Delivery Of Stereotactic Body Radiation Therapy Research Articles

Daily Diagnostic Quality Computed Tomography-on-Rails (CTOR) Image Guidance for Abdominal Stereotactic Body Radiation Therapy (SBRT).

Stereotactic body radiation therapy (SBRT) for abdominal targets faces a variety of challenges, including motion caused by the respiration and digestion and a relatively poor level of contrast between the tumor and the surrounding tissues. Breath-hold treatments with computed tomography-on-rails (CTOR) image guidance is one way of addressing these challenges, allowing for both the tumor and normal tissues to be well-visualized. Using isodose lines (IDLs) from CT simulations as a guide, the anatomical information can be used to shift the alignment or trigger a replan, such that normal tissues receive acceptable doses of radiation. This study aims to describe the workflow involved when using CTOR for pancreas and liver SBRT and demonstrates its effectiveness through several case studies. In these case studies, using the anatomical information gained through diagnostic-quality CT guidance to make slight adjustments to the alignment, resulted in reductions in the maximum dose to the stomach. High-quality imaging, such as CTOR, and the use of IDLs to estimate the doses to OARs, enable the safe delivery of SBRT, without the added complexity and resource commitment required by daily online adaptive planning.

An Economic Analysis of SC24 in Canada: A Randomized Study of SBRT Compared With Conventional Palliative RT for Spinal Metastases

Purposexx.xx was a multicenter randomized controlled phase 2/3 trial conducted in Canada and Australia. Patients with painful spinal metastases were randomized to either 24 Gy/2 stereotactic body radiotherapy (SBRT) or 20 Gy/5 conventional external beam radiotherapy (CRT). The study met its primary endpoint demonstrating superior complete pain response rates (CRR) at 3 months following SBRT (35%) vs CRT (14%). SBRT planning and delivery is resource intensive. Given its benefits in xx.xx, we performed an economic analysis to determine the incremental cost-effectiveness of SBRT compared to CRT. MethodsThe trial recruited 229 patients. Cost-effectiveness was assessed using a Markov model taking into account observed survival, treatments costs, including retreatment, and quality of life (QoL) over the lifetime of the patient. The EORTC-QLU-C10D was used to determine QoL values. Transition probabilities for outcomes were from available patient data. Health system costs were from the Canadian health care perspective and based on 2021 Canadian dollars (CDN). The incremental cost-effectiveness ratio (ICER) was expressed as the ratio of incremental cost to quality-adjusted life years (QALY). Impact of parameter uncertainty was investigated using deterministic and probabilistic sensitivity analyses. RESULTSThe base case for SBRT compared to CRT had an ICER of $9,040CDN per QALY gained. Sensitivity analyses demonstrated that the ICER was most sensitive to variations in the utility assigned to the “No local failure” ($5,457CDN to $241,051CDN per QALY), adopting low and high estimates of utility) and the cost of the SBRT (ICERs ranging from $7,345 to $123,361CDN per QALY). It was more robust to variations in assumptions around survival and the response rate. ConclusionsSBRT is associated with higher upfront costs compared to CRT. The ICER shows that, within the Canadian health care system, SBRT with 2 fractions is likely to be cost-effective relative to CRT.

Impact of Maximum Point Dose Within the Planning Target Volume on Local Control of Nonsmall Cell Lung Cancer Treated With Stereotactic Body Radiotherapy.

No consensus exists on the maximum dose delivered to the planning target volume (PTV) in the delivery of stereotactic body radiotherapy (SBRT) for primary lung cancer. We investigated whether higher biologically effective doses (BED) within the PTV were associated with improved tumor control. We reviewed patients with early-stage, node-negative nonsmall cell lung cancer who received curative-intent SBRT between 2005 and 2018. We calculated the maximum BED (maxBED) within the PTV for all patients, analyzing outcomes using the cumulative incidence method and Fine-Gray test statistics to assess prognostic impact. We analyzed 171 patients (median age, 70.2; range, 43 to 90y) with 181 lung nodules. Median follow-up was 2.7 years (range, 0.1 to 12y) for all patients and 4.2 years (range, 0.2 to 8.4y) for living patients. Median maximum tumor diameter was 1.9cm (range, 0.7 to 5.6cm). Patients received a prescription of 48 or 50 Gy in 4 or 5 fractions, respectively, except for one who received 60 Gy in 5 fractions. Median maxBED was 120 Gy (range, 101 to 171 Gy). There was no difference in the 3-year local control (LC) rate among patients treated with a maxBED<120 Gy versus ≥120 Gy ( P =0.83). No significant differences in LC were observed between patients with early-stage nonsmall cell lung cancer treated with SBRT in 4 or 5 fractions with a maxBED≥120 Gy. However, a higher maxBED trended toward improved LC rates, suggesting a maxBED threshold greater than 120 Gy may be needed to improve LC rates.

