Peri-SRS Administration of Immune Checkpoint Therapy for Melanoma Metastatic to the Brain: Investigating Efficacy and the Effects of Relative Treatment Timing on Lesion Response

Long-Term Intracranial Outcomes With Combination Dual Immune-Checkpoint Blockade and Stereotactic Radiosurgery in Patients With Melanoma and Non-Small Cell Lung Cancer Brain Metastases

PURPOSE

The intracranial benefit of offering dual immune-checkpoint inhibition (D-ICPI) with ipilimumab and nivolumab to patients with melanoma or non-small cell lung cancer (NSCLC) receiving stereotactic radiosurgery (SRS) for brain metastases (BMs) is unknown. We hypothesized that D-ICPI improves local control compared with SRS alone.

METHODS AND MATERIALS

Patients with melanoma or NSCLC treated with SRS from 2014 to 2022 were evaluated. Patients were stratified by treatment with D-ICPI, single ICPI (S-ICPI), or SRS alone. Local recurrence, intracranial progression (IP), and overall survival were estimated using competing risk and Kaplan-Meier analyses. IP included both local and distant intracranial recurrence.

RESULTS

Two hundred eighty-eight patients (44% melanoma, 56% NSCLC) with 1,704 BMs were included. Fifty-three percent of patients had symptomatic BMs. The median follow-up was 58.8 months. Twelve-month local control rates with D-ICPI, S-ICPI, and SRS alone were 94.73% (95% CI, 91.11%-96.90%), 91.74% (95% CI, 89.30%-93.64%), and 88.26% (95% CI, 84.07%-91.41%). On Kaplan-Meier analysis, only D-ICPI was significantly associated with reduced local recurrence (P = .0032). On multivariate Cox regression, D-ICPI (hazard ratio [HR], 0.4003; 95% CI, 0.1781-0.8728; P = .0239) and planning target volume (HR, 1.022; 95% CI, 1.004-1.035; P = .0059) correlated with local control. One hundred seventy-three (60%) patients developed IP. The 12-month cumulative incidence of IP was 41.27% (95% CI, 30.27%-51.92%), 51.86% (95% CI, 42.78%-60.19%), and 57.15% (95% CI, 44.98%-67.59%) after D-ICPI, S-ICPI, and SRS alone. On competing risk analysis, only D-ICPI was significantly associated with reduced IP (P = .0408). On multivariate Cox regression, D-ICPI (HR, 0.595; 95% CI, 0.373-0.951; P = .0300) and presentation with >10 BMs (HR, 2.492; 95% CI, 1.668-3.725; P < .0001) remained significantly correlated with IP. The median overall survival after D-ICPI, S-ICPI, and SRS alone was 26.1 (95% CI, 15.5-40.7), 21.5 (16.5-29.6), and 17.5 (11.3-23.8) months. S-ICPI, fractionation, and histology were not associated with clinical outcomes. There was no difference in hospitalizations or neurologic adverse events between cohorts.

CONCLUSIONS

The addition of D-ICPI for patients with melanoma and NSCLC undergoing SRS is associated with improved local and intracranial control. This appears to be an effective strategy, including for patients with symptomatic or multiple BMs.

The Safety and Efficacy of Concurrent Immune Checkpoint Blockade and Stereotactic Radiosurgery Therapy with Practitioner and Researcher Recommendations

BACKGROUND

Immune checkpoint inhibitors (ICIs) have shown growing promise in the treatment of brain metastases, especially combined with stereotactic radiosurgery (SRS). The combination of ICIs with SRS has been studied for efficacy as well as increasing radiation necrosis risks. In this review, we compare clinical outcomes of radiation necrosis, intracranial control, and overall survival between patients with brain metastases treated with either SRS alone or SRS-ICI combination therapy.

METHODS

A literature search of PubMed, Scopus, Embase, Web of Science, and Cochrane was performed in May 2023 for articles comparing the safety and efficacy of SRS/ICI versus SRS-alone for treating brain metastases.

