Interstitial High Dose Rate Research Articles

CT-guided interstitial HDR-brachytherapy for recurrent glioblastoma multiforme: a20-year single-institute experience.

To report our results of computed tomography-guided interstitial high-dose-rate (HDR) brachytherapy (BRT) in the treatment of patients with recurrent inoperable glioblastoma multiforme (GBM). Between 1995 and 2014, 135patients were treated with interstitial HDR BRT for inoperable recurrent GBM located within previously irradiated volumes. Patient's median age was 57.1years (14-82years). All patients were pretreated with surgery, postoperative external beam radiation therapy (EBRT) and systemic chemotherapy (ChT). The median recurrent tumor volume was 42 cm3 (2-207 cm3). The prescribed HDR dose was median 40 Gy (30-50 Gy) delivered in twice-daily fractions of 5.0 Gy over consecutive days. No repeat surgery or ChT was administered in conjunction with BRT. Survival from BRT, progression-free survival (PFS), toxicity as well as the impact of several prognostic factors were evaluated. At amedian follow-up of 9.2months, the median overall survival following BRT and the median PFS were 9.2 and 4.6months, respectively. Of the prognostic variables evaluated in univariate analysis, extent of surgery at initial diagnosis, tumor volume at recurrence, as well as time from EBRT to BRT reached statistical significance, retained also in multivariate analysis. Eight patients (5.9%) developed treatment-associated complications including intracerebral bleeding in 4patients (2.9%), symptomatic focal radionecrosis in 3patients (2.2%), and severe convulsion in 1patient (0.7%). For patients with recurrent GBM, interstitial HDR BRT is an effective re-irradiation method for even larger tumors providing palliation without excessive toxicity.

Comparison of Planned vs Delivered Doses to Organs at Risk in Patients Treated with Interstitial High-Dose Rate Brachytherapy for Gynecologic Malignancy

Comparison of Planned vs Delivered Doses to Organs at Risk in Patients Treated with Interstitial High-Dose Rate Brachytherapy for Gynecologic Malignancy

Dermatofibrosarcoma protruberans of the scalp treated with customised surface mould high-dose-rate (HDR) brachytherapy: a case report

AbstractDermatofibrosarcoma protuberans (DFSP) is a rare, locally aggressive soft tissue tumor commonly occurring in the trunk or extremities, lesser than 5% being located on the scalp. Surgery is the mainstay of management of this locally infiltrative cutaneous soft tissue sarcoma, with a high probability of recurrence if margin remains positive or inadequate. Adjuvant radiotherapy to a dose of 40–60 Gy decreases this chance of recurrence considerably. Radiotherapy is generally delivered by interstitial HDR brachytherapy, opposed photon or electron beam. We report a case of a 24 year old female, presenting with a small, painless nodule over right frontal area of scalp, diagnosed as DFSP post surgery with close margin that was treated with adjuvant radiation customized HDR surface mould brachytherapy with good local control and cosmesis.

Treatment of hepatic metastases with computed tomography-guided interstitial brachytherapy.

The aim of the present study was to evaluate the efficacy, safety and tolerability of local treatment of liver metastases of various types of cancer using brachytherapy with computed tomography (CT) imaging. Retrospective analysis of 61 patients with unresectable hepatic metastases treated with CT-guided interstitial high dose rate (HDR) brachytherapy of the liver between April 2014 and December 2016 was performed. Patients were treated with a single fractional dose of 15-25 Gy. Statistical analysis was performed on local relapse free survival (LRFS), progression free survival (PFS) and overall survival (OS) rates across the group. In the 6 and 12-month follow-up periods, the 6- and 12-month LRFS rates were 88.7 and 70.7%, PFS rates were 78.1 and 53.8% and the OS rates were 96.7 and 79.6%, respectively. In the Cox regression analysis, the 100% isodose was a statistically significant predictor of LRFS (P=0.01) and PFS (P=0.02), but it was not significant in OS (P=0.07). The 90% isodose was a statistically significant predictor of LRFS (P=0,03) but not significant in PFS (P=0.17) or OS (P=0.25). In all patients, no serious complications were observed. Overall, 30% of patients experienced pain at the injection site, and 50% exhibited nausea or vomiting. In 2 patients, minor subcapsular bleeding occurred without clinical significance, and 1 patient was diagnosed with a pneumothorax that was not clinically significant. Brachytherapy HDR with CT imaging is an effective and safe method of local treatment of liver metastases. The effectiveness of the treatment is probably dose-dependent, and increases with increasing dosage.

