Vertebral Compression Fracture After Spine Stereotactic Body Radiotherapy: The Role of Vertebral Endplate Disruption

BACKGROUND AND OBJECTIVES

Vertebral compression fracture (VCF) is a common, but serious toxicity of spinal stereotactic body radiotherapy (SBRT). Several variables that place patients at high risk of VCF have previously been identified, including advanced Spinal Instability Neoplastic Score (SINS), a widely adopted clinical decision criterion to assess spinal instability. We examine the role of tumoral endplate (EP) disruption in the risk of VCF and attempt to incorporate it into a simple risk stratification system.

METHODS

This study was a retrospective cohort study from a single institution. Demographic and treatment information was collected for patients who received spinal SBRT between 2013 and 2019. EP disruption was noted on pre-SBRT computed tomography scan. The primary end point of 1-year cumulative incidence of VCF was assessed on follow-up MRI and computed tomography scans at 3-month intervals after treatment.

RESULTS

A total of 111 patients were included. The median follow-up was 18 months. Approximately 48 patients (43%) had at least one EP disruption. Twenty patients (18%) experienced a VCF at a median of 5.2 months from SBRT. Patients with at least one EP disruption were more likely to experience VCF than those with no EP disruption (29% vs 6%, P < .001). A nomogram was created using the variables of EP disruption, a SINS of ≥7, and adverse histology. Patients were stratified into groups at low and high risk of VCF, which were associated with 2% and 38% risk of VCF ( P < .001).

CONCLUSION

EP disruption is a novel risk factor for VCF in patients who will undergo spinal SBRT. A simple nomogram incorporating EP disruption, adverse histology, and SINS score is effective for quickly assessing risk of VCF. These data require validation in prospective studies and could be helpful in counseling patients regarding VCF risk and referring for prophylactic interventions in high-risk populations.

Initial Report of Boswellia Serrata for Management of Cerebral Radiation Necrosis after Stereotactic Radiosurgery for Brain Metastases

PURPOSE/OBJECTIVE(S)

Radiation necrosis (RN) is a concerning late toxicity after radiation therapy (RT) for brain metastases. Oral corticosteroids are the mainstay of management; however, they are not optimal for long-term use given multiple side effects and drug interactions, particularly with the emergence of immunotherapy for several cancers. Boswellia serrata (BS) is an over-the-counter supplement used for its anti-inflammatory properties and has been recently shown to reduce cerebral edema after brain RT. We evaluated the response rates with BS in a series of patients with brain metastases treated with stereotactic radiosurgery (SRS) who developed RN.

MATERIALS/METHODS

We included patients who developed RN after SRS for brain metastases at our institution from 2020-2022 and were treated with BS. Patients were prescribed over the counter BS 4.2-4.5g daily in divided doses. Follow-up MRI imaging was obtained every 2-3 months after starting BS. Response was assessed using Response Assessment in Neuro-Oncology (RANO) criteria. Primary endpoint was ≥25% decrease in edema volume on T2-FLAIR MRI from baseline. Patients were censored if they had tumor progression or repeat RT to necrotic area, or death. Kaplan-Meier curves were used for survival estimates.

RESULTS

A total of 50 patients received BS for Grade 1-3 CTCAE v5.0 RN (G1 = 11, G2 = 36, and G3 = 3). Median age was 62.8 years (range 36.9 - 50) and median RT dose was 24 Gy in 3 fractions. Median time to RN after SRS was 10 months(m). Median follow-up after starting BS was 6m and 40 patients had at least 1 follow up MRI available to evaluate response. The best response was complete response (CR) in 15% patients and partial response (PR) in 40% while 35% had stable disease (SD) and 10% had progressive disease. Median time to CR was 9m (6-12m) and PR was 6m (3-12m). Percentage of patients who had any response (CR or PR) at 3, 6, 9 and 12 months was 25%, 60%, 43% and 50%, respectively. 56% patients had symptomatic RN, of which 35.7% had improvement in symptoms with BS alone, while 64% required steroid use. Overall, median duration of response in patients with CR, PR or SD was 7.5m(range 2-31m). Salvage treatment for RN was steroids (33), surgery (4), Bevacizumab (5) or hyperbaric oxygen therapy (1). No patients had any CTCAE grade 3 or higher toxicities. 3 patients (6%) had any side-effects all of whom had Grade 1-2 gastrointestinal intolerance or diarrhea. 2 patients stopped treatment due to enrolment on an immunotherapy clinical trial. Overall, 39 patients remained on BS at last follow-up or death.

CONCLUSION

We observed >50% response rates with use of BS in our cohort of patients with Grade 1-3 RN after SRS. More than 1/3rd patients with symptomatic RN were able to avoid long-term steroid use. BS is an easily available over-the-counter drug that appears to be a safe and promising treatment option for RN, and can potentially decrease steroid dependence in these patients, reducing the risk of several side-effects. Further prospective studies to compare Boswellia with placebo is warranted.

WBRT is Associated with Higher Rates of Hematologic Toxicity than Stereotactic Radiosurgery in Brain Metastasis Patients

PURPOSE/OBJECTIVE(S)

Whole brain radiotherapy (WBRT) has historically been a standard of care in patients with multiple brain metastases. Studies show that WBRT may be associated with a transient detriment in hematological parameters because of exposure to a larger proportion of circulating lymphocytes, platelets and hematopoietic cells within the bone marrow of the cranium. In this study, we tested the hypothesis that stereotactic radiotherapy (SRS) may cause reduced hematologic toxicity in patients compared to WBRT.

MATERIALS/METHODS

We retrospectively identified 100 patients treated for brain metastasis, with either SRS or WBRT from 2016 to 2019, and queried their pre- and post-treatment hematological parameters including hemoglobin, total white blood cell (WBC), absolute neutrophil count (ANC), absolute lymphocyte count, and platelet count. CTCAE v5.0 was used for grading hematologic toxicities. Serial values were compared by treatment type and controlled for age, gender, and systemic therapy. Student t-test was used for intergroup comparison and p-value <0.05 was considered significant.

RESULTS

Of 100 patients, median brain metastases was 3 (range 1-22), 51 received SRS and 49 received WBRT. We observed that patients treated with WBRT had a significantly higher post-treatment reduction in platelet count (-51.2 vs 9.8; p = 0.001) and higher incidence of any grade thrombocytopenia (31.2% vs 10%; p = 0.019) compared to patients treated with SRS. We also noted that compared with SRS, WBRT was associated with a higher post-treatment reduction in circulating lymphocytes (-0.80 vs 0.14; p = 0.071) and higher incidence of G3+ lymphopenia (43.2% vs 22.2%; p = 0.07). Numerical incidence of any G3+ hematological toxicity was also higher in the WBRT group but the difference was not statistically significant (40% vs 28%, p = 0.162). Hemoglobin count, WBC, and ANC were not meaningfully different pre- and post-treatment for either group.

CONCLUSION

WBRT results in an increased amount and duration of radiation exposure to circulating intracranial blood volume. In our study, patients treated with WBRT experienced higher rates of clinically significant lymphopenia & thrombocytopenia compared to patients treated with SRS. In addition to the cognitive benefits of SRS compared to WBRT, there may be significant hematologic benefits as well. Further studies are warranted to clarify and validate these findings.

Volumetric Modulated Arc Therapy Craniospinal Irradiation Utilizing a Vertebral Body Sparing Approach: A Toxicity Analysis

PURPOSE/OBJECTIVE(S)

Craniospinal irradiation (CSI) is indicated for adult patients diagnosed with leptomeningeal disease (LMD). Proton-based vertebral-body-sparing (VBS) CSI has been explored with pediatric patients to minimize hematologic toxicity; however, utilization of VBS in an adult population is limited. A recent phase II trial (Yang et al, JCO 2022) has shown efficacy of proton-based CSI to treat non-small cell lung and breast cancer with LMD. We hypothesize that VBS-CSI utilizing volumetric modulated arc therapy (VMAT) could also effectively reduce dose to vertebral bodies and surrounding organs-at-risk (OARs), minimizing toxicity for adult patients with LMD and comparing favorably to proton-based CSI.