RESULTS

The search criteria identified 1961 articles, of which 48 met inclusion criteria. Combination therapy with SRS and ICI does not lead to significant increases in incidence of radiation necrosis either radiographically or symptomatically. Overall, no difference was found in intracranial control between SRS-alone and SRS-ICI combination therapy. Combination therapy is associated with increased median overall survival. Notably, some comparative studies observed decreased neurologic deaths, challenging presumptions that improved survival is due to greater systemic control. The literature supports SRS-ICI administration within 4 weeks of another for survival but remains inconclusive, requiring further study for other outcome measures.

CONCLUSIONS

Combination SRS-ICI therapy is associated with significant overall survival benefit for patients with brain metastases without significantly increasing radiation necrosis risks compared to SRS alone. Although intracranial control rates appear to be similar between the 2 groups, timing of treatment delivery may improve control rates and demands further study attention.

Stereotactic radiosurgery with immune checkpoint inhibitors for brain metastases: a meta-analysis study

BACKGROUND

Immune checkpoint inhibitors (ICIs) are an emerging tool in the treatment of brain metastases (BMs), Stereotactic radiosurgery (SRS), traditionally used for BMs, elicits an immune brain response and can act synergistically with ICIs. We aim to investigate the efficacy of ICI administered with SRS and determine the impact of timing on BM response.

METHODS

A systematical search was performed to identify potential studies concerning BMs managed with SRS alone or with SRS + ICI with relative timing administration (ICI concurrent with SRS, ICI nonconcurrent with SRS, SRS before ICI, SRS after ICI). The overall survival (OS), 12-month OS, local progression-free survival (LPFS), 12-month local brain control (LBC), distant progression-free survival (DPFS), 12-month distant brain control (DBC), and adverse events (intracranial hemorrhage, radionecrosis) were analyzed using the random-effects model.

RESULTS

A total of 16 retrospective studies with 1356 BM patients were included. Compared to nonconcurrent therapy, concurrent therapy revealed a significantly longer OS (HR= 1.43; p = 0.008) and 12-months LBC (HR = 1.91; p = 0.04), a similar 12-months DBC (HR = 1.12; p = 0.547) and higher complication rate (R = 0.77; p = 0.346). Concurrent therapy leads to a significantly higher OS compared to ICI before SRS (HR = 2.55; p = 0.0003).

CONCLUSION

The combination of SRS with ICI improves patients' clinical and radiological outcomes. The effectiveness of the combination is subject to the identification of an optimal therapeutic window.

Optimizing the synergy between stereotactic radiosurgery and immunotherapy for brain metastases

Solid tumors metastasizing to the brain are a frequent occurrence with an estimated incidence of approximately 30% of all cases. The longstanding conventional standard of care comprises surgical resection and whole-brain radiotherapy (WBRT); however, this approach is associated with limited long-term survival and local control outcomes. Consequently, stereotactic radiosurgery (SRS) has emerged as a potential alternative approach. The primary aim of SRS has been to improve long-term control rates. Nevertheless, rare observations of abscopal or out-of-field effects have sparked interest in the potential to elicit antitumor immunity via the administration of high-dose radiation. The blood-brain barrier (BBB) has traditionally posed a significant challenge to the efficacy of systemic therapy in managing intracranial metastasis. However, recent insights into the immune-brain interface and the development of immunotherapeutic agents have shown promise in preclinical and early-phase clinical trials. Researchers have investigated combining immunotherapy with SRS to enhance treatment outcomes in patients with brain metastasis. The combination approach aims to optimize long-term control and overall survival (OS) outcomes by leveraging the synergistic effects of both therapies. Initial findings have been encouraging in the management of various intracranial metastases, while further studies are required to determine the optimal order of administration, radiation doses, and fractionation regimens that have the potential for the best tumor response. Currently, several clinical trials are underway to assess the safety and efficacy of administering immunotherapeutic agents concurrently or consecutively with SRS. In this review, we conduct a comprehensive analysis of the advantages and drawbacks of integrating immunotherapy into conventional SRS protocols for the treatment of intracranial metastasis.

Long duration of immunotherapy before radiosurgery might improve intracranial control of melanoma brain metastases

PURPOSE

Despite significant advances that have been made in management of metastatic melanoma with immune checkpoint therapy, optimal timing of combination immune checkpoint therapy and stereotactic radiosurgery is unknown. We have reported toxicity and efficiency outcomes of patients treated with concurrent immune checkpoint therapy and stereotactic radiosurgery.