Accelerated partial breast irradiation in a single 18 Gy fraction with high-dose-rate brachytherapy: preliminary results.

PurposeTo evaluate the feasibility of acute and chronic toxicity in patients suitable for accelerated partial breast irradiation (APBI) in a single 18 Gy fraction with multicatheter high-dose-rate (HDR) brachytherapy, as well as cosmetic and oncological outcomes.Material and methodsBetween September 2014 and March 2016, twenty consecutive patients with low-risk invasive and ductal carcinoma in situ were treated with interstitial multicatheter HDR brachytherapy in a single 18 Gy fraction.ResultsMedian age was 63.5 years (range, 51-79). Acute toxicity was observed in seven patients, while the pain during following days and hematoma were seen in four patients. With a median follow-up of 24 months, late toxicity was found in one patient with fat necrosis g2 and fibrosis g2 in another patient. The overall survival (OS) and locoregional control (LC) was 100%. Disease-free survival (DFS) and distant control was 95%. Good to excellent cosmetic outcomes were noted in 80% of patients and fair in 4 patients (20%).ConclusionsThis is the first report in the medical literature that focuses on feasibility and acute and chronic toxicity, with a median follow-up of 24 months (range, 20-40). The protocol is viable and convenient. However, a longer follow-up is needed to know chronic toxicity and oncologic outcomes.

Accelerated partial breast irradiation for suitable elderly women using a single fraction of multicatheter interstitial high-dose-rate brachytherapy: Early results of the Single-Fraction Elderly Breast Irradiation (SiFEBI) Phase I/II trial

Purpose/ObjectiveTo evaluate feasibility and early clinical outcomes of a single fraction of multi-catheter interstitial high-dose rate brachytherapy for accelerated partial breast irradiation (APBI) in the elderly. Material/MethodsFrom November 2012 to September 2014, 26 patients (≥70) with early breast cancer were enrolled in a prospective phase II trial (NCT01727011). After lumpectomy, intra-operative catheter implant was performed for post-operative APBI (single fraction 16 Gy). Surveillance was achieved at 1, 3 and 6 months after APBI, then twice a year. Acute toxicity was investigated. Early cosmetic outcome was analyzed (patient, radiation oncologist, 2 observers). Local and regional relapse-free survival, cancer specific survival and overall survival were analyzed. ResultsMedian age was 77 years [69–89]. Median CTV was 41 cc [22-95]. Acute toxicity was observed in 18 pts (70%) with a total of 44 events: G1: 75.7%; G2: 22.8%; G3: 4.5%. Breast fibrosis (31.8%), puncture site inflammation (13.6%) and skin hyperpigmentation (11.4%) were the most frequent side effects. Cosmetic evaluation at 6 months was excellent/good in 88%, 92%, 85% and 88% for patient, radiation oncologist, observer #1 and #2 respectively. With a median follow-up of 37.2 months [35.6-42.3], side effects were G1: 4 pts (15%) and G2: 1 pt (4%). Three-year Local and regional relapse-free survival, cancer specific survival and overall survival rates were 100%, 100%, 100% and 95.2% respectively. ConclusionsFor elderly early breast cancer, a post-operative multi-catheter interstitial high-dose rate brachytherapy single dose (16 Gy) appears feasible. Acute toxicity is acceptable as well as early cosmetic outcome. Oncologic outcome seems encouraging and allows going forward with new clinical trials focusing on single fraction APBI.

A fast inverse treatment planning strategy facilitating optimized catheter selection in image-guided high-dose-rate interstitial gynecologic brachytherapy.