Performance characterization of a novel hybrid dosimetry insert for simultaneous spatial, temporal, and motion-included dosimetry for MR-linac.

Several (online) adaptive radiotherapy procedures are available to maximize healthy tissue sparing in the presence of inter/intrafractional motion during stereotactic body radiotherapy (SBRT) on an MR-linac. The increased treatment complexity and the motion-delivery interplay during these treatments require MR-compatible motion phantoms with time-resolved dosimeters to validate end-to-end workflows. This is not possible with currently available phantoms. Here, we demonstrate a new commercial hybrid film-scintillator cassette, combining high spatial resolution radiochromic film with four time-resolved plastic scintillator dosimeters (PSDs) in an MRI-compatible motion phantom. First, the PSD's performance for consistency, dose linearity, and pulse repetition frequency (PRF) dependence was evaluated using an RW3 solid water slab phantom. We then demonstrated the MRI4D scintillator cassette's suitability for time-resolved and motion-included quality assurance for adapt-to-shape (ATS), trailing, gating, and multileaf collimator (MLC) tracking adaptations on a 1.5 T MR-linac. To do this, the cassette was inserted into the Quasar MRI4D phantom, which we used statically or programmed with artificial and patient-derived motion. Simultaneously with dose measurements, the beam-gating latency was estimated from the time difference between the target entering/leaving the gating window and the beam-on/off times derived from the time-resolved dose measurements. Experiments revealed excellent detector consistency (standard deviation 0.6%), dose linearity (R2 = 1), and only very low PRF dependence ( 0.4%). The dosimetry cassette demonstrated a near-perfect agreement during an ATS workflow between the time-resolved PSD and treatment planning system (TPS) dose (0%-2%). The high spatial resolution film measurements confirmed this with a 1%/1-mm local gamma pass-rate of 90%. When trailing patient-derived prostate motion for a prostate SBRT delivery, the time-resolved cassette measurements demonstrated how trailing mitigated the motion-induced dose reductions from 1%-17% to 1%-2% compared to TPS dose. The cassette's simultaneously measured spatial dose distribution highlighted the dosimetric gain of trailing by improving the 3%/3-mm local gamma pass-rates from 80% to 97% compared to the static dose. Similarly, the cassette demonstrated the benefit of real-time adaptations when compensating patient-derived respiratory motion by showing how the TPS dose was restored from 2%-56% to 0%-12% (gating) and 1%-26% to 1%-7% (MLC tracking) differences. Larger differences are explainable by TPS-PSD coregistration uncertainty combined with a steep dose gradient outside the PTV. The cassette also demonstrated how the spatial dose distributions were drastically improved by the real-time adaptations with 1%/1-mm local gamma pass-rates that were increased from 8 to 79% (gating) and from 35 to 89% (MLC tracking). The cassette-determined beam-gating latency agreed within 12 ms with the ground truth latency measurement. Film and PSD dose agreed well for most cases (differences relative to TPS dose 4%), while film-PSD coregistration uncertainty caused relative differences of 5%-8%. This study demonstrates the excellent suitability of a new commercial hybrid film-scintillator cassette for simultaneous spatial, temporal, and motion-includeddosimetry.

Endoscopic Ultrasound-Guided Fiducial Placement for Stereotactic Body Radiation Therapy in Patients with Pancreatic Cancer.

Accurate delivery of stereotactic body radiotherapy (SBRT) to pancreatic tumors relies on successful EUS-guided placement of fiducial markers. The aim of this study is to report the technical feasibility and safety of EUS-guided fiducial placement and to evaluate the characteristics and technical benefit of SBRT in a cohort of patients with pancreatic cancer (PC). A retrospective chart review was performed for all (n = 82) PC patients referred for EUS-guided fiducial placement by a single endosonographer at a tertiary cancer center. Data regarding EUS-related technical details, SBRT characteristics, adverse events, and continuous visibility of fiducials were recorded and analyzed. Most patients included in the study had either locally advanced disease (32 patients, 39%) or borderline resectable disease (29 patients, 35%). Eighty-two PC patients underwent the placement of 230 fiducial markers under EUS guidance. The technical success rate of the fiducial placement was 98%. No immediate EUS-related adverse events were reported. The average time to the simulation CT after fiducial placement was 3.1 days. Of the 216 fiducial markers used for the SBRT delivery, 202 fiducial markers were visible on both the simulation CT and the cone beam CT scan. A median dose of 40cGY was given to all the patients in five fractions. Of these, 41% of the patients reported no SBRT-related toxicities during the follow-up. Fatigue and nausea were the most reported SBRT-related toxicities, which were seen in 35% of the patients post-SBRT. Our results demonstrate that EUS-guided fiducial placement is safe and effective in target volume delineation, facilitating SBRT delivery in PC patients. Further clinical trials are needed to determine the SBRT-related survival benefits in patients with pancreatic cancer.

