Preoperative treatment planning with intraoperative optimization can achieve consistent high-quality implants in prostate brachytherapy

A CALL TO ARMS: The Case for MRI-Assisted Radiosurgery (MARS) vs. Stereotactic Body Radiation Therapy or Robotic-Assisted Radical Prostatectomy

Brachytherapy using permanent seed implants has been an effective treatment for prostate cancer. However, seeds will migrate after implant, thus making the evaluation of post-implant dosimetry difficult. In this study, we developed a computer program to simulate seed migration and analyzed dosimetric changes due to seed migration at various migration amounts. The study was based on 14 patients treated with Pd-103 at the James Cancer Hospital. Modeling of seed migration, including direction, distance as well as day of migration, was based on clinical observations. Changes of commonly used dosimetric parameters as a function of migration amount (2, 4, 6 mm respectively), prostate size (from 20 to 90 cc), and prostate region (central vs peripheral) were studied. Change of biological outcome (tumor control probability) due to migration was also estimated. Migration reduced prostate D90 to 99+/-2% of original value in 2 mm migration, and the reduction increased to 94+/-6% in 6 mm migration. The reduction of prostate dose led to a 14% (40%) drop in the tumor control probability for 2 mm (6 mm) migration, assuming radiosensitive tumors. However, migration has less effect on a prostate implanted with a larger number of seeds. Prostate V100 was less sensitive to migration than D90 since its mean value was still 99% of original value even in 6 mm migration. Migration also showed a different effect in the peripheral region vs the central region of the prostate, where the peripheral mean dose tended to drop more significantly. Therefore, extra activity implanted in the peripheral region during pre-plan can be considered. The detrimental effects of migration were more severe in terms of increasing the dose to normal structures, as rectum V50 may be 70% higher and urethra V100 may be 50% higher in the case of 6 mm migration. Quantitative knowledge of these effects is helpful in treatment planning and post-implant evaluation.

The University of Texas Southwestern and Providence Portland Medical Center have both treated a number of Stereotactic Body Radiotherapy patients in recent years. This presentation will be a joint presentation between Lech Papiez Ph.D. from UT Southwestern and Joanna Harper M.Sc. at PPMC. The talk will be divided into the following segments and one or both speakers may speak on any given segment 1. Background and Rationale 2. Equipment and Methodology 3. Treatment Planning and plan evaluation 4. Specific Sites and Challenges 5. Results 6. Future Directions 7. Conclusions Learning Objectives: After watching this presentation the attendee should have a familiarity with methods of planning and treating SBRT patients. The attendee should also have an understanding of the reasons for the success and growth of SBRT future plans for additional usages of this technique and get some idea why the radiation oncology community is so excited about the future potential of this relatively new modality.

Biochemical outcomes for patients with intermediate risk prostate cancer treated with I-125 interstitial brachytherapy monotherapy

Use of 3D transabdominal ultrasound imaging for treatment planning in cervical cancer brachytherapy: Comparison to magnetic resonance and computed tomography

To achieve the optimal treatment goal, radiobiological parameters have to evaluate and predict the outcome of this treatment plan in terms of both TCP and NTCP. Different types of radiobiological model were used to achieve prescribed treatment dose of radiation during the tumor control. Where TCP models play an important role in order to achieve desired dose to the tumor. A suitable NTCP model was theoretically found among different models that can be used in treatment plan evaluation. Theoretically, six different radiobiological dose response models were analyzed in this project. Lyman–Kutcher–Burman, Critical element, critical volume, Relative Seriality, Parallel architecture, Weibull distribution models were analyzed from the derivation. All models were discussed elaborately with its various parameters and were used in the calculation of normal tissue complication probability during the treatment in radiotherapy. Further, all models were compared with each other. The models denote the dose for 50% complication probability (D50) parameters is the most commonly used radiobiological models for the normal tissues. The functional subunit response models (critical element & Relative seriality, Critical Volume, parallel architecture) are used in the derivation of the formulae for the normal tissue. Since all complicated NTCP model predict same as the simple NTCP model that is Lyman–Kutcher–Burman model as well as it is computationally efficient. Also Lyman–Kutcher–Burman model can be used in different treatment planning system incorporating with other model. For this reason, our suggested model is Lyman–Kutcher–Burman NTCP model which can be used in treatment plan evaluation. After analyzing six different model of NTCP, finding of the study is the treatment plan evaluation in where Lyman–Kutcher–Burman model is the best model for biological plan evaluation.