MATERIALS/METHODS

Consecutive patients with leptomeningeal disease received VMAT VBS-CSI, 30 Gy in 10 fractions, as a part of a prospective registry. Full VMAT arcs for the brain fields matched to two spine isocenters for the upper and lower spine were created utilizing limited posterior arcs. The PTV was created with margins of 3mm uniformly around the brain contour and 7mm around the spinal canal. To further decrease the vertebral body dose, an avoid entry and exit contour was created. This structure was a margin on the PTV anteriorly designed to carve dose out of the vertebral bodies while still maintaining coverage to the PTV. Acute toxicity data were collected using Common Terminology Criteria for Adverse Events (CTCAE) v5 and was defined as toxicity occurring within 30 days of treatment conclusion.

RESULTS

Ten adult patients were treated in this cohort. All patients completed radiation treatment. One patient experienced Grade 2 neutropenia with the remaining nine experiencing Grade 1 hematologic toxicity (three Grade 1 pancytopenia, six Grade 1 thrombocytopenia). Three patients experienced Grade 2 gastrointestinal toxicity (Grade 2 nausea, Grade 2 esophagitis, Grade 2 esophagitis/Grade 2 diverticulitis) with the remaining seven experiencing Grade 1 nausea. No patient experienced Grade 3+ toxicities in this cohort. One patient experienced a 5-day delay in systemic therapy initiation due to neutropenia; otherwise, all patients planned for systemic therapy started without delay.

CONCLUSION

VMAT VBS-CSI is an effective technique to reduce dose to surrounding OARs and vertebral bodies. In this study, VMAT VBS-CSI led to acceptable toxicity compared to patients treated with proton CSI on a phase 2 clinical trial. An NRG phase 3 clinical trial may be developed to evaluate the efficacy of proton-based CSI for patients with LMD. However, these data show how VMAT VBS-CSI may be an acceptable alternative for centers without proton therapy capabilities. Given its promising early results, future prospective evaluation of the technique is warranted.

Patient-Reported Cognitive Outcomes and Survival after Stereotactic Radiosurgery for 15 or More Brain Metastases

PURPOSE/OBJECTIVE(S)

Overall survival (OS) in metastatic cancer patients has been improving with continued advancements, necessitating greater attention to treatment related toxicities. Patients with ≥ 15 brain metastases (BM) continue to be treated with whole brain radiation therapy (WBRT), despite poor neurocognitive outcomes. We analyzed our institutional experience of treating these patients with stereotactic radiosurgery (SRS), with the aim of evaluating safety, cognitive outcomes, and survival metrics.

MATERIALS/METHODS

Patients who received SRS for ≥ 15 BMs in 1-5 fractions from 2014-2022 using the previously described single isocenter multi-target technique were included. Cognitive outcomes were objectively evaluated using serial Patient-Reported Outcome Measurement Information System (PROMIS) scores. Kaplan-Meier method was used for survival analysis and log-rank test was used for intergroup comparisons.

RESULTS

A total of 118 patients underwent 124 courses of LINAC-based SRS. The mean and median number of lesions treated per patient was 24.8 and 20, respectively (range 15 - 94). Most common primary histologies were lung (47.6%), melanoma (21.0%), and breast (14.5%). The median SRS dose was 24 Gy (range 18 - 30 Gy) with 87.9% receiving 3 fraction SRS. At the time of SRS, 19.4% patients had received prior WBRT and 24.2% had received at least one prior SRS course. The rate of any grade radiation necrosis (RN) and ≥ grade 3 RN were 15.3% and 3.2% respectively. New onset seizures were seen in 2.4%, alopecia in 2.4%, and subjective cognitive decline in 4% of patients. Median follow-up by reverse Kaplan-Meier method was 17.8 months (m). Cognitive data was available for 38 patients. Mean PROMIS scores at baseline, 3m, 6m and 9m after SRS were 32.0, 31.6, 30.4 and 28.7 out of 40, respectively. When longitudinal trends were available, 25 of 31 patients had a stable or improved PROMIS score. The 12m local control was 97.6%. Cumulative incidence of distant intracranial failure was 79.2%. One year freedom from neurological death, leptomeningeal disease, and salvage WBRT were 85.6%, 87.6% and 71.7% respectively. Median OS from brain metastases diagnosis was 11.3m (95% CI 7.2m - 15.3m) overall, while it was 9.2m (6.5 - 11.8m) after excluding patients who had prior WBRT or SRS (n = 79). One-year survival was 40% from diagnosis and 38.7% from SRS. On Cox regression analysis, prior WBRT (p = 0.002), higher KPS (p = 0.050), systemic therapy after SRS (p<0.001), and controlled extracranial disease (p = 0.007) predicted for improved OS.

CONCLUSION

We present here the largest study evaluating SRS for patients with ≥ 15 BMs. We found that SRS was safe, had favorable cognitive outcomes, and comparable survival outcomes to contemporary studies evaluating WBRT in this patient population. Treatment-naïve patients had a median survival of > 6 months, long enough to benefit from cognitive sparing with SRS. Our study supports further randomized studies comparing SRS and memory avoidance WBRT approaches for patients with ≥ 15 BMs.

Advancing beyond the Hippocampus to Preserve Cognition for Patients with Brain Metastases: Dosimetric Results from a Phase 2 Trial of Memory-Avoidance Whole Brain Radiotherapy

PURPOSE/OBJECTIVE(S)

Recent advances to preserve neurocognitive function in patients treated for brain metastases include stereotactic radiosurgery (SRS), hippocampal avoidance whole brain radiation therapy (HA-WBRT), and memantine administration. However, 23% of patients receiving HA-WBRT and memantine on NRG-CC001 still experienced executive function deterioration at 4 months, with 12% experiencing total recall and delayed recognition deterioration at 6 months. The hippocampus, corpus callosum, fornix, and amygdala are key neurocognitive substructures with a low propensity for brain metastases. Herein, we report our preliminary experience using an advanced "memory-avoidance" WBRT (MA-WBRT) approach sparing these substructures for patients with multiple (>15) brain metastases.

MATERIALS/METHODS

Ten consecutive patients treated with MA-WBRT on a phase 2 clinical trial (OSU-21074) were reviewed. In each patient, the hippocampi, amygdalae, corpus callosa, and fornix were contoured. Patients were not eligible for MA-WBRT if they had metastases in these substructures. A memory- avoidance region created using a 5mm volumetric expansion around these substructures. Hotspots were avoided in the hypothalamus and pituitary gland. Dose constraints for these avoidance structures were modeled after NRG CC-001 and include a D100% ≤ 9 Gy and a D0.03 cc ≤ 16 (acceptable to 20 Gy). Coverage of brain metastases was prioritized over memory avoidance dose constraints. Linac-based volumetric modulated arc therapy (VMAT) plans were generated for a prescription dose of 30 Gy in 10 fractions.

RESULTS

On average, the memory avoidance structure volume was 37.1 ccs (Range: 25.2-44.6 ccs), occupying 2.5% of the entire whole brain target volume. All treatment plans met the D100% dose constraint, and 8/10 plans met the D0.03cc constraint, with priority given to tumor coverage for the remaining 2 cases. VMAT spared the memory avoidance structures with a median dose range of 10.8-14.2 Gy and a maximum dose (D0.03cc) range of 15.6-22.7 Gy. The mean dose to the memory avoidance structures was 12.7 Gy (Range: 11.5-13.8 Gy). Target coverage (D98% > 25 Gy) and homogeneity (D2% ≤ 37.5 Gy) were achieved for all plans.

CONCLUSION

Modern VMAT techniques allow for sparing of the hippocampus, amygdala, corpus callosum, and fornix with good target coverage and homogeneity. Prospective quality of life and cognitive data including are being collected and include the Functional Assessment of Cancer Therapy - Brain (Fact-Br), Hopkins Verbal Learning Test (HLVT-R), Trail Making Test A/B (TMT-A/B) and Controlled Oral Word Association Test (COWAT). After enrollment is completed, these data will be evaluated to assess the efficacy of MA-WBRT to mitigate declines in quality of life and cognition after whole brain radiation.