ESTRO clinical practice guideline: Stereotactic body radiotherapy for spine metastases

Background and purposeRecent progress in diagnostics and treatment of metastatic cancer patients have improved survival substantially. These developments also affect local therapies, with treatment aims shifting from short-term palliation to long-term symptom or disease control. There is consequently a need to better define the value of stereotactic body radiotherapy (SBRT) for the treatment of spinal metastases. MethodsThis ESTRO clinical practice guideline is based on a systematic literature review conducted according to PRISMA standards, which formed the basis for answering four key questions about the indication and practice of SBRT for spine metastases. ResultsThe analysis of the key questions based on current evidence yielded 22 recommendations and 5 statements with varying levels of endorsement, all achieving a consensus among experts of at least 75%. In the majority, the level of evidence supporting the recommendations and statements was moderate or expert opinion, only, indicating that spine SBRT is still an evolving field of clinical research. Recommendations were established concerning the selection of appropriate patients with painful spine metastases and oligometastatic disease. Recommendations about the practice of spinal SBRT covered technical planning aspects including dose and fractionation, patient positioning, immobilization and image-guided SBRT delivery. Finally, recommendations were developed regarding quality assurance protocols, including description of potential SBRT-related toxicity and risk mitigation strategies. ConclusionsThis ESTRO clinical practice guideline provides evidence-based recommendations and statements regarding the selection of patients with spinal metastases for SBRT and its safe implementation and practice. Enrollment of patients into well-designed prospective clinical trials addressing clinically relevant questions is considered important.

Total ablative stereotactic body radiotherapy to primary and oligometastatic renal cell carcinoma in medically inoperable cases: An institutional analysis

ABSTRACT Introduction: Stereotactic body radiotherapy (SBRT) has been found to be an effective and safe modality with excellent oncological outcome in medically inoperable primary renal cell carcinoma (RCC) and oligometastases. There is scarcity of data on the synchronous delivery of SBRT to primary and oligometastatic RCC in patients unfit for nephrectomy. Here, we report the findings of a retrospective study of prospectively collected data on “total ablative SBRT.” Methods: Oligometastatic RCC patients with intact primary tumors were enrolled between May 2021 and June 2022. SBRT was synchronously delivered to the primary tumor and metastases. Demographics, treatment, oncologic outcomes, and toxicity were assessed. Kaplan–Meier estimates were generated for oncologic outcomes. The primary endpoint of this study was feasibility and tolerability. Results: Eleven patients were enrolled between May 2021 and June 2022. One patient died at 2 months after SBRT due to viral pneumonitis (possibly COVID pneumonia). Nine patients (82%) had metastatic disease, while 2 (18%) were stage II. The average maximal diameter of primary was 68.7 mm (range, 23–128 mm). The SBRT doses for primary and metastasis ranged from 40 to 55 Gray (Gy) in 5 to 7 fractions and 22 to 40Gy in 2 to 5 fractions, respectively. The median follow-up period was 10.5 months (Range: 4–15 months). Response assessment was available for ten patients. Local control, marginal control, regional control and initial oligometastatic control (OMC) rates were 100%. OMC declined to 87.5% as one patient had recurrence in irradiated subcarinal lymphnode at 7 months. The metastatic control rate was 80% and loco-regional progression-free survival was 8 months (range, 4–15 months). Toxicities were minimal and manageable. At the last follow–up, 7 of 11 patients were alive with an overall survival of 63.5%. Six patients received systemic therapy after SBRT. Conclusions: Synchronous delivery of SBRT to primary and oligometastatic sites in patients unfit for nephrectomy was feasible and tolerable with good locoregional control. The total ablative SBRT strategy needs to be explored in similar cohorts.

Dosimetric Risk Estimation of Chest Wall Pain Following 5-Fraction Lung Stereotactic Body Radiotherapy

