Genomic analysis of human brain metastases treated with stereotactic radiosurgery reveals unique signature based on treatment failure

Stereotactic radiosurgery (SRS) has been shown to be efficacious for the treatment of limited brain metastasis (BM); however, the effects of SRS on human brain metastases have yet to be studied. We performed genomic analysis on resected brain metastases from patients whose resected lesion was previously treated with SRS. Our analyses demonstrated for the first time that patients possess a distinct genomic signature based on type of treatment failure including local failure, leptomeningeal spread, and radio-necrosis. Examination of the center and peripheral edge of the tumors treated with SRS indicated differential DNA damage distribution and an enrichment for tumor suppressor mutations and DNA damage repair pathways along the peripheral edge. Furthermore, the two clinical modalities used to deliver SRS, LINAC and GK, demonstrated differential effects on the tumor landscape even between controlled primary sites. Our study provides, in human, biological evidence of differential effects of SRS across BM's.

Patient Education Practices and Preferences of Radiation Oncologists and Interprofessional Radiation Therapy Care Teams: A Mixed-Methods Study Exploring Strategies for Effective Patient Education Delivery

PURPOSE

Patients' understanding of radiation therapy (RT) and data regarding optimal approaches to patient education (PE) within radiation oncology (RO) are limited. We aimed to evaluate PE practices of radiation oncologists and interprofessional RT care team members to inform recommendations for delivering inclusive and accessible PE.

METHODS AND MATERIALS

An anonymous survey was administered to all Radiation Oncology Education Collaborative Study Group members (10/5/22-11/23/22). Respondent demographics, individual practices/preferences, and institutional practices were collected. Qualitative items explored strategies, challenges, and desired resources for PE. Descriptive statistics summarized survey responses. The Fisher exact test compared PE practices by respondent role and PE timing. Thematic analysis was used for qualitative responses.

RESULTS

One hundred thirteen Radiation Oncology Education Collaborative Study Group members completed the survey (28.2% response rate); RO attendings comprised 68.1% of respondents. Most practiced in an academic setting (85.8%) in North America (80.5%). Institution-specific materials were the most common PE resource used by radiation oncologists (67.6%). Almost half (40.2%) reported that their PE practices differed based on clinical encounter type, with paper handouts commonly used for in-person and multimedia for telehealth visits. Only 57.7% reported access to non-English PE materials. PE practices among radiation oncologists differed according to RT clinical workflow timing (consultation versus simulation versus first RT, respectively): one-on-one teaching: 88.5% versus 49.4% versus 56.3%, P < .01, and paper handouts: 69.0% versus 28.7% versus 16.1%, P < .01. Identified challenges for PE delivery included limited time, administrative barriers to the development or implementation of new materials or practices, and a lack of customized resources for tailored PE. Effective strategies for PE included utilization of visual diagrams, multimedia, and innovative education techniques to personalize PE delivery/resources for a diverse patient population, as well as fostering interprofessional collaboration to reinforce educational content.

CONCLUSIONS

Radiation oncologists and interprofessional RO team members engage in PE, with most using institution-specific materials often available only in English. PE practices differ according to clinical encounter type and RT workflow timing. Increased adoption of multimedia materials and partnerships with patients to tailor PE resources are needed to foster high-quality, patient-centered PE delivery.

Palliative whole brain radiation therapy: an international state of practice

BACKGROUND

Improvements in radiation delivery and systemic therapies have resulted in few remaining indications for palliative whole brain radiation therapy (WBRT). Most centers preferentially use stereotactic radiotherapy (SRT) and reserve WBRT for those with >15 lesions, leptomeningeal presentation, rapidly progressive disease, or limited estimated survival. Despite regional differences among preferred dose, fractionation, and treatment technique, we predict survival post-WBRT will remain poor-indicating appropriate application of WBRT in this era of SRT and improved systemic therapies.

METHODS

A multi-center, international retrospective analysis of patients receiving WBRT in 2022 was performed. Primary end point was survival after WBRT. De-identified data were analyzed centrally. Patients receiving WBRT as part of a curative regimen, prophylactically, or as bridging therapy were excluded. The collected data consisted of patient parameters including prescription dose and fractionation, use of neurocognitive sparing techniques and survival after WBRT. Survival was calculated via the Kaplan-Meier method.

RESULTS

Of 29,943 international RT prescriptions written at ten participating centers in 2022, 462 (1.5%) were for palliative WBRT. Participating centers were in the United States (n=138), the United Kingdom (n=111), Hong Kong (n=72), Italy (n=49), Belgium (n=45), Germany (n=27), Ghana (n=15), and Cyprus (n=5). Twenty-six different dose regimens were used. The most common prescriptions were for 3,000 cGy over 10 fractions (45.0%) and 2,000 cGy over 5 fractions (43.5%) with significant regional preferences (P<0.001). Prior SRT was delivered in 32 patients (6.7%), hippocampal avoidance (HA) was used in 44 patients (9.5%), and memantine was prescribed in 93 patients (20.1%). Survival ranged from 0 days to still surviving at 402 days post-treatment. The global median overall survival (OS) was 84 days after WBRT [95% confidence interval (CI): 68.0-104.0]. Actuarial survival at 7 days, 1 month, 3 months, and 6 months were 95%, 78%, 48%, and 32%, respectively. Twenty-seven patients (5.8%) were unable to complete their prescribed WBRT.

CONCLUSIONS

This moment-in-time analysis confirms that patients with poor expected survival are being appropriately selected for WBRT-illustrating the dwindling indications for WBRT-and demonstrates the variance in global practice. Since poor survival precludes patients from deriving benefit, memantine and HA are best suited in carefully selected cases.

Radiosurgery Dose Reduction for Brain Metastases on Immunotherapy (RADREMI): One-Year Safety and Efficacy Outcomes from a Multicenter Phase I Trial

PURPOSE/OBJECTIVE(S)

The combination of immunotherapy and single-fraction stereotactic radiosurgery (SRS) for treatment of metastatic brain disease has yielded symptomatic radiation necrosis rates as high as 20% (PMID: 29327059). Consequently, the Radiosurgery Dose Reduction for Brain Metastases on Immunotherapy (RADREMI) multicenter phase I trial (registered at clinicaltrials.gov, NCT04047602) was created to address whether reduced-dose SRS can improve morbidity without compromising efficacy. In this report we present our one-year findings.

MATERIALS/METHODS

Eligibility for RADREMI enrollment required brain metastases patients with: a) Histologically-confirmed primary malignancy, b) Receipt of immunotherapy within 30 days of SRS, c) 1-10 MRI-visible brain metastases, d) Estimated median survival of at least 6 months (via disease-specific graded prognostic assessment), and e) No history of whole brain radiation therapy. Reduced-dose SRS utilized 18 Gy for lesions 0-2 cm, 14 Gy for lesions 2.1-3 cm, and 12 Gy for lesions 3.1-4 cm. Symptomatic radiation necrosis was defined as imaging findings consistent with radiation necrosis combined with clinical symptoms requiring steroid administration and/or operative intervention. Local control was defined by Response Assessment in Neuro-Oncology (RANO) criteria.

RESULTS

From December 18, 2019 to June 30, 2022, 54 lesions in 17 patients were treated on RADREMI with at least one-year of follow-up. One-year local control occurred in 52 of 54 lesions and in 15 of 17 patients, yielding control rates of 96% per lesion and 88% per patient. Radiographic radiation necrosis occurred in 2 of 54 lesions (4%). No symptomatic radiation necrosis occurred.

CONCLUSION

Our findings of concurrent immunotherapy + reduced-dose SRS at one-year post-treatment revealed excellent local control (96%) with no symptomatic radiation necrosis, and minimal radiographic radiation necrosis. These results attest to the durability of the safety and efficacy of reduced-dose SRS with immunotherapy for metastatic brain disease.