Patterns of relapse and outcomes following Single-Fraction High-Dose-Rate brachytherapy monotherapy for Intermediate-Risk prostate cancer.

Monte Carlo (MC) simulations of radiation transport may provide more accurate estimates of dose delivered to permanent implant brachytherapy patients compared to the clinical AAPM TG-43 dose calculation paradigm. However, MC dose calculations are burdened by sensitivity to required modelling assumptions, especially with low energy photon sources typical of permanent implant brachytherapy (20-30 keV). MC simulations require a detailed virtual model of the patient, often derived from post-treatment CT images containing imaging artifacts due to the brachytherapy sources present during image acquisition. For the first time, several metallic artifact reduction algorithms, of varied approach, are explored in phantom and clinical prostate brachytherapy CT images to determine their ability to mitigate artifacts and to quantify their sensitivity on dose calculations. Permanent implant breast brachytherapy is a challenge to model due to the radiologically different adipose and fibrogland soft tissues in and near the treatment volume. Further, the geometry of breast treatments is especially non-water like suggesting the clinical TG-43 dose calculation paradigm may yield significantly inaccurate results. The dose calculation sensitivity due to metallic artifact reduction, tissue differentiation approach and simulated tissue composition are explored in permanent implant breast brachytherapy clinical patient data, in addition to presenting differences between realistic and TG-43 conditions for target and organ-at-risk dosimetric endpoints. This work presents the largest cohort of permanent implant prostate brachytherapy MC dose calculations published to-date, providing quantitative differences between realistic and TG-43 conditions and a detailed sensitivity analysis of organ-at-risk simulated tissue composition, calcification modelling approach and calcification tissue composition. Clinical radiotherapy is increasingly considering radiobiological endpoints to judge treatment quality. Various radiobiological indices are evaluated using a large cohort of prostate brachytherapy dose calculations to explore the differences between these models and differences between applying TG-43 or realistic tissue MC dose calculations. This work identifies challenges related to applying dose calculations in heterogeneous tissue models to existing radiobiological models. The contributions of this thesis improve the understanding of realistic brachytherapy dose calculations, pave the way for the clinical adoption of Monte Carlo dose calculations and challenge and build upon the current frontier of radiobiological modelling for permanent implant brachytherapy.

The dose to critical structures plays a very important role in treatment plan evaluation and forms a major challenging parameter in radiotherapy treatment planning. In this study, a simple index, Plan Normal tissue complication Index (PNI) has been proposed for treatment plan evaluation based on the dose to surrounding critical structures. To demonstrate the proposed index, four different critical treatment sites that include the prostate, upper abdominal cancer, lung, and head and neck were selected for this study. A software progam (PNIcalc) has been developed to compute the PNI from the exported dose-volume histogram data and from the tissue tolerance data published by Emami et al. and Kehwar et al. The software also shows the parameters that exceed the threshold limits of dose-volume parameters presented in the QUANTEC recommendations (2010). In all the studied cases, PNI gave an overall picture of the dose received by the critical structures and also indicate the fractional volume exceeding the tolerance limit. The proposed index, PNI gives a quick comparison and selection of treatment plans that result in reduced dose to the critical structures. It can be used as an additional tool for routine treatment plan evaluation in external beam radiotherapy.