Interstitial high-dose rate (HDR) brachytherapy is an important therapeutic strategy for the treatment of locally advanced gynecologic (GYN) cancers. The outcome of this therapy is determined by the quality of dose distribution achieved. This paper focuses on a novel yet simple heuristic for catheter selection for GYN HDR brachytherapy and their comparison against state of the art optimization strategies. The proposed technique is intended to act as a decision-supporting tool to select a favorable needle configuration. The presented heuristic for catheter optimization is based on a shrinkage-type algorithm (SACO). It is compared against state of the art planning in a retrospective study of 20 patients who previously received image-guided interstitial HDR brachytherapy using a Syed Neblett template. From those plans, template orientation and position are estimated via a rigid registration of the template with the actual catheter trajectories. All potential straight trajectories intersecting the contoured clinical target volume (CTV) are considered for catheter optimization. Retrospectively generated plans and clinical plans are compared with respect to dosimetric performance and optimization time. All plans were generated with one single run of the optimizer lasting 0.6-97.4 s. Compared to manual optimization, SACO yields a statistically significant (P ≤ 0.05) improved target coverage while at the same time fulfilling all dosimetric constraints for organs at risk (OARs). Comparing inverse planning strategies, dosimetric evaluation for SACO and "hybrid inverse planning and optimization" (HIPO), as gold standard, shows no statistically significant difference (P > 0.05). However, SACO provides the potential to reduce the number of used catheters without compromising plan quality. The proposed heuristic for needle selection provides fast catheter selection with optimization times suited for intraoperative treatment planning. Compared to manual optimization, the proposed methodology results in fewer catheters without a clinically significant loss in plan quality. The proposed approach can be used as a decision support tool that guides the user to find the ideal number and configuration of catheters.

Evaluation of interfractional variation of organs and displacement of catheters during high-dose-rate interstitial brachytherapy for gynecologic malignancies

PurposeTo investigate the dosimetric effects due to interfractional changes in catheter position and variation in patient's anatomy during the course of interstitial high-dose-rate (HDR) brachytherapy. Methods and MaterialsA total of 15 patients with either cervical or vaginal cancer underwent interstitial HDR brachytherapy. Interstitial catheters and fiducials were placed under fluoroscopy and intraoperative 3T MRI to confirm the desired catheter placement for adequate target volume coverage. Single plan was generated from first-fraction CT fused with the MRI and used for all fractions of treatment. CT image was acquired before each treatment and registered to the first-fraction CT. Displacement of fiducials and catheters was calculated for each fraction and its effects on dosimetric parameters such as dose covering 90% for high-risk clinical target volume and intermediate-risk clinical target volume and dose to the 2 cm3 of the volume for bladder, rectum, sigmoid, and bowel were studied. ResultsAverage movements of fiducials and catheters were 1.6 mm (range: 0.1–7.1 mm) and 1.7 mm (range: 0.1–4.5 mm), respectively. Overall, deviation of the delivered dose to the target in each fraction was insignificant for all patients (p-value: 0.66 for high-risk clinical target volume and 0.87 for intermediate-risk clinical target volume). The mean dose to organs at risk showed maximum difference up to 0.9, 2.7, 1.6, and 2.1 Gy for bladder, rectum, sigmoid, and bowel, respectively (p-value: 0.88, 0.34, 0.68, and 0.85 for bladder, rectum, sigmoid, and bowel, respectively). ConclusionsThe interfractional dosimetric variation for both target and organs at risk was within clinically acceptable limit throughout the entire course of interstitial HDR-Syed brachytherapy. Only 6% of cases performed replanning, which could be readily identified using CT imaging.

A novel urethral sparing technique for high-dose-rate prostate brachytherapy after transurethral resection of the prostate

PurposeThe purpose of this study was to assess retrospectively the variability of the urethral dose optimized using a Foley catheter versus urethral contrast injected using a new modified triple-lumen catheter, in CT-based high-dose-rate (HDR) prostate brachytherapy of posttransurethral resection of prostate (TURP) patients. Methods and MaterialsAt our institution, there were six post-TURP patients with prostate carcinoma between July 2014 and April 2016 who underwent transperineal interstitial HDR brachytherapy (16 needles). A custom modified triple-lumen catheter was placed to inject contrast into the TURP defect. Three-dimensional optimal plans using inverse planning simulated annealing algorithm was generated according to radiation therapy oncology group dose requirements. Alternative plans were retroactively generated for comparison using standard technique based on a Foley catheter as a urethral constraint volume for each patient with the same weighting factors. We compared the dosimetry parameters in each planning using Wilcoxon's ranked sum nonparametric test. ResultsThe median followup of all patients was 17.5 months. No significant genitourinary or gastrointestinal toxicity was noted using this technique. In the dosimetric analysis, the prostate V100 values and TURP urethral V100 were significantly different between plans with and without the contrast (V100 [mean]: 92.4 [%] vs. 94.4 [%], p = 0.046; TURP UV100 [mean]: 1.4 cc vs. 2.2 cc, p = 0.028). There were no statistical differences in the mean values of planning target volume V150%, V200%, and D90, and each bladder V75 and rectum V75. ConclusionsPost-TURP HDR brachytherapy with urethral contrast showed significantly more volume effect of the TURP defect than that with a Foley catheter alone. Better visualization of the TURP defect should lead to more accurate urethral sparing administration of HDR brachytherapy which is necessary to prevent urethral complication.