Influence of Radiation Fractionation on Immune Repertoire Diversity in Solid Tumor Patients

PURPOSE/OBJECTIVE(S)

Radiation (RT)-induced lymphopenia (RIL) occurs in up to 75% of patients undergoing RT and is associated with worse tumor control and survival across a spectrum of solid tumors. Patients undergoing hypofractionated RT are at lower risk of RIL compared with patients treated with more prolonged RT courses. However, it is unknown whether immune repertoire diversity is similarly affected by fractionation scheme in patients undergoing RT. This prospective study analyzed RT-induced changes in immune repertoire diversity in patients treated with conventionally (CFRT) vs hypofractionated RT (HFRT).

MATERIALS/METHODS

RNA-based T and B cell receptor sequencing was performed on peripheral lymphocytes collected prospectively before RT and within 4 weeks of the last RT fraction from 23 patients (18 men, 5 women, median age 67 y) with primary solid tumors undergoing CFRT (≤3 Gy/day x ≥10 days, n = 13) or HFRT (≥5 Gy/day x ≤5 days, n = 10). Absolute lymphocyte counts (ALC; cells/μL) were obtained from clinical laboratory data. The number of unique CDR3 receptors (uCDR3) and Shannon entropy were used to monitor changes in T (TCR Vβ) and B (BCR IgH) receptor diversity.

RESULTS

ALC decreased after RT in 90% (20/22) of patients (mean pre-RT ALC 1830 vs 1040 post-RT, p <0.001). Mean % ALC loss was greater in CFRT vs HFRT patients (44.3 vs. 35.2%). After RT, entropy in IgH and Vβ decreased in 18/23 (78%) and 17/23 (74%) patients, respectively; uCDR3 in IgH and Vβ decreased in 14/23 (61%) and 15/23 (65%). Among patients with concordant decreases in ALC and uCDR3, a moderate correlation between magnitude of ALC loss and uCDR3 levels in the T-cell receptor Vβ was observed (r = 0.64, p = 0.02). For both receptor species studied (IgH and Vβ), HFRT patients were more likely to have an increase in either entropy or uCDR3 in the face of decreased ALC (36 vs 15%, X2 p = 0.03). Furthermore, while decreases in entropy were observed among the CFRT patients for both IgH (median entropy 10.4 vs 9.4, p = 0.06) and Vβ (9.7 vs 8.1, p = 0.02), entropy did not significantly change following RT in the HFRT patients (IgH 10.6 vs 10.4, p = 0.74 and Vβ 10.9 vs 10.8, p = 0.24).

CONCLUSION

RT-induced changes in immune repertoire diversity are variably reflected in the peripheral ALC. Both HFRT and CFRT depleted circulating lymphocytes, but patients undergoing HFRT were more likely to experience increases in T and B cell diversity metrics despite lymphopenia. It is therefore possible that relative sparing of repertoire diversity among patients undergoing HFRT could increase the likelihood of tumor antigen recognition by peripheral blood lymphocytes. As immune repertoire diversity is associated with the likelihood of response to immunotherapy, these findings also have implications for RT-immunotherapy combinations. Further study is required to understand the relationship between RT exposure to circulating lymphocyte populations and immune repertoire diversity.

Palliative Whole Brain Radiotherapy: International State of Practice 2022

PURPOSE/OBJECTIVE(S)

Increasing technology of radiation treatment planning and delivery, better systemic therapies, and randomized trials in the population of patients (pts) with brain metastases have provided robust targeted options. This has resulted in palliative whole brain radiation therapy (WBRT) being used far less frequently than previously. Most centers preferentially use stereotactic radiation surgery (SRS) for pts with several lesions and may reserve WBRT for those with poor performance, with rapidly progressive disease, or with leptomeningeal presentation. We hypothesize that different trends in current WBRT regimens exist across different continents with varying rates of use of hippocampal avoidance (HA) and memantine. Despite differences in dose, fractionation, and treatment technique, we predict that survival post-WBRT will remain poor-indicating appropriate application of whole brain treatment in this era of SRS and improved systemic therapies.

MATERIALS/METHODS

A multi-center international analysis of pts receiving WBRT in 2022 was performed. Primary end point was survival after WBRT. Participating centers were located in Belgium, the United Kingdom, Hong Kong, Cyprus, Italy, Germany, Ghana, and the United States. De-identified data were collected and analyzed centrally. Pts receiving WBRT as part of a curative regimen (e.g., medulloblastoma, primary CNS lymphomas), prophylactically in small cell lung cancer, or as bridging prior to CAR-T were excluded. The collected data consisted of pt parameters including prior stereotactic radiosurgery (SRS), prescription dose and fractionation, use of HA technique with or without memantine, and survival after WBRT. Survival was calculated via the Kaplan-Meier method.

RESULTS

Of 23,332 RT prescriptions written at these centers in 2022, 399 (1.7%) were for palliative WBRT. Most frequent primary cancers were lung (42%) and breast (28%). Twenty-seven different dose regimens were used. The most common prescriptions were for 3 Gy daily fractions for 10 fractions (45%) and 4 Gy daily for 5 fractions (37%). Prior CNS SRS was delivered in 32 pts (7%). HA technique was used in 44 pts (10%); this technique was almost exclusively used in the United States. Memantine was prescribed in 93 pts (20%). Survival ranged from zero days to still surviving. The global median overall survival was 84 days after completion of treatment (95% CI: 68.0-104.0). Cumulative 3-month and 6-month actuarial survivals were 48% and 32%.

CONCLUSION

This "moment in time" analysis confirms that pts with poor expected survival are being appropriately selected for WBRT and demonstrates the variance in global practice. Since poor survival precludes these pts from deriving much benefit, memantine and HA may be best suited only for carefully selected cases; use of these is not Standard of Care in the participating European, Asian, and African centers.

Dosimetric Impact of Seed Segmentation in GammaTile Surgically Targeted Radiation Therapy for Gliomas and Brain Metastases Cases

PURPOSE/OBJECTIVE(S)

To assess the variability of dose reporting variability due to uncertainty in segmentation of Cs-131 seeds in GammaTile therapy for gliomas and brain metastases.

MATERIALS/METHODS

Ten patients with either glioma or brain metastases had 4-11 GammaTiles placed along resection bed during craniotomy. A dose of 60 Gy is prescribed to 5 mm depth. Each GammaTile has four Cs-131 seeds imbedded in a biodegradable collagen sponge. GammaTile Post-Op workflow in MIM Symphony software is used for post-implant dose evaluation and reporting. This workflow requires a post-surgery CT to identify seeds, and a post-surgery MR for residual disease and OAR contours. Seeds are segmented using a threshold tool. Threshold levels may change depending on the CT used, thus users need to manually change the HU threshold value in each data set. Since GammaTiles are lined along the resection bed, PTVs are generated automatically by adding 8 mm expansion on the seed contours and later combined with residual disease contours. We simulate the seed contour uncertainty by applying -0.5 mm, -1.0 mm, +0.5 mm & +1.0 mm concentric margins to the current seed contours to create 4 new seed contours per patient. New PTVs are generated by adding 8 mm expansion on the new seed contours combined with residual disease contours. PTV volume, PTV volume receiving 100% and 150% of prescription dose (V100, V150), and percentage of the prescription dose received by 90% of the PTV (D90) are calculated to evaluate dose reporting variability due to seed segmentation uncertainty.

