Purpose/Objective(s) To implement an efficient Prostate SABR program into a regional service without real-time seed-tracking capability utilizing automated template-based planning. Materials/Methods Our regional service uses multileaf collimator linear accelerators which are not equipped to perform real-time seed-tracking prompting the exploration of alternatives to mitigate the risk of tumor motion during treatment. A protocol was developed using EVIQ Guidelines as well as PACE-B and PACE-C clinical trial constraints. A treatment planning template was developed using a treatment planning software with a single 10MV FFF beam to minimize treatment delivery time, minimizing the risk of intra-fraction motion. Using scripting 200 plans were calculated and dosimetric criteria exported without therapist intervention. Plans were analyzed using ideal, minor, or major violation criterion. A Cone Beam Computer Tomography (CBCT) protocol was developed to optimize image quality; without increasing image acquisition time. An Intra-fraction CBCT protocol was developed for post treatment review to assess possible variation during treatment and patient stability. A Surface Guided Radiation Therapy (SGRT) protocol was developed to assist with monitoring during treatment. Results A treatment Planning Template developed using 200 plans achieved clinically acceptable plans over 80% of the time with no intervention. The clinical template met treatment criteria or required only minor changes in 95% of patients. Running the template via script allowed 57% more plans to be assessed for template performance, giving increased confidence that dosimetric results can be consistent without therapist intervention. Treatment delivery quality was assessed using routine Physics Quality Assurance (QA) methods. 30 plans were delivered on an arc check with all plans passing QA with a minimum pass rate of 95% using Gamma Analysis with 2% and 2mm. Treatment delivery time was assessed for 30 plans with an average delivery time of 90 seconds. Use of template-based planning allowed consistent plan quality, improved efficiency, and consistent treatment delivery times. The use of scripting further enhanced efficiency. Data from pre-treatment CBCT’s, Intra-Fraction CBCT and SGRT will allow assessment of patient stability. Conclusion An efficient Prostate SABR program can be successfully implemented in a regional service without real-time seed-tracking. Template-based planning allows shorter planning time frames and more consistent treatment plans and treatment delivery times. Script-based planning allowed more plans to be assessed for template performance, increasing confidence that dosimetric results can be consistent without therapist intervention. The use of Intra-Faction CBCT in conjunction with SGRT will allow verification of patient stability during treatment.

Purpose: To investigate the sensitivity and specificity of a novel verification methodology for image‐guided skin HDR brachytherapy plans using a TRAK‐based reasonableness test, compared to a typical manual verification methodology. Methods: Two methodologies were used to flag treatment plans necessitating additional review due to a potential discrepancy of 3 mm between planned dose and clinical target in the skin. Manual verification was used to calculate the discrepancy between the average dose to points positioned at time of planning representative of the prescribed depth and the expected prescription dose. Automatic verification was used to calculate the discrepancy between TRAK of the clinical plan and its expected value, which was calculated using standard plans with varying curvatures, ranging from flat to cylindrically circumferential. A plan was flagged if a discrepancy >10% was observed. Sensitivity and specificity were calculated using as a criteria for true positive that >10% of plan dwells had a distance to prescription dose >1 mm different than prescription depth (3 mm + size of applicator). All HDR image‐based skin brachytherapy plans treated at our institution in 2013 were analyzed. Results: 108 surface applicator plans to treat skin of the face, scalp, limbs, feet, hands or abdomen were analyzed. Median number of catheters was 19 (range, 4 to 71) and median number of dwells was 257 (range, 20 to 1100). Sensitivity/specificity were 57%/78% for manual and 70%/89% for automatic verification. Conclusion: A check based on expected TRAK value is feasible for irregularly shaped, image‐guided skin HDR brachytherapy. This test yielded higher sensitivity and specificity than a test based on the identification of representative points, and can be implemented with a dedicated calculation code or with pre‐calculated lookup tables of ideally shaped, uniform surface applicators.

