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Purpose: Plan reconstruction for permanent implant prostate brachytherapy is the process of determining the correspondence between planned and implanted seeds in postimplant analysis. Plan reconstruction informs many areas of brachytherapy quality assurance, including the verification of seed segmentation, misplacement and migration assessment, implant simulations, and the dosimetry of mixed-activity or mixed-species implants. Methods: An algorithm has been developed for stranded implants which uses the interseed spacing constraints imposed by the suture to improve the accuracy of reconstruction. Seventy randomly selected clinical cases with a mean of 23.6 (range 18-30) needles and mean density of 2.0 (range 1.6-2.6) 2.0 (range 1.6-2.6) seeds/cm3 were automatically reconstructed and the accuracy compared to manual reconstructions performed using a custom 3D graphical interface. Results: Using the automatic algorithm, the mean accuracy of the assignment relative to manual reconstruction was found to be 97.7±0.5%. Fifty-two of the 70 cases (74%) were error-free; of seeds in the remaining cases, 96.7±0.3% were found to be attributed to the correct strand and 97.0±0.3% were correctly connected to their neighbors. Any necessary manual correction using the interface is usually straightforward. For the clinical data set tested, neither the number of seeds or needles, average density, nor the presence of clusters was found to have an effect on reconstruction accuracy using this method. Conclusions: Routine plan reconstruction of stranded implants can be performed with a high degree of accuracy to support postimplant dosimetry and quality analyses. [ABSTRACT FROM AUTHOR]

Purpose: The optimal SABR treatment delivery schedule in stage I non-small cell lung cancer (NSCLC) remains unclear. This population-based study investigated grade ≥2 toxicity rates, local failure (LF), and overall survival (OS) in patients treated with 48 Gy in 4 fractions scheduled every other day versus daily with weekends and consecutive daily without weekends., Methods and Materials: Between January 2019 and June 2022, treatment records using 48 Gy in 4 fractions were extracted from a provincial cancer registry and grouped by delivery as every other day, daily with weekends, or consecutive daily without weekends. Toxicity events were recorded using National Cancer Institute Common Terminology Criteria for Adverse Events, version 5.0. The Kaplan-Meier method was used to compute OS and LF was calculated using cumulative incidence methods with death as a competing risk. Cox regression analyses and Fine-Gray modeling was used to assess for variables associated with OS and LF, respectively., Results: Of 404 patients meeting study criteria, 190, 111, and 103 received SABR every other day, daily with weekends, and consecutive daily without weekends, respectively. More patients receiving SABR daily with weekends were medically inoperable and more patients receiving SABR consecutive daily without weekends had tumors abutting the chest wall. Median follow-up time was 29.5 months (IQR, 19.2-38.4 months). Overall toxicity was low, with crude rates of acute and late grade ≥2 toxicity not being statistically different among the groups. No grade 4 or 5 toxicities were recorded. LF rates at 24 months were not different at 7.5% (95% CI, 3.7-11.3), 9.5% (95% CI, 3.9-15.1), and 11.0% (95% CI, 4.9-17.2) for the every other day, daily with weekends, and consecutive daily without weekends groups, respectively (P = .60). Schedules of daily with weekends and consecutive daily without weekends were not associated with LF. Similarly, no significant differences in median OS were found among the every other day, daily with weekends, and consecutive daily without weekends groups at 47.5 months (95% CI, 39.26-55.74), 52.7 months (95% CI, 34.7-70.7), and 49.0 months (95% CI, 31.6-66.4), respectively. Schedules of daily with weekends and consecutive daily without weekends were not associated with OS., Conclusions: This population-based study demonstrated no statistically significant differences in grade ≥2 toxicity rates, LF, and OS for patients with stage I NSCLC treated with lung SABR using 48 Gy in 4 fractions delivered every other day, daily with weekends, and consecutive daily without weekends. Patient convenience and optimization of resources may be considered when choosing a lung SABR treatment delivery schedule., Competing Interests: Disclosures Sarah Baker has received honoraria from AstraZeneca unrelated to this work. Devin Schellenberg has received honoraria for multidisciplinary presentations and discussions from AstraZeneca, Pfizer, and BMS unrelated to this work; has participated in advisory boards for AstraZeneca unrelated to this work; and is employed in a leadership position as Provincial Director of Radiation Oncology at BC Cancer. Benjamin Mou has received honoraria from Amgen, AstraZeneca, and Bristol Myers Squibb unrelated to this work. The other authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 American Society for Radiation Oncology. Published by Elsevier Inc. All rights reserved.)