Vertebral Compression Fracture Post Spine Stereotactic Body Radiotherapy: The Role of Vertebral Endplate

PURPOSE/OBJECTIVE(S)

Maintaining hydrostatic pressure -via Pascal's Principle- between vertebral bodies is essential to decrease the chance of vertebral compression fracture (VCF). Vertebral endplates (EP) play an essential role in this matter through maintaining the mechanical environment as well as the proper nutrition of avascular discs. The purpose of this study is to establish the correlation of VCF with disrupted EP by tumor involvement.

MATERIALS/METHODS

A retrospective analysis of de novo spine metastases treated with stereotactic body radiotherapy (SBRT) between 2013-2019. Patients (pts) with previous surgical intervention were excluded. VCF defined as new or progression of existing loss of vertebral body height. The vertebral EP region defined in relation to the vertebral body as superior EP vs inferior EP. Kaplan-Meier curves used to analyze the variables. A multivariate proportional hazard model used to assess the risk of all covariates.

RESULTS

A total of 111 pts were treated with SBRT with a median dose of 27 Gy (10-35 Gy). Median follow-up was 18 months (1.2-107). The median age was 60 years (24-87) and 59 were males (53%) and 52 were females (47%). The median body mass index (BMI) was 27 kg/m2 (16-47). Almost 9 pts diagnosed with osteoporosis prior radiation. Twelve pts received prolonged steroids. Twenty pts received bisphosphonate and 8 pts received denosumab. The median PTV was 50cc (8-465) and median Conformity Index was 1.05 (0.42-1.4). Almost 75% of pts received >95% of the dose covering 100% of the PTV. The most common histopathologies were renal cell carcinoma (25%), lung (13%) and breast (11%). Most of the pts (77%) had SINS score of 7 or less. 48 pts (43%) had either superior or inferior EP disruption secondary to the tumor at the time of radiation. Twenty pts (18%) had both superiorly and inferiorly disrupted EP. Around 20 pts (18%) developed VCF. The median time to VCF was 5.2 months (1.1-57.4). The one-year cumulative incidence of VCF was 18%. The 1-year cumulative incidence of VCF with either superiorly and/or inferiorly disrupted EP was 29% vs 6%, p value <0.001. The 1-year cumulative incidence of VCF with both superiorly and inferiorly disrupted EP was 57% vs 7% (p value <0.001). The median time to VCF was earlier in pts with both disrupted EP (2.4 months vs 5.7 months, p value <0.05). Other risk factors like SINS score of >7 and local recurrence (LR) associated with higher risk of VCF. On multivariate analysis, LR (HR 8.2 [CI 2.4-28, p- value <0.001]), tumor disrupting the EP (HR 4.5 [CI 1.3-16, p-value<0.018]) and SINS score of seven and above (HR 1.7 [CI 1.3-2.25, p-value <0.001]) correlated with the VCF risk.

CONCLUSION

In this retrospective analysis, tumor disrupting the EP, disease recurrence and high SINS score increased the risk of VCF. Cement augmentation either prophylactically or immediately following SBRT is currently being studied in a prospective trial within our institution.

Brachial Plexus Tolerance to Standard Fractionation Re-Irradiation: The Ohio State University Experience

PURPOSE/OBJECTIVE(S)

Factors contributing to brachial plexopathy (BPP) in the re-irradiation setting need further assessment. Preliminary work revealed that higher the doses and the use of concurrent cisplatin were associated with higher risk of BPP. Here, we expand our cohort and increase our follow-up duration, given the late nature of BPP development.

MATERIALS/METHODS

Sixty-two BP sites with 41 patients (pts), treated between 2015 and 2020 for recurrent H&N cancer, were assessed. Contours and plans were reviewed via a prospective multidisciplinary chart rounds prior to treatment delivery and re-verified by two authors prior to this analysis. Kaplan-Meier and logistic regression were used to test the correlation between variables and outcomes. ROC was used to evaluate the cutoff values. Common terminology criteria of adverse events were used to define BPP.

RESULTS

The median age of pts was 63 (29-78) and 65% were males. Median prescription dose was 70 Gy (60-70) for the 1st course and 66 Gy (44-70) for the 2nd course. 13% received intraoperative radiotherapy (IORT) during salvage treatment ranging from 10-15 Gy. 30% of pts in the 1st course and 80% in the 2nd course of pts had surgery. Concurrent chemotherapy was delivered to 71% of pts in the 1st course (Cisplatin 34%, Cetuximab 22%, Carboplatin +/- Paclitaxel 15%) and 76% in the 2nd course (Carboplatin/Paclitaxel 41%, Cisplatin 19%, Cetuximab 12%, Nivolumab 4%). The median interval between courses was 26.5 months (8-221). The median cumulative Dmax (0.03cc) and mean dose to the BP were 96.5 Gy (51-144) and 61.5 Gy (15-110), respectively. The median V60, V70, V80, V90, and V100 were 3.6cc (0.03-10.4), 2.4cc (0-9.9), 1.3cc (0-9.3), 0.6cc (0-8.4), and 0.0015cc (0-7.2), respectively. The median follow-up after the completion of the 2nd RT course was 19 months (1.4-71.5). The 1-yr incidence of BPP was 17%, with a median time to onset of 8.9 months (1-16.6). Factors associated with development of BPP were cumulative Dmax > 100 Gy (HR 1.06, [CI 1.014-1.1], p = 0.009), cumulative mean dose >70 Gy (HR 1.05, [CI 1.01-1.09], p = 0.03), V80 > 1.6cc (HR 1.2. [CI 0.99- 1.52], p = 0.06), V90 > 1cc (HR 1.3, [CI 1.013-1.58], p = 0.038), V100 > 0.3cc (HR 1.33, [1.044-1.69], p = 0.021) and the usage of concurrent cisplatin during the 2nd course (HR 8.9, [CI 2.36-33.75], p = 0.001). Other factors including gender, age, surgery, treatment interval between the two courses, IORT, V60, and V70 were not associated with increased risk of BPP. The incidence of grade 1, grade 2, and grade 3 BPP were 9.6%, 3% and 2.4%, respectively. The 1-yr OS was 70% and LC was 60%.

CONCLUSION

At a median follow up of 19 months, the 1-yr incidence of grade 2 and 3 BPP was approximately 5%. Cisplatin during the 2nd course, cumulative metrics of Dmax 100 Gy, mean 70 Gy, V80 1.6cc, V90 1cc and V100 0.3cc were associated with development of BPP. Prospective study, longer follow up, and higher numbers are warranted. To our knowledge, this represents the largest cohort and longest follow up yet reported for BPP in the re-irradiation setting.

Neoadjuvant Arterial Embolization of Spine Metastases Associated With Improved Local Control in Patients Receiving Surgical Decompression and Stereotactic Body Radiotherapy

BACKGROUND

Spine metastases often cause significant pain, instability, and/or neurological morbidity. Local control (LC) of spine metastases has been augmented with advances in systemic therapies, radiation, and surgical technique. Prior reports suggest an association between preoperative arterial embolization and improved LC and palliative pain control.

OBJECTIVE

To further elucidate the role of neoadjuvant embolization on LC of spine metastases and the potential for improved pain control in patients receiving surgery and stereotactic body radiotherapy (SBRT).

METHOD

A retrospective single-center review between 2012 and 2020 identified 117 patients with spinal metastases from various solid tumor malignancies managed with surgery and adjuvant SBRT with or without preoperative spinal arterial embolization. Demographic information, radiographic studies, treatment characteristics, Karnofsky Performance Score, Defensive Veterans Pain Rating Scale, and mean daily doses of analgesic medications were reviewed. LC was assessed using magnetic resonance imaging obtained at a median 3-month interval and defined as progression at the surgically treated vertebral level.

RESULTS

Of 117 patients, 47 (40.2%) underwent preoperative embolization, followed by surgery and SBRT and 70 (59.8%) underwent surgery and SBRT alone. Within the embolization cohort, the median LC was 14.2 months compared with 6.3 months among the nonembolization cohort ( P = .0434). Receiver operating characteristic analysis suggests ≥82.5% embolization predicted significantly improved LC (area under the curve = 0.808; P < .0001). Defensive Veterans Pain Rating Scale mean and maximum scores significantly decreased immediately after embolization ( P < .001).