PATIENTS AND METHODS

From January 2014 to December 2016, we analyzed 62 consecutive patients presenting 296 melanoma brain metastases, treated with gamma-knife and receiving concurrent immune checkpoint therapy with anti-CTLA4 or anti-PD1 within the 12 weeks of SRS procedure. Median follow-up time was 18 months (mo) (13-22). Minimal median dose delivered was 18 gray (Gy), with a median volume per lesion of 0.219 cm³.

RESULTS

The 1-year control rate per irradiated lesion was 89% (CI 95%: 80.41-98.97). Twenty-seven patients (43.5%) developed distant brain metastases after a median time of 7.6 months (CI 95% 1.8-13.3) after gamma-knife. In multivariate analysis, positive predictive factors for intracranial tumor control were: delay since the initiation of immunotherapy exceeding 2 months before gamma-knife procedure (P=0.003) and use of anti-PD1 (P=0.006). Median overall survival (OS) was 14 months (CI 95%: 11-NR). Total irradiated tumor volume<2.1 cm³ was a positive predictive factor for overall survival (P=0.003). Ten patients (16.13%) had adverse events following irradiation, with four grade≥3. Predictive factors of all grade toxicity were: female gender (P=0.001) and previous treatment with MAPK (P=0.05).

CONCLUSION

A long duration of immune checkpoint therapy before stereotactic radiosurgery might improve intracranial tumor control, but this relationship and its ideal timing need to be assessed in prospective trials.

Optimal timing and sequence of combining stereotactic radiosurgery with immune checkpoint inhibitors in treating brain metastases: clinical evidence and mechanistic basis

Recent evidence has shown that immune checkpoint inhibitors (ICIs) are efficacious for treating brain metastases of various primary tumors. However, the immunosuppressive tumor microenvironment and the blood-brain barrier (BBB) or blood-tumor barrier (BTB) essentially restrict the efficacy of ICIs. Stereotactic radiosurgery (SRS) can be a powerful ally to ICIs due to its trait of disrupting the BBB/BTB and increasing the immunogenicity of brain metastases. The combination of SRS + ICI has shown synergy in brain metastases in several retrospective studies. Nevertheless, the optimal schedule for the combination of SRS and ICI in brain metastases is yet to be determined. In this review, we summarized the current clinical and preclinical evidence on the timing and sequence of SRS + ICI to provide insight into the current state of knowledge about this important area in patient care.

Comparison of immunotherapy combined with stereotactic radiotherapy and targeted therapy for patients with brain metastases: A systemic review and meta-analysis

Advances in brain imaging have led to a higher incidence of brain metastases (BM) being diagnosed. Stereotactic radiotherapy (SRS), systemic immunotherapy, and targeted drug therapy are commonly used for treating BM. In this study, we summarized the differences in overall survival (OS) between several treatments alone and in combination. We carried out a systematic literature search on Pubmed, EMBASE, and Cochrane Library. Differences in OS associated with Immune checkpoint inhibitors (ICI) alone versus targeted therapy alone and SRS + ICI or ICI alone were evaluated. This analysis was conducted on 11 studies involving 4,154 patients. The comprehensive results of fixed effect model showed that the OS of SRS + ICI group was longer than that of the ICI group (hazard ratio, 1.72; 95% CI: 1.41-2.11; P = 0.22; I ² = 30%). The combined fixed-effect model showed that the OS time of ICI was longer than that of targeted therapy (hazard ratio, 2.09; 95% CI: 1.37-3.20; P = 0.21; I ² = 35%). The study had a low risk of bias. In conclusion, our analysis confirmed that immunotherapy alone showed a higher OS benefit in BM patients than targeted therapy alone. The total survival time of patients with SRS combined with ICI was higher than that of patients with single ICI.

Systematic literature review and meta-analysis of clinical outcomes and prognostic factors for melanoma brain metastases

Background

More than 60% of all stage IV melanoma patients develop brain metastases, while melanoma brain metastases (MBM) is historically difficult to treat with poor prognosis.

Objectives

To summarize clinical outcomes and prognostic factors in MBM patients.

