Image-Guided Robotic Radiosurgery for the Treatment of Lung Metastases of Renal Cell Carcinoma—A Retrospective, Single Center Analysis

Pulmonary metastases are the most frequent site of metastases in renal cell carcinoma (RCC). Metastases directed treatment remains an important treatment option despite advances in systemic therapies. However, the safety and efficacy of robotic radiosurgery (RRS) for the treatment of lung metastases of RCC remains unclear. Patients with metastatic RCC and lung metastases treated by RRS were retrospectively analyzed for overall survival (OS), progression-free survival (PFS), local recurrence free survival (LRFS) and adverse events. The Kaplan–Meier method was used for survival analysis and the common terminology criteria for adverse events (CTCAE; Version 5.0) classification for assessment of adverse events. A total of 50 patients were included in this study. Median age was 64 (range 45–92) years at the time of RRS. Prior to RRS, 20 patients (40.0%) had received either tyrosine kinase inhibitors or immunotherapy and 27 patients (54.0%) were treatment naïve. In our patient cohort, the median PFS was 13 months (range: 2–93). LRFS was 96.7% after two years with only one patient revealing progressive disease of the treated metastases 13 months after RRS. Median OS was 35 months (range 2–94). Adverse events were documented in six patients (12%) and were limited to grade 2. Fatigue (n = 4) and pneumonitis (n = 2) were observed within 3 months after RRS. In conclusion, RRS is safe and effective for patients with metastatic RCC and pulmonary metastases. Radiation induced pneumonitis is specific in the treatment of pulmonary lesions, but not clinically relevant and survival rates seem favorable in this highly selected patient cohort. Future directions are the implementation of RRS in multimodal treatment approaches for oligometastatic or oligoprogressive disease.

The Role of Stereotactic Radiosurgery in the Management of Foramen Magnum Meningiomas—A Multicenter Analysis and Review of the Literature

Background: Foramen magnum meningiomas (FMMs) represent a considerable neurosurgical challenge given their location and potential morbidity. Stereotactic radiosurgery (SRS) is an established non-invasive treatment modality for various benign and malignant brain tumors. However, reports on single-session or multisession SRS for the management and treatment of FMMs are exceedingly rare. We report the largest FMM SRS series to date and describe our multicenter treatment experience utilizing robotic radiosurgery. Methods: Patients who underwent SRS between 2005 and 2020 as a treatment for a FMM at six different centers were eligible for analysis. Results: Sixty-two patients met the inclusion criteria. The median follow-up was 28.9 months. The median prescription dose and isodose line were 14 Gy and 70%, respectively. Single-session SRS accounted for 81% of treatments. The remaining patients received three to five fractions, with doses ranging from 19.5 to 25 Gy. Ten (16%) patients were treated for a tumor recurrence after surgery, and thirteen (21%) underwent adjuvant treatment. The remaining 39 FMMs (63%) received SRS as their primary treatment. For patients with an upfront surgical resection, histopathological examination revealed 22 World Health Organization grade I tumors and one grade II FMM. The median tumor volume was 2.6 cubic centimeters. No local failures were observed throughout the available follow-up, including patients with a follow-up ≥ five years (16 patients), leading to an overall local control of 100%. Tumor volume significantly decreased after treatment, with a median volume reduction of 21% at the last available follow-up (p < 0.01). The one-, three-, and five-year progression-free survival were 100%, 96.6%, and 93.0%, respectively. Most patients showed stable (47%) or improved (21%) neurological deficits at the last follow-up. No high-grade adverse events were observed. Conclusions: SRS is an effective and safe treatment modality for FMMs. Despite the paucity of available data and previous reports, SRS should be considered for selected patients, especially those with subtotal tumor resections, recurrences, and patients not suitable for surgery.