Standardization of prostate brachytherapy treatment plans

Non-invasive imaging plays a crucial role in the management of patients with primary gliomas. Since their introduction in the clinical setting, 18F/11C-Choline and afterwards 18F/68Ga-PSMA and 18F-Fluciclovine gained widespread in the evaluation of prostate cancer. More recently, multiple reports and original studies documented the utility of these prostate cancer positron emission tomography (pcPET) radiotracers in the assessment of gliomas. To evaluate the potential role of pcPET radiotracers currently used in brain tumors, we present a review of these radiotracers in the different settings of the diagnostic work-up of patients with gliomas. A literature search regarding articles published from 2000 to July 2020 regarding the use of pcPET radiotracers in gliomas was performed in the PubMed and Scopus databases, using combinations of search strings including the following words and acronyms: “choline”, “CHO”, “prostatic specific membrane antigen”, “PSMA”, “Fluciclovine”, FACBC, “Positron Emission Tomography”, “PET”, “brain tumor”, “glioma”, “glioblastoma”. A total of 27 articles about pcPET radiotracers (Choline N = 14, PSMA N = 7; Fluciclovine N = 6) evaluating every phase of disease in glioma (diagnosis, grading and prognosis, evaluation of recurrence, treatment planning and response to therapy assessment) were discussed. pcPET tracers present potential utility in the differential diagnosis, estimation of prognosis, evaluation of recurrence and treatment planning in patients with glioma. These radiotracers may hold a complementary role in conjunction with advanced MRI techniques in the non-invasive grading of gliomas.

During the last 2 years we have been working on developing a DICOM-RT (Radiation Therapy) ePR (Electronic Patient Record) with decision support that will allow physicists and radiation oncologists during their decision-making process. This ePR allows offline treatment dose calculations and plan evaluation, while at the same time it compares and quantifies treatment planning algorithms using DICOM-RT objects. The ePR framework permits the addition of visualization, processing, and analysis tools, which combined with the core functionality of reporting, importing and exporting of medical studies, creates a very powerful application that can improve the efficiency while planning cancer treatments. Usually a Radiation Oncology department will have disparate and complex data generated by the RT modalities as well as data scattered in RT Information/Management systems, Record & Verify systems, and Treatment Planning Systems (TPS) which can compromise the efficiency of the clinical workflow since the data crucial for a clinical decision may be time-consuming to retrieve, temporarily missing, or even lost. To address these shortcomings, the ACR-NEMA Standards Committee extended its DICOM (Digital Imaging & Communications in Medicine) standard from Radiology to RT by ratifying seven DICOM RT objects starting in 1997 [1,2]. However, they are not broadly used yet by the RT community in daily clinical operations. In the past, the research focus of an RT department has primarily been developing new protocols and devices to improve treatment process and outcomes of cancer patients with minimal effort dedicated to integration of imaging and information systems. Our attempt is to show a proof-of-concept that a DICOM-RT ePR system can be developed as a foundation to perform medical imaging informatics research in developing decision-support tools and knowledge base for future data mining applications.

Purpose: To develop an exact approach to direct aperture optimization that can be applied to a large class of IMRT fluence map optimization (FMO) models that employ convex treatment plan evaluation criteria in the objective function and/or constraints and test its ability to obtain high-quality treatment plans using a reduced number of apertures and limited beam-on-time. Method and Materials: An exact approach was developed that iteratively adds high-quality deliverable apertures while the treatment plan quality can be improved. The most promising new apertures are found by solving a subproblem, which can account for deliverability constraints imposed by the multi-leaf collimator (MLC) system such as interdigitation, connectedness, or rectangular shapes. The approach can explicitly account for transmission through the leaves that are not shielded by backup jaws in the MLC system. It was compared to the traditional method of solving a beamlet-based FMO model followed by a leaf-sequencing step to determine apertures and intensities. Results: For a set of ten clinical head-and-neck cancer cases, treatment plans comparable in quality to plans obtained by the traditional method were obtained with a reduction of more than 75% in number of apertures and a reduction of more than 50% in beam-on-time, with only a modest increase in computational effort. The importance of incorporating transmission effects when assessing treatment plan quality was shown as well. Conclusion: This work provides a direct aperture optimization method that incorporates many physical and biological treatment plan evaluation criteria, accounts for leaf transmission effects, and significantly limits both total treatment time and beam-on-time. The iterative nature of the approach allows it to be implemented in an interactive system where a trade-off can be made between treatment plan efficiency and efficacy. The ability of the approach to account for different MLC deliverability constraints allows for a comparison of different MLC architectures.

