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Stereotactic body radiation therapy (SBRT) is a relatively new technology, and its use among patients with benign spinal tumors has limited prospective data. Similar to intracranial benign tumors treated successfully with SBRT, benign spinal tumors of the same histology can also develop, and SBRT may be an effective treatment alternative in inoperable or recurrent cases. Outcomes in patients with neurofibromatosis type 1, neurofibromatosis type 2, or schwannomatosis treated with SBRT have also been reported. Single institution reports have shown local control rates over 90% and improvement in clinical symptoms. The optimum dose and fractionation to maximize local control and minimize toxicity is unknown, with few incidences of radiation treatment-related toxicities. Given the location and benign nature of these tumors, careful management of dose to critical organs is essential. With continued follow-up, the optimum use of SBRT in patients with benign spinal tumors can be better defined.

Spinal metastases are increasingly becoming a focus of attention with respect to treating with locally "ablative" intent, as opposed to locally "palliative" intent. This is due to increasing survival rates among patients with metastatic disease, early detection as a result of increasing availability of spinal MRI, the recognition of the oligometastatic state as a distinct sub-group of favorable metastatic patients and the advent of stereotactic body radiotherapy (SBRT). Although conventionally fractionated radiation therapy has been utilized for decades, the rates of complete pain relief and local control for complex tumors are sub-optimal. SBRT has the advantage of delivering high total doses in few fractions (typically, 24 Gy in 1 or 2 fractions to 30-45 Gy in 5 fractions) that can be considered "ablative". With mature clinical experience emerging among early adopters, we are realizing beyond efficacy the limitations of spine SBRT. In particular, toxicities such as vertebral compression fracture, and epidural disease progression as the most common pattern of local tumor progression. As a result, the multidisciplinary evaluation of cases prior to SBRT is emphasized with the intent to identify patients who could benefit from surgical stabilization or down-staging of epidural disease. The purpose of this review is to provide an overview of the current literature with respect to outcomes, technical details for safe delivery, patient selection criteria, common and uncommon side effects of therapy, and the increasing use of minimally invasive surgical techniques that can improve both safety and local control.

Simple Summary: Patients with localized renal cell carcinoma often have medical comorbidities limiting their surgical candidacy, thus necessitating less invasive treatment options. Stereotactic ablative radiotherapy has emerged as a safe and effective management option with a growing body of evidence supporting its use. This article discusses recent advances in the use of stereotactic ablation radiotherapy for localized renal cell carcinoma, while guiding providers on practical points for patient selection and clinical application. Localized renal cell carcinoma is primarily managed surgically, but this disease commonly presents in highly comorbid patients who are poor operative candidates. Less invasive techniques, such as cryoablation and radiofrequency ablation, are effective, but require percutaneous or laparoscopic access, while generally being limited to cT1a tumors without proximity to the renal pelvis or ureter. Active surveillance is another management option for small renal masses, but many patients desire treatment or are poor candidates for active surveillance. For poor surgical candidates, a growing body of evidence supports stereotactic ablative radiotherapy (SABR) as a safe and effective non-invasive treatment modality. For example, a recent multi-institution individual patient data meta-analysis of 190 patients managed with SABR estimated a 5.5% five-year cumulative incidence of local failure with one patient experiencing grade 4 toxicity, and no other grade ≥3 toxic events. Here, we discuss the recent developments in SABR for the management of localized renal cell carcinoma, highlighting key concepts of appropriate patient selection, treatment design, treatment delivery, and response assessment. [ABSTRACT FROM AUTHOR]