Methods

A systematic review with meta-analysis was conducted, and a literature search for relevant studies was performed on November 1, 2020. Weighted average of median overall survival (OS) was calculated by treatments. The random-effects model in conducting meta-analyses was applied.

Results

A total of 41 observational studies and 12 clinical trials with our clinical outcomes of interest, and 31 observational studies addressing prognostic factors were selected. The most common treatments for MBM were immunotherapy (IO), MAP kinase inhibitor (MAPKi), stereotactic radiosurgery (SRS), SRS+MAPKi, and SRS+IO, with median OS from treatment start of 7.2, 8.6, 7.3, 7.3, and 14.1 months, respectively. Improved OS was observed for IO and SRS with the addition of IO and/or MAPKi, compared to no IO and SRS alone, respectively. Several prognostic factors were found to be significantly associated with OS in MBM.

Conclusion

This study summarizes pertinent information regarding clinical outcomes and the association between patient characteristics and MBM prognosis.

Stereotactic radiosurgery combined with immune checkpoint inhibitors for brain metastasis: A systematic review and meta-analysis

Many studies have reported the combination of radiosurgery and immune checkpoint inhibitors (ICI) in the treatment of brain metastasis, but these studies have not reached a consistent conclusion. Therefore, we conducted this systematic review and meta-analysis to evaluate the effect of combination therapy compared with radiosurgery alone on the prognosis of patients with brain metastasis. The Pubmed-MEDLINE and Ovid-EMBASE databases were comprehensively searched to identify relevant articles until May 5, 2022. The search results were filtered by the inclusion and exclusion criteria described in this paper. The pooled hazard ratios (HR) with 95% confidence intervals (CI) were presented as estimates effect to reflect the effect of combined therapy on each outcome. A total of 17 eligible studies covering 2079 patients were included in this meta-analysis. The pooled results showed that the use of targeted drugs could significantly improve the overall survival (HR = 0.62, 95%CI: 0.51-0.76; P<0.01), reduce the risk of local recurrence (HR = 0.48, 95%CI: 0.38-0.62; P<0.01) and distant brain recurrence (HR = 0.70, 95%CI: 0.50-0.97; P<0.05). Overall, SRS combined with ICIs could significantly improve overall survival, local control, and distant brain control of patients with brain metastasis compared to SRS alone, but the effect varies for different pathological types. Our results verified the rationality of the current treatment strategy for brain metastasis which emphasizes the combination of local and systematic therapy.

Narrative Review of Synergistics Effects of Combining Immunotherapy and Stereotactic Radiation Therapy

Stereotactic radiotherapy (SRT) has become an attractive treatment modality in full bloom in recent years by presenting itself as a safe, noninvasive alternative to surgery to control primary or secondary malignancies. Although the focus has been on local tumor control as the therapeutic goal of stereotactic radiotherapy, rare but intriguing observations of abscopal (or out-of-field) effects have highlighted the exciting possibility of activating antitumor immunity using high-dose radiation. Furthermore, immunotherapy has revolutionized the treatment of several types of cancers in recent years. However, resistance to immunotherapy often develops. These observations have led researchers to combine immunotherapy with SRT in an attempt to improve outcomes. The benefits of this combination would come from the stimulation and suppression of various immune pathways. Thus, in this review, we will first discuss the immunomodulation induced by SRT with the promising results of preclinical studies on the changes in the immune balance observed after SRT. Then, we will discuss the opportunities and risks of the combination of SRT and immunotherapy with the preclinical and clinical data available in the literature. Furthermore, we will see that many perspectives are conceivable to potentiate the synergistic effects of this combination with the need for prospective studies to confirm the encouraging data.

Stereotactic Body Radiation Therapy (SBRT) for Oligorecurrent/Oligoprogressive Mediastinal and Hilar Lymph Node Metastasis: A Systematic Review

Simple Summary

This paper is a review of the literature on oligorecurrent/oligoprogressive mediastinal and hilar lymph node metastasis treated with SBRT. The use of mediastinal SBRT had historically been not feasible in view of the expected toxicity due to the proximity of critical structures such as the airways and esophagus. Despite the heterogeneity and lack of some data in the studies analyzed, this literature review is the first published and can be a valid guide for the radiotherapist in the management of oligometastatic/oligoprogressive patients, with particular regard to the radiotherapy doses, dose constraints for organs at risk, and clinical outcomes.