CONCLUSION

Preoperative embolization was associated with improved LC and pain control suggesting a novel role for its use. Additional prospective study is warranted.

Assessment of MRI image distortion based on 6 consecutive years of annual QAs and measurements on 14 MRI scanners used for radiation therapy

PURPOSE

To determine the magnitude of MRI image distortion based on 6 consecutive years of annual quality assurances/measurements on 14 MRI scanners used for radiation therapy and to provide evidence for the inclusion of additional margin for treatment planning.

METHODS AND MATERIALS

We used commercial MRI image phantoms to quantitatively study the MRI image distortion over period of 6 years for up to 14 1.5 and 3 T MRI scanners that could potentially be used to provide MRI images for treatment planning. With the phantom images collected from 2016 to 2022, we investigated the MRI image distortion, the dependence of distortion on the distance from the imaging isocenter, and the possible causes of large distortion discovered.

RESULTS

MRI image distortion increases with the distance from the imaging isocenter. For a region of interest (ROI) with a radius of 100 mm centered at the isocenter, the mean magnitude of distortion for all MRI scanners is 0.44 ± 0.18 mm $0.44 \pm 0.18\;{\rm{mm}}$ , and the maximum distortion varies from 0.52 to 1.31 mm $0.52\;{\rm{to}}\;1.31\;{\rm{mm}}$ depending on MRI scanners. For an ROI with a radius of 200 mm centered at the isocenter, the mean magnitude of distortion increases to 0.84 ± 0.45 mm $0.84 \pm 0.45\;{\rm{mm}}$ , and the range of the maximum distortion increases to 1.92 - 5.03 mm $1.92 - 5.03\;{\rm{mm}}$ depending on MRI scanners. The distortion could reach 2 mm at 150 mm from the isocenter.

CONCLUSION

An additional margin to accommodate image distortion should be considered for treatment planning. Imaging with proper patient alignment to the isocenter is vital to reducing image distortion. We recommend performing image distortion checks annually and after major upgrade on MRI scanners.

RADT-12. PRE- AND POST-OPERATIVE RADIATION TREATMENT PLANNING FOR PATIENTS RECEIVING STEREOTACTIC RADIOSURGERY FOR BRAIN METASTASES: A VOLUMETRIC ANALYSIS

BACKGROUND

Pre-operative stereotactic radiosurgery (SRS) has emerged as a recent treatment option to treat large or symptomatic brain metastases. Compared to post-operative SRS, pre-operative treatment may reduce rates of radiation necrosis (RN) and meningeal disease through treating a smaller treatment volume and by preventing post-operative tumor seeding. We hypothesize that pre-operative radiation volumes will be smaller than post-operative volumes, which in turn may lead to a decreased treatment morbidity.

METHODS

A retrospective analysis was conducted and patients who had surgical resection and post-operative SRS or fractionated stereotactic radiosurgery (FSRT) for a posterior fossa brain metastasis were eligible for inclusion. Both pre-operative and post-operative MRIs were required to allow for accurate radiation target delineation. A pre-operative tumor volume was added for each patient, and the post-operative clinical treatment volume (CTV) used for radiation treatment was included. Pre-operative tumor and post-operative cavity volumes were compared using Wilcoxon signed rank test.

RESULTS

28 patients who received post-operative SRS or FSRT from 1/1/2016-12/31/2020 were included in this analysis. The mean pre-operative tumor volume was 14.9 ccs, and the mean post-operative CTV was 21.0 ccs (p &lt; 0.01). 75% of patients had a smaller initial tumor size compared to the post-operative CTV used for radiation treatment planning. For patients with at least 4 follow up MRIs (n = 8), the size of the post-operative cavity progressively decreased with a mean initial cavity volume of 18.9 ccs and mean follow up volumes of 8.1, 7.1, 6.9, and 6.2 ccs.

CONCLUSIONS

In this study evaluating patients who received post-operative SRS, the pre-operative tumor volume was lower than the post-operative CTV for most patients. Previous studies including PROPS-BM have shown how pre-operative treatment may reduce the risk of RN because smaller radiation volumes are used. Pre-operative radiosurgery for patients with brain metastases requires prospective validation.

RADT-07. RADIOGRAPHIC “NECROSIS" FOLLOWING SINGLE-FRACTION SRS AND IMMUNE CHECKPOINT INHIBITION IS ASSOCIATED WITH IMPROVED SURVIVAL IN PATIENTS WITH BRAIN METASTASES: AN INTERNATIONAL MULTICENTER STUDY

OBJECTIVE

Immune checkpoint inhibitors (ICI) and stereotactic radiosurgery (SRS) are commonly utilized in the management of brain metastases. Treatment-related imaging changes (TRIC) are a frequently observed clinical manifestation and are commonly classified as radiographic radiation necrosis. However, these findings are not well characterized and may predict for response to SRS and ICI.

METHODS

The diagnosis-specific graded prognostic assessment was used to guide variable selection. TRIC were determined based upon MRI, PET/CT, or MR spectroscopy and a consensus by local clinical providers was required.

RESULTS

The analysis included 697 patients with 4,536 brain metastases across 11 institutions in 4 countries. The median follow-up after SRS was 13.6 months. The median age was 66 years, 54.1% of patients were male, and 57.3%, 36.3%, and 6.4% were non-small cell lung cancer, melanoma, and renal cell carcinoma (RCC) histology, respectively. TRIC were observed in 9.8%. On univariable analysis, Karnofsky Performance Status (KPS) (hazard ratio [HR]: 0.98; p &lt; 0.001), presence of TRIC (HR: 0.67; p = 0.03), female sex (HR: 0.67; p &lt; 0.001), and prior resection (HR: 0.60; p = 0.03) were associated with improved OS. On multivariable analysis, KPS (HR: 0.98; p &lt; 0.001) and the presence of TRIC (HR: 0.66; p = 0.03) were associated with improved OS. A V12 Gy ≥ 10 cm3 (Odds Ratio [OR]: 2.78; p &lt; 0.001), prior whole brain radiation therapy (OR: 3.46; p = 0.006), and RCC histology (OR: 3.10; p = 0.01) were associated with an increased probability of developing TRIC. The median OS in patients with and without TRIC was 29.0 and 23.1 months, respectively (log-rank p = 0.03).

CONCLUSION

TRIC following ICI and SRS are associated with a median OS benefit of approximately 6 months. Further prospective study is warranted to further elucidate the role and etiology of this common clinical scenario.

RADT-05. VOLUMETRIC MODULATED ARC THERAPY CRANIOSPINAL IRRADIATION UTILIZING A VERTEBRAL BODY SPARING APPROACH: A DOSIMETRIC ANALYSIS

BACKGROUND

Craniospinal irradiation (CSI) is indicated for adult patients diagnosed with leptomeningeal disease (LMD). Proton-based vertebral-body-sparing (VBS) CSI has been explored with pediatric patients to minimize hematologic toxicity; however, utilization of VBS in an adult population is limited. We hypothesize that VBS-CSI utilizing volumetric modulated arc therapy (VMAT) will effectively reduce vertebral body dose while minimizing dose to surrounding organs-at-risk (OAR) for adult patients with LMD.

METHODS

Ten adult patients with LMD received CSI, 30 Gy in 10 fractions. These patients were initially treated with a variety of VMAT and IMRT treatment techniques. These patients were then retrospectively replanned using VMAT VBS-CSI. For their VBS-CSI replan, full VMAT arcs for the brain fields matched to two spine isocenters for the upper and lower spine were created utilizing limited posterior arcs. The PTV was created with margins of 3mm uniformly around the brain contour and 7mm around the spinal canal. To further decrease the vertebral body dose, an avoid entry and exit contour was created. This structure was a margin on the PTV anteriorly designed to carve dose out of the vertebral bodies while still maintaining coverage to the PTV.