RESULTS

Mean PTV volume decreases by 8.4 cc & 10.2 cc for PTVs generated from seed contours with -0.5 mm & -1.0 mm margin, respectively, and increases by 5.8 cc & 8.2 cc, respectively, when +0.5 mm & +1 mm margins are applied to the original seed contours. We observe up to 10% change in V100 due to seed segmentation uncertainty. Mean V100 increases by 4.0% (range: 0.2% - 8.9%) & 4.9% (range: 0.5% - 11.0%) for cases with -0.5 m & -1.0 mm seed margin, respectively, and reduces by 4.2% (range: 0.5% - 6.7%) & 5.9% (range: 0.6% - 10.4%) for cases with +0.5 mm and +1.0 mm seed margin, respectively. Mean D90 increases by 7.7% (range: 4.0% - 12.6%) & 9.9% (range: 4.0% - 17.4%) for cases with -0.5 m & -1.0 mm seed margin, respectively, and reduces by 5.5% (range: 3.6% - 7.8%) & 7.4% (range: 5.2% - 9.6%) for cases with +0.5 mm and +1.0 mm seed margin, respectively. We also observe up to 8.0% changes in mean V150 when margins are applied to the seed contours.

CONCLUSION

Our results show significant impact of seed segmentation uncertainty on dose reporting in GammaTile therapy. Variability in dose reporting parameters highlight the need for a more standardized and automated approach to seed segmentation to ensure consistent and accurate dose reporting. The current manual threshold adjustment method is subject to user dependence and therefore unreliable. Development of a more robust tool could help to minimize variability and improve reliability of dose reporting.

Patient Education Practices and Preferences of Interprofessional Radiation Oncology Providers

PURPOSE/OBJECTIVE(S)

Patient understanding of radiotherapy (RT) processes and data regarding optimal approaches to patient education (PE) within radiation oncology (RO) are limited. Our objective was to evaluate PE practices and preferences of interprofessional RO providers to inform recommendations for delivering inclusive, accessible, and patient-centered education.

MATERIALS/METHODS

An anonymous 17-item online survey, approved by an ethics review board, was administered to all members of the Radiation Oncology Education Collaborative Study Group (ROECSG) between 10/5/22 to 11/23/22. Respondent demographics, provider practices/preferences, and institutional practices were collected. Qualitative items explored key strategies, challenges, and desired resources for PE. Descriptive statistics summarized survey responses. Fisher's exact test compared PE practices by provider role and PE timing. Thematic analysis was used for qualitative responses.

RESULTS

A total of 123 ROECSG members, including RO attendings (64%), RO trainees (21%), medical physicists (7%), physician assistants/nurses (2%), and radiation therapists (2%), completed the survey (31% response rate). Most practiced in an academic setting (86%) in North America (82%). The most common PE resources used were custom created institution-specific (61%) and electronic health system generated materials (38%). PE was delivered primarily by one-on-one teaching (72%), paper handouts (69%), and organizational websites (21%) (e.g., RTanswers.org). Almost half (41%) reported that PE practices differed based on type of clinical encounter, for example paper handouts for in-person visits and multimedia for virtual visits. The majority (86%) stated that their institution has disease site-specific PE materials, with nearly all having breast cancer materials (91%). Only 58% reported access to non-English PE materials. RO attendings/trainees were more likely than other team members to deliver PE at consultation (98% vs 71%, p = 0.03). PE practices amongst radiation oncologists differed according to the timing along the RT care path (consultation vs simulation vs first fraction, respectively): one-on-one teaching: 89% vs 49% vs 56%, p<0.01 and paper handouts: 69% vs 28% vs 16%, p<0.01. Key PE strategies included incorporating multimedia resources, personalizing delivery, and repetition at multiple timepoints by the interprofessional team. Limited time, inadequate administrative support, and lack of customized resources were identified as challenges in PE delivery.

CONCLUSION

Interprofessional RO providers engage in PE, with most utilizing institution-specific materials. PE practices differ according to the type of clinical encounter and timing in the RT care path. Increased adoption of multimedia materials and partnerships with patients to tailor PE resources based on language, learning styles, and cultural preferences are needed to foster high-quality, patient-centered PE delivery.

Dosimetric Impact of Source Displacement in GammaTile Surgically Targeted Radiation Therapy for Gliomas

Background This study aims to evaluate dosimetric changes that happened during the first month after GammaTile surgically targeted radiation therapy (STaRT) for gliomas due to Cesium-131 (Cs-131) seed displacement caused by cavity shrinkage in brain brachytherapy. Methodology In this study, 10 glioma patients had 4-11 GammaTiles placed along the resection bed after maximal safe resection during craniotomy. Each GammaTile is composed of four Cs-131 seeds embedded in a biodegradable collagen sponge to minimize seed movement and maintain seed-to-cavity surface distance. The Cs-131 seed positions were identified using VariSeed on day one. On day 30, post-implant computed tomography (CT) images and dosimetry parameters were calculated. An iterative closest point (ICP) algorithm was used to compute rigid transformation between the day one and day 30 seed clouds. The seed displacement was calculated after registration. The volume receiving 100% of the prescription dose (V100), the dose received by 90% of the planning target volume (D90_PTV), the planning target volume receiving 100% of the prescription dose (V100_PTV), and the dose to organs at risk (OARs) were calculated for both CT images to determine the dosimetric changes from any seed displacement. Results The mean seed displacement of 1.8 ± 1.0 mm for all patients was observed between day one and day 30. The maximum seed displacement for each patient ranged from 2.3 mm to 7.3 mm. The mean V100 difference between day one and day 30 was 2.5 cc (range = 0.5-6.5 cc). The mean D90_PTVs were 95.5% (range = 69.0%-131.0%) and 98.1% (range = 19.9%-149.0%) on day one and day 30, respectively. The mean V100_PTVs were 88.4% (range = 81.3%-99.1%) and 87.9% (range = 47.0%-99.7%) on day one and day 30, respectively. On day one, the brainstem dose was 63.5 Gy for one case and 28.1 Gy for another case; while on day 30, the brainstem dose was 55.8 Gy and 20.6 Gy for the same patients, contributing to 7.7 Gy (12.8%) and 7.5 Gy (12.5%) dose reductions to brainstem for these patients, respectively. Only two patients received a dose to the optic nerves (34.1 Gy and 5.2 Gy). There were small changes (1.8 Gy and 0.5 Gy, respectively) in the dose to optic nerves when comparing the dose calculated on day one and the dose calculated on day 30 CT images. The same two patients received 30.4 Gy and 6.8 Gy to the chiasm, respectively. Small changes in the dose to the chiasm (≤1.1 Gy) were noted between day one and day 30. Conclusions A maximum seed displacement of up to 7.3 mm and a mean seed displacement of 1.8 mm caused by cavity shrinkage were observed during the first month after GammaTile STaRT for gliomas. There were noticeable changes in dosimetry parameters. Changes in the doses to OARs, particularly the brainstem, were large (up to 12.8% of the prescription dose). These changes in dosimetry should be considered when evaluating treatment outcomes and planning future GammaTile treatments.

Genomic Analysis of Human Brain Metastases Treated with Stereotactic Radiosurgery Under the Phase-II Clinical Trial (NCT03398694) Reveals DNA Damage Repair at the Peripheral Tumor Edge

Stereotactic Radiosurgery (SRS) is one of the leading treatment modalities for oligo brain metastasis (BM), however no comprehensive genomic data assessing the effect of radiation on BM in humans exist. Leveraging a unique opportunity, as part of the clinical trial (NCT03398694), we collected post-SRS, delivered via Gamma-knife or LINAC, tumor samples from core and peripheral-edges of the resected tumor to characterize the genomic effects of overall SRS as well as the SRS delivery modality. Using these rare patient samples, we show that SRS results in significant genomic changes at DNA and RNA levels throughout the tumor. Mutations and expression profiles of peripheral tumor samples indicated interaction with surrounding brain tissue as well as elevated DNA damage repair. Central samples show GSEA enrichment for cellular apoptosis while peripheral samples carried an increase in tumor suppressor mutations. There are significant differences in the transcriptomic profile at the periphery between Gamma-knife vs LINAC.