Purpose: To quantify changes in prostate size and seed movement over time after transperineal implantation of stranded 125 I seeds, and to determine their impact on prostate dosimetry., Methods: CT and MR (T2, balanced steady-state free precession) image triplets were acquired on days 0, 3, 10, and 30 for a cohort of 20 patients and registered automatically. Prostate contours were drawn on MR-T2 images; seeds were found and matched in successive CT images. Prostate volume and dimensions, seed movements, and prostate dose metrics V200, V150, V100 and D90 were calculated, and their dynamic behaviors quantified in an operationally defined prostate coordinate system., Results: Cohort-averaged reductions in prostate A-P dimension (∼8%) and L-R dimension (∼5%) inferred from seed movements agreed with those obtained from contour measurements, whereas prostate volume and S-I dimension (implant direction) reductions inferred from seed movements were overestimated by about 30%. Average overall seed movement was 4.8 ± 3.0 mm, of which the only identifiable systematic component was resolution of prostate edema. Cohort-averaged ratios of prostate V200, V150, V100, and D90 on day 30 relative to day 0 were 1.67, 1.33, 1.02, and 1.08, respectively., Conclusions: Postimplant prostate size reduction in the SI (implant) direction cannot reliably be inferred from stranded seed movements. Apart from large-scale migration, residual seed movements relative to the prostate after accounting for edema resolution appear to be random. Prostate V100 and D90 changes 30 days post implant are modest, whereas those for V150 and V200 are substantial., (Copyright © 2024 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.)

Purpose: The optimal sequencing of local and systemic therapy for oligometastatic cancer has not been established. This study retrospectively compared progression-free survival (PFS), overall survival (OS), and SABR-related toxicity between upfront versus delay of systemic treatment until progression in patients in the SABR-5 trial., Methods and Materials: The single-arm phase 2 SABR-5 trial accrued patients with up to 5 oligometastases across SABR-5 between November 2016 and July 2020. Patients received SABR to all lesions. Two cohorts were retrospectively identified: those receiving upfront systemic treatment along with SABR and those for whom systemic treatment was delayed until disease progression. Patients treated for oligoprogression were excluded. Propensity score analysis with overlap weighting balanced baseline characteristics of cohorts. Bootstrap sampling and Cox regression models estimated the association of delayed systemic treatment with PFS, OS, and grade ≥2 toxicity., Results: A total of 319 patients with oligometastases underwent treatment on SABR-5, including 121 (38%) and 198 (62%) who received upfront and delayed systemic treatment, respectively. In the weighted sample, prostate cancer was the most common primary tumor histology (48%) followed by colorectal (18%), breast (13%), and lung (4%). Most patients (93%) were treated for 1 to 2 metastases. The median follow-up time was 34 months (IQR, 24-45). Delayed systemic treatment was associated with shorter PFS (hazard ratio [HR], 1.56; 95% CI, 1.15-2.13; P = .005) but similar OS (HR, 0.90; 95% CI, 0.51-1.59; P = .65) compared with upfront systemic treatment. Risk of grade 2 or higher SABR-related toxicity was reduced with delayed systemic treatment (odds ratio, 0.35; 95% CI, 0.15-0.70; P < .001)., Conclusions: Delayed systemic treatment is associated with shorter PFS without reduction in OS and with reduced SABR-related toxicity and may be a favorable option for select patients seeking to avoid initial systemic treatment. Efforts should continue to accrue patients to histology-specific trials examining a delayed systemic treatment approach., (Crown Copyright © 2024. Published by Elsevier Inc. All rights reserved.)

