Long-term treatment of metastatic adenoid cystic carcinoma with sequential brachytherapy and stereotactic body radiotherapy.

Adenoid cystic carcinoma is a malignancy that is difficult to treat and often metastasizes to the lung. Systemic chemotherapies are not effective for this tumor type, thus local therapies are frequently used. Here, we report a case demonstrating the use of extensive ablative interventions in controlling the progression of metastatic adenoid cystic carcinoma. A patient with adenoid cystic carcinoma developed numerous metastases to his lungs and liver. Local ablative therapies including interstitial brachytherapy and SBRT were used to treat approximately 80 different metastases over the course of a decade. Over 850 brachytherapy seeds were implanted in this patient, and the tumor control and patient outcome were good. As of the most recent follow-up in March 2024, the patient has survived for approximately 12 years since his diagnosis of adenoid cystic carcinoma. To our knowledge, this case represents the most brachytherapy treatments reported in a single patient. It highlights the utility of interstitial brachytherapy and SBRT in treating extensive lung and liver metastases.

HDR brachytherapy of rectal cancer using a novel grooved-shielding applicator design.

PURPOSE: The aim of this work was to design a novel high-dose rate (HDR) ((192)Ir) brachytherapy applicator for treatment of rectal carcinomas that uses tungsten shielding for possibly improved dosimetric results over commercial brachytherapy applicator(s). METHODS: A set of 15 single-depth applicators and one dual-depth applicator were designed and simulated using Monte Carlo (MCNPX). All applicators simulated were high-density tungsten alloy cylinders, 16-mm in diameter, and 60-mm long, with longitudinal grooves within which an (192)Ir source can be placed. The single-depth designs varied regarding the number and depth of these grooves, ranging from 8 to 16 and 1-mm to 3-mm, respectively. The dual-depth design had ten channels, each of which had two depths at which the source could be placed. Optimized treatment plans were generated for each design on data from 13 treated patients (36 fractions) with asymmetrical clinical target volumes (CTVs). All results were compared against the clinically treated plans which used intracavitary mold applicator (ICMA), as well as a recently designed, highly automated, and collimated intensity modulation device named dynamic modulated brachytherapy (DMBT) device. RESULTS: All applicator designs outperformed the ICMA in every calculated dosimetric criteria, except the total dwell times (∼30% increase). There were clear, but relative, tradeoffs regarding both the number of channels and the depth of each channel. Overall, the 12-channel, 1-mm depth, and 14-channel 2-mm depth designs had the best results of the simpler designs, sparing the healthy rectal tissues the most while achieving comparable CTV coverage with the dose heterogeneity index and lateral spill doses improving by over 10% and the contralateral healthy rectum dose dropping over 30% compared to ICMA. The ten-channel dual-depth design outperformed each single-depth design, yielding the best coverage and sparing. CONCLUSIONS: New grooved tungsten HDR-brachytherapy devices have been designed and simulated. The results of this work attest to the capability of these new, highly anisotropic, intelligently shielded applicators to limit dose to healthy tissues while maintaining a conformal prescription dose to the CTV.

Dynamic modulated brachytherapy (DMBT) for rectal cancer.

PURPOSE: All forms of past and current high-dose-rate brachytherapy utilize immobile applicators during treatment delivery. The only moving part is the source itself. This paradigm misses an important degree of freedom that, if explored, can in some instances produce previously unachievable dose conformality; that is, the dynamic motion of the applicator itself during treatment delivery. Monte Carlo and treatment planning simulations were used to illustrate the potential benefits of moving applicators for rectal cancer applications in particular. This concept is termed dynamic modulated brachytherapy (DMBT). METHODS: The DMBT system uses a high-density, 18.0 g∕cm(3), 45 mm long tungsten alloy shield, cylindrical in shape, with a small window on one side to encapsulate a (192)Ir source, to create collimation that results in a highly directional beam profile. This shield can be dynamically translated and rotated, using an attached robotic arm, during treatment to create a volumetric modulated arc therapy-type delivery, but from inside the rectal cavity. Monte Carlo simulations and planning optimization algorithms were developed inhouse to evaluate the effectiveness of this new approach using 36 clinical treatment plans comprised of 13 patients each treated using the intracavitary mold applicator (ICMA, Nucletron, The Netherlands) to quantify the potential clinical benefit. The prescription dose was 10 Gy∕fx and the group had an average clinical target volume of 9.0 ± 3.5 cm(3). Ideal phantom geometries were used to evaluate the impact of various shield dimensions and designs on the resulting plan quality. RESULTS: Simulations of ideal phantom geometries found that shields as small as 10 mm in diameter can produce high quality plans. For the clinical patient cases, compared to the ICMA, for equal prescription tumor coverage, the DMBT plans provided >30% decrease in D(5) (high dose volume) resulting in a ∼40% decrease in dose heterogeneity index. In addition, mean dose and D(98) showed a reduction (typically 40%-60%) on all critical structures evaluated. However, for a 10 Gy prescribed dose there was an increase in total treatment time on average from 7.6 to 20.8 min for a source with an air-kerma strength of 40.25 kU (10 Ci). CONCLUSIONS: Dosimetric properties of a novel DMBT system have been described and evaluated. Comparison with the ICMA commercial applicator has shown it to be a prospective step forward in high-dose-rate brachytherapy (192)Ir technology. Dynamic motion of an applicator during treatment, for any applicator and site in general, can provide additional degrees of freedom that, if properly considered, can potentially increase the plan quality significantly.