Simple Summary: Clear cell renal cell carcinoma (ccRCC) frequently occurs in patients with von Hippel–Lindau disease and is a leading cause of mortality in patients with this hereditary disorder. Partial nephrectomy, which is the standard treatment, is often complicated by multilocular tumor occurrence in both kidneys requiring repeated surgeries. Consequently, nephron-sparing resections become increasingly difficult ultimately leading to chronic kidney failure. In these patients or in patients who refuse surgery, alternative treatment approaches are needed. In this study, we investigated the outcome and toxicities especially for the kidney after stereotactic body radiotherapy (SBRT). We could demonstrate that SBRT in this highly vulnerable group of patients is feasible without any high-grade adverse events in the long-term and results in excellent local control at the site of treatment. Efficacy of SBRT is already proven for other anatomic sites and it could represent a valuable, non-invasive treatment option for ccRCC as well, especially for patients who are extremely vulnerable to any kidney injury. Further prospective trials evaluating SBRT for localized ccRCC are necessary to verify the promising findings and to examine its role as an alternative to surgery in inoperable patients. Von Hippel–Lindau disease (VHL) is a hereditary disorder associated with malignant tumors including clear cell renal cell carcinoma (ccRCC). Partial nephrectomy is complicated by multilocular tumor occurrence and a high recurrence rate. The aim of this study was to evaluate the potential of stereotactic body radiotherapy (SBRT) as an alternative treatment approach in VHL patients with multiple ccRCC. Patients with VHL and a diagnosis of ccRCC were enrolled. SBRT was conducted using five fractions of 10 Gy or eight fractions of 7.5 Gy. The primary endpoint was local control (LC). Secondary endpoints included alteration of renal function and adverse events. Seven patients with a total of eight treated lesions were enrolled. Median age was 44 years. Five patients exhibited multiple bilateral kidney cysts in addition to ccRCC. Three patients underwent at least one partial nephrectomy in the past. After a median follow-up of 43 months, 2-year LC was 100%, while 2-year CSS, 2-year PFS and 2-year OS was 100%, 85.7% and 85.7%, respectively. SBRT was very well tolerated with no acute or chronic toxicities grade ≥ 2. Mean estimated glomerular filtration rate (eGFR) at baseline was 83.7 ± 13.0 mL/min/1.73 m2, which decreased to 76.6 ± 8.0 mL/min/1.73 m2 after 1 year. Although the sample size was small, SBRT resulted in an excellent LC rate and was very well tolerated with preservation of kidney function in patients with multiple renal lesions and cysts. [ABSTRACT FROM AUTHOR]

Aim: Oligometastatic cancer is being increasingly managed with aggressive local therapy using stereotactic body radiation therapy (SBRT). However, few guidelines exist. We summarize the results of an international survey reviewing technical factors for extracranial SBRT for oligometastatic disease to guide safe management. Materials & methods: Seven high-volume centers contributed. Levels of agreement were categorized as strong (6-7 common responses), moderate (4-5), low (2-3) or no agreement. Results & conclusion: We present the results of a multi-national and multi-institutional survey of technical factors of SBRT for extracranial oligometastases. Key methods including target delineation, prescription doses, normal tissue constraints, imaging and set-up for safe implementation and practice of SBRT for oligometastasis have been identified. This manuscript will serve as a foundation for future clinical evaluations. [ABSTRACT FROM AUTHOR]

Aim: To provide a multi-institutional description of current practices of stereotactic body radiotherapy (SBRT) for head and neck cancer. Materials & methods: 15 international institutions with significant experience in head and neck SBRT were asked to complete a questionnaire covering clinical and technical factors. Results: SBRT is used 10-100% of the time for recurrent primary head and neck cancer, and 0-10% of the time in newly diagnosed disease. Five centers use a constraint for primary disease of 3-5 cm and 25-30 cc. Nine institutions apply a clinical target volume expansion of 1-10 mm and 14 use a planning target volume margin of 1-5 mm. Fractionation regimens vary between 15 and 22 Gy in 1 fraction to 30-50 Gy in 5 or 6 fractions. The risk of carotid blowout quoted in the re-irradiation setting ranges from 3 to 20%. Conclusion: There is considerable heterogeneity in patient selection and techniques in head and neck SBRT practice among experienced centers. [ABSTRACT FROM AUTHOR]

Aim: This systematic review summarizes the clinical data on focal therapy (FT) when used alone as definitive therapy for primary prostate cancer (PCa). Methods: The protocol is detailed in the online PROSPERO database, registration No. CRD42014014765. Articles evaluating any form of FT alone as a definitive treatment for PCa in adult male patients were included. Results: Of 10,419 identified articles, 10,401 were excluded, and thus leaving 18 for analysis. In total, 2288 patients were treated using seven modalities. The outcomes of FT in PCa seem to be similar to those observed with whole gland therapy and with fewer side effects. Conclusion: Further research, including prospective randomized trials, is warranted to elucidate the potential advantages of focal radiation techniques for treating PCa. Prospero Registration Number: CRD42014014765. [ABSTRACT FROM AUTHOR]