Background: Radiotherapy delivery regimens can vary between a single fraction (SF) and multiple fractions (MF) given daily for up to several weeks depending on the location of the cancer or metastases. With limited evidence comparing fractionation regimens for oligometastases, there is support to explore toxicity levels to nearby organs at risk as a primary outcome while using SF and MF stereotactic ablative radiotherapy (SABR) as well as explore differences in patient-reported quality of life and experience., Methods: This study will randomize 598 patients in a 1:1 ratio between the standard arm (MF SABR) and the experimental arm (SF SABR). This trial is designed as two randomized controlled trials within one patient population for resource efficiency. The primary objective of the first randomization is to determine if SF SABR is non-inferior to MF SABR, with respect to healthcare provider (HCP)-reported grade 3-5 adverse events (AEs) that are related to SABR. Primary endpoint is toxicity while secondary endpoints include lesional control rate (LCR), and progression-free survival (PFS). The second randomization (BC Cancer sites only) will allocate participants to either complete quality of life (QoL) questionnaires only; or QoL questionnaires and a symptom-specific survey with symptom-guided HCP intervention. The primary objective of the second randomization is to determine if radiation-related symptom questionnaire-guided HCP intervention results in improved reported QoL as measured by the EuroQoL-5-dimensions-5levels (EQ-5D-5L) instrument. The primary endpoint is patient-reported QoL and secondary endpoints include: persistence/resolution of symptom reporting, QoL, intervention cost effectiveness, resource utilization, and overall survival., Discussion: This study will compare SF and MF SABR in the treatment of oligometastases and oligoprogression to determine if there is non-inferior toxicity for SF SABR in selected participants with 1-5 oligometastatic lesions. This study will also compare patient-reported QoL between participants who receive radiation-related symptom-guided HCP intervention and those who complete questionnaires alone., Trial Registration: Clinicaltrials.gov identifier: NCT05784428. Date of Registration: 23 March 2023., (© 2024. The Author(s).)