RESULTS

All 10 patients had a reduction in vertebral body dose with VMAT VBS-CSI when compared to their initial plan. The mean vertebral dose for the VBS-CSI plans had an average reduction of 33% compared to the initial plans. The mean dose to the small bowel and esophagus were reduced by 46% and 67%, respectively.

CONCLUSIONS

VBS-CSI may be utilized to minimize dose to surrounding OARs and vertebral bodies. In this study, VMAT VBS-CSI led to significant reductions in vertebral body dose while also minimizing dose to other OARs. VMAT VBS-CSI may be an acceptable alternative to proton-based VBS-CSI in an adult population with LMD. Prospective evaluation is warranted.

RADT-35. A PROSPECTIVE REGISTRY STUDY OF 68GA-DOTATATE PET INCORPORATION INTO TREATMENT PLANNING OF INTRACRANIAL MENINGIOMAS

Introduction

The current standard for meningioma radiation planning involves MRI-based image guidance. SSTR ligands such as 68Ga-DOTATATE are being explored for meningioma radiotherapy treatment planning due to universal expression of somatostatin receptor 1/2 in meningioma tissue. We hypothesize that 68Ga-DOTATATE PET utilization can reduce the risk of local failure (LF) through precise radiation planning and may also suggest that patients who have local PET avidity after a perceived GTR may be poor observation candidates.

METHODS

A single institution prospective registry study was created and included intracranial meningioma patients who received a 68Ga-DOTATATE PET scan to assist with radiation oncologist decision-making. These were ordered for all meningioma patients as a departmental standard. Patients who received a PET scan from 1/1/2018-2/25/2022 were eligible for inclusion.

RESULTS

60 patients were treated in this prospective registry. 22%, 72%, and 7% were World Health Organization (WHO) high, intermediate, and low-risk, respectively. After completing their PET scan, 48, 11, and 1 patient(s) proceeded with RT, observation, or redo craniotomy. The median follow up was 16 months (IQR 8.3-23.1). 3 patients (5%) experienced LF between 9.2-28.5 months after diagnosis. 2 patients with LF had PET-avid disease in their post-operative cavity and elected for observation prior to recurrence, and 1 high-risk patient with multifocal disease experienced LF 2 years after a second radiation course and multiple previous recurrences. LF rates after radiation were 0%, 0%, and 8% in the low, intermediate, and high-risk cohorts, respectively. There were no Grade 3 or higher toxicities attributed to PET-guided radiation.

CONCLUSION

This is the largest known population of intracranial meningioma patients followed by physicians who utilized 68Ga-DOTATATE PET guided therapy. Only 1 patient experienced LF after receiving PET-guided radiation therapy, likely due to a radioresistant histology. Incorporating 68Ga-DOTATATE PET into future trials may assist with clinician decision-making and improve patient outcomes.

68Ga-DOTATATE PET-based Radiation Contouring Creates More Precise Radiation Volumes for Meningioma Patients

INTRODUCTION

Radiation treatment planning for meningiomas traditionally involves MRI contrast enhanced images to define residual tumor. However, the gross tumor volume may be difficult to delineate for patients with a meningioma in the skull base, sagittal sinus, or post resection. Advanced PET imaging using ⁶⁸Ga-DOTATATE PET, which has been shown to be more sensitive and specific than MRI imaging, can be used for target volume delineation in these circumstances. We hypothesize that ⁶⁸Ga-DOTATATE PET scan-based treatment planning will lead to smaller radiation volumes and will detect additional areas of disease compared to standard MRI alone.

METHODS

Our data evaluated retrospective, deidentified, and blinded gross tumor volume (GTV) contour delineation with 7 central nervous system (CNS) specialists (4 CNS radiation oncologists and 3 neuroradiologists) for 25 patients diagnosed with a meningioma who received both a ⁶⁸Ga-DOTATATE PET and an MRI for radiation treatment planning. Both the MRI and the PET were non-sequentially contoured by each physician for each patient.

RESULTS

The median MRI volume for each physician ranged from 16.94-25.53 ccs. The median PET volume for each physician ranged from 2.09-8.36 ccs. The median PET volume was smaller for each physician. In addition, 7/25 (28%) patients had new non-adjacent areas contoured on PET by at least 6 of the 7 physicians that were not contoured by these physicians on the corresponding MRI. These new areas would not have been in the traditional MRI based volumes.

CONCLUSION

Our study supports that ⁶⁸Ga-DOTATATE PET imaging may help radiation oncologists create more precise radiation treatment volumes through finding undetected areas of disease not seen on MRI. ⁶⁸Ga-DOTATATE PET guided treatment planning should be studied prospectively.

NIMG-62. 68(GA)DOTATATE PET-BASED RADIATION CONTOURING CREATES SMALLER AND MORE PRECISE RADIATION VOLUMES FOR MENINGIOMA PATIENTS

PURPOSE

Radiation treatment planning for meningiomas conventionally involves MRI contrast enhanced images to define residual tumor. However, the gross tumor volume may be difficult to delineate for patients with a meningioma in the skull base, sagittal sinus, or post resection. Advanced PET imaging using 68(GA)DOTATATE PET, which has been shown to be more sensitive and specific than MRI imaging, can be used for target volume delineation in these circumstances. We hypothesize that 68(GA)DOTATATE PET scan-based treatment planning will lead to smaller radiation volumes and will detect additional areas of disease compared to standard MRI alone.

METHODS

Our data evaluated retrospective, deidentified, and blinded gross tumor volume (GTV) contour delineation with 7 CNS specialists (3 neuroradiologists, 4 CNS radiation oncologists) for 26 patients diagnosed with a meningioma who received both a 68(GA)DOTATATE PET and an MRI for radiation treatment planning. Both the MRI and the PET were non-sequentially contoured by each physician for each patient.

RESULTS

The mean MRI volume for each physician ranged from 24.14-35.52 ccs. The mean PET volume for each physician ranged from 10.59-20.54 ccs. The PET volumes were significantly smaller for 6 out of the 7 physicians. In addition, 7/26 (27%) patients had new non-adjacent areas contoured on PET by at least 6 of the 7 physicians that were not contoured by these physicians on the corresponding MRI. These new areas would not have been in the traditional MRI based volumes.

CONCLUSION

Our study supports that 68(GA)DOTATATE PET imaging can help radiation oncologist create smaller and more precise radiation treatment volumes. Utilization of 68(GA)DOTATATE PET may find undetected areas of disease which in turn can improve local control and progression free survival. 68(GA)DOTATATE PET guided treatment planning should be studied prospectively.

CTNI-37. ISOEFFECTIVE HYPOFRACTIONATION FOR ELDERLY OR FRAIL PATIENTS WITH A NEWLY DIAGNOSED GLIOBLASTOMA: A POOLED INTERNATIONAL STUDY

PURPOSE

The standard of care (SOC) for elderly or frail glioblastoma (GBM) patients is 40 Gy in 15 fraction radiotherapy. However, this regimen has a lower BED compared to the Stupp regimen, 60 Gy in 30 fractions. We hypothesize that isoeffective hypofractionated radiation of 52.5 Gy in 15 fractions (BED equivalent to Stupp) will have superior survival compared to standard of care.

METHODS

Elderly GBM patients treated with 52.5 Gy in 15 fractions were pooled from 2 phase II studies, 1 phase 1 and a prospective observation study. Overall survival (OS) and progression free survival (PFS) were defined as the time elapsed between surgery/biopsy and death from any cause or progression. Univariate and multivariate analyses were performed.

RESULTS

62 newly-diagnosed patients were eligible for this analysis. Median follow-up was 10 months. The median OS and PFS was 10.3 and 6.9 mos, respectively. Patients with KPS ≥ 70 and &lt; 70 had a median OS of 15.3 and 9.5 mos. No survival difference was seen between unmethylated and methylated patients with a median OS of 10.2 and 10.3 months, respectively. Multivariable analysis demonstrated that concurrent chemotherapy was an independent prognostic factor for improved PFS and OS. Grade 3 neurologic toxicity was seen in 2 patients (3.2%).