Precision Radiation for Brain Metastases With a Focus on Hypofractionated Stereotactic Radiosurgery

There are multiple published randomized controlled trials supporting single-fraction stereotactic radiosurgery (SF-SRS) for patients presenting with 1 to 4 brain metastases, with the benefit of minimizing radiation-induced neurocognitive sequelae as compared to whole brain radiotherapy . More recently, the dogma of SF-SRS as the only means of delivering an SRS treatment has been challenged by hypofractionated SRS (HF-SRS). The ability to deliver 25-35 Gy in 3-5 HF-SRS fractions is a direct consequence of the evolution of radiation technologies to allow image guidance, specialized treatment planning, robotic delivery and/or patient positioning corrections in all 6 degrees-of-freedom, and frameless head immobilization. The intent is to mitigate the potentially devastating complication of radiation necrosis and improve rates of local control for larger metastases. This narrative review provides an overview of outcomes specific to HF-SRS in addition to the more recent developments of staged SRS, preoperative SRS, and hippocampal avoidance-whole brain radiotherapy with simultaneous integrated boost.

Radiosurgery dose reduction for brain metastases on immunotherapy (RADREMI): Results of an a priori interim analysis of a multicenter phase I trial

2013

Background: Symptomatic radiation necrosis rates in patients treated with immune checkpoint inhibitor (ICI) therapy and concomitant single-fraction stereotactic radiosurgery (SRS) are as high as 20% (PMID: 29327059). We present updated results from the Radiosurgery Dose Reduction for Brain Metastases on Immunotherapy (RADREMI) trial following completion of an a priori interim analysis, aimed to identify reduced-dose SRS that is safe and efficacious for this patient population. Methods: RADREMI (clinicaltrials.gov, NCT04047602) is a prospective multicenter single arm Phase I trial involving patients age > 18 receiving ICI with SRS for 1-10 brain metastases on MRI. Patients had biopsy-confirmed primary malignancy with disease-specific graded prognostic assessment estimated median survival of at least 6 months and no previous whole brain radiation therapy. Six-month symptomatic radiation necrosis (radiographic radiation necrosis + clinical symptoms requiring steroid administration and/or operative intervention) was the primary endpoint, based on an expected rate of 5% and a historical rate of 16%. Secondary endpoints included 6-month local control and radiographic radiation necrosis. Response Assessment in Neuro-Oncology criteria defined local control; findings were compared to historical 6-month local control of 87-91% with RTOG 90-05 SRS dosing. A pre-determined interim futility analysis (based on the null hypothesis of no fewer than 15 of the first 20 patients reaching the primary endpoint achieving 6-month local control for RADREMI dosing) was performed using the Fisher’s exact test. Results: Between December 18, 2019 and September 10, 2021, 43 lesions were treated in 16 patients receiving ICI delivered within 30 days before SRS who were enrolled on trial and met the primary endpoint (median follow-up = 9.1 months). All patients received RADREMI SRS dosing (18 Gy for lesions 0-2 cm, 14 Gy for lesions 2.1-3 cm, and 12 Gy for lesions 3.1-4 cm). The most common ICI used was single-agent pembrolizumab (51% of lesions, 56% of patients), followed by single-agent nivolumab (28% of lesions, 13% of patients). The six-month rates of symptomatic and radiographic radiation necrosis were zero; the six-month local control rate was 98% per treated lesion (42/43), and 94% per treated patient (15/16), comparable to historical controls (p > 0.05) and sufficient to not reject the interim futility analysis null hypothesis. Conclusions: Interim analysis reveals that the safety and efficacy of RADREMI dosing for reducing SRS dose in brain metastasis patients receiving concomitant ICI persists with excellent local control and no morbidity in a multi-institutional collaborative trial. Further results following completion of trial enrollment will provide additional evidence regarding the safety and efficacy of RADREMI SRS dosing. Clinical trial information: NCT04047602.

Local and distant brain control in melanoma and NSCLC brain metastases with concurrent radiosurgery and immune checkpoint inhibition

INTRODUCTION

The treatment of brain metastases with stereotactic radiosurgery (SRS) in combination with immune checkpoint inhibitors (ICI) has become more common in recent years, but there is a lack of prospective data on cancer control outcomes when these therapies are administered concurrently.

METHODS

Data were retrospectively reviewed for patients with non-small cell lung cancer (NSCLC) and melanoma brain metastases treated with SRS at a single institution from May 2008 to January 2017. A parametric proportional hazard model is used to detect the effect of concurrent ICI within 30, 60, or 90 days of ICI administration on local control and distant in-brain control. Other patient and lesion characteristics are treated as covariates and adjusted in the regression. A frailty term is added in the baseline hazard to capture the within-patient correlation.

RESULTS

We identified 144 patients with 477 total lesions, including 95 NSCLC patients (66.0%), and 49 (34.0%) melanoma patients. On multivariate analysis, concurrent SRS and ICI (SRS within 30 days of ICI administration) was not associated with local control but was associated with distant brain control. When controlling for prior treatment to lesion, number of lesions, and presence of extracranial metastases, patients receiving this combination had a statistically significant decrease in distant brain failure compared to patients that received non-concurrent ICI or no ICI (HR 0.15; 95% CI 0.05-0.47, p = 0.0011).

CONCLUSION

Concurrent ICI can enhance the efficacy of SRS. Prospective studies would allow for stronger evidence to support the impact of concurrent SRS and ICI on disease outcomes.

Literature review of management of brain metastases from germ cell tumors: a narrative review

OBJECTIVE

In this review article, we discuss the role of chemotherapy, surgery, and radiation therapy in the treatment of brain metastases from germ cell tumors (GCT).

BACKGROUND

GCT rarely metastasize to the brain and there is limited data to guide management. Most instances of brain metastases occur in patients with non-seminomatous germ cell tumors (NSGCT).

METHODS

We searched PubMed using the terms 'CNS metastases' or 'brain metastases' and 'germ cell' from 2011 through August 2021. Review articles and prospective trials related to the treatment of brain metastases in GCT were included in addition to articles obtained by hand search of the references and clinical practice guidelines.

CONCLUSIONS

We highlight the importance of using chemotherapy as first-line therapy in most situations. We discuss the very minimal data regarding surgery and its primary role when there is significant mass effect or brain shift. We also compare whole brain radiation therapy (WBRT) with the use of radiosurgery. We then provide overall recommendations based on the reviewed data and our experience as a referral center for GCT.

GammaTile for Gliomas: A Single-Center Case Series

GammaTile® (GT Medical Technologies, Tempe, Arizona) is a surgically targeted radiation source, approved by FDA for brachytherapy in primary and secondary brain neoplasms. Each GammaTile is composed of a collagen sponge with four seeds of cesium 131 and is particularly useful in recurrent tumors. We report our early experience in seven patients with recurrent gliomas to assess this type of brachytherapy with particular attention to ease of use, complication, and surgical planning. This study represents a retrospective chart review of surgical use and early clinical outcomes of GammaTile in recurrent gliomas. The number of tiles was planned using pre-operative imaging and dosimetry was planned based on post-operative imaging. Patients were followed during their hospital stay and were followed up after discharge. Parameters such as case length, resection extent, complication, ICU length of stay (LOS), hospital LOS, pre-operative Glasgow Coma Scale (GCS), immediate post-operative GCS, post-operative imaging findings, recurrence at follow-up, length of follow-up, and dosimetry were collected in a retrospective manner. Seven patients were identified that met the inclusion criteria. Two patients were diagnosed with recurrent glioblastoma multiforme (GBM), one lower-grade glioma that recurred as a GBM, one GBM that recurred as a gliosarcoma, and two recurrent oligodendrogliomas. We found that operation time, ICU LOS, hospital LOS, pre- and post-operative GCS, and post-operative complications were within the expected ranges for tumor resection patients. Further, dosimetry data suggests that six out of seven patients received adequate radiation coverage, with the seventh having implantation limitations due to nearby organs at risk. We report no postoperative complications that can be attributed to the GammaTiles themselves. In our cohort, we report seven cases where GammaTiles were implanted in recurrent gliomas. No implant-related post-operative complications were identified. This early data suggests that GammaTile can be a safe form of brachytherapy in recurrent gliomas.