Background and Purpose: Stereotactic ablative radiotherapy (SABR) for oligometastases may improve survival, however concerns about safety remain. To mitigate risk of toxicity, target coverage was sacrificed to prioritize organs-at-risk (OARs) during SABR planning in the population-based SABR-5 trial. This study evaluated the effect of this practice on dosimetry, local recurrence (LR), and progression-free survival (PFS)., Methods: This single-arm phase II trial included patients with up to 5 oligometastases between November 2016 and July 2020. Theprotocol-specified planning objective was to cover 95 % of the planning target volume (PTV) with 100 % of the prescribed dose, however PTV coverage was reduced as needed to meet OAR constraints. This trade-off was measured using the coverage compromise index (CCI), computed as minimum dose received by the hottest 99 % of the PTV (D99) divided by the prescription dose. Under-coverage was defined as CCI < 0.90. The potential association between CCI and outcomes was evaluated., Results: 549 lesions from 381 patients were assessed. Mean CCI was 0.88 (95 % confidence interval [CI], 0.86-0.89), and 196 (36 %) lesions were under-covered. The highest mean CCI (0.95; 95 %CI, 0.93-0.97) was in non-spine bone lesions (n = 116), while the lowest mean CCI (0.71; 95 % CI, 0.69-0.73) was in spine lesions (n = 104). On multivariable analysis, under-coverage did not predict for worse LR (HR 0.48, p = 0.37) or PFS (HR 1.24, p = 0.38). Largest lesion diameter, colorectal and 'other' (non-prostate, breast, or lung) primary predicted for worse LR. Largest lesion diameter, synchronous tumor treatment, short disease free interval, state of oligoprogression, initiation or change in systemic treatment, and a high PTV Dmax were significantly associated with PFS., Conclusion: PTV under-coverage was not associated with worse LR or PFS in this large, population-based phase II trial. Combined with low toxicity rates, this study supports the practice of prioritizing OAR constraints during oligometastatic SABR planning., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Purpose: SABR may improve survival in patients with oligometastases, but for some lesions, safe delivery of SABR may require a reduction in delivered dose or target coverage. This study assessed the association between target coverage compromise and oncologic and survival outcomes., Methods and Materials: Patients with a controlled primary malignancy and 1 to 5 oligometastases were randomized (1:2) between standard of care (SOC) treatment and SOC plus SABR. In patients receiving SABR, the target dose coverage was reduced to meet organ at risk (OAR) constraints, if necessary. The D99 value (minimum dose received by the hottest 99% of the planning target volume [PTV]) was used as a measure of PTV coverage for each treatment plan, and the relationship between the coverage compromise index (CCI, defined as D99/prescription dose) and patient outcomes was assessed., Results: Sixty-two patients in the SABR arm had dosimetric information available and a total of 109 lesions were evaluated. The mean CCI per lesion was 0.96 (95% CI, 0.56-1.61). Of the 109 lesions evaluated, 29.4% (n = 32) required coverage compromise (CCI <0.9). Adrenal metastases required coverage compromise in 100% of analyzed lesions (n = 7). CCI was not significantly associated with lesional control, adverse events, overall survival (OS), or progression-free survival (PFS)., Conclusions: Target compromise was required in a substantial minority of cases, but PTV coverage was not associated with OS, progression-free survival, or lesional control. This suggests that OAR constraints used for SABR treatments in the oligometastatic setting should continue to be prioritized during planning., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Purpose: A subset of patients with oligometastatic cancer experience early widespread cancer dissemination and do not benefit from metastasis-directed therapy such as SABR. This study aimed to identify factors associated with early polymetastatic relapse (PMR)., Methods and Materials: The SABR-5 trial was a single arm phase 2 study conducted at all 6 regional cancer centers across British Columbia (BC), Canada. SABR for oligometastases was only offered on trial. Patients with up to 5 oligometastatic lesions (total, progressing, or induced) received SABR to all lesions. Patients were 18 years of age or older, Eastern Cooperative Oncology Group 0 to 2 and life expectancy ≥6 months. This secondary analysis evaluated factors associated with early PMR, defined as disease recurrence within 6 months of SABR, which is not amenable to further local treatment. Univariable and multivariable analyses were performed using binary logistic regression. The Kaplan-Meier method and log-rank tests assessed PMR-free survival and differences between risk groups, respectively., Results: Between November 2016 and July 2020, 381 patients underwent treatment on SABR-5. A total of 16% of patients experienced PMR. Worse performance status (Eastern Cooperative Oncology Group 1-2 vs 0; hazard ratio [HR] = 2.01, P = .018), nonprostate/breast histology (HR = 3.64, P <.001), and oligoprogression (HR = 3.84, P <.001) were independent predictors for early PMR. Risk groups were identified with median PMR-free survival ranging from 5 months to not yet reached at the time of analysis. Rates of 3-year overall survival were 0%, 53% (95% confidence interval [CI], 48-58), 77% (95% CI, 73-81), and 93% (95% CI, 90-96) in groups 1 to 4, respectively (P <.001)., Conclusions: Four distinct risk groups for early PMR are identified, which differ significantly in PMR-free survival and overall survival. The group with all 3 risk factors had a median PMR-free survival of 5 months and may not benefit from local ablative therapy alone. This model should be externally validated with data from other prospective trials., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Purpose: Despite increasing utilization of SABR for oligometastatic cancer, prospective outcomes are lacking. The purpose of this study was to determine progression-free survival (PFS), local control (LC), and prognostic factors from the population-based phase 2 SABR-5 trial., Methods and Materials: The SABR-5 trial was a single-arm phase 2 study with the primary endpoint of toxicity, conducted at the 6 regional cancer centers across British Columbia (BC), Canada, during which time SABR for oligometastases was only offered on trial. Patients with up to 5 oligometastases (total or not controlled by prior treatment and including induced oligometastatic disease) underwent SABR to all lesions. Patients were 18 years of age or older, had an Eastern Cooperative Oncology Group score of 0 to 2, and had life expectancy ≥ 6 months. The secondary outcomes of PFS and LC are presented here., Results: Between November 2016 and July 2020, 381 patients underwent SABR on trial. Median follow-up was 27 months (interquartile range, 18-36). Median PFS was 15 months (95% confidence interval [CI], 12-18). LC at 1 and 3 years were 93% (95% CI, 91-95) and 87% (95% CI, 84-90), respectively. On multivariable analysis, increasing tumor diameter (hazard ratio [HR], 1.09; P < .001), declining performance status (HR, 2.13; P < .001), disease-free interval <18 months (HR, 1.52; P = .003), 4 or more metastases at SABR (HR, 1.48; P = .048), initiation or change in systemic treatment (HR, 0.50; P < .001), and oligoprogression (HR, 1.56; P = .008) were significant independent predictors of PFS. Tumor diameter (sub-hazard ratio [SHR], 1.28; P < .001), colorectal histology (SHR, 4.33; P = .002), and "other" histology (SHR, 3.90; P < .001) were associated with worse LC., Conclusions: In this population-based cohort including patients with genuine oligometastatic, oligoprogressive, and induced oligometastatic disease, the median PFS was 15 months and LC at 3 years was 87%. This supports ongoing efforts to randomize patients in phase 3 trials, even outside the original 1 to 5 metachronous oligometastatic paradigm., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Importance: After the publication of the landmark SABR-COMET trial, concerns arose regarding high-grade toxic effects of treatment with stereotactic ablative body radiotherapy (SABR) for oligometastases., Objective: To document toxic effects of treatment with SABR in a large cohort from a population-based, provincial cancer program., Design, Setting, and Participants: From November 2016 to July 2020, 381 patients across all 6 cancer centers in British Columbia were treated in this single-arm, phase 2 trial of treatment with SABR for patients with oligometastatic or oligoprogressive disease. During this period, patients were only eligible to receive treatment with SABR in these settings in trials within British Columbia; therefore, this analysis is population based, with resultant minimal selection bias compared with previously published SABR series., Interventions: Stereotactic ablative body radiotherapy to up to 5 metastases., Main Outcomes and Measures: Rate of grade 2, 3, 4, and 5 toxic effects associated with SABR., Findings: Among 381 participants (122 women [32%]), the mean (SD; range) age was 68 (11.1; 30-97) years, and the median (range) follow-up was 25 (1-54) months. The most common histological findings were prostate cancer (123 [32%]), colorectal cancer (63 [17%]), breast cancer (42 [11%]), and lung cancer (33 [9%]). The number of SABR-treated sites were 1 (263 [69%]), 2 (82 [22%]), and 3 or more (36 [10%]). The most common sites of SABR were lung (188 [34%]), nonspine bone (136 [25%]), spine (85 [16%]), lymph nodes (78 [14%]), liver (29 [5%]), and adrenal (15 [3%]). Rates of grade 2, 3, 4, and 5 toxic effects associated with SABR (based on the highest-grade toxic effect per patient) were 14.2%; (95% CI, 10.7%-17.7%), 4.2% (95% CI, 2.2%-6.2%), 0%, and 0.3% (95% CI, 0%-0.8%), respectively. The cumulative incidence of grade 2 or higher toxic effects associated with SABR at year 2 by Kaplan-Meier analysis was 8%, and for grade 3 or higher, 4%., Conclusions and Relevance: This single-arm, phase 2 clinical trial found that the incidence of grade 3 or higher SABR toxic effects in this population-based study was less than 5%. Furthermore, the rates of grade 2 or higher toxic effects (18.6%) were lower than previously published for SABR-COMET (29%). These results suggest that SABR treatment for oligometastases has acceptable rates of toxic effects and potentially support further enrollment in randomized phase 3 clinical trials., Trial Registration: ClinicalTrials.gov Identifier: NCT02933242.

