachytherapy

Purpose:The portability of Xoft Axxent Electronic Brachytherapy (EBx) System has made it a viable option for intraoperative radiation therapy (IORT) treatment of early‐stage breast cancer. The low energy (50kVp) of the X‐ray source makes the shielding easy, but also means its dose distribution is sensitive to the medium's composition. Current treatment planning systems (TPS) typically assume homogenous water for brachytherapy dose calculations, including the pre‐calculated atlas plans for the Xoft IORT cases. However, Xoft recommends using saline to fill the balloon applicator. This study investigates the dosimetric difference due to the increased effective atomic number (Zeff) from water (7.42) to saline (7.56).Methods:The diameter of the balloon applicators ranges from 3–6cm, with 4cm being most frequently used. For the 4‐cm and 6‐cm diameter applicators, MCNP Monte Carlo program was used to calculate the dose at the surface (Ds) of the middle section of the balloon and 1 cm away (D1cm) for water‐ and saline‐filled balloons: one plan with a single dwell at the center and another with multiple dwells as in the atlas plans. The single dwell plan is a simple estimation of the dosimetry, while the atlas plan is representative of the actual dose distribution.Results:The single‐dwell plan showed a 5.1% and 6.1% decrease in Ds for the 4‐ and 6‐cm applicators, respectively, due to the saline. The atlas plan showed similarResults:4.8% and 6.4% decrease, respectively. The decrease in D1cm is 4.3%–5.2% and 3.3%–5.3s% in the single‐dwell and atlas plans, respectively, for the 4‐ and 6‐cm applicator.Conclusion:The dosimetric effect introduced by saline is on the order of 5%. This effect should be taken into account during both treatment planning and patient outcome studies.

SU‐E‐T‐421: Failure Mode and Effects Analysis (FMEA) of Xoft Electronic Brachytherapy for the Treatment of Superficial Skin Cancers

Purpose:To perform a failure mode and effects analysis (FMEA) of the process for treating superficial skin cancers with the Xoft Axxent electronic brachytherapy (eBx) system, given the recent introduction of expanded quality control (QC) initiatives at our institution.Methods:A process map was developed listing all steps in superficial treatments with Xoft eBx, from the initial patient consult to the completion of the treatment course. The process map guided the FMEA to identify the failure modes for each step in the treatment workflow and assign Risk Priority Numbers (RPN), calculated as the product of the failure mode's probability of occurrence (O), severity (S) and lack of detectability (D). FMEA was done with and without the inclusion of recent QC initiatives such as increased staffing, physics oversight, standardized source calibration, treatment planning and documentation. The failure modes with the highest RPNs were identified and contrasted before and after introduction of the QC initiatives.Results:Based on the FMEA, the failure modes with the highest RPN were related to source calibration, treatment planning, and patient setup/treatment delivery (Fig. 1). The introduction of additional physics oversight, standardized planning and safety initiatives such as checklists and time‐outs reduced the RPNs of these failure modes. High‐risk failure modes that could be mitigated with improved hardware and software interlocks were identified.Conclusion:The FMEA analysis identified the steps in the treatment process presenting the highest risk. The introduction of enhanced QC initiatives mitigated the risk of some of these failure modes by decreasing their probability of occurrence and increasing their detectability. This analysis demonstrates the importance of well‐designed QC policies, procedures and oversight in a Xoft eBx programme for treatment of superficial skin cancers. Unresolved high risk failure modes highlight the need for non‐procedural quality initiatives such as improved planning software and more robust hardware interlock systems.

SU‐E‐T‐171: Characterization of the New Xoft Axxent Electronic Brachytherapy Source Using PRESAGE Dosimeters