Abstract

Introduction: Mediastinal or hilar lymph node metastases are a challenging condition in patients affected by solid tumors. Stereotactic body radiation therapy (SBRT) could play a crucial role in the therapeutic management and in the so-called “no-fly zone”, delivering high doses of radiation in relatively few treatment fractions with excellent sparing of healthy surrounding tissues and low toxicity. The aim of this systematic review is to evaluate the feasibility and tolerability of SBRT in the treatment of mediastinal and hilar lesions with particular regard to the radiotherapy doses, dose constraints for organs at risk, and clinical outcomes. Materials and methods: Two blinded investigators performed a critical review of the Medline, Web of Knowledge, Google Scholar, Scopus, and Cochrane databases according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement (PRISMA), starting from a specific question: What is the clinical impact of SBRT for the treatment of oligorecurrent/oligoprogressive mediastinal and hilar metastasis? All retrospective and prospective clinical trials published in English up to February 2022 were analyzed. Results: A total of 552 articles were identified and 12 of them were selected with a total number of 478 patients treated with SBRT for mediastinal or hilar node recurrence. All the studies are retrospective, published between 2015 and 2021 with a median follow-up ranging from 12 to 42.2 months. Studies following SBRT for lung lesions or retreatments after thorax radiotherapy for stage III lung cancer were also included. The studies showed extensive heterogeneity in terms of patient and treatment characteristics. Non-small cell lung cancer was the most frequently reported histology. Different dose schemes were used, with a higher prevalence of 4–8 Gy in 5 or 6 fractions, but dose escalation was also used up to 52 Gy in 4 fractions with dose constraints mainly derived from RTOG 0813 trial. The radiotherapy technique most frequently used was volumetric modulated arc therapy (VMAT) with a median PTV volume ranging from 7 to 25.7 cc. The clinical outcome seems to be very encouraging with 1-year local control (LC), overall survival (OS) and progression-free survival (PFS) rates ranging from 84 to 94%, 53 to 88% and 23 to 53.9%, respectively. Half of the studies did not report toxicity greater than G3 and only five cases of fatal toxicity were reported. CONCLUSIONS: From the present review, it is not possible to draw definitive conclusions because of the heterogeneity of the studies analyzed. However, SBRT appears to be a safe and effective option in the treatment of mediastinal and hilar lymph node recurrence, with a good toxicity profile. Its use in clinical practice is still limited, and there is extensive heterogeneity in patient selection and fractionation schedules. Good performance status, small PTV volume, absence of previous thoracic irradiation, and administration of a high biologically effective dose (BED) seem to be factors that correlate with greater local control and better survival rates. In the presence of symptoms related to the thoracic lymph nodes, SBRT determines a rapid control that lasts over time. We look forward to the prospective studies that are underway for definitive conclusions.

Multi-Omics Approaches for the Prediction of Clinical Endpoints after Immunotherapy in Non-Small Cell Lung Cancer: A Comprehensive Review

Immune checkpoint inhibitors (ICI) have revolutionized the management of locally advanced and advanced non-small lung cancer (NSCLC). With an improvement in the overall survival (OS) as both first- and second-line treatments, ICIs, and especially programmed-death 1 (PD-1) and programmed-death ligands 1 (PD-L1), changed the landscape of thoracic oncology. The PD-L1 level of expression is commonly accepted as the most used biomarker, with both prognostic and predictive values. However, even in a low expression level of PD-L1, response rates remain significant while a significant number of patients will experience hyperprogression or adverse events. The dentification of such subtypes is thus of paramount importance. While several studies focused mainly on the prediction of the PD-L1 expression status, others aimed directly at the development of prediction/prognostic models. The response to ICIs depends on a complex physiopathological cascade, intricating multiple mechanisms from the molecular to the macroscopic level. With the high-throughput extraction of features, omics approaches aim for the most comprehensive assessment of each patient. In this article, we will review the place of the different biomarkers (clinical, biological, genomics, transcriptomics, proteomics and radiomics), their clinical implementation and discuss the most recent trends projecting on the future steps in prediction modeling in NSCLC patients treated with ICI.