Analysis of Virtual Versus In-Person Prospective Peer Review Workflow in a Multisite Academic Radiation Oncology Department

PURPOSE

In radiation oncology, peer review is a process where subjective treatment planning decisions are assessed by those independent of the prescribing physician. Before March 2020, all peer review sessions occurred in person; however due to the COVID-19 pandemic, the peer-review workflow was transitioned from in-person to virtual. We sought to assess any differences between virtual versus in-person prospective peer review.

METHODS AND MATERIALS

Patients scheduled to receive nonemergent nonprocedural radiation therapy (RT) were presented daily at prospective peer-review before the start of RT administration. Planning software was used, with critical evaluation of several variables including treatment intent, contour definition, treatment target coverage, and risk to critical structures. A deviation was defined as any suggested plan revision.

RESULTS

In the study, 274 treatment plans evaluated in-person in 2017 to 2018 were compared with 195 plans evaluated virtually in 2021. There were significant differences in palliative intent (36% vs 22%; P = .002), but not in total time between simulation and the start of treatment (9.2 vs 10.0 days; P = .10). Overall deviations (8.0% in-person vs 2.6% virtual; P = .015) were significantly reduced in virtual peer review.

CONCLUSIONS

Prospective daily peer review of radiation oncology treatment plans can be performed virtually with similar timeliness of patient care compared with in-person peer review. A decrease in deviation rate in the virtual peer review setting will need to be further investigated to determine whether virtual workflow can be considered a standard of care.

Radiosurgery dose reduction for brain metastases on immunotherapy (RADREMI): Early results from a multicenter phase I trial

2025

Background: The rate of symptomatic radiation necrosis in patients treated with immune checkpoint inhibitor (ICI) therapy and concomitant single-fraction stereotactic radiosurgery (SRS) is as high as 20% (Martin et al., JAMA Oncology 2018). Here, we present the first results from the Radiosurgery Dose Reduction for Brain Metastases on Immunotherapy (RADREMI) trial, aimed to identify reduced-dose SRS that is safe and efficacious for this patient population. Methods: RADREMI is a prospective multicenter, single arm phase I pilot study. Patients age > 18 receiving ICI with SRS for 1-10 brain metastases on MRI from biopsy-confirmed primary malignancy with estimated median survival of at least 6 months (by disease-specific graded prognostic assessment) and no history of whole brain radiation therapy were eligible. The primary endpoint was six-month symptomatic radiation necrosis (defined as a six-month rate of clinical symptomatology requiring steroid administration and/or operative intervention concomitant with imaging findings consistent with radiation necrosis), based on a historical six-month symptomatic radiation necrosis rate of 16% and an expected rate of 5%. Secondary endpoints included six-month local control and six-month radiographic radiation necrosis. Local control was defined according to Response Assessment in Neuro-Oncology (RANO) criteria, and was compared to historical controls of 87-91% six-month local control with RTOG 90-05 SRS dosing. The Fisher’s exact test was used for statistical analysis. This trial is registered at clinicaltrials.gov, NCT04047602. Results: Between December 18, 2019 and January 21, 2021, 39 lesions were treated in 17 patients receiving ICI delivered within 30 days before SRS from whom we recruited and obtained consent. All patients were treated with RADREMI dosing, which involved SRS doses of 18 Gy for lesions 0-2 cm, 14 Gy for lesions 2.1-3 cm, and 12 Gy for lesions 3.1-4 cm. The most common ICI used was single-agent pembrolizumab (49% of lesions, 59% of patients), followed by single-agent nivolumab (31% of lesions, 12% of patients). For the 11 lesions (six patients) meeting the primary endpoint (median follow-up = 259 days), the six-month symptomatic radiation necrosis rate was 0% per treated lesion, and 0% per treated patient, which was not significantly different from historical controls (p = 0.478). The six-month local control rate was 100% per treated lesion, and 100% per treated patient, comparable to historical controls (p = 0.476). Conclusions: In the first prospective trial to investigate dose-reduced SRS with concomitant ICI in treating metastatic brain disease, early results support the safety and efficacy of RADREMI dosing in this patient population. These findings warrant further multi-institutional collaborative trials of RADREMI dosing for this population. Clinical trial information: NCT04047602.

RADT-42. ADJUVANT RADIATION THERAPY FOR SUBTOTALLY RESECTED CEREBELLAR LIPONEUROCYTOMA

INTRODUCTION

Classified as a benign glioneural tumor, cerebellar liponeurocytoma is a rare disease (fewer than 80 reported cases) and was upgraded from WHO grade I to grade II in 2007 due to its high recurrence rate. The authors report a case of definitive radiation therapy for recurrent subtotally resected cerebellar liponeurocytoma.

METHODS

An 80-year-old man having undergone seven resections for his left cerebellar liponeurocytoma without adjuvant therapy over the previous decade at outside institutions was referred for radiation therapy two months following his eighth resection, where gross total resection was limited by the lesion proximity to his brainstem resulting in a 2 cm residual left cerebellar lesion. Pathology revealed tumor cells strongly positive for synaptophysin and a Ki-67 labeling index &lt; 1%. Due to the propensity of this disease to recur following resection, his entire resection cavity was treated with external beam radiation therapy (EBRT) to 46 Gy, followed by a 10 Gy boost to his residual disease yielding a total of 56 Gy to the residual disease.

RESULTS

Reimaging following the initial 46 Gy revealed the residual disease remained amenable (&lt; 3 cm) to stereotactic radiosurgery (SRS), which was delivered via linear accelerator (10 Gy to the 80% isodose line) in a single fraction. Following EBRT + SRS, the patient responded well. At last follow-up, he has demonstrated no evidence of disease progression, brainstem-related morbidity or surgical incision-related morbidity.

CONCLUSIONS

The first reported case of SRS treatment of cerebellar liponeurocytoma as the culmination of a coordinated definitive plan beginning with EBRT supports the applicability and feasibility of this treatment strategy following subtotal resection. This case indicates that a radiation treatment plan similar to that for central neurocytoma may be an optimal strategy, and suggests that adjuvant radiation therapy following operative resection of this rare disease may be underutilized.

RADT-43. TREATMENT OF RETROPERITONEAL LEIOMYOSARCOMA BRAIN METASTASES WITH STEREOTACTIC RADIOSURGERY

INTRODUCTION

Retroperitoneal leiomyosarcoma is a relatively rare disease, with infrequent metastatic spread to the CNS. We present the first report of radiosurgical treatment of this disease.