Joint deformable liver registration and bias field correction for MR-guided HDR brachytherapy.

In interstitial high-dose rate brachytherapy, liver cancer is treated by internal radiation, requiring percutaneous placement of applicators within or close to the tumor. To maximize utility, the optimal applicator configuration is pre-planned on magnetic resonance images. The pre-planned configuration is then implemented via a magnetic resonance-guided intervention. Mapping the pre-planning information onto interventional data would reduce the radiologist's cognitive load during the intervention and could possibly minimize discrepancies between optimally pre-planned and actually placed applicators. We propose a fast and robust two-step registration framework suitable for interventional settings: first, we utilize a multi-resolution rigid registration to correct for differences in patient positioning (rotation and translation). Second, we employ a novel iterative approach alternating between bias field correction and Markov random field deformable registration in a multi-resolution framework to compensate for non-rigid movements of the liver, the tumors and the organs at risk. In contrast to existing pre-correction methods, our multi-resolution scheme can recover bias field artifacts of different extents at marginal computational costs. We compared our approach to deformable registration via B-splines, demons and the SyN method on 22 registration tasks from eleven patients. Results showed that our approach is more accurate than the contenders for liver as well as for tumor tissues. We yield average liver volume overlaps of 94.0±2.7% and average surface-to-surface distances of 2.02±0.87mm and 3.55±2.19mm for liver and tumor tissue, respectively. The reported distances are close to (or even below) the slice spacing (2.5-3.0mm) of our data. Our approach is also the fastest, taking 35.8±12.8s per task. The presented approach is sufficiently accurate to map information available from brachytherapy pre-planning onto interventional data. It is also reasonably fast, providing a starting point for computer-aidance during intervention.

Ten Year Results of Accelerated Partial Breast Irradiation (APBI) Using Interstitial Multicatheter High Dose Rate Brachytherapy (HDR BT) After Breast Conserving Surgery for Low Risk Invasive In Situ Breast Cancer

Ten Year Results of Accelerated Partial Breast Irradiation (APBI) Using Interstitial Multicatheter High Dose Rate Brachytherapy (HDR BT) After Breast Conserving Surgery for Low Risk Invasive In Situ Breast Cancer

Iridium-Knife: Another knife in radiation oncology

PurposeIntratarget dose escalation with superior conformity is a defining feature of three-dimensional (3D) iridium-192 (192Ir) high-dose-rate (HDR) brachytherapy (BRT). In this study, we analyzed the dosimetric characteristics of interstitial 192Ir HDR BRT for intrathoracic and cerebral malignancies. We examined the dose gradient sharpness of HDR BRT compared with that of linear accelerator–based stereotactic radiosurgery and stereotactic body radiation therapy, usually called X-Knife, to demonstrate that it may as well be called a Knife. Methods and MaterialsTreatment plans for 10 patients with recurrent glioblastoma multiforme or intrathoracic malignancies, five of each entity, treated with X-Knife (stereotactic radiosurgery for glioblastoma multiforme and stereotactic body radiation therapy for intrathoracic malignancies) were replanned for simulated HDR BRT. For 3D BRT planning, we used identical structure sets and dose prescription as for the X-Knife planning. The indices for qualitative treatment plan analysis encompassed planning target volume coverage, conformity, dose falloff gradient, and the maximum dose–volume limits to different organs at risk. ResultsVolume coverage in HDR plans was comparable to that calculated for X-Knife plans with no statistically significant difference in terms of conformity. The dose falloff gradient—sharpness—of the HDR plans was considerably steeper compared with the X-Knife plans. ConclusionsBoth 3D 192Ir HDR BRT and X-Knife are effective means for intratarget dose escalation with HDR BRT achieving at least equal conformity and a steeper dose falloff at the target volume margin. In this sense, it can reasonably be argued that 3D 192Ir HDR BRT deserves also to be called a Knife, namely Iridium-Knife.

Image-guided interstitial high-dose-rate brachytherapy in the treatment of inoperable recurrent head and neck malignancies: An effective option of reirradiation.

