Robotic SBRT Research Articles

2015: MRI-based robotic SBRT microboost with nodal irradiation in treatment of aggressive prostate cancer

2015: MRI-based robotic SBRT microboost with nodal irradiation in treatment of aggressive prostate cancer

2589: Hyaluronic acid versus balloon rectal spacers in robotic SBRT for prostate cancer: QoL and toxicity

2589: Hyaluronic acid versus balloon rectal spacers in robotic SBRT for prostate cancer: QoL and toxicity

Planning Target Volume Margin Assessment of Retroperitoneal Tumors Using Robotic SBRT With Spine Tracking

Planning Target Volume Margin Assessment of Retroperitoneal Tumors Using Robotic SBRT With Spine Tracking

Quality assessment of automatically planned O-Ring linac SBRT plans for pelvic lymph node metastases, finding the optimal minimum target size by comparison with robotic SBRT.

The purpose of this study is to assess the quality of automatic planned O-Ring Halcyon linac SBRT plans for pelvic lymph node metastases and to establish an absolute PTV volume threshold as a plan quality prediction criterion. Compliance of the plans to institutional SBRT plan evaluation criteria and differences in plan quality and treatment delivery times between Halcyon Linac and CyberKnife robotic SBRT were evaluated. Twenty-one CyberKnife treatment plans were replanned for Halcyon. Prescription doses range was 26-40Gy in mean three fractions. The mean/median planning target volume was 4.0/3.6 cm3 . Institutional criteria for the plan evaluation were: New Conformity Index (NCI), Conformity Index (CI), Modified Gradient Index (MGI), selectivity index reciprocal (PIV/TVPIV ), and the target coverage by prescription isodose (%PIV). Statistical analysis based on the receiver operating characteristic (ROC) curve was used to determine a plan quality predictor threshold of the PTV volume. Comparative analysis of normal tissue complication probabilities (NTCP) was used to assess the risk of toxicity in healthy tissues. Seventy-one percent (n=15)/95% (n=20) of Halcyon and 81% (n=17)/100% (n=21) of CK plans fulfilled all ideal/tolerance criteria. For PTVs above a found optimal threshold of 2.6 cm3 (71%, n=15), no statistically significant difference was observed between the CI, NCI, PIV/TVPIV , and MGI indexes of both groups, while the coverage (%PIV) was statistically but not clinically significantly different between cohorts. Significantly shorter delivery times are expected with Halcyon. No significant differences in NTCP were observed. All but one automatically optimized Halcyon treatment plans demonstrated ideal or acceptable performance. PTV threshold of 2.6 cm3 can be used as decision criteria in clinical settings. The results of our study demonstrated the promising performance of the Halcyon for pelvic SBRT, although plan-specific QA is required to verify machine performance during plan delivery.

PO-1391 Dose intensification in Locally Advanced Pancreatic Cancer using Robotic SBRT

PO-1391 Dose intensification in Locally Advanced Pancreatic Cancer using Robotic SBRT

Penile Bulb Dose Predicts Sexual Quality of Life after Prostate SBRT: Secondary Analysis of a Multi-Institutional Trial