METHODS

A 49-year-old woman developed leiomyosarcoma of the inferior vena cava and retroperitoneum with lung metastases on diagnosis. Following multiple courses of systemic and operative treatment, she developed a tender ulcerating mass in the left upper maxillary incisor associated with numbness along the upper gum, lip, and premaxillary area. CT revealed a 3.0 cm left posterior alveolar ridge gum lesion with bone invasion, for which she elected to undergo palliative radiation therapy (30 Gy in 10 fractions). Due to potential maxillary nerve involvement altering the intended radiation therapy treatment fields, an orbit/face MRI was performed to better delineate the lesion. On this MRI, two frontal lobe lesions were visualized; subsequent dedicated brain MRI revealed a total of five metastases (0.9 cm right superior frontal gyrus, 0.9 cm left middle frontal gyrus, 0.9 cm right postcentral gyrus, 0.7 cm right occipital, and 1.6 cm left occipital). Consequently, the decision was made to treat the brain metastases with linear accelerator (LINAC) stereotactic radiosurgery (SRS) to allow simultaneous treatment of the maxillary lesion and brain metastases.

RESULTS

A single CT simulation was performed for her intracranial and extracranial disease, using the Encompass face mask to allow for simultaneous head immobilization and optimal SRS targeting accuracy. LINAC SRS was delivered simultaneously during maxillary lesion radiation therapy to all five lesions (22 Gy to the 80% isodose line) in a single fraction with a 0.2 cm planning target volume (PTV) margin for each lesion.

CONCLUSIONS

The first reported case of metastatic retroperitoneal leiomyosarcoma brain metastases treated with SRS demonstrates the flexibility of LINAC (rather than Gamma Knife) SRS in allowing for simultaneous treatment of intracranial and extracranial metastatic disease.

Baseline Karnofsky performance status is independently predictive of death within 30 days of intracranial radiation therapy completion for metastatic disease

Introduction

For patients with brain metastases, palliative radiation therapy (RT) has long been a standard of care for improving quality of life and optimizing intracranial disease control. The duration of time between completion of palliative RT and patient death has rarely been evaluated.

Methods

A compilation of two prospective institutional databases encompassing April 2015 through December 2018 was used to identify patients who received palliative intracranial radiation therapy. A multivariate logistic regression model characterized patients adjusting for age, sex, admission status (inpatient versus outpatient), Karnofsky Performance Status (KPS), and radiation therapy indication.

Results

136 consecutive patients received intracranial palliative radiation therapy. Patients with baseline KPS <70 (OR = 2.2; 95%CI = 1.6-3.1; p < 0.0001) were significantly more likely to die within 30 days of treatment. Intracranial palliative radiation therapy was most commonly delivered to provide local control (66% of patients) or alleviate neurologic symptoms (32% of patients), and was most commonly delivered via whole brain radiation therapy in 10 fractions to 30 Gy (38% of patients). Of the 42 patients who died within 30 days of RT, 31 (74%) received at least 10 fractions.

Conclusions

Our findings indicate that baseline KPS <70 is independently predictive of death within 30 days of palliative intracranial RT, and that a large majority of patients who died within 30 days received at least 10 fractions. These results indicate that for poor performance status patients requiring palliative intracranial radiation, hypofractionated RT courses should be strongly considered.

Radiosurgery dose reduction for brain metastases on immunotherapy (RADREMI): A prospective phase I study protocol

INTRODUCTION

Up to 20% of patients with brain metastases treated with immune checkpoint inhibitor (ICI) therapy and concomitant stereotactic radiosurgery (SRS) suffer from symptomatic radiation necrosis. The goal of this study is to evaluate Radiosurgery Dose Reduction for Brain Metastases on Immunotherapy (RADREMI) on six-month symptomatic radiation necrosis rates.

METHODS

This study is a prospective single arm Phase I pilot study which will recruit patients with brain metastases receiving ICI delivered within 30 days before SRS. All patients will be treated with RADREMI dosing, which involves SRS doses of 18 Gy for 0-2 cm lesions, 14 Gy for 2.1-3 cm lesions, and 12 Gy for 3.1-4 cm lesions. All patients will be monitored for six-month symptomatic radiation necrosis (defined as a six-month rate of clinical symptomatology requiring steroid administration and/or operative intervention concomitant with imaging findings consistent with radiation necrosis) and six-month local control. We expect that RADREMI dosing will significantly reduce the symptomatic radiation necrosis rate of concomitant SRS + ICI without significantly sacrificing the local control obtained by the present RTOG 90-05 SRS dosing schema. Local control will be defined according to the Response Assessment in Neuro-Oncology (RANO) criteria.

DISCUSSION

This study is the first prospective trial to investigate the safety of dose-reduced SRS in treatment of brain metastases with concomitant ICI. The findings should provide fertile soil for future multi-institutional collaborative efficacy trials of RADREMI dosing for this patient population.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT04047602 (registration date: July 25, 2019).

Impact of Lung Parenchymal-Only Failure on Overall Survival in Early-Stage Lung Cancer Patients Treated With Stereotactic Ablative Radiotherapy

INTRODUCTION

The impact of lung parenchymal-only failure on patient survival after stereotactic ablative body radiotherapy (SABR) for early-stage non-small-cell lung cancer (NSCLC) remains unclear.

PATIENTS AND METHODS

The study population included 481 patients with early-stage NSCLC who were treated with 3- to 5-fraction SABR between 2000 and 2016. The primary study objective was to assess the impact of out-of-field lung parenchymal-only failure (OLPF) on overall survival (OS).

RESULTS

At a median follow-up of 5.9 years, the median OS was 2.7 years for all patients. Patients with OLPF did not have a significantly different OS compared to patients without failure (P = .0952, median OS 4.1 years with failure vs. 2.6 years never failure). Analysis in a 1:1 propensity score-matched cohort for Karnofsky performance status, comorbidity score, and smoking status showed no differences in OS between patients without failure and those with OLPF (P = .8). In subgroup analyses exploring the impact of time of failure on OS, patients with OLPF 6 months or more after diagnosis did not have significantly different OS compared to those without failure, when accounting for immortal time bias (P = .3, median OS 4.3 years vs. 3.5 years never failure). Only 7 patients in our data set experienced failure within 6 months of treatment, of which only 4 were confirmed to be true failures; therefore, limited data are available in our cohort on the impact of OLPF for ≤ 6 months on OS.

CONCLUSION

OLPF after SABR for early-stage NSCLC does not appear to adversely affect OS, especially if occurring at least 6 months after SABR. More studies are needed to understand if OLPF within 6 months of SABR is associated with adverse OS. These data are useful when discussing prognosis of lung parenchymal failures after initial SABR.

Exploiting tumor position differences between deep inspiration and expiration in lung stereotactic body radiation therapy planning

PURPOSE

We demonstrate proof of principle that normal tissue doses can be greatly reduced in lung stereotactic body radiation therapy (SBRT) for mobile tumors, if the delivered dose is split between opposite respiratory states.

METHODS

Patients that underwent 5 fraction lung SBRT at our institution and had deep inspiration breath hold (DIBH) and free breathing 4D computed tomography scans were included. Volumetric modulated arc therapy plans were generated on both respiratory phases and a third composite plan was generated delivering half the dose using the DIBH plan and the other half using the expiratory phase plan for each fraction. Computed tomography scans for the composite plan were fused based on ribs adjacent to the tumor to evaluate the dose volume histogram of critical structures.

RESULTS

Four patients with 4 total tumors had requisite planning scans available. Tumor size was between 0.7 to 2.9 cm and tumor movement 1.4 to 2.9 cm. Median reduction in the chest wall (CW) V30Gy for the composite plan was 74.6% (range 33.7 to 100%), 76.9% (range 32.9 to 100%), and 89.3% (range 69.5 to 100%) compared to the DIBH, expiration phase, and free breathing plans, respectively. Median reduction in CW maximum dose for the composite plan was 23.3% (range 0.27% to 46.4%), 23.5% (range 3.2 to 48.2%), and 23.4% (range 0.27% to 48.4%) compared to the DIBH, expiration phase, and free breathing plans, respectively. Greater reduction in CW maximum dose was observed when patients had no overlap in planning target volumes between DIBH and expiration phases (median reduction 43.9% for no overlap vs 2.7% with overlap). Between all plans, lung V20Gy absolute differences were within 1.3%. For 2 of 4 patients, the composite plan met constraints for 3 fraction SBRT, while standard plans did not.