Development of chest wall pain (CWP) following lung stereotactic body radiotherapy (SBRT) is a known toxicity, particularly for peripheral lesions. While CW V30 has been most consistently associated with development of post-SBRT CWP, existing series included heterogeneous dose-fractionation regimens, most commonly 48-54 Gy in 3-4 fractions. The present study aims to identify clinical and dosimetric variables associated with development of CWP among patients treated with 5 fraction lung SBRT. Intradepartmental quality assurance database of SBRT patients was queried to identify lung targets treated to a minimum of 45 Gy in 5 fractions. Retrospective chart and plan reviews were performed on these cases to collect patient, tumor, and treatment-related data, selecting for patients with peripheral lesions (any histology), and recording presence or absence of CWP during or following SBRT. Patients with less than 6 months of post-SBRT clinical follow-up were excluded. The CW was defined as a 2 cm expansion of the ipsilateral lung (inclusive of intercostal musculature, ribs, and superficial soft tissue). Logistic regression analyses were performed on continuous and nominal data to determine statistically significant (p<0.05) correlations between clinical (age, gender, known osteopenia/osteoporosis, diabetes, prior thoracic radiotherapy, lesion distance to CW), treatment (interval of SBRT delivery, dose prescribed), and dosimetric (Dose to 0.1/1/5/10cc; V30, V40) factors with CWP. Between February 2011 and January 2022, 93 patients were identified for inclusion in the present analysis, treated to 100 total lesions in 99 courses of treatment. Median patient age was 75 years (range 34-90), 48 (52%) were female, and 29 (of 99 treatment courses; 29%) had received prior thoracic radiotherapy. Median SBRT dose was 50 Gy (45-60), delivered over a median of 9 days (4-18). At a median post-SBRT follow-up of 21 months, 11 patients developed CWP at a median of 9 months post-SBRT (0-32). Statistically significant correlations were identified between CWP and known pre-existing osteopenia or osteoporosis, target distance to CW, and CW D0.1cc, D1cc, D5cc, and D10cc, but not CW V30 or V40. Crude risk of CWP for selected clinically practical dose-volume thresholds are presented in Table 1: CONCLUSION: For patients treated with lung SBRT in 5 fractions, dose to CW volume thresholds appears to correlate more closely than V30 or V40 for CWP estimation. Further investigation and validation of optimal CW volume thresholds, as well as integration of pre-existing condition clinical factors in risk estimation, appears warranted.

Stereotactic Body Radiation Therapy: A Radiosurgery Society Guide to the Treatment of Localized Prostate Cancer Illustrated by Challenging Cases

Traditionally, external beam radiotherapy (EBRT) for localized prostate cancer (PCa) involved lengthy courses with low daily doses. However, advancements in radiation delivery and a better understanding of prostate radiobiology have enabled the development of shorter courses of EBRT. Ultrahypofractionated radiotherapy, administering doses greater than 5 Gy per fraction, is now considered a standard of care regimen for localized PCa, particularly for intermediate-risk disease. Stereotactic body radiotherapy (SBRT), a specific type of ultrahypofractionated radiotherapy employing advanced planning, imaging, and treatment technology to deliver in five or fewer fractions, is gaining prominence as a cost-effective, convenient, and safe alternative to longer radiotherapy courses. It is crucial to address practical considerations related to patient selection, fractionation scheme, target delineation, and planning objectives. This is especially important in challenging clinical situations where clear evidence for guidance may be lacking. The Radiosurgery Society endorses this case-based guide with the aim of providing a practical framework for delivering SBRT to the intact prostate, exemplified by two case studies. The article will explore common SBRT dose/fractionation schemes and dose constraints for organs-at-risk. Additionally, it will review existing evidence and expert opinions on topics such as SBRT dose escalation, the use of rectal spacers, the role of androgen deprivation therapy in the context of SBRT, SBRT in special patient populations (e.g., high-risk disease, large prostate, high baseline urinary symptom burdens, and inflammatory bowel disease), as well as new imaging-guidance techniques like Magnetic Resonance Imaging for SBRT delivery.

Long-term outcomes of single and five fraction schedules of stereotactic body radiation therapy for early-stage central or peripheral NSCLC: Neither fractionation nor location matter?

8538 Background: Due to concerns with toxicity, treatment of early-stage non-small cell lung cancer (NSCLC) with stereotactic body radiation therapy (SBRT) often involves different fractionation schemes for peripheral and centrally located tumors. There is a paucity of long-term SBRT survival outcomes comparing peripheral versus central NSCLC. Methods: This is a single-institution observational cohort study of patients diagnosed with early-stage NSCLC (T1-2N0M0) who underwent 27 Gy in 1 fraction or 50 Gy in 5 fractions with heterogeneity correction at Roswell Park Comprehensive Cancer Center between September 2008 to December 2018. All patients treated with single-fraction SBRT had peripheral NSCLC and those treated with five-fraction SBRT had central NSCLC. Clinically relevant variables including age, gender, race, Karnofsky Performance Status (KPS), histology (adenocarcinoma, squamous cell carcinoma, NSCLC not otherwise specified), T stage, smoking status, tumor location, and the year of SBRT delivery were obtained retrospectively. Cox multivariable analysis (MVA), Kaplan-Meier plot, and log-rank test were performed to evaluate progression-free survival (PFS) and overall survival (OS). Fine-Gray competing risk MVA was performed to evaluate local failure (LF), nodal failure (NF), and distant failure (DF) with death as a competing event. To reduce selection bias, propensity score matching was performed between single- versus five-fraction SBRT cohorts. Results: A total of 265 patients (142 female [53.6%]; median age 77 years) met our criteria. There were 74 (27.9%) and 191 (72.1%) patients with central tumors treated with five-fraction SBRT and peripheral tumors treated with single-fraction SBRT, respectively. On Cox MVA, there was no statistically significant difference in OS (peripheral vs central tumors: adjusted hazards ratio [aHR] 1.04, 95% confidence interval [CI] 0.74-1.46, p=0.81) and PFS (peripheral vs central tumors: aHR 1.05, 95% CI 0.76-1.45, p=0.77). On Fine-Gray competing risk MVA comparing peripheral vs. central tumors, there was no statistically significant difference in LF, NF, and DF. After propensity score matching, 68 matched pairs were identified for peripheral vs. central tumors with similar results. Conclusions: Among patients with early-stage NSCLC treated with SBRT central versus peripheral location was associated with similar long-term survival and tumor recurrence outcomes.