Background: Bone metastases in the lower spine and pelvis are effectively palliated with radiotherapy (RT), though this can come with side effects such as radiation induced nausea and vomiting (RINV). We hypothesize that high rates of RINV occur in part because of the widespread use of inexpensive simple unplanned palliative radiotherapy (SUPR), over more complex and resource intensive 3D conformal RT, such as volumetric modulated arc therapy (VMAT)., Methods: This is a randomized, multi-centre phase III trial of SUPR versus VMAT. We will accrue 250 patients to assess the difference in patient-reported RINV. This study is powered to detect a difference in quality of life between patients treated with VMAT vs. SUPR., Discussion: This trial will determine if VMAT reduces early toxicity compared to SUPR and may provide justification for this more resource-intensive and costly form of RT., Trial Registration: Clinicaltrials.gov identifier: NCT03694015 . Date of registration: October 3, 2018.

Background: Oligometastases refer to a state of disease where cancer has spread beyond the primary site, but is not yet widely metastatic, often defined as 1-3 or 1-5 metastases in number. Stereotactic ablative radiotherapy (SABR) is an emerging radiotherapy technique to treat oligometastases that require further prospective population-based toxicity estimates., Methods: This is a non-randomized phase II trial where all participants will receive experimental SABR treatment to all sites of newly diagnosed or progressing oligometastatic disease. We will accrue 200 patients to assess toxicity associated with this experimental treatment. The study was powered to give a 95% confidence on the risk of late grade 4 toxicity, anticipating a < 5% rate of grade 4 toxicity., Discussion: SABR treatment of oligometastases is occurring off-trial at a high rate, without sufficient evidence of its efficacy or toxicity. This trial will provide necessary toxicity data in a population-based cohort, using standardized doses and organ at risk constraints, while we await data on efficacy from randomized phase III trials., Trial Registration: Registered through clinicaltrials.gov NCT02933242 on October 14, 2016 prospectively before patient accrual.