State of the Art in Combination Immuno/Radiotherapy for Brain Metastases: Systematic Review and Meta-Analysis

Objectives: Common origins for brain metastases (BMs) are melanoma, lung, breast, and renal cell cancers. BMs account for a large share of morbidity and mortality caused by these cancers. The advent of new immunotherapeutic treatments has made a revolution in the treatment of cancer patients and particularly, as a new concept, if it is combined with radiotherapy, may lead to considerably longer survival. This systematic review and meta-analysis aimed to evaluate the survival rate and toxicities of such a combination in brain metastases. Methods: To perform a systematic review of the literature until January 2021 using electronic databases such as PubMed, Cochrane Library, and Embase; the Newcastle–Ottawa Scale was used to evaluate the quality of cohort studies. For data extraction, two reviewers extracted the data blindly and independently. Hazard ratio with 95% confidence interval (CI), fixed-effect model, and inverse-variance method was calculated. The meta-analysis has been evaluated with the statistical software Stata/MP v.16 (The fastest version of Stata). Results: In the first step, 494 studies were selected to review the abstracts, in the second step, the full texts of 86 studies were reviewed. Finally, 28 studies were selected consisting of 1465 patients. The addition of IT to RT in the treatment of brain metastasis from melanoma and non-small-cell lung carcinoma was associated with a 39% reduction in mortality rate and has prolonged overall survival, with an acceptable toxicity profile. The addition of IT to RT compared with RT alone has a hazard ratio of 0.39(95% CI 0.34–0.44). Conclusions: A combination of immuno/radiotherapy (IR) for the treatment of patients with BMs from melanoma and non-small-cell lung carcinoma has prolonged overall survival and reduced mortality rate, with acceptable toxicity. In terms of timing, RT seems to have the best effect on the result when performed before or simultaneously with immunotherapy.

Radiotherapy and immunotherapy in melanoma brain metastases

BACKGROUND AND OBJECTIVE

Melanoma brain metastasis (MBM) generally portends a dismal prognosis. Simultaneous use of radiotherapy (RT) and immune checkpoint inhibitor (ICI) therapy demonstrated tremendous promise and emerged as the new standard. This meta-analysis was conducted to evaluate survival outcomes and toxicities of this combination in patients with MBM. Data analyses were performed using Comprehensive Meta-Analysis software (version 2) and IBM SPSS software (version 27).

METHODS

A systematic literature search of PubMed, EMBASE, and the Cochrane Library (via Wiley) was conducted using PICOS/PRISMA selection protocol and included studies to evaluate survival and safety-associated outcomes of ICI + RT for the treatment of MBM.

RESULTS

A total 44 studies involving 2498 patients were reviewed. The pooled effect size (ES) for overall survival (OS) to compare the ICI + RT arm and ICI alone arm (HR: 0.693 [0.526-0.913, p = .001]), and compare the ICI + RT arm and brain RT alone (HR: 0.595 [0.489-0.723, p < .001)] indicated better survival outcomes in ICI + RT versus RT alone and ICI alone arms. Comparing central nervous system toxicity in the ICI + RT arm and RT alone arm, the pooled ES Grade ≥ 3 neurologic adverse events (NAEs) risk ratio ([RR] = 1.425; 95% confidence interval [CI]: 0.485-4.183; p = .519) indicated that ICI + RT nonsignificantly increased Grade 3-4 NAEs. Comparing Grade ≥ 3 radiation necrosis in the ICI + RT arm and RT alone arm, the pooled ES RR (RR = 2.73; 95% CI: 0.59-12.59; p = .199) indicated that ICI + RT nonsignificantly increased Grade ≥ 3 radiation necrosis.

CONCLUSION

Concurrent administration of RT and ICI evinced favorable OS outcomes and acceptable safety profile in MBM patients. Planned prospective trials are required to demonstrate the issue.

Stereotactic radiosurgery for melanoma brain metastases: dose-size response relationship in the era of immunotherapy

PURPOSE/OBJECTIVE(S)

To determine, for intact melanoma brain metastases (MBM) treated with single-fraction stereotactic radiosurgery (SRS), whether planning parameter peripheral dose per lesion diameter (PDLDm, Gy/mm) and lesion control (LC) differs with versus without immunotherapy (IO).