The Role of Stereotactic Body Radiation Therapy in the Management of Liver Metastases

The liver is a common site for metastatic spread for various primary tumor histologies. Stereotactic body radiation therapy (SBRT) is a non-invasive treatment technique with broad patient candidacy for the ablation of tumors in the liver and other organs. SBRT involves focused, high-dose radiation therapy delivered in one to several treatments, resulting in high rates of local control. Use of SBRT for ablation of oligometastatic disease has increased in recent years and emerging prospective data have demonstrated improvements in progression free and overall survival in some settings. When delivering SBRT to liver metastases, clinicians must balance the priorities of delivering ablative tumor dosing while respecting dose constraints to surrounding organs at risk (OARs). Motion management techniques are crucial for meeting dose constraints, ensuring low rates of toxicity, maintaining quality of life, and can allow for dose escalation. Advanced radiotherapy delivery approaches including proton therapy, robotic radiotherapy, and real-time MR-guided radiotherapy may further improve the accuracy of liver SBRT. In this article, we review the rationale for oligometastases ablation, the clinical outcomes with liver SBRT, tumor dose and OAR considerations, and evolving strategies to improve liver SBRT delivery.

Outcome of the first 200 patients with prostate cancer treated with MRI-Linac at Assuta MC.

We present our experience with MR-guided stereotactic body radiotherapy (SBRT) for 200 consecutive patients with prostate cancer with minimum 3-month follow-up. Treatment planning included fusion of the 0.35-Tesla planning MRI with multiparametric MRI and PET-PSMA for Group Grade (GG) 2 or higher and contour review with an expert MRI radiologist. No fiducials or rectal spacers were used. Prescription dose was 36.25 Gy in 5 fractions over 2 weeks to the entire prostate with 3-mm margins. Daily plan was adapted if tumor and organs at risk (OAR) doses differed significantly from the original plan. The prostate was monitored during treatment that was automatically interrupted if the target moved out of the PTV range. Mean age was 72 years. Clinical stage was T1c, 85.5%; T2, 13%; and T3, 1.5%. In addition, 20% were GG1, 50% were GG2, 14.5% were GG3, 13% were GG4, and one patient was GG5. PSA ranged from 1 to 77 (median, 6.2). Median prostate volume was 57cc, and 888/1000 (88%) fractions required plan adaptation. The most common acute GU toxicity was Grade I, 31%;dysuria and acutegastrointestinal toxicity were rare. Three patients required temporary catheterization. Prostate size of over 100cc was associated with acute fatigue, urinary hesitance, and catheter insertion. Prostate Specific Antigen (PSA) decreased in 99% of patients, and one patient had regional recurrence. MR-guided prostate SBRT shows low acute toxicity and excellent short-term outcomes. Real-time MRI ensures accurate positioning and SBRT delivery.

Evaluation of the feasibility of cardiac gating for SBRT of ventricular tachycardia based on real-time ECG signal acquisition.

To investigate the feasibility of cardiac synchronized gating in stereotactic body radiation therapy (SBRT) of ventricular tachycardia (VT) using a real-time electrocardiogram (ECG) signal acquisition. Stability of beam characteristics during simulated ECG gating was examined by developing a microcontroller interface to a Varian Clinac iX linear accelerator allowing gating at frequencies and duty cycles relevant to cardiac rhythm. Delivery accuracy was evaluated by measuring dose linearity with an ionization chamber, and flatness and symmetry with a two-dimensional detector array, for different gating windows within typical human cardiac cycle periods. To establish a practical method of gating based on actual ECG signals, an AD8232 Heart Monitor board was used to acquire the ECG signal and synchronize the beam delivery. Real-time cardiac gated delivery measurements were performed for a single 10×10cm2 field and for a VT-SBRT plan using intensity-modulated radiation therapy (IMRT). Dose per monitor unit (MU) values were found to be linear within most gating windows investigated with maximum differences relative to non-gated delivery of <2% for gating windows ≥200ms and for >10MUs. Beam profiles for both gated and non-gated modes were also found to agree with maximum differences of 0.5% relative to central axis dose for all sets of beam-on/beam-off combinations. Comparison of dose distributions for intensity-modulated SBRT plans between non-gating and cardiac gating modes provided a gamma passing rate of 97.2% for a 2% 2mm tolerance. Beam output is stable with respect to linearity, flatness, and symmetry for gating windows within cardiac cycle periods. Agreement between dose distributions for VT-SBRT using IMRT in non-gated and cardiac cycle gated delivery modes shows that the proposed methodology is feasible. Technically, gating for delivery of SBRT for VT is possible with regard to beam stability.