5024 Background: In 1999, the American Brachytherapy Society (ABS) recommended brachytherapy monotherapy (BT) be limited to low-risk prostate cancer, in part because a high-impact 1998 publication suggested that intermediate or high-risk disease had worse outcomes with BT than with external beam radiation (EBRT) or radical prostatectomy (RP). We studied temporal patterns of BT use before and after the 1999 ABS published guidelines as compared with 4 other treatment options. Methods: A retrospective analysis was performed of all men with T1c-T3cN0M0 prostate cancer treated definitively in the United States from 1990 to 2011 in the Cancer of the Prostate Strategic Urologic Research Endeavor (CaPSURE) registry. Logistic regression was used to estimate adjusted odds ratios (AOR) comparing BT use with other treatment groups between the 1990-1998 and 1999-2011 periods, controlling for age, disease characteristics, and clinic site type. Results: 8128 men received BT (n=1117), BT+EBRT (n=313), EBRT alone (n=596), EBRT+androgen deprivation therapy (ADT, n=613), or RP (n=5489) for modified D’Amico low (n=3506), intermediate (n=2938) or high-risk (n=1684) disease. By t-tests, BT patients were younger than either EBRT or EBRT+ADT patients (both p<0.001), older than RP patients (p<0.001), and had lower risk disease than men in any of the four treatment groups (all Cochran-Mantel-Haenszel chi-square p<0.001). BT comprised 6.1% and 16.6% of all treatments in 1990-1998 and 1999-2011, respectively (Pearson p<0.01). The odds of BT use remained increased after adjusting for potential confounders (AOR 4.50, p<0.001). Increased BT use was seen only among low (AOR 5.06, p<0.001) and intermediate-risk patients (AOR 4.59, p<0.001). Among men with low or intermediate-risk disease, BT use increased compared with EBRT (AORLOW 10.00; AORINT 12.66, both p<0.001), EBRT+ADT (AORLOW 2.90, p=0.0037; AORINT 2.15, p=0.0041) and RP (AORLOW 4.76; AORINT5.10, both p<0.001). Conclusions: Despite national guidelines to the contrary, brachytherapy monotherapy for intermediate-risk prostate cancer increased over time relative to other treatments. Further studies are needed to identify factors that contribute to this evidence-practice gap.

PurposeHigh dose-rate prostate brachytherapy has been implemented in Sweden in the late 1980s and early 1990s in six clinics using the same schedule: 20 Gy in two fractions combined with 50 Gy in 25 fractions with external beam radiation therapy. Thirty years have passed and during these years, various aspects of the treatment process have developed, such as ultrasound-guided imaging and treatment planning system. An audit was conducted, including a questionnaire and treatment planning, which aimed to gather knowledge about treatment planning methods in Swedish clinics.Material and methodsA questionnaire and a treatment planning case (non-anatomical images) were sent to six Swedish clinics, in which high-dose-rate prostate brachytherapy is performed. Treatment plans were compared using dosimetric indices and equivalent 2 Gy doses (EQD2). Treatment planning system report was used to compare dwell positions and dwell times.ResultsFor all the clinics, the planning aim for the target was 10.0 Gy, but the volume to receive the dose differed from 95% to 100%. Dose constraints for organs at risk varied with up to 2 Gy. The dose to 90% of target volume ranged from 10.0 Gy to 11.1 Gy, equivalent to 26.0 Gy EQD2 and 31.3 Gy EQD2, respectively. Dose non-homogeneity ratio differed from 0.18 to 0.32 for clinical target volume (CTV) in treatment plans and conformity index ranged from 0.52 to 0.59 for CTV.ConclusionsDose constraints for the organs at risk are showing a larger variation than that reflected in compared treatments plans. In all treatment plans in our audit, at least 10 Gy was administered giving a total treatment of 102 Gy EQD2, which is in the upper part of the prescription doses published in the GEC/ESTRO recommendations.