Purpose:To characterize the Xoft Axxent electronic brachytherapy source using PRESAGE™ dosimeters to obtain independent confirmation of TG‐43U1 dosimetry values from previous studies and ascertain its reproducibility in HDR brachytherapy.Methods:PRESAGE™ dosimeters are solid, polyurethane‐based dosimeters doped with radiochromic leucodyes that produce a linear optical‐density response when exposed to radiation. Eight 1‐kg dosimeters were scanned prior to irradiation on an optical‐CT scanner to eliminate background signal and any optical imperfections from each dosimeter. To quantify potential imaging artifacts due to oversaturated responses in the immediate range of the source, half of the eight dosimeters were cast with a smaller channel diameter of 5.4 mm, and the other half were cast with a larger channel diameter of 15mm. During irradiation, the catheters were placed in the center of each channel. Catheters fit the 5.4mm diameters channels whereas polyurethane plugs were inserted into the larger channels to create a sturdy, immobile catheter which allowed uniform dose distributions. Two dosimeters of each 5.4mm and 15mm were irradiated at either 1517.3 cGy or 2017.5 cGy. Post‐irradiation scans were performed within 48 hours of irradiation. A 3D reconstruction based on subtraction of these two images and the relative dose measurements were made using in‐house software.Results:Comparing measured radial dose rates with previous results revealed smaller percent errors when PRESAGE™ irradiations were at lower maximum dose. The dosimeters showed small deviations in radial dose function, gp (r), from previous studies. Among the dosimeters irradiated at 1517.3 cGy, the gp(r) compared to previous studies fluctuated from 0.0043 to 0.3922. This suggests small fluctuations can drastically change radial dose calculations.Conclusion:The subtraction of pre‐irradiation and post‐irradiation scans of PRESAGE™ dosimeters using an optical‐CT scanner shows promising results in determining 3D dosimetry for Xoft Axxent devices; however, further research is recommended.NIH Grant#: 5‐U24‐CA081647‐13; ROI Grant#: 5R01CA100835

A revised dosimetric characterization of the model S700 electronic brachytherapy source containing an anode-centering plastic insert and other components not included in the 2006 model

The model S700 Axxent electronic brachytherapy source by Xoft, Inc., was characterized by Rivard et al. in 2006. Since then, the source design was modified to include a new insert at the source tip. Current study objectives were to establish an accurate source model for simulation purposes, dosimetrically characterize the new source and obtain its TG-43 brachytherapy dosimetry parameters, and determine dose differences between the original simulation model and the current model S700 source design. Design information from measurements of dissected model S700 sources and from vendor-supplied CAD drawings was used to aid establishment of an updated Monte Carlo source model, which included the complex-shaped plastic source-centering insert intended to promote water flow for cooling the source anode. These data were used to create a model for subsequent radiation transport simulations in a water phantom. Compared to the 2006 simulation geometry, the influence of volume averaging close to the source was substantially reduced. A track-length estimator was used to evaluate collision kerma as a function of radial distance and polar angle for determination of TG-43 dosimetry parameters. Results for the 50 kV source were determined every 0.1 cm from 0.3 to 15 cm and every 1° from 0° to 180°. Photon spectra in water with 0.1 keV resolution were also obtained from 0.5 to 15 cm and polar angles from 0° to 165°. Simulations were run for 10(10) histories, resulting in statistical uncertainties on the transverse plane of 0.04% at r = 1 cm and 0.06% at r = 5 cm. The dose-rate distribution ratio for the model S700 source as compared to the 2006 model exceeded unity by more than 5% for roughly one quarter of the solid angle surrounding the source, i.e., θ ≥ 120°. The radial dose function diminished in a similar manner as for an (125)I seed, with values of 1.434, 0.636, 0.283, and 0.0975 at 0.5, 2, 5, and 10 cm, respectively. The radial dose function ratio between the current and the 2006 model had a minimum of 0.980 at 0.4 cm, close to the source sheath and for large distances approached 1.014. 2D anisotropy function ratios were close to unity for 50° ≤ θ ≤ 110°, but exceeded 5% for θ < 40° at close distances to the sheath and exceeded 15% for θ > 140°, even at large distances. Photon energy fluence of the updated model as compared to the 2006 model showed a decrease in output with increasing distance; this effect was pronounced at the lowest energies. A decrease in photon fluence with increase in polar angle was also observed and was attributed to the silver epoxy component. Changes in source design influenced the overall dose rate and distribution by more than 2% in several regions. This discrepancy is greater than the dose calculation acceptance criteria as recommended in the AAPM TG-56 report. The effect of the design change on the TG-43 parameters would likely not result in dose differences outside of patient applicators. Adoption of this new dataset is suggested for accurate depiction of model S700 source dose distributions.

SU‐E‐T‐284: Revisiting Reference Dosimetry for the Model S700 Axxent 50 KVp Electronic Brachytherapy Source