Cyberknife Radiosurgery for the Treatment of Head and Neck Cancer: A Systematic Review

Cyberknife radiosurgery is a frameless stereotactic robotic radiosurgery which has shown to deliver better treatment outcomes in the treatment of advanced head and neck (H&N) carcinomas, especially in previously irradiated and recurrent cases. The aim of the study was to perform a systematic review of the available data on the outcomes of Cyberknife radiosurgery for treatment of head and neck cancer and to evaluate its collective outcomes. This systematic review was registered with the university with the registration no. FRP/2019/63 and was approved by the Institutional Review Board (RC/IRB/2019/132). Literature search was performed in the following: PubMed, Science direct, SciELO, MyScienceWork, Microsoft Academ EMBASE, Directory of Open Access Journals, and Cochrane databases with the keywords “Cyberknife,” “oral cancer,” “oropharyngeal cancer,” and “head and neck cancer” and data was extracted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The records identified were 147 manuscripts. Excluded articles included 5 duplicate articles, 33 abstracts, 101 full text articles due to being off-topic, case reports, review, non-English, 1 survey, and 2 other articles containing data extracted from a main study which was already included. A total of 5 articles were evaluated for qualitative synthesis. The mean dose of Cyberknife radiosurgery delivered for previously irradiated recurrent H&N carcinoma patients was 34.57 Gy, with a mean sample size of 5 studied during the period of 2000 to 2016. The available evidence from the systematic review indicates that Cyberknife can be an efficacious treatment option for recurrent previously irradiated H&N carcinoma, especially for nonresectable tumors. There is paucity of homogenous data and studies in this arena; hence, meta-analysis could not be performed. Further standardized studies are essential, especially where the treatment of H&N carcinoma is considered.

Impact of prescription isodose level and collimator selection on dose homogeneity and plan quality in robotic radiosurgery

Purpose In stereotactic radiosurgery (SRS), prescription isodoses and resulting dose homogeneities vary widely across different platforms and clinical entities. Our goal was to investigate the physical limitations of generating dose distributions with an intended level of homogeneity in robotic SRS. Methods Treatment plans for non-isocentric irradiation of 4 spherical phantom targets (volume 0.27–7.70 ml) and 4 clinical targets (volume 0.50–5.70 ml) were calculated using Sequential (phantom) or VOLOTM (clinical) optimizers (Accuray, Sunnyvale, CA, USA). Dose conformity, volume of 12 Gy isodose (V12Gy) as a measure for dose gradient, and treatment time were recorded for different prescribed isodose levels (PILs) and collimator settings. In addition, isocentric irradiation of phantom targets was examined, with dose homogeneity modified by using different collimator sizes. Results Dose conformity was generally high (nCI ≤ 1.25) and varied little with PIL. For all targets and collimator sets, V12Gy was highest for PIL ≥ 80% and lowest for PIL ≤ 65%. The impact of PIL on V12Gy was highest for isocentric irradiation and lowest for clinical targets (VOLOTM optimization). The variability of V12Gy as a function of collimator selection was significantly higher than that of PIL. V12Gy and treatment time were negatively correlated. Plans utilizing a single collimator with a diameter in the range of 70–80% of the target diameter were fastest, but showed the strongest dependence on PIL. Conclusion Inhomogeneous dose distributions with PIL ≤ 70% can be used to minimize dose to normal tissue. PIL ≥ 90% is associated with a marked and significant increase in off-target dose exposure. Careful selection of collimators during planning is even more important.

RADT-30. MULTISESSION RADIOSURGERY ALONE FOR TREATMENT OF PRESUMED MENINGIOMAS: AN INTERIM REPORT FROM A SINGLE INSTITUTION PROTOCOL