Topical therapies can suppress mycosis fungoides (MF) but none appear curative. We previously reported that low-dose radiation (LDR, 4 gray x 2) could lead to remission and malignant T cell depletion in skin. We now extend our findings in 11 patients. Before therapy malignant T cells were on average 29% of the total T cell population as measured by TCR sequencing (HTS). 8 weeks after LDR 9/11 patients had a complete response (CR), 1 had a partial response (PR) and 1 had stable disease (SD). In patients with CR, malignant T cells were reduced by 99%. 3 patients had eradication of the clone and remaining patients had on average 3.3 malignant T cells/100ng of DNA, down from 1,335 /100ng DNA before therapy. The total number of T cells in skin decreased by 4-fold after therapy but benign T cells were relatively spared. 38% of the benign T cell clones present in skin before therapy were also present after. LDR also led to recruitment of new T cell clones into skin; new benign clones were 51% of the total T cell population after therapy. We carried out NanoString based immune profiling to further characterize the effects of LDR. Pretreatment MF skin expressed many pro-inflammatory genes including chemokines and cytokine receptors as well as markers of cellular exhaustion including PD-1 and Tim-3. This inflammatory/exhausted phenotype was completely reversed by LDR in patients with CR. 8 weeks after therapy post-radiation biopsies were indistinguishable from normal skin by using principal component analysis. One patient each with PR and SD had persistent inflammatory signatures and continued expression of exhaustion associated genes. In summary, LDR was highly effective in 80% of MF patients and has led to long-term clinical cures extending up to five years. LDR led to complete or near eradication of malignant T cells from skin and complete normalization of the MF-associated inflammatory/exhausted gene signature.

Purpose To update brachytherapy recommendations for pretreatment evaluation, treatment, and dosimetric issues for thoracic brachytherapy for lung cancer. Methods and Materials Members of the American Brachytherapy Society with expertise in thoracic brachytherapy updated recommendations for thoracic brachytherapy based on literature review and clinical experience. Results The American Brachytherapy Society consensus guidelines recommend the use of endobronchial brachytherapy for disease palliation in patients with central obstructing lesions, particularly in patients who have previously received external beam radiotherapy. The use of interstitial implants after incomplete resection may improve outcomes and provide enhanced palliation. Early reports support the use of CT-guided intratumoral volume implants within clinical studies. The use of brachytherapy routinely after sublobar resection is not generally recommended, unless within the confines of a clinical trial or a registry. Conclusions American Brachytherapy Society recommendations for thoracic brachytherapy are provided. Practitioners are encouraged to follow these guidelines and to develop further clinical trials to examine this treatment modality to increase the evidence base for its use.

Purpose: Contemporary brachytherapy treatment planning systems-(TPS) include the applicator model libraries to improve digitization; however, the library of surface-flap-applicators-(SFA) is not incorporated into the commercial TPS. We propose the dynamic library-(DL) for SFA and investigate if such library can eliminate applicator reconstruction, source activation and dose normalization. Methods: DL was generated for the SFA using the C++class libraries of the Visualization Toolkit-(VTK) and Qt-application framework for complete abstraction of the graphical interface. DL was designed such that the user can initially choose the size of the applicator that corresponds to the one clinically placed to the patient. The virtual applicator-(VA) has an elastic property so that it can be registered to the clinical CT images with a real applicator-(RA) on it. The VA and RA matching is performed by adjusting the position and curvature of the VA. The VA does not elongate or change its size so each catheter could always be at a distance of 5mm from the skin and 10mm apart from the closest catheter maintaining the physical accuracy of the clinical setup. Upon the applicator placement, the dwell positions were automatically activated, and the dose is normalized to the prescription depth. The accuracy of source positioning was evaluated using various applicator sizes. Results: The accuracy of the applicator placement was in the sub-millimeter range. The time-study reveals that up to 50% of the planning time can be saved depending on the complexity of the clinical setup. Unlike in the classic approach, the planning time was not highly dependent on the applicator size. Conclusion: The practical benefits of the DL of the SFA were demonstrated. The time demanding planning processes can be partially automated. Consequently, the planner can dedicate effort to fine tuning, which can result in the improvement of the quality of treatment plans in surface brachytherapy.