Purpose:The model S700 Axxent electronic brachytherapy source by Xoft was characterized in 2006 by Rivard et al. The source design was modified in 2006 to include a plastic centering insert at the source tip to more accurately position the anode. The objectives of the current study were to establish an accurate Monte Carlo source model for simulation purposes, to dosimetrically characterize the new source and obtain its TG‐43 brachytherapy dosimetry parameters, and to determine dose differences between the source with and without the centering insert.Methods:Design information from dissected sources and vendor‐supplied CAD drawings were used to devise the source model for radiation transport simulations of dose distributions in a water phantom. Collision kerma was estimated as a function of radial distance, r, and polar angle, θ, for determination of reference TG‐43 dosimetry parameters. Simulations were run for 1010 histories, resulting in statistical uncertainties on the transverse plane of 0.03% at r=1 cm and 0.08% at r=10 cm.Results:The dose rate distribution the transverse plane did not change beyond 2% between the 2006 model and the current study. While differences exceeding 15% were observed near the source distal tip, these diminished to within 2% for r&gt;1.5 cm. Differences exceeding a factor of two were observed near θ=150° and in contact with the source, but diminished to within 20% at r=10 cm.Conclusions:Changes in source design influenced the overall dose rate and distribution by more than 2% over a third of the available solid angle external from the source. For clinical applications using balloons or applicators with tissue located within 5 cm from the source, dose differences exceeding 2% were observed only for θ&gt;110°. This study carefully examined the current source geometry and presents a modern reference TG‐43 dosimetry dataset for the model S700 source.

Brachytherapy in breast cancer: an effective alternative.

Breast conserving surgery (BCS) with following external beam radiation therapy (EBRT) of the conserved breast has become widely accepted in the last decades for the treatment of early invasive breast cancer. The standard technique of EBRT after BCS is to treat the whole breast up to a total dose of 42.5 to 50 Gy. An additional dose is given to treated volume as a boost to a portion of the breast. In the early stage of breast cancer, research has shown that the area requiring radiation treatment to prevent the cancer from local recurrence is the breast tissue that surrounds the area where the initial cancer was removed. Accelerated partial breast irradiation (APBI) is an approach that treats only the lumpectomy bed plus a 1-2 cm margin rather than the whole breast and as a result allows accelerated delivery of the radiation dose in four to five days. There has been a growing interest for APBI and various approaches have been developed under phase I-III clinical studies; these include multicatheter interstitial brachytherapy, balloon catheter brachytherapy, conformal external beam radiation therapy (3D-EBRT) and intra-operative radiation therapy (IORT). Balloon-based brachytherapy approaches include MammoSite, Axxent electronic brachytherapy, Contura, hybrid brachytherapy devices. Another indication for breast brachytherapy is reirradiation of local recurrence after mastectomy. Published results of brachytherapy are very promising. We discuss the current status, indications, and technical aspects of breast cancer brachytherapy.

1229 ROBOT-ASSISTED LAPAROSCOPIC INTRAOPERATIVE BRACHYTHERAPY: A PORCINE TRIAL

You have accessJournal of UrologyTechnology & Instruments: Robotics - Malignant Disease & Benign Disease I1 Apr 20121229 ROBOT-ASSISTED LAPAROSCOPIC INTRAOPERATIVE BRACHYTHERAPY: A PORCINE TRIAL Jennifer Yates, Dan Smith, Stephen Musialek, Ravi Munver, Ihor Sawczuk, Samay Jain, and Loren Godfrey Jennifer YatesJennifer Yates Hackensack, NJ More articles by this author , Dan SmithDan Smith Teaneck, NJ More articles by this author , Stephen MusialekStephen Musialek Hackensack, NJ More articles by this author , Ravi MunverRavi Munver Hackensack, NJ More articles by this author , Ihor SawczukIhor Sawczuk Hackensack, NJ More articles by this author , Samay JainSamay Jain Hackensack, NJ More articles by this author , and Loren GodfreyLoren Godfrey Hackensack, NJ More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2012.02.1519AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Intraoperative brachytherapy using an electronic brachytherapy source is currently utilized for dermatologic and breast malignancies. Patients with advanced urologic disease are often treated with multimodal therapy, including surgical excision and postoperative radiotherapy. Delivery of intraoperative brachytherapy at the time of surgery is limited in part by the radiation source and a means of delivering the brachytherapy in a minimally-invasive fashion. The Xoft electronic brachytherapy device is portable and does not require operative room shielding. A minimally-invasive intraoperative radiotherapy (IORT) technique has been developed which utilizes the robotic platform, the Xoft electronic brachytherapy source, and minimally-invasive applicators. The feasibility of applying this system to a pelvic target in the porcine model was explored. METHODS In-vivo trials were conducted at the David Jurist Research Institute at Hackensack University Medical Center after obtaining IACUC Board approval. A DaVinci standard Robotic Surgical System was used to manipulate minimally-invasive brachytherapy applicators and Axxent electronic brachytherapy catheters (Xoft Inc., Sunnyvale, CA). A porcine pelvic target was identified that served as a surrogate for periprostatic tissue in the human patient. RESULTS Trocars were placed in a fashion similar to a prostatectomy template, with three robotic arms (8 mm trocars) and one 12 mm assistant trocar utilized. Two of the robotic arms were equipped with grasping instruments, and the third robotic arm was equipped with a forceps to manipulate the GafChromic paper. The Axxent electronic brachytherapy applicator was advanced through the 12 mm assistant trocar. While the minimally-invasive applicator was held in position with the robotic instruments, the brachytherapy catheter was used to deliver a prescribed brachytherapy treatment plan to the target. The minimally-invasive applicator could access the targeted site. Optimal stability of the applicator required two robotic arms. On average, five minutes were required to introduce, place, and stabilize the applicator. CONCLUSIONS The minimally invasive IORT system described above can be reproducibly deployed in-vivo. Additional in-vivo studies are needed to further characterize systematic and operator dependent variance and perform quantitative dose analysis. © 2012 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 187Issue 4SApril 2012Page: e497 Advertisement Copyright & Permissions© 2012 by American Urological Association Education and Research, Inc.MetricsAuthor Information Jennifer Yates Hackensack, NJ More articles by this author Dan Smith Teaneck, NJ More articles by this author Stephen Musialek Hackensack, NJ More articles by this author Ravi Munver Hackensack, NJ More articles by this author Ihor Sawczuk Hackensack, NJ More articles by this author Samay Jain Hackensack, NJ More articles by this author Loren Godfrey Hackensack, NJ More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