Purpose: Current methods of low dose rate brachytherapy source strength verification for sources preloaded into needles consist of either assaying a small number of seeds from a separate sample belonging to the same lot used to load the needles or performing batch assays of a subset of the preloaded seed trains. Both of these methods are cumbersome and have the limitations inherent to sampling. The purpose of this work was to investigate an alternative approach that uses an image-based, autoradiographic system capable of the rapid and complete assay of all sources without compromising sterility., Methods: The system consists of a flat panel image detector, an autoclavable needle holder, and software to analyze the detected signals. The needle holder was designed to maintain a fixed vertical spacing between the needles and the image detector, and to collimate the emissions from each seed. It also provides a sterile barrier between the needles and the imager. The image detector has a sufficiently large image capture area to allow several needles to be analyzed simultaneously.Several tests were performed to assess the accuracy and reproducibility of source strengths obtained using this system. Three different seed models (Oncura 6711 and 9011 (125)I seeds, and IsoAid Advantage (103)Pd seeds) were used in the evaluations. Seeds were loaded into trains with at least 1 cm spacing., Results: Using our system, it was possible to obtain linear calibration curves with coverage factor k = 1 prediction intervals of less than ±2% near the centre of their range for the three source models. The uncertainty budget calculated from a combination of type A and type B estimates of potential sources of error was somewhat larger, yielding (k = 1) combined uncertainties for individual seed readings of 6.2% for (125)I 6711 seeds, 4.7% for (125)I 9011 seeds, and 11.0% for Advantage (103)Pd seeds., Conclusions: This study showed that a flat panel detector dosimetry system is a viable option for source strength verification in preloaded needles, as it is capable of measuring all of the sources intended for implantation. Such a system has the potential to directly and efficiently estimate individual source strengths, the overall mean source strength, and the positions within the seed-spacer train.

Purpose: To describe in detail British Columbia (BC) Cancer Agency (BCCA) Provincial Prostate Brachytherapy (PB) Quality Assurance (QA) Program., Methods and Materials: The BCCA PB Program was established in 1997. It operates as one system, unified and supported by electronic and information systems, making it a single PB treatment provider for province of BC and Yukon. To date, >4000 patients have received PB (450 implants in 2011), making it the largest program in Canada. The Program maintains a large provincial prospective electronic database with records on all patients, including disease characteristics, risk stratification, pathology, preplan and postimplant dosimetric data, follow-up of prostate-specific antigen, and toxicity outcomes., Results: QA was an integral part of the program since its inception. A formal QA Program was established in 2002, with key components that include: unified eligibility criteria and planning system, comprehensive database, physics and oncologist training and mentorship programs, peer review process, individual performance outcomes and feedback process, structured continuing education and routine assessment of the program's dosimetry, toxicity and prostate-specific antigen outcomes, administration and program leadership that promotes a strong culture of patient safety. The emphasis on creating a robust, broad-based network of skilled providers has been achieved by the program's requirements for training, education, and the QA process., Conclusions: The formal QA process is considered a key factor for the success of cancer control outcomes achieved at BCCA. Although this QA model may not be wholly transferable to all PB programs, some of its key components may be applicable to other programs to ensure quality in PB and patient safety., (Crown Copyright © 2013. Published by Elsevier Inc. All rights reserved.)

Purpose: To demonstrate that manual prostate segmentation in transrectal ultrasound images can be replaced with semiautomatic segmentation., Methods and Materials: Semiautomatic segmentation using a tapered ellipsoid model was applied to transrectal ultrasound images. Region-based volumetric evaluation was performed between original and physician-reviewed semiautomatic contours. For dosimetric assessment, treatment plans generated on semiautomatic contours were overlaid on physician-reviewed semiautomatic contours and dose parameters were computed. To establish a threshold for the acceptable amount of dosimetric degradation below which the adoption of semiautomatic planning is unacceptable, the range of variability in dosimetric quality attributed to manual variability was obtained and compared with that of semiautomatic contours., Results: An average volume error (1-Dice similarity coefficient) of less than 7% between semiautomatic and manual volumes (140 cases) was obtained. The difference between the mean V(100) of plans created for semiautomatic contours then overlaid on physician-reviewed semiautomatic contours and the original V(100) values, that is, before overlaying on the physician-reviewed contours (41 cases) was lower than 5%. An average total duration of 2-4min, which includes algorithm initialization, 11.67±3.57s algorithm time, and contour modification is required per case. This algorithm is being used at the British Columbia Cancer Agency and to this date has been applied for the treatment of more than 600 patients., Conclusions: In terms of volumetric and dosimetric accuracy, the proposed algorithm is a suitable replacement for manual segmentation in the context of our planning technique. The benefits are shorter segmentation times; greater consistency; less reliance on user experience; and smooth, symmetric contours., (Copyright © 2013 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.)