In recurrent head and neck cancer, therapeutic options are limited and high-quality evidence is rare. The purpose of this report was to present our experience of CT-guided interstitial high-dose rate (HDR) brachytherapy in 4 challenging cases of inoperable recurrent head and neck cancer. A 53-year-old man with mucosal melanoma of the paranasal sinuses, a 61-year-old man with myofibroblastic sarcoma of the nasal cavity, a 51-year-old woman with nasopharyngeal cancer, and a 44-year-old woman with orbital leiomyosarcoma were treated with reirradiation by HDR brachytherapy after previous comprehensive therapy, including full course external radiotherapy (RT). All patients showed response to brachytherapy with 1 patient experiencing locoregional failure. The mean lesion-specific disease control was 15 months. Currently, 1 patient is alive and 3 patients died after mean 20 months after treatment. In patients with inoperable recurrent head and neck cancer, CT-guided interstitial HDR brachytherapy can play a role in providing palliation and tumor control. © 2017 Wiley Periodicals, Inc. Head Neck 39: E61-E68, 2017.

Electromagnetic tracking (EMT) technology for improved treatment quality assurance in interstitial brachytherapy.

Electromagnetic Tracking (EMT) is a novel technique for error detection and quality assurance (QA) in interstitial high dose rate brachytherapy (HDR‐iBT). The purpose of this study is to provide a concept for data acquisition developed as part of a clinical evaluation study on the use of EMT during interstitial treatment of breast cancer patients. The stability, accuracy, and precision of EMT‐determined dwell positions were quantified. Dwell position reconstruction based on EMT was investigated on CT table, HDR table and PDR bed to examine the influence on precision and accuracy in a typical clinical workflow. All investigations were performed using a precise PMMA phantom. The track of catheters inserted in that phantom was measured by manually inserting a 5 degree of freedom (DoF) sensor while recording the position of three 6DoF fiducial sensors on the phantom surface to correct motion influences. From the corrected data, dwell positions were reconstructed along the catheter's track. The accuracy of the EMT‐determined dwell positions was quantified by the residual distances to reference dwell positions after using a rigid registration. Precision and accuracy were investigated for different phantom‐table and sensor‐field generator (FG) distances. The measured precision of the EMT‐determined dwell positions was ≤ 0.28 mm (95th percentile). Stability tests showed a drift of 0.03 mm in the first 20 min of use. Sudden shaking of the FG or (large) metallic objects close to the FG degrade the precision. The accuracy with respect to the reference dwell positions was on all clinical tables < 1 mm at 200 mm FG distance and 120 mm phantom‐table distance. Phantom measurements showed that EMT‐determined localization of dwell positions in HDR‐iBT is stable, precise, and sufficiently accurate for clinical assessment. The presented method may be viable for clinical applications in HDR‐iBT, like implant definition, error detection or quantification of uncertainties. Further clinical investigations are needed.

SU‐F‐T‐55: Reproducibility of Interstitial HDR Brachytherapy Plans

Purpose:Treating gynecological cancers with interstitial high‐dose‐rate (HDR) brachytherapy requires precise reconstruction of catheter positions to obtain accurate dosimetric plans. In this study, we investigated the degree of reproducibility of dosimetric plans for Syed HDR brachytherapy.Methods:We randomly selected five patients having cervix‐vaginal cancer who were recently treated in our clinic with interstitial HDR brachytherapy with a prescription dose of 25–30 Gy in five fractions. Interstitial needles/catheters were placed under fluoroscopic guidance and intra‐operative 3T MRI scan was performed to confirm the desired catheter placement for adequate target volume coverage. A CT scan was performed and fused with the MRI for delineating high‐risk CTV (HR‐CTV), intermediate‐risk CTV (IR‐CTV) and OARs. HDR treatment plans were generated using Oncentra planning software. A single plan was used for all five fractions of treatment for each patient. For this study, we took the original clinical plan and removed all the reconstructed catheters from the plan keeping the original contours unchanged. Then, we manually reconstructed all the catheters and entered the same dwell time from the first original clinical plan. The dosimetric parameters studied were: D90 for HR‐CTV and IR‐CV, and D2cc for bladder, rectum, sigmoid and bowel.Results:The mean of absolute differences in dosimetric coverage (D90) were (range): 1.3% (1.0–2.0%) and 2.0% (0.9–3.6%) for HR‐CTV and IR‐CTV, respectively. In case of OARs, the mean of absolute variations in D2cc were (range): 4.7% (0.7–8.9%) for bladder, 1.60% (0.3–3.2%) for rectum, 1.6% (0–3.9%) for sigmoid, and 1.8% (0–5.1%) for bowel.Conclusion:Overall, the reproducibility of interstitial HDR plans was within clinically acceptable limit. Observed maximum variation in D2cc for bladder. If number of catchers and dwell points were relatively low or any one catheter was heavily loaded, then reproducibility of the plan was more sensitive to the accuracy of catheter reconstruction.