<h3>Purpose/Objective(s)</h3> Prostate radiation is associated with erectile dysfunction. Recently, secondary analyses of the CHIPP (19 vs. 20 vs. 37 fractions) and Hypo-RT trials (7 vs. 39 fractions) demonstrated an association between penile bulb (PB) dose and sexual outcomes. Though stereotactic body radiation (SBRT, 4-5 fractions) is increasingly used, minimal data exist regarding dosimetric predictors of sexual function after SBRT. We herein analyze predictors of erectile dysfunction in patients treated with SBRT on a prospective trial. <h3>Materials/Methods</h3> Patients with low or intermediate risk prostate cancer were enrolled on a multi-institutional phase 2 trial from 2007 to 2012. Patients were treated with robotic SBRT to 38 Gy in 4 fractions on consecutive days, without androgen deprivation therapy. The clinical target volume was prostate alone for low-risk patients or prostate+1 cm of proximal seminal vesicles for intermediate-risk patients. Selected dosimetric parameters for PB and neurovascular bundle were prospectively collected. Erectile function was assessed using the Sexual Health Inventory for Men (SHIM) Questionnaire at baseline and after treatment at protocol-specified time points. The SHIM is a patient reported questionnaire scored from 1-30, with lower scores indicating worse erectile function. Linear regression was used to assess factors associated with SHIM score at 2 years. We chose one PB metric (D10%) for use in multivariable analyses given collinearity of dosimetric variables. <h3>Results</h3> 251 patients with PB data were included and received SBRT at 18 institutions. SHIM score was available in 97% and 79% of patients at baseline and 2 years, respectively. Mean SHIM was 14.1 at baseline, declining to 9.8 at 2 years. Median age was 69 years and median PB D10% was 16 Gy. On univariate analysis, higher age, lower baseline SHIM and each PB metric were all significantly associated with worse erectile function (lower SHIM score) at 2 years (Table). On multivariate analysis accounting for age and baseline SHIM, PB D10% remained significantly associated with lower SHIM score at 2 years (Table). In contrast, dose to the neurovascular bundle was not associated with erectile dysfunction (data not shown). Mean SHIM score at 2 years was 11.2 vs. 8.7 in patients with PB D10% below vs. above the median, respectively (t-test p=0.04). <h3>Conclusion</h3> To the authors' knowledge, this is the largest analysis of dosimetric predictors of erectile dysfunction after SBRT. In addition to known factors such as age and baseline function, penile bulb dose appears to correlate with late erectile dysfunction and should be minimized to preserve sexual QOL in patients receiving SBRT. Table: Linear regression analyses of 2-year SHIM score.

Combining computed tomography and biologically effective dose radiomics improves prediction of tumor response to robotic lung SBRT

Combining computed tomography and biologically effective dose radiomics improves prediction of tumor response to robotic lung SBRT

Long-Term Characterization of MRI-Morphologic Alterations After Active Motion-Compensated Liver SBRT

<h3>Purpose/Objective(s)</h3> To characterize the post-SBRT MRI-morphologic alterations in long-term survivors with MRI-based follow-up (FU) in patients treated by actively motion managed gantry-based and robotic liver SBRT. <h3>Materials/Methods</h3> Patients treated with gantry-based (with breath-hold-gating and ultrasound tracking) or robotic-based SBRT (with real-time fiducial tracking) who had long-term follow-up (FU, ≥ 90 days) were evaluated. Post-SBRT MRI-evidenced morphologic alterations (MMAs) were contoured manually on each T1-weighted contrast-enhanced. Volumetric data and liver volume were documented at each FU. Change's dynamics and significance was assessed for each time point. <h3>Results</h3> The median follow-up was 12.5 months [0.5 - 84]. Seventy PTVs from 62 patients were assessable. After 3 - 6 months, 95.7% (<b>n =</b> 67) of treated lesions developed MMAs with a median volume of 122.44 cc [8.17 – 699.34]. Characterization included 48 (71.6%) hypointense and 19 (28.4%) hyperintense MMAs. Twenty-one (31.3%) MMAs completely resolved after median 12 months [6 – 36] post-SBRT. At the last follow-up, 68.7% were still present (6 – 84 months). Thirty-seven (55.2%) MMAs did not resolve completely and reduced in volume with longer FU. Since the 3-month control baseline, a significant volume reduction to a median of 43.3% after 6 months (<i>P</i> < 0.001), 31% after 9 months (<i>P</i> = 0.022) and 13% after 12 – 24 months (<i>P</i> = 0.041), was observed. Liver volumes reduced to a mean 95.1% from the baseline at 3 months (<i>P</i> = 0.001) and remained afterwards unmodified. <h3>Conclusion</h3> Post-radiogenic MRI-morphologic alterations in peritumoral healthy liver tissue either completely resolve or significantly reduce in volume along the first 2 years after treatment. Clinical correlation should be further investigated.