Purpose: In postimplant dosimetry for prostate brachytherapy, dose is commonly calculated using the TG-43 1D formalism, because seed orientations are difficult to determine from CT images, the current standard for the procedure. However, the orientation of stranded seeds soon after implantation is predictable, as these seeds tend to maintain their relative spacing, and orient themselves along the implant trajectory. The aim of this study was to develop a method for determining seed orientations from reconstructed strand trajectories, and to use this information to investigate the dosimetric impact of applying the TG-43 2D formalism to clinical postimplant analysis., Methods: Using in-house software, the preplan to postimplant seed correspondence was determined for a cohort of 30 patients during routine day-0 CT-based postimplant dosimetry. All patients were implanted with stranded-seed trains. Spline curves were fit to each set of seeds composing a strand, with the requirement that the distance along the spline between seeds be equal to the seed spacing within the strand. The orientations of the seeds were estimated by the tangents to the spline at each seed centroid. Dose distributions were then determined using the 1D and 2D TG-43 formalisms. These were compared using the TG-137 recommended dose metrics for the prostate, prostatic urethra, and rectum., Results: Seven hundred and sixty one strands were analyzed in total. Defining the z-axis to be cranial-positive and the x-axis to be left-lateral positive in the CT coordinate system, the average seed had an inclination of 21° ± 10° and an azimuth of -81° ± 57°. These values correspond to the average strand rising anteriorly from apex to base, approximately parallel to the midsagittal plane. Clinically minor but statistically significant differences in dose metrics were noted. Compared to the 2D calculation, the 1D calculation underestimated prostate V100 by 1.1% and D90 by 2.3 Gy, while overestimating V150 and V200 by 1.6% and 1.3%, respectively. Urethral and rectal dose quantifiers tended to be underestimated by the 1D calculation. The most pronounced differences were in the urethral D30 and rectal D2cc, which rose by 3.8 and 1.9 Gy, respectively, using the 2D calculation. The total volume of the 100% isodose region as a percentage of the prostate volume was found to increase by 0.4%., Conclusions: Stranded seeds in the supine patient are not oriented in a uniformly random manner, nor are they aligned along the axis of the CT scanner. Instead, this study identified a consistent anterior pitch that is likely attributable to differences in patient pose between implant and CT imaging. The angle of the ultrasound probe with respect to the patient during implant may have also been a contributing factor. The dose metrics derived using the 1D formalism were found to be within 2%, on average, of those derived using the 2D formalism. For greater accuracy, 2D dosimetry can be pursued using the strand-fitting method described in this work. If a 1D representation is used, integrating over the empirically determined seed orientation density reported here may be more appropriate than assuming that seed inclinations are distributed uniformly.

Purpose: Quantify the migration of iodine-125 RAPIDStrands ("strands") from Day 0 to Day 30 postoperatively in patients treated with prostate brachytherapy., Methods and Materials: Gold fiducial markers were inserted into the prostate before implants to serve as a fixed reference point within the prostate. Study patients underwent CT scans of the pelvis on Day 0 and Day 30 postimplant to image the prostate. In-house MATLAB software reconstructed each strand and determined its location relative to the center of mass of the fiducial markers. The recorded migration was taken to be the difference in these locations between Day 0 and Day 30., Results: A total of 232 strands containing 1069 sources were implanted in 10 patients. Overall, 84% of strands migrated by less than 5mm in any direction. The collection of strands were displaced a mean distance of +0.22mm laterally (95% confidence interval [CI]: +0.08 to +0.37mm), -0.22mm posteriorly (95% CI: -0.51 to +0.06mm), and +0.41mm superiorly (95% CI: +0.03 to +0.79mm). Strands located in the anterior prostate demonstrated the greatest degree of migration in any direction, moving a mean of +1.55mm superiorly. These strands also moved a mean distance of 0.84mm posteriorly, whereas posteriorly located strands moved by a mean distance of 0.82mm anteriorly, consistent with movement because of the resolution of edema., Conclusions: This study did not identify any clinically significant patterns of mean migration of iodine-125 RAPIDStrands from Day 0 to Day 30 postimplant., (Crown Copyright © 2011. Published by Elsevier Inc. All rights reserved.)