CONCLUSION

This is the first pooled, prospective analysis of elderly/frail GBM patients treated with dose-escalated hypofractionated radiation. Treatment was well tolerated and demonstrated excellent OS and PFS, exceeding that from prior elderly trials (Roa; 6.5 mo [poor KPS]/Perry; 9.3mo [good KPS]). This treatment regimen gives the elderly population an alternative to Stupp that is not de-escalating therapy. Future prospective trials are needed to validate these results.

Postoperative Stereotactic Body Radiotherapy for Spinal Metastasis and Predictors of Local Control

BACKGROUND

Spine surgery is indicated for select patients with mechanical instability, pain, and/or malignant epidural spinal cord compression, with or without neurological compromise. Stereotactic body radiotherapy (SBRT) is an option for durable local control (LC) for metastatic spine disease.

OBJECTIVE

To determine factors associated with LC and progression-free survival (PFS) for patients receiving postoperative stereotactic spine radiosurgery.

METHODS

We analyzed consecutive patients from 2013 to 2019 treated with surgical intervention followed by SBRT. Surgical interventions included laminectomy and vertebrectomy. SBRT included patients treated with 1 to 5 fractions of radiosurgery. We analyzed LC, PFS, overall survival (OS), and toxicity. Univariate and multivariate analyses were performed.

RESULTS

A total of 63 patients were treated with a median follow-up of 12.5 mo. Approximately 75% of patients underwent vertebrectomy and 25% underwent laminectomy. One-year cumulative incidence of local failure was 19%. LC was significantly improved for patients receiving radiosurgery ≤40 d from surgery compared to that for patients receiving radiosurgery ≥40 d from surgery, 94% vs 75%, respectively, at 1 yr (P = .03). Patients who received preoperative embolization had improved LC with 1-yr LC of 88% vs 76% for those who did not receive preoperative embolization (P = .037). Significant predictors for LC on multivariate analysis were time from surgery to radiosurgery, higher radiotherapy dose, and preoperative embolization. The 1-yr PFS and OS was 56% and 60%, respectively.

CONCLUSION

Postoperative radiosurgery has excellent and durable LC for spine metastasis. An important consideration when planning postoperative radiosurgery is minimizing delay from surgery to radiosurgery. Preoperative embolization and higher radiotherapy dose were associated with improved LC warranting further study.

Where Are the Women in Radiation Oncology? A Cross-Sectional Multi-Specialty Comparative Analysis

Purpose

We aimed to evaluate the growth of women within the general radiation oncology (RO) workforce in comparison to the growth among other medical specialties. We also sought to create a predictive model for gender diversity to guide future recruitment efforts.

Methods and Materials

We identified 16 medical specialties, including RO, for analyses. We used data from the Association of American Colleges and assessed female representation at 4 time points (2006, 2011, 2016, and 2020). Additionally, we determined characteristics of medical specialties that were predictive of increased gender diversity. We performed univariate statistical analysis with linear regression to evaluate factors predictive of greater gender diversity among the medical specialties in our cohort.

Results

The proportion of women within the represented specialties increased over time. Obstetrics/gynecology (14,750 [2006], 23,921 [2020]; 18.7% absolute growth) and dermatology (3568 [2006], 6329 [2020]; 15.1% absolute growth) experienced the highest absolute growth in female representation between 2006 and 2020. When assessing changes between various time points in RO, the absolute change in female physicians increased by 1.5% between 2006 and 2011, by 2.2% between 2011 and 2016, and by only 0.4% between 2016 and 2020, which was the lowest growth pattern relative to the other 15 specialties. Factors predictive of gender diversity among specialties were lower average step 1 scores (P = .0056), fewer years of training (P = .0078), fewer work hours (P = .046), the availability of a standard third year clerkship for a given specialty (P = .0061), and a high baseline number of female physicians within a specialty (P = .0078). Research activities (P = .099) and interest among matriculating medical students (P = .28) were not statistically significant.

Conclusions

The percentage of women in RO lags behind other medical specialties and has been notably low in the last few years. Interventions that incorporate novel initiatives proposed within this study may accelerate current recruitment milestones.

The role of VEGF receptor inhibitors in preventing cerebral radiation necrosis: a retrospective cohort study

Background

Radiation necrosis (RN) is a potential complication after radiation therapy for brain tumors. It is hypothesized that VEGF plays an important role in the pathophysiology of RN. Bevacizumab, a monoclonal antibody against VEGF-A, is often successful in the management of RN. The objective of this study is to assess whether VEGF receptor (VEGFR) inhibitors, a group of oral tyrosine kinase inhibitors (TKIs), can prevent or reverse RN.

Methods

We retrospectively studied a cohort of 102 patients with renal cell carcinoma and brain metastases seen at The Ohio State University James Cancer Center between January 1, 2011 and April 30, 2019. We identified those who developed RN and analyzed the temporal relationship between the use of VEGFR TKIs and the development of RN.

Results

The cumulative incidence of RN is 13.7% after radiation treatments that included LINAC-based stereotactic radiosurgery, fractionated stereotactic radiotherapy, or Gamma Knife radiosurgery. There was no statistically significant difference in the cumulative incidence of RN between patients taking TKIs and patients who were off TKIs (9.9% and 11.5% respectively, P = .741). The median time to development of RN was only numerically shorter in patients taking TKIs (151 vs 315 days, P = .315). One patient developed RN after stopping cabozantinib. Eight patients developed RN while on cabozantinib, pazopanib, or sunitinib. One patient was started on axitinib during active RN without significant improvement subsequently.

Conclusions

VEGFR TKIs do not consistently prevent RN. The therapeutic effects of VEGFR TKIs against RN warrant further research.

NCMP-01. THE ROLE OF VASCULAR ENDOTHELIAL GROWTH FACTOR RECEPTOR INHIBITORS IN PREVENTING CEREBRAL RADIATION NECROSIS: A RETROSPECTIVE COHORT STUDY

INTRODUCTION

Radiation necrosis (RN) is a potential complication after radiation therapy to primary brain tumors and brain metastases. The pathophysiology of RN is not well understood but it is hypothesized that vascular endothelial growth factor (VEGF) plays an important role. Bevacizumab, a monoclonal antibody against VEGF-A, is often successful in the management of RN. The objective of this study is to assess whether VEGF receptor (VEGFR) inhibitors, a group of oral tyrosine kinase inhibitors (TKIs), can prevent or reverse cerebral radiation necrosis

METHODS

We retrospectively studied a cohort of 102 patients with renal cell carcinoma (RCC) and brain metastases seen at The Ohio State University James Cancer Center between 01/01/2011 and 04/30/2019. We identified those who developed RN and analyzed the temporal relationship between the use of VEGFR TKIs and the development of RN.

RESULTS

The cumulative incidence of RN in our cohort is 13.7% after radiation treatments that included LINAC-based stereotactic radiosurgery, fractionated stereotactic radiotherapy, or Gamma Knife radiosurgery. There was no statistically significant difference in the cumulative incidence of RN between patients taking TKIs and patients who were off TKIs (9.9% and 11.5% respectively, p= 0.741). The median time to development of RN was only numerically shorter in patients taking TKIs (151 versus 315 days, p=0.315). One patient developed RN after stopping cabozantinib. Three other patients developed RN while on cabozantinib. Two patients developed RN while on pazopanib, and 3 patients developed RN while on sunitinib. One patient was started on axitinib during active RN without significant improvement subsequently.

CONCLUSIONS

VEGFR TKIs do not consistently prevent or reverse cerebral radiation necrosis and do not seem to have the efficacy that bevacizumab has against RN.

NCMP-07. TREATMENT-INDUCED CEREBRAL NECROSIS IN GLIOMAS: THE OHIO STATE UNIVERSITY COMPREHENSIVE CANCER CENTER (OSUCCC) EXPERIENCE

INTRODUCTION

Treatment-induced cerebral necrosis (TN) is a challenging complication encountered in neuro-oncology. Diagnosis and treatment of TN remains poorly defined.