SU-E-T-85: Ionization Chamber Measured Dose-Rate Constant of the Xoft Axxent Electronic Brachytherapy Source

Purpose: To measure the dose‐rate constant of the Xoft Axxent electronic brachytherapy source with an air‐kerma calibrated ionization chamber. Methods: An air‐kerma calibrated chamber was used in TG‐43 geometry (source and chamber in liquid water) to measure the dose rate of the Axxent source at several distances. The air‐kerma strength was determined with the University of Wisconsin Attix free‐air chamber. Since there is no national standard for absorbed dose to water at Axxent energies, this work followed the formalism of AAPM's TG‐61 protocol to obtain dose to water from the air‐kerma calibrated chamber. A Monte Carlo model of the chamber was created to calculate the necessary corrections to use the air‐kerma calibrated chamber to obtain dose to water from chamber measurements. The chamber model was benchmarked with energy dependence simulations. The dose‐rate constant was calculated from chamber measured dose rates and free‐air chamber measured air‐kerma strengths. Results: The simulated energy dependence using the PinPoint chamber model showed agreement to within 4.2% of the measured values. The chamber‐measured dose‐rate constant was 4.6% higher than the Monte Carlo dose‐rate constant and 13% higher than the TLD value, but the difference between the chamber‐measured values and TLD‐measured values decreased as the distance increased. Conclusions: Using an accurate chamber model to calculate corrections allows an air‐kerma calibrated chamber to be used for dose‐rate measurements of a brachytherapy source. The chamber values agree with TLD values as distance increases implying that positioning uncertainties may cause greater discrepancies at shorter distances and the spectrum used for simulations may be more accurate at the larger distances. An air‐kerma calibrated chamber was used to measure the dose‐rate constant of the Axxent source provided corrections were calculated with an accurate chamber model. This work was partially sponsored by Xoft, Inc.

Accelerated Partial Breast Irradiation (APBI): A review of available techniques.

Breast conservation therapy (BCT) is the procedure of choice for the management of the early stage breast cancer. However, its utilization has not been maximized because of logistics issues associated with the protracted treatment involved with the radiation treatment. Accelerated Partial Breast Irradiation (APBI) is an approach that treats only the lumpectomy bed plus a 1-2 cm margin, rather than the whole breast. Hence because of the small volume of irradiation a higher dose can be delivered in a shorter period of time. There has been growing interest for APBI and various approaches have been developed under phase I-III clinical studies; these include multicatheter interstitial brachytherapy, balloon catheter brachytherapy, conformal external beam radiation therapy and intra-operative radiation therapy (IORT). Balloon-based brachytherapy approaches include Mammosite, Axxent electronic brachytherapy and Contura, Hybrid brachytherapy devices include SAVI and ClearPath. This paper reviews the different techniques, identifying the weaknesses and strength of each approach and proposes a direction for future research and development. It is evident that APBI will play a role in the management of a selected group of early breast cancer. However, the relative role of the different techniques is yet to be clearly identified.