CONCLUSIONS

We conclude that composite DIBH-expiration SBRT planning has the potential to improve organ at risk sparing.

Isocitrate dehydrogenase 1 mutant glioblastomas demonstrate a decreased rate of pseudoprogression: a multi-institutional experience

BACKGROUND

Pseudoprogression (psPD) represents false radiologic evidence of tumor progression and is observed in some glioblastoma (GBM) patients after postoperative chemoradiation (CRT) with temozolomide (TMZ). The ambiguity of the psPD diagnosis confounds identification of true progression and may lead to unnecessary interventions. The association between psPD and isocitrate dehydrogenase 1 (IDH1) mutational (mut) status is understudied, and its incidence may alter clinical decision making.

METHODS

We retrospectively evaluated 120 patients with IDH1-mut (n = 60) and IDH1-wild-type (IDH-WT; [n = 60]) GBMs who received postoperative CRT with TMZ at 4 academic institutions. Response Assessment in Neuro-Oncology criteria were used to identify psPD rates in routine brain MRIs performed up to 90 days after CRT completion.

RESULTS

Within 90 days of completing CRT, 9 GBM patients (1 [1.7%] IDH1-mut and 8 [13.3%] IDH1-WTs) demonstrated true progression, whereas 17 patients (3 [5%] IDH1-muts and 14 [23.3%] IDH1-WTs) demonstrated psPD (P  =  .004). IDH1-mut GBMs had a lower probability of psPD (hazard ratio: 0.173, 95% CI, 0.047-0.638, P = .008). Among the patients with radiologic signs suggestive of progression (n = 26), psPD was found to be the cause in 3 of 4 (75.0%) of the IDH1-mut GBMs and 14 of 22 (63.6%) of the IDH1-WT GBMs (P = .496). Median overall survival for IDH1-mut and IDH1-WT GBM patients was 40.3 and 23.0 months, respectively (P  < .001).

CONCLUSIONS

IDH1-mut GBM patients demonstrate lower absolute rates of psPD expression. Irrespective of GBM subtype, psPD expression was more likely than true progression within 90 days of completing CRT. Continuing adjuvant treatment for IDH1-mut GBMs is suggested if radiologic progression is suspected during this time interval.

Predictors of death for patients treated with palliative intent radiation using prospective databases

e18325

Background: Radiation therapy (RT) effectively palliates pain and other symptoms due to cancer and is frequently offered to patients with metastatic disease. Standard palliative RT schedules range from one to ≥10 fractions; however, prognostic variables related to survival following palliative RT are not well studied. A better understanding of prognostic factors in this setting will assist in selecting appropriate palliative RT regimens for patients with short life expectancies. Methods: Prospectively maintained institutional databases tracking morbidity and mortality and outcomes of a departmental peer review process were used to identify patients who received palliative RT between April 2015 - December 2018. Cox proportional hazards model was used to identify factors correlated with overall survival (OS) and mortality within 30 days (30DM) after completing palliative RT, including age, sex, admission status (inpatient versus outpatient), Karnofsky Performance Status (KPS), treated site and primary site. Results: Of 421 patients, 389 received palliative RT; 30DM rate was 25.7% (n = 100). Median age was 61, median KPS was 70, and 196 patients (50.4%) were female. The most common primary sites were thorax (N = 121, 31.1%) and genitourinary tract (N = 60, 15.4%), while the most commonly treated sites were brain (N = 136, 35.0%) and bone (N = 71, 18.3%). KPS and treatment site were strong independent predictors of both OS and 30DM. Patients with KPS < 70 had an HR 2.61 (95% CI 1.54 – 4.43, p < 0.0001) for 30DM and an HR of 2.22 (95% CI 1.57 – 3.13, p < 0.0001) for death at any time after RT. Treatment site was also independently associated with OS and 30DM (p = 0.01 and p = 0.03, respectively). Median OS durations (95%CI) were: abdomen/pelvis not reached, bone 340 days (133.9-546.1), spine 207 days (28.0 – 386.0), head and neck 184 days (55.2 – 312.8), brain 104 days (34.3 – 173.7) and thorax 76 days (10.3 – 141.7). Age, sex, admission status and primary site were not correlated with OS or 30DM. Conclusions: RT can effectively palliate distressing symptoms related to primary or metastatic cancers. However, early mortality is common following palliative RT and is associated with poor performance status and treated site. Hypofractionated RT courses should be considered in patients with such risk factors to reduce the burden of prolonged therapy on patients and their families at the end of life.

How often do metastatic brain disease patients prescribed ten fractions of whole brain radiation therapy die without completing treatment?

e23146

Background: Palliative whole brain radiation therapy (WBRT) is an established treatment modality for optimizing intracranial disease control in patients with metastatic brain disease, most commonly prescribed to a dose of 30 Gy in 10 fractions. The fidelity of WBRT course completion has not been rigorously evaluated. Methods: Two prospective institutional databases evaluating patients treated from April 2015 through December 2018 identified patients who received WBRT. Information analyzed included prescribed and delivered dose/fractionation, Karnofsky Performance Status (KPS), admission status, treatment duration, and time between WBRT completion and patient hospice referral/death. Results: 52 consecutive patients prescribed WBRT to 30 Gy in 10 fractions were evaluated. Twenty-six (50%) were inpatients, and only 17 (33%) had a KPS of 70 or greater (able to care for self). More than 30% failed to finish more than 5 of their 10 scheduled fractions before either death or hospice referral; only 29 of 52 patients (56%) finished WBRT as prescribed. Twenty-five patients (48%) died within 30 days of WBRT. Of the 29 patients who finished WBRT as prescribed, 9 (31%) died within 30 days of completing treatment. Of the 23 patients who failed to complete standard fractionation WBRT, nearly 70% died within 30 days of receiving their final radiation therapy fraction. Conclusions: These findings indicate that greater than 40% of patients prescribed the standard 10 fraction regimen of WBRT do not remain well enough to tolerate the full duration of treatment. With nearly half of patients dying within 30 days of standard fraction WBRT, there should be strong incentive to reduce the physical and financial burden on this patient population by prescribing WBRT with significantly shorter (i.e. single-fraction or 20 Gy in 5 fractions) fractionation schemes.

Predictors of Nodal and Metastatic Failure in Early Stage Non-small-cell Lung Cancer After Stereotactic Body Radiation Therapy

INTRODUCTION/BACKGROUND

Many patients with early stage non-small-cell lung cancer (ES-NSCLC) undergoing stereotactic body radiation therapy (SBRT) develop metastases, which is associated with poor outcomes. We sought to identify factors predictive of metastases after lung SBRT and created a risk stratification tool.

MATERIALS AND METHODS

We included 363 patients with ES-NSCLC who received SBRT; the median follow-up was 5.8 years. The following patient and tumor factors were retrospectively analyzed for their association with metastases (defined as nodal and/or distant failure): gender; age; lobe involved; centrality; previous NSCLC; smoking status; gross tumor volume (GTV); T-stage; histology; dose; minimum, maximum, and mean GTV dose; and parenchymal lung failure. A metastasis risk-score linear-model using beta coefficients from a multivariate Cox model was built.