METHODS

In this single institution, retrospective study, consecutive patients with gliomas and TN between 01/01/2012 and 04/20/2020 at the OSUCCC were identified. Details of the tumor treatment, molecular markers, radiological and pathological findings of TN, as well as treatment, recurrence rate and management upon recurrence were collected.

RESULTS

Of the 53 patients analyzed, 37 had glioblastoma, 7 had anaplastic oligodendroglioma and 9 had grade II or III astrocytoma. MGMT promoter hypermethylation was present in 31/50 (59%) and IDH mutation in 17/53 (32%). Diagnosis of TN was based on histology in 43/53 (81%) or clinical/radiographic features in 10/53 (19%). Worsening of focal weakness (36%), seizures (9%) or being (30%) were common presentations at TN diagnosis. Patient with right compared to left hemisphere involvement were more symptomatic at TN diagnosis. (p=0.049). Bevacizumab (BEV) (51%), resection (28%), steroids only (9%) or Laser Interstitial Thermal Therapy (6%) were used to treat TN. Steroids were weaned off in 20/27 (74%) after receiving BEV. Among all treatments, BEV was significantly associated with a better outcome (resolution or partial improvement of enhancement in 84.6%) (p=0.0006, Bonferroni corrected p&lt; 0.005). TN Recurrence occurred in 36%, 70% and 100% of the patients treated with BEV, resection and LITT respectively. The median duration to TN recurrence was 10 weeks (range: 3–70 weeks). Initial treatment used for TN, MGMT methylation and IDH mutation status did not predict TN recurrence. (p=0.074; p=0.819; p=0.607 respectively).

CONCLUSIONS

BEV appears to be a superior treatment to control TN overall. Recurrence of TN in patients previously treated with BEV was 36%. There was no difference in the risk of developing recurrent TN based on MGMT or IDH status.

IMMU-19. TARGETING GLIOBLASTOMA IMMUNOSUPPRESSION AND TREATMENT RESISTANCE WITH IBRUTINIB IN COMBINATION WITH STEREOTACTIC RADIATION AND IMMUNE CHECKPOINT BLOCKADE

BACKGROUND

Glioblastoma (GBM) is associated with systemic and intratumoral immunosuppression. Part of this immunosuppression is mediated by myeloid derived suppressor cells (MDSCs). Preclinical evidence shows that ibrutinib, a tyrosine kinase inhibitor FDA approved for use in chronic lymphocytic leukemia and known to be CNS penetrant, can decrease MDSC generation and function. Also, focal radiation therapy (RT) synergizes with anti-PD-1 therapy in mouse GBM models. Thus, we aimed to test the combination of these approaches on immune activation and survival in a preclinical immune-intact GBM mouse model.

METHODS

C57BL/6 mice intracranially implanted with the murine glioma cell line GL261-Luc2 were divided into 8 groups consisting of treatments with ibrutinib, RT (10 Gy SRS), or anti-PD-1 individually or in each combination (along with a no treatment control group). Immune cell subset changes (flow-cytometry) and animal survival (Kaplan-Meier) were assessed (n=10 mice per group).

RESULTS

Median survival of the following groups including control (28 days), ibrutinib (27 days), RT (30 days) or anti-PD-1 (32 days) showed no significant differences. However, a significant improvement in median survival was seen in mice given combinations of ibrutinib+RT (35 days), ibrutinib+anti-PD-1 (38 days), and triple therapy with ibrutinib+RT+anti-PD-1 (48 days, p &lt; 0.05) compared to controls or single treatment groups. The reproducible survival benefit of triple combination therapy was abrogated in the setting of CD4+ and CD8+ T cell depletion. Contralateral intracranial tumor re-challenge in long-term surviving mice suggested generation of tumor-specific immune memory responses. The immune profile of the tumor microenvironment (TME) showed increased cytotoxic CD8+ T cells and decreased MDSCs and regulatory T cells in the triple combination therapy mice compared to controls.

CONCLUSION

The combination of ibrutinib, focal RT, and anti-PD-1 immune checkpoint blockade led to a significant survival benefit compared to controls in a preclinical model of GBM.

Characterizing benefit from temozolomide in MGMT promoter unmethylated and methylated glioblastoma: a systematic review and meta-analysis

Background

The current standard of care for the management of patients with newly diagnosed glioblastoma (GBM) includes maximal safe resection followed by radiotherapy (RT) with concurrent and adjuvant temozolomide (TMZ). While it is well established that TMZ has better efficacy in patients with MGMT promoter methylation, it remains an area of debate whether TMZ should be omitted when treating GBM patients with unmethylated MGMT.

Methods

We conducted a systematic review and meta-analysis to provide separate estimates of median overall survival (OS) and progression-free survival (PFS) for patients with methylated and unmethylated GBM treated with RT with or without TMZ. We searched multiple databases from inception to January 13, 2020.

Results

The median OS for patients with unmethylated GBM treated with RT/TMZ pooled from 5 phase III studies (N = 655) was 14.11 months (95% confidence interval [CI], 13.18–15.04) with a median PFS of 4.99 months (95% CI, 4.25–5.72). In contrast, the median OS for patients with methylated GBM pooled from 6 studies (N = 753) was 24.59 months (95% CI, 22.19–26.99) with a median PFS pooled from 7 studies (N = 805) of 9.51 months (95% CI, 7.41–11.61). There is a paucity of prospective data pertaining to OS/PFS in unmethylated patients treated with RT only and therefore a direct comparison was not possible.

Conclusions

This meta-analysis provides estimates of survival for patients with MGMT methylated or unmethylated GBM treated with RT/TMZ. Further research is needed to delineate whether TMZ should be withheld for patients with unmethylated GBM outside of the setting of clinical trials.

Clinical Outcomes and Multidisciplinary Patterns of Failure for Olfactory Neuroblastoma: The Ohio State Experience

Purpose  Olfactory neuroblastoma (ONB) is a rare head and neck cancer believed to be originated from neural crest cells of the olfactory membrane located in the roof of the nasal fossa. This study evaluates clinical outcomes and failure patterns in ONB patients of those patients treated with surgical resection at a high-volume tertiary cancer center. Methods and Materials  Thirty-nine ONB patients who underwent surgical resection at our institution from 1996 to 2017 were retrospectively identified. Univariate, multivariate, and survival analysis were calculated using Cox regression analysis and Kaplan-Meier log-rank. Results  Median follow-up time was 59 months (range: 5.2-236 months). The median overall survival (OS) and disease-free survival (DFS) for the entire cohort were 15 and 7.6 years, respectively. The 5-year cumulative OS and DFS were 83 and 72%, respectively. The 5-year OS for low Hyams grade (LHG) versus high Hyams grade (HHG) was 95 versus 61% ( p  = 0.041). LHG was found in 66% of the early Kadish stage patients compared with 28% in the advanced Kadish stage patients ( p  = 0.057). On multivariate analysis, HHG and positive node status predicted for worse OS and only HHG predicted for worse DFS. Of note, five patients (all Kadish stage A) who received surgical resection alone had no observed deaths or recurrences with a median follow-up of 44 months (range: 5-235 months). Conclusion  In this retrospective cohort, patients with positive nodes or HHG have significantly worse clinical outcomes. Future studies should explore treatment intensification for HHG or positive nodes.

Erratum: Clinical Outcomes and Multidisciplinary Patterns of Failure for Olfactory Neuroblastoma: The Ohio State Experience

[This corrects the article DOI: 10.1055/s-0039-1692479.].

Linear accelerator-based radiosurgery is associated with lower incidence of radionecrosis compared with gamma knife for treatment of multiple brain metastases

BACKGROUND

Gamma knife (GK) and linear accelerator (LINAC)-based stereotactic radiosurgery (SRS) both offer excellent local control in the management of multiple brain metastases. The efficacy and toxicity of LINAC and GK SRS have not been directly compared in the modern era. We studied outcomes in patients treated with LINAC SRS and GK at two separate institutions.

METHODS

We identified patients treated with either LINAC or GK who were treated to ≥2 lesions and had available follow up. LINAC patients were treated using single-isocenter multitarget technique. We used Cox regression, Fine and Gray competing risks regression, and nearest neighbor propensity score matching to account for confounders and imbalance between cohorts. Kaplan-Meier curves were used to estimate overall survival and rates of radionecrosis.