Interstitial High Dose Rate (HDR) Brachytherapy with Open Laparotomy for Locally Advanced Primary or Recurrent Gynaecological Cancer: Peter MacCallum Cancer Centre Experience

To report the technique and treatment outcomes of open interstitial brachytherapy performed at the Peter MacCallum Cancer Centre between 2007- 2013. Between June 2007 and December 2013, 11 patients were treated with curative intent using open interstitial implants as a radiotherapy boost (in combination with external beam radiotherapy (EBRT) and weekly platinum chemotherapy. Patients had no evidence of nodal or distant metastasis, and were receiving either upfront treatment for carcinoma of the vagina (n=2) or cervix stump (n=1) or isolated vault recurrence following primary surgery (cervix- 4; endometrium - 3; vagina-1). The main rationale for laparotomy was to minimise toxicity to bowel by allowing 1) placement of a spacer between interstitial needles and the bowel 2) adhesion lysis, if required 3) direct visualization of needle placement. RT planning was performed using MRI and CT. With a minimum follow up of 2 years, 10 of 11 patients were alive and 6 patients were disease-free and remained asymptomatic. These patients were either receiving primary treatment or had a prolonged disease-free interval between their initial primary treatment and presentation with recurrent disease. Of the remaining 5 patients, all had either persistent disease or relapsed at primary site. 1 of them developed distant metastasis and died of disease. 2 of these patients progressed in the inguinal nodes. 4 patients were alive with disease at 12 months, 3.5 years, 3 years and 2 years from the date of implant. Open Interstitial Implant is feasible and tolerated with acceptable toxicity. However, patient selection and adequate expertise are of utmost importance.

Interstitial High-Dose Rate (HDR) Brachytherapy: A Risk Adapted Treatment for Breast Cancer

Interstitial High-Dose Rate (HDR) Brachytherapy: A Risk Adapted Treatment for Breast Cancer

The Curie–Da Vinci Connection: 5-Years' Experience With Laparoscopic (Robot-Assisted) Implantation for High-Dose-Rate Brachytherapy of Solitary T2 Bladder Tumors

To report experience and early results of laparoscopic implantation for interstitial brachytherapy (BT) of solitary bladder tumors and the feasibility of a high-dose-rate (HDR) schedule. From December 2009 to April 2015, 57 patients with a T2 solitary bladder tumor were treated in Arnhem with transurethral bladder resection followed by external beam irradiation, applied to the bladder and regional iliac lymph nodes, 40Gy in 20 fractions, 5 fractions per week, and within 1week interstitial HDR BT, in selected cases combined with partial cystectomy and lymph node dissection. The BT catheters were placed via a transabdominal approach with robotic assistance from a Da Vinci robot after a successful initial experience with a nonrobotic laparoscopic approach. The fraction schedule for HDR was 10 fractions of 2.5Gy, 3 fractions per day. This was calculated to be equivalent to a reference low-dose-rate schedule of 30Gy in 60hours. Data for oncologic outcomes and toxicity (Common Toxicity Criteria version 4) were prospectively collected. These modifications resulted in an average postoperative hospitalization of 6days, minimal blood loss, and no wound healing problems. Two patients had severe acute toxicity: 1 pulmonary embolism grade 4 and 1 cardiac death. Late toxicity was mild (n=2 urogenital grade 3 toxicity). The median follow-up was 2years. Using cumulative incidence competing risk analysis, the 2-year overall, disease-free, and disease-specific survival and local control rates were 59%, 71%, 87%, and 82%, respectively. The benefits of minimally invasive surgery for implantation of BT catheters and the feasibility of HDR BT in bladder cancer are documented. The patient outcome and adverse events are comparable to the best results published for a bladder-sparing approach.

Validation of a novel robot-assisted 3DUS system for real-time planning and guidance of breast interstitial HDR brachytherapy.