The Initial Experience of Electronic Brachytherapy for the Treatment of Non-melanomatous Cutaneous Malignancies

To evaluate the acute adverse effects and early cosmetic outcomes of patients treated with electronic brachytherapy for the treatment of cutaneous malignancies. From July 2009 till March 2010, 34 patients with 40 cutaneous malignancies were treated with Xoft Axxent Electronic Brachytherapy system using surface applicators to a dose of 40.0 Gy in 8 fractions, 5 Gy per fraction, delivered twice weekly with minimum of 48 hour interval. The appropriately sized surface applicator, 10mm, 20mm, 35mm, or 50mm, was selected to allow for complete coverage of target lesion with acceptable margin. CT scan was performed to assess skin depth. The prescription depth was 3-7mm, 5mm for 83% of the lesions, 3mm for 15% of the fractions, and 7mm for the patient with T-cell lymphoma. All patients were treated outside of a linear accelerator vault in CT simulator room. Photographs were taken for all patients at initial consultation and follow-up visits. Acute safety outcomes and cosmetic results were analyzed. Cosmetic results were documented in the patient record using a standardized cosmesis scale. There were 34 T1 lesions and 6 T2 lesions; 38 were primary cancers, and 2 were recurrences. 26 skin lesions were basal cell carcinoma, 12 were squamous cell carcinoma, 1 was Merkle cell carcinoma, and 1 was T-cell lymphoma. 17 lesions were located on the nose, 5 on the ear, 10 on the face, 4 on the scalp, and 4 on the extremities. Median follow-up was 3.2 months (range, 1-7.3). Average treatment time was 6.8 minutes per fraction. 91% developed radiation dermatitis grade 1 or 2 during treatment and resolved by the 1 month, 3 month or 6 month visit. There were no severe (Grade 3 or higher) acute toxicities. 1 patient developed moist desquamation during treatment which resolved at 1-month follow-up. One patient developed hypopigmentation at 3 months, and 3 patients developed hypopigmentation at 6 months. Cosmetic assessments of the treated areas done at various intervals from the last fraction are grouped for reporting: 25 were assessed at 1 month, 17 at 3 months, 8 at 6 months, and 1 at 7 months. The cosmetic results showed 88.0%, 94.1% 71.4%, 100.0% excellent at 1, 3, 6 and 7 months respectively and 12%, 5.9%, and 28.6% showed good results at 1, 3, and 6 months respectively. There was no evidence of tumor recurrence for all lesions. The early outcomes of electronic brachytherapy for the treatment of non-melanomatous cutaneous malignancies appear to show acceptable acute toxicities and favorable early cosmesis. The early results seem comparable to High Dose Rate Brachytherapy. The hypofractionated approach provides patient convenience approach with effective early outcomes. Long-term follow-up is being collected to further assess efficacy and cosmesis.

Initial Results of a Multi-center Trial Utilizing Xoft Axxent Electronic Brachytherapy to Deliver Intraoperative Radiation Therapy in the Treatment of Early-stage Breast Cancer

CONCLUSION Post-operative whole breast radiation therapy (WBRT) has been shown to decrease local cancer recurrence rates by 30%, as well as to improve overall survival compared to surgery alone. However, delivered over a period of 6 to 7 weeks, WBRT can become a burdensome undertaking due to required commitment of time and resources, thus necessitating many women to either elect mastectomy or omit post-operative radiation altogether.

Twelve-Month Follow-Up Results of a Trial Utilizing Axxent Electronic Brachytherapy to Deliver Intraoperative Radiation Therapy for Early-Stage Breast Cancer

Accelerated partial breast irradiation (APBI) is emerging as a valid alternative to whole-breast radiation therapy (WBRT) in breast-conserving therapy (BCT) for early-stage breast cancer. Axxent electronic brachytherapy (EBX) is a form of portable, balloon-based APBI that utilizes an electronic source of kilovoltage irradiation delivery with minimal shielding requirements. As such, EBX becomes a logical and convenient modality for delivery of intraoperative radiation therapy (IORT). We report 1-year results and clinical outcomes of a trial that utilizes EBX to deliver IORT for patients with early-stage breast cancer. Eleven patients were enrolled on an institutional review board (IRB)-approved protocol. Inclusion criteria were patient age >45years, unifocal tumors with infiltrating ductal or ductal carcinoma in situ (DCIS) histology, tumors ≤3cm, and uninvolved lymph nodes. Preloaded radiation plans were used to deliver radiation prescription dose of 20Gy to the balloon surface. The mean time for radiation delivery was 22min; the total mean procedure time was 1h 39min. All margins of excision were negative on final pathology. At mean follow-up of 12months, overall cosmesis was excellent in 10 of 11 patients. No infection, fat necrosis, desquamation, rib fracture or cancer recurrence has been observed. There was no evidence of fibrosis at last follow-up. IORT utilizing EBX is emerging as a feasible, well-tolerated alternative to postsurgical APBI. Further research and longer follow-up data on EBX and other IORT methods are needed to establish the clinical efficacy and safety of this treatment.