RESULTS

A total of 111 (27.3%) of 406 lesions metastasized. GTV and dose were significantly associated with metastases on univariate and multivariate Cox proportional hazards modeling (P < .001 and hazard ratio [HR], 1.02 per mL; P < .05 and HR, 0.99 per Gy, respectively). Histology, T-stage, centrality, lung parenchymal failures, and previous NSCLC were not associated with development of metastasis. A metastasis risk-score model using GTV and prescription dose was built: risk score = (0.01611 × GTV) - (0.00525 × dose [BED₁₀]). Two risk-score cutoffs separating the cohort into low-, medium-, and high-risk subgroups were examined. The risk score identified significant differences in time to metastases between low-, medium-, and high-risk patients (P < .001), with 3-year estimates of 81.1%, 63.8%, and 38%, respectively.

CONCLUSION

GTV and radiation dose are associated with time to metastasis and may be used to identify patients at higher risk of metastasis after lung SBRT.

Histology, Tumor Volume, and Radiation Dose Predict Outcomes in NSCLC Patients After Stereotactic Ablative Radiotherapy

INTRODUCTION

It remains unclear if histology should be independently considered when choosing stereotactic ablative body radiotherapy dose prescriptions for NSCLC.

METHODS

The study population included 508 patients with 561 lesions between 2000 and 2016, of which 442 patients with 482 lesions had complete dosimetric information. Eligible patients had histologically or clinically diagnosed early-stage NSCLC and were treated with 3 to 5 fractions. The primary endpoint was in-field tumor control censored by either death or progression. Involved lobe control was also assessed.

RESULTS

At 6.7 years median follow-up, 3-year in-field control, involved lobe control, overall survival, and progression-free survival rates were 88.1%, 80.0%, 49.4%, and 37.2%, respectively. Gross tumor volume (GTV) (hazard ratio [HR] = 1.01 per mL, p = 0.0044) and histology (p = 0.0225) were independently associated with involved lobe failure. GTV (HR = 1.013, p = 0.001) and GTV dose (cutoff of 110 Gy, biologically effective dose with α/β = 10 [BED10], HR = 2.380, p = 0.0084) were independently associated with in-field failure. For squamous cell carcinomas, lower prescription doses were associated with worse in-field control (12 Gy × 4 or 10 Gy × 5 versus 18 Gy or 20 Gy × 3: HR = 3.530, p = 0.0447, confirmed by propensity score matching) and was independent of GTV (HR = 1.014 per mL, 95% confidence interval: 1.005-1.022, p = 0.0012). For adenocarcinomas, there were no differences in in-field control observed using the above dose groupings (p = 0.12 and p = 0.31, respectively).

CONCLUSIONS

In the absence of level I data, GTV and histology should be considered to personalize radiation dose for stereotactic ablative body radiotherapy. We suggest lower prescription doses (i.e., 12 Gy × 4 or 10 G × 5) should be avoided for squamous cell carcinomas if normal tissue tolerances are met.

Using Higher Isodose Lines for Gamma Knife Treatment of 1 to 3 Brain Metastases Is Safe and Effective

BACKGROUND:

Higher isodose lines (IDLs) in Gamma Knife (GK) Perfexion treatment of brain metastases (BMet) could result in lower local control (LC) or higher radiation necrosis (RN) rates, but reduce treatment time.

OBJECTIVE:

To assess the impact of the heterogeneity index (HI) and conformality index (CFI) ion local failure (LF) for patients treated with GK for 1 to 3 BMet.

METHODS:

From an institutional review board—approved database, 320 patients with 496 BMet were identified, treated for 1 to 3 BMet from July 2007 to April 2011 on GK Perfexion. Cox proportional hazards regression was used to analyze significance of HI, CFI, IDL, dose, tumor diameter, recursive partitioning analysis class, tumor radioresistance, primary, smoking history, metastasis location, and whole-brain radiation therapy (WBRT) history with LF and RN.

RESULTS:

Median follow-up by lesion was 6.8 months (range, 0-49.6). The series median survival was 14.2 months. Per RECIST, 9.5% of lesions failed, 33.9% were stable, 38.3% partially responded, 17.1% responded completely, and 1.2% could not be assessed. The 12-month LC rate was 87.3%. On univariate analysis, a dose less than 20 Gy (hazard ratio [HR]: 2.940, P &lt; .001); tumor size (HR: 1.674, P &lt; .001); and cerebellum/brainstem location vs other (HR: 1.891, P = .043) were significant for LF. Non-small cell lung cancer (HR: 0.333, P = .0097) was associated with better LC. On multivariate analysis, tumor size (HR: 1.696, P &lt; .001) and cerebellum/brainstem location vs other (HR: 1.959, P = .033) remained significant for LF. Variables not significant for LF included CI, IDL, and HI.

CONCLUSION:

Our study of patients with 1 to 3 BMet treated with GK demonstrated no difference in LC or RN with varying HI, indicating that physicians can treat to IDL at 70% or higher IDL to reduce treatment time without increased LF or RN.

Stereotactic body radiation therapy for metastasis in the lung: an undervalued treatment option with future prospects

SUMMARY The lung is a common site of metastatic disease from solid tumors. Most cancers can develop lung metastases, and sarcoma and epithelial (especially colorectal) malignancies are prone to metastasize to the lung. In particular, the International Registry of Lung Metastases describes 5206 cases of lung metastasectomy, of which 43% were epithelial and 42% were sarcomatoid. Common presenting symptoms include cough, hemoptysis, shortness of breath, chest pain and back pain. Data in the literature suggest the existence of an oligometastatic state, where metastases are limited in number and location. For selected patients with lung oligometastases, local therapy such as surgery, stereotactic body radiotherapy (SBRT) and radiofrequency ablation may potentially yield prolonged survival. Data from retrospective series and prospective trials on the use of SBRT for lung metastases are emerging, showing promising results. Most studies show high local control rates rivaling those found in studies of surgical management (the usual treatment of choice) for lung metastases, while SBRT also has the benefit of low rates of significant toxicities. This review will provide an overview of the utilization of SBRT in the management of lung oligometastases.

Intraoperative radiotherapy for parotid cancer: a single-institution experience

PURPOSE

Our practice policy has been to provide intraoperative radiotherapy (IORT) at resection to patients with head-and-neck malignancies considered to be at high risk of recurrence. The purpose of the present study was to review our experience with the use of IORT for primary or recurrent cancer of the parotid gland.

METHODS AND MATERIALS

Between 1982 and 2007, 96 patients were treated with gross total resection and IORT for primary or recurrent cancer of the parotid gland. The median age was 62.9 years (range, 14.3-88.1). Of the 96 patients, 33 had previously undergone external beam radiotherapy as a component of definitive therapy. Also, 34 patients had positive margins after surgery, and 40 had perineural invasion. IORT was administered as a single fraction of 15 or 20 Gy with 4-6-MeV electrons. The median follow-up period was 5.6 years.

RESULTS

Only 1 patient experienced local recurrence, 19 developed regional recurrence, and 12 distant recurrence. The recurrence-free survival rate at 1, 3, and 5 years was 82.0%, 68.5%, and 65.2%, respectively. The 1-, 3-, and 5-year overall survival rate after surgery and IORT was 88.4%, 66.1%, and 56.2%, respectively. No perioperative fatalities occurred. Complications developed in 26 patients and included vascular complications in 7, trismus in 6, fistulas in 4, radiation osteonecrosis in 4, flap necrosis in 2, wound dehiscence in 2, and neuropathy in 1. Of these 26 patients, 12 had recurrent disease, and 8 had undergone external beam radiotherapy before IORT.

CONCLUSIONS

IORT results in effective local disease control at acceptable levels of toxicity and should be considered for patients with primary or recurrent cancer of the parotid gland.