MR Guided SBRT for Early Prostate Cancer: Initial Experience with 270 Consecutive Patients

<h3>Purpose/Objective(s)</h3> Stereotactic body radiotherapy (SBRT) is a recommended treatment for localized prostate cancer. We present our experience with the first consecutive 270 patients (8.2019-11.2022) treated with MR-guided SBRT with minimum 3 months follow-up and acute side effects. <h3>Materials/Methods</h3> This IRB approved series includes histologically confirmed prostate cancer patients, consecutively treated with MR-guided SBRT. Staging included diagnostic MRI (86%) and PET-PSMA (78.5%) for patients with grade >1 disease. No fiducials or rectal spacers were used. Treatment planning included fusion with pre-treatment imaging and contour review with an expert MRI radiologist. Prescription dose was 36.25Gy in 5fx delivered over 2 weeks to the entire prostate with 3mm margins. High-risk area identified on MRI (PIRADS4-5) or PET received 40Gy. On each fraction, MRI was performed and plan adapted if tumor and OAR doses differed significantly from the simulation-based plan. During radiation, the prostate was monitored and treatment automatically interrupted if the target volume moved out of the PTV range. <h3>Results</h3> Mean age was 71.2(35-90) years. Clinical stage was I-85.5%, II-13%, III-1.5%. MRI showed suspected ECE- 12.5%, NVB involvement-9.5%, SV involvement-1.5%. Group grade was 1-20.5%, 2-52.0%, 3-13.5%,4-13.5%, 5-0.5%. 77 (38%) patients had involvement of ≥50% cores. Pre-treatment PSA ranged from 1-to 77, PSA was>10 in 53 patients (26.5%). Median prostate volume-57cc (16-171). Sixteen (36%) received adjuvant hormone therapy. 739/1000 (73.9%) daily treatments required plan adaptation. Significant prostate movement during treatment noted in 7 patients. Acute GU toxicity was Grade I-21%, II-14% (4 patients required temporary catheter). Acute GI toxicity was grade I-7.5%, II-1.5%. All grade II and 95% of grade I toxicities resolved by 3 months follow-up. No grade III toxicity reported. Three-month post-treatment PSA decreased in 99% of patients, range 0.14-23 (median 2.87). 99.5% are disease free with median follow up of 14 months. Four patients required a temporary catheter during treatment, one following a previous event unrelated to radiation and the other three following radiation. Two of them after three fractions and one after two fractions of radiation. The catheter was removed after 5-7 days except in one patient who was weaned after 3 weeks. Age was significantly associated with acute nocturia, (p=0.005). Number of adapted fractions, catheter insertion was not associated with age, PSA at dx, prostate volume and BMI. Prostate size was not associated with either ISUP or Gleason. <h3>Conclusion</h3> MR guided prostate SBRT shows very low risk of transient's acute toxicity, little long-term toxicity and excellent response (median 14 months). Real-time MR imaging and plan adaptation when required is important for ensuring accurate positioning and SBRT delivery, and prevents geographical miss and inadvertent dose delivery to OAR.

Patterns of Care and Outcomes in Non-Operative, Early-Stage Non-Small Cell Lung Cancer when Stereotactic Body Radiation Therapy is not Feasible

<h3>Purpose/Objective(s)</h3> Stereotactic body radiation therapy (SBRT) is the standard of care treatment for non-operative patients with early-stage non-small cell lung cancer (NSCLC). However, there are cases where safe delivery of SBRT is precluded (e.g., ultracentral tumors or those abutting brachial plexus/stomach) or where SBRT is not available (e.g., centers without SBRT capability). The optimal management with regards to radiation dose/fractionation and whether sensitizing chemotherapy should be considered is unclear. <h3>Materials/Methods</h3> We identified node-negative NSCLC patients with tumors <3 cm (cT1 N0) who received definitive RT in the National Cancer Data Base from 2004-2016. Patients receiving SBRT (defined as 48-60 Gy in £5 fractions or BED₁₀≥100 Gy) were excluded. The use of chemotherapy (none vs. sequential vs. concurrent) and RT type was examined (conventionally fractionated, [CFRT], defined as 59.4-70.2 Gy in 30-39 fractions; and hypofractionated RT [HFRT] defined as 50-72 Gy in >5 fractions using >2 Gy/fraction). Factors associated with receipt of chemotherapy were analyzed via univariable (UV) and multivariable (MV) logistic regression. Overall survival (OS) was evaluated with Kaplan-Meier analyses and log-rank test as well as UV and MV Cox proportional hazards. Propensity score matching was also performed for comparison of OS between groups. P-values less than 0.05 were considered significant. <h3>Results</h3> A total of 2,851 patients were included with 69% receiving CFRT and 31% receiving HFRT. Nearly 26% of patients received chemotherapy, delivered either concurrently (21%) or sequentially (5%). On MV analysis, receipt of chemotherapy was associated with younger age (<70 years, p<0.001), larger tumor size (2+ cm, p<0.001), BED₁₀<80 Gy (p<0.001) and receipt of CFRT (p<0.001). OS was significantly improved for patients receiving concurrent chemotherapy with CFRT compared to patients receiving CFRT alone (p<0.001) and HFRT alone (p=0.003), which remained significant after propensity score matching. On MV analysis, improved OS remained associated with concurrent chemotherapy (p<0.001), as was younger age (<70 years, p=0.024), female gender (p<0.001), fewer comorbidities (Charlson-Deyo score <2, p<0.001), private insurance (p<0.001), treatment at an academic center (p=0.026), smaller tumor size (<2 cm, p<0.001), and non-squamous histology (p=0.004). <h3>Conclusion</h3> Patterns of care for non-operative early-stage NSCLC patients when SBRT is not feasible vary greatly. A surprising proportion of patients (21%) receive concurrent chemotherapy. Interestingly, concurrent chemotherapy with CFRT was associated with improved OS compared to HFRT or CFRT alone, however this finding requires additional validation given the inherent biases of our study.