IMPORTANCE Cutaneous T-cell lymphoma (CTCL) of the hands and feet can be challenging to treat and cause significant disability for patients. Although CTCL is a highly radiosensitive tumor, the complex topography of acral surfaces presents challenges to achieving homogeneous superficial dosing of traditional electron beam therapy. In addition, traditional dosing may result in substantial acute cutaneous toxic effects. Recent reports demonstrate that low-dose palliative radiotherapy may be as effective as traditional regimens in CTCL. High dose-rate (HDR) brachytherapy allows for control of the depth of radiation penetration over complex curved surfaces. This study investigated the role of low-dose HDR brachytherapy for acral CTCL lesions.OBSERVATIONS Six patients with a total of 8 acral CTCL lesions received low-dose HDR brachytherapy during a 3-year period. Rapid improvement and clinical clearance were observed in all treated lesions with minimal to no acute cutaneous toxic effects. During a mean follow-up period of 15.8 months, 1 lesion recurred locally; the remaining 7 lesions had sustained clinical remission. No long-term sequelae were observed.CONCLUSIONS AND RELEVANCE This case series demonstrates that low-dose HDR brachytherapy provides excellent palliation for local control of acral CTCL lesions, offering homogeneous, controlled dosing for complex topographic sites with minimal to no cutaneous toxic effects.

Purpose:Most HDR brachytherapy treatment planning systems (TPS) use TG‐43 formalism to calculate dose without including transit dose corrections. Historically, measurement of this contribution has required sophisticated apparatus unavailable in most hospitals. We use Matrixx to investigate several scenarios where transit dose contribution may effect a clinical treatment.Methods:Treatment plans were generated using Oncentra Brachy TPS (Version 4.3.0.410, Nucletron ) on a CT scan of a 24‐catheter Freiburg applicator (Nucletron ) laid flat on the MatriXX (IBA) detector. This detector is an array of 1020 parallel plate ion chambers. All 24 catheters were digitized and dwells within a central square region of 5×5cm of the applicator were activated. Each of the active catheters had 6 dwells in increments of 1.0cm. The plans were normalized to 10mm. This places the 100% isodose line at the correct effective point of measurement, which lies half‐way between the parallel plates of the ion chambers. It is also within the clinically relevant treatment depth for superficial applications. A total of 6 plans were delivered for 3 prescription doses, 1Gy, 2Gy and 4Gy using source activities of 2.9Ci and 11.2Ci. The MatriXX array was operated to capture dosimetric snaps every 500ms and yielded an integral dose at the end of treatment.Results:A comparison of integral dose from 2 different source activities shows that the transit dose contribution is larger when the source activity is higher. It is also observed that the relative transit dose contribution decreases as prescription dose increases. This is quantified by the Gamma analysis.Conclusion:We have demonstrated that the Matrixx detector can be used to evaluate the contribution for a HDR source during transit from the HDR afterloader to a dwell location, and between adjacent dwell locations.

Purpose: There are unique obstacles to implementing the MatriXX ionchamber array as a QA tool in Brachytherapy given that the device is designed for use in the MV energy range. One of the challenges we investigate is the affect of acquisition rates on dose measurement accuracy for HDR treatment plans. Methods: A treatment plan was optimized in Oncentra Brachy TPS to deliver a planar dose to a 5×5cm region at 10mm depth. The applicator was affixed to the surface of the MatriXX array. The plan was delivered multiple times using a Nucleatron HDR afterloader with a 2.9Ci Ir192 source. For each measurement the sampling rate of the MatriXX movie mode was varied (30ms and 500ms). This experiment was repeated with identical parameters, following a source exchange, with an 11.2Ci Ir192 source. Finally, a single snap measurement was acquired. Analysis was preformed to evaluate the fidelity of the dose delivery for each iteration of the experiment. Evaluation was based on the comparison between the measured and TPS predicted dose. Results: Higher sample rates induce a greater discrepancy between the predicted and measured dose. Delivering the plan using a lower activity source also produced greater discrepancy in the measurement due to the increased delivery time. Analyzing the single snap measurement showed little difference from the 500ms integral dose measurement. Conclusion: The advantage of using movie mode for HDR treatment delivery QA is the ability for real time source tracking in addition to dose measurement. Our analysis indicates that 500ms is an optimal frame rate.