PD-0747 Knowledge-based approach for DVH prediction in robotic spine SBRT.

PD-0747 Knowledge-based approach for DVH prediction in robotic spine SBRT.

Largely reduced OAR doses, and planning and delivery times for challenging robotic SBRT cases, obtained with a novel optimizer.

Recently, VOLO™ was introduced as a new optimizer for CyberKnife® planning. In this study, we investigated possibilities to improve treatment plans for MLC‐based prostate SBRT with enhanced peripheral zone dose while sparing the urethra, and central lung tumors, compared to existing Sequential Optimization (SO). The primary focus was on reducing OAR doses. For 25 prostate and 25 lung patients treated with SO plans, replanning with VOLO™ was performed with the same planning constraints. For equal PTV coverage, almost all OAR plan parameters were improved with VOLO™. For prostate patients, mean rectum and bladder doses were reduced by 34.2% (P < 0.001) and 23.5% (P < 0.001), with reductions in D0.03cc of 3.9%, 11.0% and 3.1% for rectum, mucosa and bladder (all P ≤ 0.01). Urethra D5% and D10% were 3.8% and 3.0% lower (P ≤ 0.002). For lung patients, esophagus, main bronchus, trachea, and spinal cord D0.03cc was reduced by 18.9%, 11.1%, 16.1%, and 13.2%, respectively (all P ≤ 0.01). Apart from the dosimetric advantages of VOLO™ planning, average reductions in MU, numbers of beams and nodes for prostate/lung were 48.7/32.8%, 26.5/7.9% and 13.4/7.9%, respectively (P ≤ 0.003). VOLO™ also resulted in reduced delivery times with mean/max reductions of: 27/43% (prostate) and 15/41% (lung), P < 0.001. Planning times reduced from 6 h to 1.1 h and from 3 h to 1.7 h for prostate and lung, respectively. The new VOLO™ planning was highly superior to SO planning in terms of dosimetric plan quality, and planning and delivery times.

External Validation of Early Quality of Life (QOL) Declines Correlated with Late QOL after Intensity Modulated, Low Dose Rate Brachytherapy, or Stereotactic Radiation for Prostate Cancer within a Prospective Trial

There is data on early toxicity associated with late toxicity, but there is currently a lack of data on quality of life (QOL) outcomes and evaluation for possible surrogacy between early and late toxicity. This is an evaluation of early QOL for prostate cancer across RT options with a validation within QOL from a SBRT prospective trial. An initial cohort of 898 patients (PROSTQA study and 3 institutions with prospective QOL data were pooled for analysis for IMRT (n = 162), LDR brachytherapy (n = 271), or SBRT (Robotic n = 392 and Linac n = 72) to the prostate with or without seminal vesicles) were evaluated for patient reported outcomes. Expanded Prostate Cancer Index (EPIC) QOL data for urinary, bowel, vitality, and sexual function was evaluated by pre-specified relevant thresholds for meaningful clinical differences (MCD) compared to baseline. Patients were evaluated for QOL at 1-2 month from the start of radiotherapy and at 24 months from the start of radiotherapy. Multivariate analysis (MVA) used general linear models to assess the correlation between QOL changes. This was then externally validated with QOL analysis from a prospective trial of robotic SBRT to the prostate alone to 38 Gy in 4 fractions of 259 patients assessing QOL at 1-month post-radiotherapy to predict late declines QOL at 24 months. A total of 898 patients were within the initial cohort, 94% had evaluable QOL at 24 months. On MVA, after controlling for age, baseline function, PSA, Gleason score, T-stage, prostate volume, and RT technique, an early MCD was the strongest predictor of late MCD at 24 months in all assessed domains and radiation modalities: odds ratio (OR) 3.7 [95% CI 2.2-6.4] for urinary irritation, OR 4.5 [2.9-6.9] for urinary incontinence, OR 2.4 [1.6-3.5] for bowel, OR 3.7 [2.5-5.5] for sexual function, and OR 3.4 [2.3-4.9] for hormone. Within the validation cohort of 259 patients, 83% had evaluable QOL at 24 months. Early declines of a MCD were again associated with late declines noted across all domains of QOL: OR 3.1 [95% CI 1.7-5.8] for urinary irritation, OR 2.7 [1.5-4.8] for urinary incontinence, OR 2.0 [1.1-3.7] for bowel, OR 4.0 [2.1-7.7] for sexual function, and OR 3.0 [1.2-7.3] for hormone. Early QOL decline was the strongest predictor of QOL impacts at 2 years across all domains and this appeared consistent across standard radiation treatment modalities. This was externally validated within these domains suggesting early declines in QOL are surrogates and predict for late declines.Abstract 141; TableIncidence and Correlation of an MCD in Early and Late QOLEPIC DomainEPIC MCD ThresholdEarly Decline MCDLate Decline MCDOR [95% CI]Early Decline MCDLate Decline MCDOR [95% CI]Initial CohortValidation CohortUrinary Irritative678%36%3.7 [2.2-6.4]63%39%3.1 [1.7-5.8]Urinary Incontinence7.537%24%4.5 [2.9-6.9]32%41%2.7 [1.5-4.8]Bowel554%29%2.4 [1.6-3.5]41%26%2.0 [1.1-3.7]Sexual1136%41%2.9 [2.3-3.8]30%49%2.4 [0.89-6.6] Open table in a new tab