Due to increased effectiveness of cancer treatments and increasing survival rates, metastatic disease has become more frequent compared to the past, with the spine being the most common site of bony metastases. Diagnostic imaging is an integral part of screening, diagnosis and follow-up of spinal metastases. In this article, we review the principles of multimodality imaging for tumor detection with respect to their value for diagnosis and stereotactic body radiation therapy planning for spinal metastases. We will also review the current international consensus agreement for stereotactic body radiation therapy planning, and the role of imaging in achieving the best possible treatment plan. [ABSTRACT FROM AUTHOR]

• SBRT for localized RCC is a promising treatment modality especially in poor surgical candidates. • Dose escalation from 48 - 60 Gy in 3 fractions was achieved with zero dose-limiting toxicities. • Local control following treatment was 90% at 3 years. • Interpretation of post-SBRT biopsies remains uncertain. • Studies comparing SBRT to percutaneous ablation for poor surgical candidates are warranted. We previously demonstrated the safety of doses up to 48 Gy in 4 fractions with stereotactic body radiotherapy (SBRT) in poor surgical candidates with localized renal cell carcinoma (RCC). In an additional expansion cohort, we aimed to assess the safety of further dose escalation to 48–60 Gy in 3 fractions. Patients were required to have localized RCC and be poor surgical candidates due to medical comorbidities. Dose-limiting toxicity (DLT) was defined as acute (<180 days) grade ≥3 gastrointestinal/genitourinary toxicity by CTCAEv4. Tumor response was assessed using RECIST 1.1 criteria measurements every 6 months for 3 years and optional percutaneous biopsy. Groups of 4, 4, and 3 patients received 48, 54, and 60 Gy in 3 fractions, respectively from 2012 to 2016. Median follow-up was 34.3 months. Zero DLTs were observed. Acute toxicities were limited to grade 1 fatigue and nausea in 45.5% and 18.1%. Late grade 2+ and grade 3+ possibly treatment-related events occurred in 18.1% and 9.1%, respectively. Three-year local control was 90% by RECIST 1.1 criteria. Five of 5 post-treatment biopsies in the expansion cohort were positive by Hematoxylin and Eosin staining. Three of the 5 patients with positive biopsies have been observed for 1.2–3.9 years without evidence of progression. Dose escalation to 60 Gy in 3 fractions was achieved without DLTs. Favorable local control rates were observed, and the interpretation of post-SBRT biopsies remains uncertain. Further studies comparing SBRT to percutaneous ablation for poor surgical candidates with RCC are warranted. [ABSTRACT FROM AUTHOR]

• SBRT contouring recommendations for metastatic disease to the sacrum have been established. • High degree of agreement in target delineation among spine SBRT experts. • Critical first step to standardisation of target delineation practice in the sacrum. • The sacral classification system (SCS) guides the anatomic description of contours. • The SCS will help serve as a framework for future pattern of failure analyses. To interrogate inter-observer variability in gross tumour volume (GTV) and clinical target volume (CTV) delineation specific to the treatment of sacral metastases with spinal stereotactic body radiation therapy (SBRT) and develop CTV consensus contouring recommendations. Nine specialists with spinal SBRT expertise representing 9 international centres independently contoured the GTV and CTV for 10 clinical cases of metastatic disease within the sacrum. Agreement between physicians was calculated with an expectation minimisation algorithm using simultaneous truth and performance level estimation (STAPLE) and with kappa statistics. Optimised confidence level consensus contours were obtained using a voxel-wise maximum likelihood approach and the STAPLE contours for GTV and CTV were based on an 80% confidence level. Mean GTV STAPLE agreement sensitivity and specificity was 0.70 (range, 0.54–0.87) and 1.00, respectively, and 0.55 (range, 0.44–0.64) and 1.00 for the CTV, respectively. Mean GTV and CTV kappa agreement was 0.73 (range, 0.59–0.83) and 0.59 (range, 0.41–0.70), respectively. Optimised confidence level consensus contours were identified by STAPLE analysis. Consensus recommendations for the CTV include treating the entire segment containing the disease in addition to the immediate adjacent bony anatomic segment at risk of microscopic extension. Consensus recommendations for CTV target delineation specific to sacral metastases treated with SBRT were established using expert contours. This is a critical first step to achieving standardisation of target delineation practice in the sacrum and will serve as a baseline for meaningful pattern of failure analyses going forward. [ABSTRACT FROM AUTHOR]