In current clinical practice, there is no integrated 3D ultrasound (3DUS) guidance system clinically available for breast brachytherapy. In this study, the authors present a novel robot-assisted 3DUS system for real-time planning and guidance of breast interstitial high dose rate (HDR) brachytherapy treatment. For this work, a new computer controlled robotic 3DUS system was built to perform a hybrid motion scan, which is a combination of a 6 cm linear translation with a 30° rotation at both ends. The new 3DUS scanner was designed to fit on a modified Kuske assembly, keeping the current template grid configuration but modifying the frame to allow the mounting of the 3DUS system at several positions. A finer grid was also tested. A user interface was developed to perform image reconstruction, semiautomatic segmentation of the surgical bed as well as catheter reconstruction and tracking. A 3D string phantom was used to validate the geometric accuracy of the reconstruction. The volumetric accuracy of the system was validated with phantoms using magnetic resonance imaging (MRI) and computed tomography (CT) images. In order to accurately determine whether 3DUS can effectively replace CT for treatment planning, the authors have compared the 3DUS catheter reconstruction to the one obtained from CT images. In addition, in agarose-based phantoms, an end-to-end procedure was performed by executing six independent complete procedures with both 14 and 16 catheters, and for both standard and finer Kuske grids. Finally, in phantoms, five end-to-end procedures were performed with the final CT planning for the validation of 3DUS preplanning. The 3DUS acquisition time is approximately 10 s. A paired Student t-test showed that there was no statistical significant difference between known and measured values of string separations in each direction. Both MRI and CT volume measurements were not statistically different from 3DUS volume (Student t-test: p > 0.05) and they were significantly correlated to 3DUS measurement (Pearson test: MRI p < 0.05 and CT p < 0.001). The mean angular separation distance between catheter trajectories segmented from 3DUS and CT images was 0.42° ± 0.24°, while the maximum and mean trajectory separations were 0.51 ± 0.19 and 0.37 ± 0.17 mm, respectively. Overall, the new finer grid has performed significantly better in terms of dosimetric indices. The planning target volume dosimetric indices were not found statistically different between 3DUS and CT planning (Student t-test, p > 0.05). Both the skin and the pectoral muscle dosimetric indices were within ABS guidelines. A novel robot-assisted 3DUS system was designed and validated. To their knowledge, this is the first system capable of performing real-time guidance and planning of breast multicatheter HDR brachytherapy treatments. Future investigation will test the feasibility of using the system in the clinic and for permanent breast brachytherapy.

Use of a 3-dimensional lumpectomy marker for targeting interstitial accelerated partial breast irradiation (APBI).

42 Background: APBI via high-dose-rate (HDR) interstitial catheter implants is an effective, highly customizable method of delivering radiotherapy in breast cancer patients. The technique is amenable to challenging anatomy such as pendulous and/or very small breasts, augmented breasts or superficial lumpectomy sites. The challenge for any APBI technique is identification of the lumpectomy cavity, which can be difficult to visualize after surgery due to post-surgical changes or tissue mobilization for oncoplastic closure. In the past we have used x-ray contrast injected into the cavity to facilitate the radiographic visualization of the cavity or individual clips. A new 3-D tissue marker (BioZorb, Focal Therapeutics, Inc.) has recently been used by surgeons to mark the area of the lumpectomy cavity at greatest risk for recurrence. In effect this acts as a communication tool to help guide the radiation oncologist for treatment planning and delivery. We examined this device for target volume localization in 15 patients receiving interstitial HDR APBI. Methods: The marker mimicking the tumor size was surgically sutured at the base of the lumpectomy cavity in 15 patients with T1T2N0N1 breast cancer with a variety of closure techniques. The clinical target volume (CTV) was taken as the 3-D outline made by the six embedded titanium markers and a 2 cm margin expanded around that structure (the planning target volume, PTV). Multiple interstitial catheters were spaced 1.5 cm apart within the PTV and 34 Gy was delivered in 10 fractions delivered over 5 treatment days. Results: The marker/CTV was easily visualized on CT images, without clips or injected contrast, making catheter insertion and planning more efficient, easier, and reproducible. The CTV volume was small (12.5 +/- 8.7cc; mean +/- SD, range 4.4–33.4cc) as was the PTV (137 +/- 60cc; mean +/- SD, range 75–327cc), relative to typical HDR APBI implants. Conclusions: The technique facilitated identification of the lumpectomy cavity in all patients treated regardless of surgical closure technique. The unambiguous margin demarcation facilitated target contouring and reproducibility for APBI.