Performance assessment of a new optimization system for robotic SBRT MLC-based plans

PurposeTo assess the performance of a new optimization system, VOLO, for CyberKnife MLC-based SBRT plans in comparison with the existing Sequential optimizer. MethodsMLC-plans were created for 25 SBRT cases (liver, prostate, pancreas and spine) using both VOLO and Sequential. Monitor units (MU), delivery time (DT), PTV coverage, conformity (nCI), dose gradient (R50%) and OAR doses were used for comparison and combined to obtain a mathematical score (MS) of plan quality for each solution. MS strength was validated by changing parameter weights and by a blinded clinical plan evaluation. The optimization times (OT) and the average segment areas (SA) were also compared. ResultsVOLO solutions offered significantly lower mean DT (−19%) and MU (−13%). OT were below 15 min for VOLO, whereas for Sequential, values spanned from 8 to 160 min. SAs were significantly larger for VOLO: on average 10 cm2 versus 7 cm2. VOLO optimized plans achieved a higher MS than Sequential for all tested parameter combinations. PTV coverage and OAR sparing were comparable for both groups of solutions. Although slight differences in R50% and nCI were found, the parameters most affecting MS were MU and DT. VOLO solutions were selected in 80% of cases by both physicians with 88% inter-observer agreement. ConclusionsThe good performance of the VOLO optimization system, together with the large reduction in OT, make it a useful tool to improve the efficiency of CK SBRT planning and delivery. The proposed methodology for comparing different planning solutions can be applied in other contexts.

Real-time Tracking for Robotic Pancreas SBRT: Correlation and Prediction Uncertainties and Dosimetric Implications

Real-time Tracking for Robotic Pancreas SBRT: Correlation and Prediction Uncertainties and Dosimetric Implications

Performance Assessment of a New Optimization System for Robotic SBRT Plans

Performance Assessment of a New Optimization System for Robotic SBRT Plans

Robotic stereotactic radiotherapy for liver oligometastases from colorectal cancer: a single-center experience.