• Systematic review of SBRT for pulmonary oligometastases. • The median local control was 90 % at 1 year and 79 % at 5 years. • Acute toxicity ≥3 was reported for 0.5 % and late toxicity ≥3 for 1.8 % of patients. • 21 practice recommendations for staging & selection, SBRT treatment, and follow-up. A systematic review of treatment characteristics, outcomes, and treatment-related toxicities of stereotactic body radiation therapy (SBRT) for pulmonary oligometastases served as the basis for development of this International Stereotactic Radiosurgery Society (ISRS) practice guideline. In accordance with PRISMA guidelines, a systematic review was performed of retrospective series with ≥50 patients/lung metastases, prospective trials with ≥25 patients/lung metastases, analyses of specific high-risk situations, and all randomized trials published between 2012 and July 2022 in the MEDLINE or Embase database using the key words "lung oligometastases", "lung metastases", "pulmonary metastases", "pulmonary oligometastases", "stereotactic body radiation therapy (SBRT)" and "stereotactic ablative body radiotherapy (SBRT)". Weighted random effects models were used to calculate pooled outcomes estimates. Of the 1884 articles screened, 35 analyses (27 retrospective-, 5 prospective, and 3 randomized trials) reporting on treatment of >3600 patients and >4650 metastases were included. The median local control was 90 % (Range: 57–100 %) at 1 year and 79 % (R: 70–96 %) at 5 years. Acute toxicity ≥3 was reported for 0.5 % and late toxicity ≥3 for 1.8 % of patients. A total of 21 practice recommendations covering the areas of staging & patient selection (n = 10), SBRT treatment (n = 10), and follow-up (n = 1) were developed, with agreements rates of 100 %, except for recommendation 13 (83 %). SBRT represents an effective definitive local treatment modality combining high local control rates with low risk of radiation-induced toxicities. [ABSTRACT FROM AUTHOR]

• SBRT for ultra-central lung tumors results in high rates of local control. • SBRT-related severe and fatal toxicity risks were generally uncommon, ≤6 %. • Appropriate patient, target, and dosimetric constraint selection may keep risk of severe toxicity with SBRT at an acceptable level. • Patients with high-risk factors for toxicity, such as endobronchial tumors and anticoagulant use, should be treated carefully; consider non-SBRT schedules. Stereotactic body radiotherapy (SBRT) is an effective and safe modality for early-stage lung cancer and lung metastases. However, tumors in an ultra-central location pose unique safety considerations. We performed a systematic review and meta -analysis to summarize the current safety and efficacy data and provide practice recommendations on behalf of the International Stereotactic Radiosurgery Society (ISRS). We performed a systematic review using PubMed and EMBASE databases of patients with ultra-central lung tumors treated with SBRT. Studies reporting local control (LC) and/or toxicity were included. Studies with <5 treated lesions, non-English language, re-irradiation, nodal tumors, or mixed outcomes in which ultra-central tumors could not be discerned were excluded. Random-effects meta -analysis was performed for studies reporting relevant endpoints. Meta-regression was conducted to determine the effect of various covariates on the primary outcomes. 602 unique studies were identified of which 27 (one prospective observational, the remainder retrospective) were included, representing 1183 treated targets. All studies defined ultra-central as the planning target volume (PTV) overlapping the proximal bronchial tree (PBT). The most common dose fractionations were 50 Gy/5, 60 Gy/8, and 60 Gy/12 fractions. The pooled 1- and 2-year LC estimates were 92 % and 89 %, respectively. Meta-regression identified biological effective dose (BED10) as a significant predictor of 1-year LC. A total of 109 grade 3–4 toxicity events, with a pooled incidence of 6 %, were reported, most commonly pneumonitis. There were 73 treatment related deaths, with a pooled incidence of 4 %, with the most common being hemoptysis. Anticoagulation, interstitial lung disease, endobronchial tumor, and concomitant targeted therapies were observed risk factors for fatal toxicity events. SBRT for ultra-central lung tumors results in acceptable rates of local control, albeit with risks of severe toxicity. Caution should be taken for appropriate patient selection, consideration of concomitant therapies, and radiotherapy plan design. [ABSTRACT FROM AUTHOR]