PURPOSE Meningiomas are the most commonly diagnosed primary intracranial tumor. Resection and single-fraction radiosurgery are treatment options with well-established long-term outcomes data. Multisession radiosurgery is an alternative treatment option with promising early results. However, mature outcomes literature does not yet exist. In this study, we report our institution’s interim results on the efficacy and safety of 5-fraction radiosurgery alone for radiographically diagnosed meningiomas. MATERIALS AND METHODS Between 2005-2015 all patients who completed treatment on a single institution protocol utilizing 5-fraction robotic radiosurgery alone for the treatment of progressing radiographically diagnosed meningiomas were eligible for inclusion. Local control was calculated using the Kaplan-Meier Method. RESULTS Forty-four consecutive predominately female patients (84%) ranging in age from 33-85 (median: 59) were included in the present study. Median tumor volume was 4.05mm3 (range: 0.94-15.4mm3) and the majority of tumors were located at the base of skull (66%). A median dose of 25Gy (range: 25Gy-35Gy), was delivered to a median isodose line of 82%, (range: 70%-90%) over a median of 7 days (range: 5-11 days). Acute toxicity was minimal with 7 patients (15%) requiring a short course of steroids for symptomatic edema during treatment. Of 16 patients who presented with a cranial nerve deficit, symptom improvement was noted in 11 patients (69%). No permanent treatment related toxicity was noted in our cohort. The median radiographic follow-up was 6.9 years (range: 0.5-14.8 years). The 5 and 8-year local control rates were 100% and 95%. The median time to local failure (n=2) in our cohort was 8.2 years. CONCLUSIONS The treatment of radiographically diagnosed meningiomas with 5-fraction robotic radiosurgery provides excellent local control to date, with low rates of acute and late toxicity. However, with late failures noted in our series, continued follow-up is needed to determine the optimal dose required for long-term tumor control.

A new prognostic score for predicting survival in patients treated with robotic stereotactic radiotherapy for brain metastases

The study aimed to analyze potential prognostic factors in patients treated with robotic radiosurgery for brain metastases irrespective of primary tumor location and create a simple prognostic score that can be used without a full diagnostic workup. A retrospective analysis of 142 patients with 1–9 brain metastases treated with stereotactic radiosurgery (1–4 fractions) was performed. Volumes of all lesions were calculated using linear dimensions of the tumors (CC, LR, AP) and 4/3*π*(CC/2)*(LR/2)*(AP/2) formula. Kaplan–Meier method and log-rank test were used to analyze survival. Variables significantly associated with overall survival in univariate analysis were included in Cox multivariate analysis. The validity of the model was tested with the bootstrap method. Variables from the final model were used to construct a new prognostic index by assigning points according to the impact of a specific variable on overall survival. In the multivariate analysis, four factors: Karnofsky Performance Status (p = 0.000068), number of brain metastases (p = 0.019), volume of the largest lesion (p = 0.0037), and presence of extracerebral metastases (p = 0.0017), were independent predictors of survival. Total scores ranged from 0 to 12 points, and patients were divided into four groups based on median survival of each subgroup: 0–1 points—18.8 months, 2–3 points—16.9 months, 4–5 points—5.6 months, and ≥ 6 points—4.9 months (p < 0.001). The new prognostic index is simple to calculate. It has a strong prognostic value in a heterogeneous population of patients with a various number of brain metastases, but its value requires confirmation in another cohort.

Risks and Benefits of Fiducial Marker Placement in Tumor Lesions for Robotic Radiosurgery: Technical Outcomes of 357 Implantations

Fiducial markers (FM) inserted into tumors increase the precision of irradiation during robotic radiosurgery (RRS). This retrospective study evaluated the clinical complications, marker migration, and motion amplitude of FM implantations by analyzing 288 cancer patients (58% men; 63.1 ± 13.0 years) who underwent 357 FM implantations prior to RRS with CyberKnife, between 2011 and 2019. Complications were classified according to the Society of Interventional Radiology (SIR) guidelines. The radial motion amplitude was calculated for tumors that moved with respiration. A total of 725 gold FM was inserted. SIR-rated complications occurred in 17.9% of all procedures. Most complications (32.0%, 62/194 implantations) were observed in Synchrony®-tracked lesions affected by respiratory motion, particularly in pulmonary lesions (46.9% 52/111 implantations). Concurrent biopsy sampling was associated with a higher complication rate (p = 0.001). FM migration occurred in 3.6% after CT-guided and clinical FM implantations. The largest motion amplitudes were observed in hepatic (20.5 ± 11.0 mm) and lower lung lobe (15.4 ± 10.5 mm) lesions. This study increases the awareness of the risks of FM placement, especially in thoracic lesions affected by respiratory motion. Considering the maximum motion amplitude, FM placement remains essential in hepatic and lower lung lobe lesions located >100.0 mm from the spine.