In this paper we report and characterize a semi-automatic prostate segmentation method for prostate brachytherapy. Based on anatomical evidence and requirements of the treatment procedure, a warped and tapered ellipsoid was found suitable as the a-priori 3D shape of the prostate. By transforming the acquired endorectal transverse images of the prostate into ellipses, the shape fitting problem was cast into a convex problem which can be solved efficiently. The average whole gland error between non-overlapping volumes created from manual and semi-automatic contours from 21 patients was 6.63 ± 0.9%. For use in brachytherapy treatment planning, the resulting contours were modified, if deemed necessary, by radiation oncologists prior to treatment. The average whole gland volume error between the volumes computed from semi-automatic contours and those computed from modified contours, from 40 patients, was 5.82 ± 4.15%. The amount of bias in the physicians' delineations when given an initial semi-automatic contour was measured by comparing the volume error between 10 prostate volumes computed from manual contours with those of modified contours. This error was found to be 7.25 ± 0.39% for the whole gland. Automatic contouring reduced subjectivity, as evidenced by a decrease in segmentation inter- and intra-observer variability from 4.65% and 5.95% for manual segmentation to 3.04% and 3.48% for semi-automatic segmentation, respectively. We characterized the performance of the method relative to the reference obtained from manual segmentation by using a novel approach that divides the prostate region into nine sectors. We analyzed each sector independently as the requirements for segmentation accuracy depend on which region of the prostate is considered. The measured segmentation time is 14 ± 1s with an additional 32 ± 14s for initialization. By assuming 1-3 min for modification of the contours, if necessary, a total segmentation time of less than 4 min is required, with no additional time required prior to treatment planning. This compares favorably to the 5-15 min manual segmentation time required for experienced individuals. The method is currently used at the British Columbia Cancer Agency (BCCA) Vancouver Cancer Centre as part of the standard treatment routine in low dose rate prostate brachytherapy and is found to be a fast, consistent and accurate tool for the delineation of the prostate gland in ultrasound images., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Purpose: To evaluate region-specific dose metrics as predictors of biochemical relapse in prostate brachytherapy patients., Methods and Materials: In a cohort of 1006 low-risk and "low-tier" intermediate-risk prostate brachytherapy patients treated to a planned dose of 144 Gy mPD (minimal peripheral dose), 30 of 32 with biochemical relapse (nadir+2 ng/mL definition) had postimplant CT scans available for retrospective analysis. These were matched to nonrelapsing controls from the same era. Three copies of each CT were created and, after randomization and deletion of identifiers and original contours, were re-contoured by three radiation oncologists. Prostate contours were then divided into quadrants: Anterior-Superior (ASQ), Posterior-Superior (PSQ), Anterior-Inferior (AIQ), and Posterior-Inferior (PIQ), and dosimetric parameters calculated. Results were analyzed using mixed-effects linear regression and multivariate logistic regression., Results: Whole prostate volume of the prostate receiving at least 100% of the prescribed dose (V(100)) and minimum dose, as a percentage of the prescribed dose, received by 90% of the prostate volume (D(90)) were similar for relapses and controls (p=0.40 and 0.48, respectively). Among the quadrants, the largest differences between relapses and controls were seen for the AIQ. Mean AIQ V(100)s were 91.2% (relapses) and 95.5% (controls) (p=0.096), and D(90)s were 112.8% (relapses) and 119.3% (controls) (p=0.145). Overall, the lowest doses were in the ASQ, but were not very different for relapses and controls (V(100)=76.5% and 78.5%, respectively) (p=0.54). On multivariate analysis along with various clinical parameters, AIQ metrics approached significance at the p ≤ 0.05 level in models that also included initial prostate-specific antigen, androgen suppression, and risk group., Conclusions: Although whole prostate dose metrics did not predict for biochemical relapse in our data set, dose to the AIQ was predictive in multivariate analysis., (Copyright © 2011 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.)

We aim to compute radioactive stranded-implant displacement during and after prostate brachytherapy. We present the methods used to identify corresponding seeds in planned, intra-operative and postimplant patient data that enable us to compute seed displacements. A minimum cost network flow algorithm is used, on 8 patients, for needle track detection to group seeds into needles that can be matched between datasets. An iterative best line detection algorithm is used both to help with needle detection and to register the different datasets. Our results show that there was an average seed misplacement of 5.08 +/- 2.35 mm during the procedure, which then moved another 3.10 +/- 1.91 mm by the time the quality assurance CT was taken. Several directional trends in different regions of the prostate were noted and commented on.

Prostate segmentation from trans-rectal transverse B-mode ultrasound images is required for radiation treatment of prostate cancer. Manual segmentation is a time-consuming task, the results of which are dependent on image quality and physicians' experience. This paper introduces a semi-automatic 3D method based on super-ellipsoidal shapes. It produces a 3D segmentation in less than 15 seconds using a warped, tapered ellipsoid fit to the prostate. A study of patient images shows good performance and repeatability. This method is currently in clinical use at the Vancouver Cancer Center where it has become the standard segmentation procedure for low dose-rate brachytherapy treatment.