Stereotactic body radiation therapy for spine and non-spine bone metastases. GETUG (french society of urological radiation oncologists) recommendations using a national two-round modified Delphi survey

Backround and purposeThe relevance of metastasis-directed stereotactic body radiation therapy (SBRT) remains to be demonstrated through phase III trials. Multiple SBRT procedures have been published potentially resulting in a disparity of practices. Therefore, the french society of urological radiation oncolgists (GETUG) recognized the need for joint guidelines for metastasis-directed SBRT in order to standardize practice in trials carried out by the group. Materials and methodsAfter a comprehensive litterature review, 97 recommandation statements were created regarding planning and delivery of spine bone (SBM) and non-spine bone metastases (NSBM) SBRT. These statements were then submitted to a national online two-round modified Delphi survey among main GETUG investigators. Consensus was achieved if a statement received ≥ 75 % agreements, a trend to consensus being defined as 65–74 % agreements. Any statement without consensus at round one was re-submitted in round two. ResultsTweny-one out of 29 (72.4%) surveyed GETUG investigators responded to both rounds. Consensus was achieved for 91/97 statements (93.8%) allowing the edition of comprehensive guidelines encompassing all aspects of SBM and NSBM SBRT planning and delivery: patients selection (19 statements), treatment preparation (14 statements), target volume delineation (18 statements), dose and fractionation (11 statements), prescription and dose objectives (9 statements), organs at risk dose constraints (15 statements) and image guided radiation therapy (11 statements). ConclusionGETUG guidelines for SBM and NSBM SBRT were agreed upon using a validated modified Delphi approach. These guidelines will be used as per-protocol recommendations in ongoing and further GETUG clinical trials.

Better preservation of erectile function in localized prostate cancer patients with modern proton therapy: Is it cost-effective?

Stereotactic body radiation therapy (SBRT) has gradually been recognized as favorable curative treatment for localized prostate cancer (PC). However, the high rate of erectile dysfunction (ED) after traditional photon-based SBRT remains an ongoing challenge that greatly impacts the quality of life of PC survivors. Modern proton therapy allows higher conformal SBRT delivery and has the potential to reduce ED occurrence but its cost-effectiveness remains uninvestigated. A Markov decision model was designed to evaluate the cost-effectiveness of proton SBRT versus photon SBRT in reducing irradiation-related ED. Base-case evaluation was performed on a 66-year-old (median age of PC) localized PC patient with normal pretreatment erectile function. Further, stratified analyses were performed for different age groups (50, 55, 60, 65, 70, and 75 years) and threshold analyses were conducted to estimate cost-effective scenarios. A Chinese societal willingness-to-pay (WTP) threshold (37,653 US dollars [$])/quality-adjusted life-year [QALY]) was adopted. For the base case, protons provided an additional 0.152 QALY at an additional cost of $7233.4, and the incremental cost-effectiveness ratio was $47,456.5/QALY. Protons was cost-effective for patients ≤62-year-old at the WTP of China (≤66-year-old at a WTP of $50,000/QALY; ≤73-year-old at a WTP of $100,000/QALY). For patients at median age, once the current proton cost ($18,000) was reduced to ≤$16,505.7 or the patient had a life expectancy ≥88 years, protons were cost-effective at the WTP of China. Upon assumption-based modeling, the results of current study support the use of proton SBRT in younger localized PC patients who are previously potent, for better preservation of erectile function. The findings await further validation using data from future comparative clinical trials.

State-of-the-Art Imaging Techniques in Metastatic Spinal Cord Compression.