RESULTS

We identified 391 patients who were treated in 537 courses to a total 2699 lesions (LINAC: 1014, GK: 1685). After propensity score matching, GK was associated with similar overall survival (HR = 0.86; 95% CI 0.59-1.24; p = 0.41) and higher rate of radionecrosis (HR = 3.83; 95% CI 1.66-8.84; p = 0.002) compared to LINAC. In a secondary propensity score matched analysis comparing radionecrosis in single-fraction LINAC and GK, GK remained associated with higher incidence of radionecrosis (HR = 4.42; 95% CI 1.28-15.29; p = 0.019).

CONCLUSIONS

In this multi-institutional study, we found similar overall survival with lower incidence of radionecrosis in patients treated with LINAC compared to GK SRS. These findings are hypothesis generating and should be validated in an independent cohort.

ATIM-17. A PHASE I TRIAL OF HYPOFRACTIONATED STEREOTACTIC IRRADIATION (HFSRT) COMBINED WITH NIVOLUMAB (NIVO), IPILIMUMAB (IPI) AND BEVACIZUMAB (BEV) IN PATIENTS (PTS) WITH RECURRENT HIGH GRADE GLIOMAS

BACKGROUND

There is strong pre-clinical evidence that combining CTLA4 and PD-1/PDL-1 blockade with antiangiogenic agents and HFSRT independently enhance anti-tumor immune responses and tumor regression.

METHODS

This phase I study includes a safety cohort of 6 pts followed by dose expansion cohort of 26 pts. Pts with Bev naïve recurrent WHO grade III or IV gliomas (maximum diameter of enhancing brain lesion ≤ 4 cm) are eligible. An interval of at least 6 months after the end of prior RT is required unless there is a new recurrence outside of the previous RT treatment field. Eligible pts are treated with HFSRT to the recurrent tumor (30 Gy in 5 fractions) and 4 cycles of Nivo (3 mg/kg), Ipi (1 mg/kg) and Bev (15 mg/kg) every 3 weeks followed by Nivo 240 mg and Bev 10 mg/kg every 2 weeks for 4 months. After 4 months, Nivo is administered every 4 weeks at 480 mg flat dose and Bev is continued at every 2 week schedule. The primary study objectives are to determine safety and tolerability of above treatment. Secondary endpoints include response rate, 6 and 9-months survival rates, and exploring tissue and imaging biomarkers.

RESULTS

As of June 2019, safety cohort has been completed and accrual to dose expansion cohort is ongoing. Combination of HFSRT, Nivo, Ipi and Bev as above is well tolerated. The most common toxicities were grade 1 anorexia, grade 1 diarrhea, grade 1 elevation of alanine aminotransferase, grade 1 elevation of lipase and grade 1 infusion related reaction. One patient had grade 3 confusion which was reversible with use of corticosteroids. No dose limiting toxicity has been observed.

CONCLUSIONS

Combination of HFSRT with Nivo, Ipi and Bev was considered safe to be studied in expansion cohort. Updated safety and efficacy data will be presented.

Single-Isocenter Multitarget Stereotactic Radiosurgery Is Safe and Effective in the Treatment of Multiple Brain Metastases

Purpose

Multiple studies have reported favorable outcomes for stereotactic radiosurgery (SRS) in the treatment of limited brain metastases. An obstacle of SRS in the management of numerous metastases is the longer treatment time using traditional radiosurgery. Single-isocenter multitarget (SIMT) SRS is a novel technique that permits rapid therapy delivery to multiple metastases. There is a lack of clinical evidence regarding its efficacy and safety. We report the outcomes of patients treated with this technique.

Methods and Materials

We reviewed the records of patients with intact or resected brain metastases treated with SRS in 1 to 5 fractions using SIMT technique at our institution, with at least 1 available follow-up brain magnetic resonance imaging. Survival, disease control, and toxicity were evaluated using Cox regression, logistic regression, and Kaplan-Meier analysis.

Results

We identified 173 patients with 1014 brain metastases. Median follow up was 12.7 months. Median beam-on time was 4.1 minutes. The median dose to the brain was 219.4 cGy. Median overall survival and freedom from intracranial progression were 13.2 and 6.3 months, respectively. Overall survival did not differ between patients treated with greater than or less than 4 lesions (hazard ratio, 1.03; 95% confidence interval 0.66-1.61; P = .91). Actuarial 1- and 2-year local control were 99.0% and 95.1%, respectively. Rates of grade 2 and grade 3 or higher radionecrosis were 1.4% and 0.9%, respectively.

Conclusions

SIMT radiosurgery delivered in 1 to 5 fractions offers excellent local control and acceptable toxicity in the treatment of multiple intact and postoperative brain metastases. This technique should be evaluated prospectively.

Chiral segregation driven by a dynamical response of the adsorption footprint to the local adsorption environment: bitartrate on Cu(110)

Bitartrate, a strongly bound chiral modifier, is able to restructure its adsorption footprint on Cu(110) in response to local adsorbates.

Molecular assembly at surfaces: progress and challenges

Molecules provide versatile building blocks, with a vast palette of functionalities and an ability to assemble via supramolecular and covalent bonding to generate remarkably diverse macromolecular systems. This is abundantly displayed by natural systems that have evolved on Earth, which exploit both supramolecular and covalent protocols to create the machinery of life. Importantly, these molecular assemblies deliver functions that are reproducible, adaptable, finessed and responsive. There is now a real need to translate complex molecular systems to surfaces and interfaces in order to engineer 21st century nanotechnology. ‘Top-down’ and ‘bottom-up’ approaches, and utilisation of supramolecular and covalent assembly, are currently being used to create a range of molecular architectures and functionalities at surfaces. In parallel, advanced tools developed for interrogating surfaces and interfaces have been deployed to capture the complexities of molecular behaviour at interfaces from the nanoscale to the macroscale, while advances in theoretical modelling are delivering insights into the balance of interactions that determine system behaviour. A few examples are provided here that outline molecular behaviour at surfaces, and the level of complexity that is inherent in such systems.

Pattern Formation by Staphylococcus epidermidis via Droplet Evaporation on Micropillars Arrays at a Surface

We evaluate the effect of epoxy surface structuring on the evaporation of water droplets containing Staphylococcus epidermidis (S. epidermidis). During evaporation, droplets with S. epidermidis cells yield to complex wetting patterns such as the zipping-wetting1-3 and the coffee-stain effects. Depending on the height of the microstructure, the wetting fronts propagate circularly or in a stepwise manner, leading to the formation of octagonal or square-shaped deposition patterns.4,5 We observed that the shape of the dried droplets has considerable influence on the local spatial distribution of S. epidermidis deposited between micropillars. These changes are attributed to an unexplored interplay between the zipping-wetting1 and the coffee-stain6 effects in polygonally shaped droplets containing S. epidermidis. Induced capillary flows during evaporation of S. epidermidis are modeled with polystyrene particles. Bacterial viability measurements for S. epidermidis show high viability of planktonic cells, but low biomass deposition on the microstructured surfaces. Our findings provide insights into design criteria for the development of microstructured surfaces on which bacterial propagation could be controlled, limiting the use of biocides.

Bacterial viability on chemically modified silicon nanowire arrays

The global threat of antimicrobial resistance is driving an urgent need for novel antimicrobial strategies. Functional surfaces are essential to prevent spreading of infection and reduce surface contamination. In this study we have fabricated and characterized multiscale-functional nanotopographies with three levels of functionalization: (1) nanostructure topography in the form of silicon nanowires, (2) covalent chemical modification with (3-aminopropyl)triethoxysilane, and (3) incorporation of chlorhexidine digluconate. Cell viability assays were carried out on two model microorganisms E. coli and S. aureus over these nanotopographic surfaces. Using SEM we have identified two growth modes producing distinctive multicellular structures, i.e. in plane growth for E. coli and out of plane growth for S. aureus. We have also shown that these chemically modified SiNWs arrays are effective in reducing the number of planktonic and surface-attached microorganisms.