Outcomes for patients with cervical cancer treated with extended-field intensity-modulated radiation therapy and concurrent cisplatin.

OBJECTIVE: To evaluate disease outcomes and toxicity in patients with cervical cancer treated with extended-field intensity-modulated radiotherapy. MATERIALS AND METHODS: We included all patients treated with extended-field intensity-modulated radiotherapy and concurrent weekly cisplatin from 2003 to 2010 at 2 institutions. Overall survival and disease-free survival were estimated using Kaplan-Meier method. Locoregional failure (LRF), distant failure, and competing mortality were calculated using cumulative incidence functions. Acute and late toxicity were graded using Common Terminology Criteria for Adverse Events (CTCAE) and Radiation Therapy Oncology Group late radiation morbidity scoring criteria, respectively. RESULTS: The study included 21 patients, 14 and 20 of which had positive para-aortic and pelvic nodes, respectively. The median follow-up was 22 months. Eighteen-month overall survival and disease-free survival were 59.7% (95% confidence interval [CI], 41.2%-86.4%) and 42.9% (95% CI, 26.2%-70.2%). Eighteen-month cumulative incidences of LRF, distant failure, and competing mortality were 9.5% (95% CI, 1.5-26.8%), 42.9% (95% CI, 21.3-62.9%), and 4.8% (95% CI, 0.3-20.2%), respectively. Eighteen-month cumulative incidences of late grade 3 or higher-grade genitourinary and gastrointestinal toxicity were 4.8% (95% CI, 0.2%-20.3%) and 0%, respectively. CONCLUSIONS: Intensity-modulated extended-field radiotherapy was associated with low rates of late toxicity and LRF. High rates of distant failure indicate that this group of patients could benefit from intensified systemic therapy.

SU-E-T-317: Dynamic Modulated Brachytherapy (DMBT): Robotic Applicator Design.

PURPOSE: To investigate the hardware necessary for implementing our Dynamic Modulated Brachytherapy (DMBT) treatment concept for rectal cancer. METHODS: The DMBT robot has three major parts: 1) shield and shield delivery module, 2) controlling module, and 3) DMBT controlling and monitoring software. The shield is a tungsten alloy cylinder (r=0.95cm, l=4.5cm) with a 5.5mm rectangular-shaped opening. The shield is controlled by an aluminum pipe with gear set (1:3) and linear actuator (2mm/turn). An Ir-192 radiation source will be placed through the aluminum pipe. The power source is a Nema-17 stepping motor with EvoDrive ST-17 (EVA Robotics, Queensland, Australia) and USB-6009 DAQ (National Instrument, Austin, TX). With our in-house operating program through LabView (National Instrument, Austin, TX), we can make and load plans for treatment as well as testing. Checking the shield position is also possible through the operating program. For safety, a lexan sheath tube and emergency buttons are built-in. RESULTS: The DMBT robot has 2 degrees of freedom, which are linear translation and rotation. With our power delivery system, the spatial resolutions are 0.0125mm (linear stage) and 0.012Ës (rotation). In 0.5s, motors achieve the desired position with the maximum speeds 450 step/s (1Ës), 7,500 step/s (30Ës), and 12,000 step/s (5mm). Four registers are triggered with USB-6009 DAQ signals. The operating program includes gages for checking shield position, loading treatment plans, and safety buttons. CONCLUSIONS: In all, we have designed the hardware components of the DMBT system for rectal cancer. For treatment, the system needs more elements to support the DMBT robot; lexan sheath tube holder, DMBT robot security joint, and a system for reducing friction between the tube and shield. We will also refine our system to be more compact by using DC servomotors instead of the larger Nema-17 stepping motors.

Initial clinical experience with the Strut-Adjusted Volume Implant brachytherapy applicator for accelerated partial breast irradiation.

PURPOSE: Accelerated partial breast irradiation is becoming increasingly popular. The Cianna single-entry high-dose-rate applicator, Strut-Adjusted Volume Implant (SAVI, Cianna Medical, Aliso Viejo, CA), contains peripheral struts allowing greater planning flexibility for small-breasted women, technically easier insertion, and normal tissue exposure minimization. This study evaluates early clinical experience. METHODS AND MATERIALS: Thirty patients treated with the SAVI with a median followup of 12 months were evaluated. The median age was 59.5. Tumor size averaged 0.9cm. Fifteen cancers were ductal carcinoma in situ (50%), 1 was invasive lobular (3.3%), 4 were tubular (6.7%), and the rest infiltrating ductal (40%). Most of them were estrogen receptor (ER) positive (90%). Nine women (30%) were premenopausal. RESULTS: Dosimetry was outstanding with median V90, V150, and V200 of 96.2%, 24.8, and 12.8cc. There were no symptomatic seromas, and one report of asymptomatic fat necrosis seen on mammogram at 1 year. In patients who had skin spacing of less than 1cm, the median skin dose was 245cGy/fraction. The median rib and lung dose per fraction for those patients with either structure less than 1cm was 340 and 255cGy (75% of prescribed dose), respectively. There have been no local recurrences to date. CONCLUSIONS: Early clinical experience with the SAVI demonstrates the ease of placement of a single-entry brachytherapy device combined with the increased dose modulation of interstitial brachytherapy. Dose to normal structures has remained exceedingly low. Almost half of evaluated patients were not candidates for other single-entry brachytherapy devices because of skin spacing or breast size, demonstrating an expansion of candidates for single-entry partial breast brachytherapy.