Simple SummaryMetastatic Spinal Cord Compression (MSCC) is a feared complication in oncology patients due to its potential for severe pain, permanent neurological disability and mechanical instability of the spine. This narrative review, conducted by keyword searches in PubMed and Google Scholar databases, aims to describe the important role of imaging in MSCC diagnosis and treatment. Diagnosis is typically achieved via Magnetic Resonance Imaging (MRI), although Computed Tomography (CT) Myelogram and conventional CT imaging can be performed in certain clinical situations. Metal artifact reduction techniques for MRI and CT are continually being researched to facilitate imaging in MSCC patients with spinal implants. Imaging also has an important role in pre-treatment planning, in-room image-guidance, and post-treatment follow-up for MSCC patients treated with stereotactic body radiotherapy. Recent advances in deep learning tools for image analysis can reduce the time to MSCC diagnosis, enabling earlier treatment for superior functional outcomes.Metastatic Spinal Cord Compression (MSCC) is a debilitating complication in oncology patients. This narrative review discusses the strengths and limitations of various imaging modalities in diagnosing MSCC, the role of imaging in stereotactic body radiotherapy (SBRT) for MSCC treatment, and recent advances in deep learning (DL) tools for MSCC diagnosis. PubMed and Google Scholar databases were searched using targeted keywords. Studies were reviewed in consensus among the co-authors for their suitability before inclusion. MRI is the gold standard of imaging to diagnose MSCC with reported sensitivity and specificity of 93% and 97% respectively. CT Myelogram appears to have comparable sensitivity and specificity to contrast-enhanced MRI. Conventional CT has a lower diagnostic accuracy than MRI in MSCC diagnosis, but is helpful in emergent situations with limited access to MRI. Metal artifact reduction techniques for MRI and CT are continually being researched for patients with spinal implants. Imaging is crucial for SBRT treatment planning and three-dimensional positional verification of the treatment isocentre prior to SBRT delivery. Structural and functional MRI may be helpful in post-treatment surveillance. DL tools may improve detection of vertebral metastasis and reduce time to MSCC diagnosis. This enables earlier institution of definitive therapy for better outcomes.

Radiation myelopathy following stereotactic body radiation therapy for spine metastases.

Stereotactic body radiation therapy (SBRT) is now considered a standard of care treatment option in the management of spine metastases. One of the most feared complications of spine SBRT is radiation myelopathy (RM). We provided a narrative review of RM following spine SBRT based on review of the published literature, including data on spinal cord dose constraints associated with the risk of RM, strategies to mitigate the risk, and management options for RM. There are limited published data of cases of RM following spine SBRT with detailed spinal cord dosimetry. The HyTEC report provided recommendations for the point maximal dose (Dmax) for the spinal cord that is associated with a < 5% risk of RM for 1-5 fractions spine SBRT. In the setting of spine SBRT reirradiation after previous conventional external beam radiation therapy (cEBRT), factors associated with RM are: SBRT spinal cord Dmax, cumulative spinal cord Dmax, and the time interval between previous RT and SBRT reirradiation. There are various strategies to mitigate the risk of RM, including accurate delineation of the spinal cord (or thecal sac), strict adherence to the recommended spinal cord dose constraints, and robust treatment immobilisation set-up and delivery. Limited effective treatment options are available for patients who develop RM, and these include corticosteroids, hyperbaric oxygen, and bevacizumab; however, none have been supported by high quality evidence. RM is a rare but devastating complication following SBRT for spine metastases. There are strategies to minimise the risk of RM to ensure safe delivery of spine SBRT.

Prostate MRI in Stereotactic Body Radiation Treatment Planning and Delivery for Localized Prostate Cancer.

Prostate MRI is increasingly being used to make diagnoses and guide management for patients receiving definitive radiation treatment for prostate cancer. Radiologists should be familiar with the potential uses of prostate MRI in radiation therapy planning and delivery. Radiation therapy is an established option for the definitive treatment of localized prostate cancer. Stereotactic body radiation therapy (SBRT) is an external-beam radiation therapy method used to deliver a high dose of radiation to an extracranial target in the body, often in five or fewer fractions. SBRT is increasingly being used for prostate cancer treatment and has been recognized by the National Comprehensive Cancer Network as an acceptable definitive treatment regimen for low-, intermediate-, and high-risk prostate cancer. MRI is commonly used to aid in prostate radiation therapy. The authors review the uses of prostate MRI in SBRT treatment planning and delivery. Specific topics discussed include the use of prostate MRI for identification of and dose reduction to the membranous and prostatic urethra, which can decrease the risk of acute and late toxicities. MRI is also useful for identification and appropriate dose coverage of the prostate apex and areas of extraprostatic extension or seminal vesicle invasion. In prospective studies, prostate MRI is being validated for identification of and dose intensification to dominant intraprostatic lesions, which potentially can improve oncologic outcomes. It also can be used to evaluate the placement of fiducial markers and hydrogel spacers for radiation therapy planning and delivery. ©RSNA, 2022.