To report on the safety and clinical benefit of robotic stereotactic radiotherapy (SBRT) for liver oligometastatic colorectal cancer (CRC). Robotic SBRT was applied to oligometastatic CRC patients, defined as having 1-4 liver metastases and absent or controlled extrahepatic disease. The intended prescription dose was 37.5Gy in three fractions. Treatment efficacy was estimated by clinical benefit rate (CBR), progression-free survival (PFS) and overall survival (OS). Toxicity was graded according to CTC-AE scale, v. 4.03. Regression analysis was performed to search for the presence of any predictive factors. Between 2012 and 2017, 38 patients (66 lesions) were irradiated. The median delivered biological effective maximum dose (maxBED10) was 142Gy. At a median follow-up of 11.8months (range 3.2-58.8), the 1- and 2-year OS were 67.3% and 44.1%, respectively. Actuarial LC rates for all patients at 6 and 12months were 64.2% and 60.4%, respectively. Local or distant progression occurred in 28 (77.8%) patients, with a 1- and 2-year PFS of 19.3% and 12.2%, respectively. The CBR was 71.4%, with no significant association with maxBED10. At multivariate analysis, the presence of extrahepatic disease had a detrimental impact on PFS (HR 3.98, 95% CI 1.77-8.93; p < 0.001) and OS (HR 3.58, 95% CI 1.06-12.07; p < 0.04). No acute grade 3 gastrointestinal toxicity was observed. Our analysis underlines the importance of patients' selection to identify the oligometastatic scenario most likely to benefit from SBRT. Prospective studies are needed to further assess its role among locoregional treatment options for liver metastases from CRC.

PO-0973 Residual intra-fraction error in nonimmobilized patients treated with tracked robotic spinal SBRT

PO-0973 Residual intra-fraction error in nonimmobilized patients treated with tracked robotic spinal SBRT

EP-1667 Safety and efficacy of fiducial marker implantation for robotic SBRT with fiducial tracking

EP-1667 Safety and efficacy of fiducial marker implantation for robotic SBRT with fiducial tracking

EP-1376 Robotic SBRT with fiducial tracking for medically inoperable peripheral stage I NSCLC: final report

EP-1376 Robotic SBRT with fiducial tracking for medically inoperable peripheral stage I NSCLC: final report

EP-1542 Long-term results and PSA kinetics after robotic SBRT for prostate cancer

EP-1542 Long-term results and PSA kinetics after robotic SBRT for prostate cancer

Management of isolated local failures following stereotactic body radiation therapy for low to intermediate risk prostate cancer.

66 Background: SBRT is a safe and effective treatment option for patients with low to intermediate risk prostate cancer (PCa). SBRT delivers high biologically effective doses resulting in very low PSA nadirs. Strategies to diagnose and confirm salvageable isolated local failures (ILF) are needed. This study aims to examine the incidence and approach to management of ILF after SBRT in a large single institution cohort. Methods: All patients with low or intermediate risk PCa treated with SBRT at our institution were eligible for this study. Treatment was delivered using the robotic SBRT with doses of 35-36.25 Gy in five fractions. ILF were diagnosed using mpMRI and/or biopsy prompted by PSA rise after achieving long-term nadir. Choice of salvage therapy and post-salvage PSA were ascertained on follow up. Results: Between December, 2008 to August, 2018, 998 men with low to intermediate risk prostate cancer were eligible for analysis. Twenty patients (low risk, n = 4; intermediate risk, n = 16) were found to have ILF on either MRI (n = 15) and/or biopsy (n = 17). Three patients with MRI-identified ILF elected active surveillance in lieu of biopsy. Median pre-treatment PSA was 7.5 ng/ml. Median time to diagnosis of ILF was 72 months (37-96 months) with median PSA at the time of ILF of 2.3 ng/ml (1.1-10 ng/ml). Median PSA doubling time was 17 months (5-22 months). Thirteen patients with biopsy proven ILF proceeded with salvage therapy (cryotherapy n = 12, HIFU n = 1). Of 12 patients who underwent cryotherapy, 8 had a post-treatment PSA of &lt; 0.1ng/ml, two patient’s results were unavailable, one patient had a PSA nadir of 0.7 ng/ml and one patient had yet to undergo post-salvage PSA test at the time of this report. Conclusions: The incidence of ILF is rare in our series. Diagnosis and management of ILF post-SBRT continues to evolve in the era of successful salvage therapy. Our report suggests an important role for early utilization of MRI and confirmatory biopsy at relatively low PSA levels and long PSA doubling time. Additionally, undetectable PSA post-salvage therapy supports early treatment after identifying ILF. Larger trials are needed for refinement of patient selection and most appropriate salvage modality.