MATERIALS/METHODS

We performed a retrospective analysis of patients with intact MBM treated with SRS from 2008 to 2019. Cox-frailty models were constructed to include confounders selected by penalized Cox regression models with a LASSO selector. Interaction effect testing was used to determine whether a significant effect between IO and PDLDm could be demonstrated with respect to LC.

RESULTS

The study cohort comprised 67 patients with 244 MBMs treated with SRS (30 patients with 122 lesions treated with both SRS and IO) were included. The logarithm of PDLDm was selected as a predictor of LC (HR 0.307, 95% CI 0.098-0.441), adjusting for IO receipt (HR 0.363, 95% CI 0.108-1.224). Interaction effect testing demonstrated a differential effect of PDLDm by IO receipt, with respect to LC (p = 0.048). Twelve-month LC rates for a 7.5 mm lesion receiving SRS (18 Gy) with IO versus without IO were 87.8% (95% CI 69.0-98.3%) versus 79.8% (95% CI 55.1-93.8%) respectively.

CONCLUSION

PDLDm predicted LC in patients with small MBMs treated with single-fraction SRS. We found a differential effect of dose per lesion size and LC by immunotherapy receipt. Future studies are needed to determine whether lower doses of single-fraction SRS afford similarly effective LC for patients with small MBMs receiving immunotherapy.

Immune Checkpoints Inhibitors and SRS/SBRT Synergy in Metastatic Non-Small-Cell Lung Cancer and Melanoma: A Systematic Review

Background: Several immunotherapy (IT) agents are FDA approved for treatment of melanoma and non-small-cell lung cancer (NSCLC). The addition of stereotactic radiosurgery (SRS) or stereotactic body radiation therapy (SBRT) to immunotherapy looks promising. A systematic review was conducted to evaluate the possible synergistic effects of immune checkpoints inhibitors (ICIs) and stereotactic radiation therapy in melanoma and NSCLC. Materials and methods: Pubmed databases from January 2010 to December 2020 were reviewed to identify English language studies reporting control of local and abscopal effect of the combination of ICI-SBRT/SRS in metastatic NSCLC and melanoma cancer. The inclusion criteria were followed according to PICO criteria. Results: Thirty-nine articles were included of the 2141 initial results. The reported rates for local control were 16.5–100% and 40–94% in brain and extracerebral metastases, respectively. Distant/abscopal response rates were 1–45% in extracerebral metastases. Abscopal effect could not be evaluated in brain metastases because it was not reported in studies. Treatments were well tolerated with few grade 4 toxicities and no grade 5. Conclusions: The combined treatment of ICI-SBRT/SRS achieves high local control and non-negligible abscopal response in patients with extracerebral metastases, with its benefit in cerebral metastases being more controversial. Clinical trials are needed to better characterize the potential synergism.

VEGF and Immune Checkpoint Inhibition for Prevention of Brain Metastases: Systematic Review and Meta-analysis

BACKGROUND AND OBJECTIVES

We conducted a systematic review and meta-analysis to investigate the role of vascular endothelial growth factor (VEGF) inhibitors and immune checkpoint inhibitors (ICIs) in preventing the development of brain metastases (BMs).

METHODS

We searched MEDLINE, Embase, Cochrane Database, and Google Scholar between January 1, 2000, and June 1, 2020. Included studies were randomized controlled trials (RCTs) of adults with systemic cancer that reported the incidence of BMs treated with and without VEGF inhibitors, as well as observational studies of adults with systemic cancer that reported the incidence of BMs treated with and without ICIs (no RCTs addressed the ICI question). Pooled relative risks (RR) were computed with a binary random-effects model.

RESULTS

A search for VEGF and incidence of new BMs revealed 7 studies (6,212 patients with breast, colon, and non-small-cell lung cancer). Meta-analysis showed a lower incidence of new BMs compared to control (RR 0.71, 95% confidence interval [CI] 0.56-0.89, p = 0.003). A search for ICIs and incidence of new BMs yielded 8 studies (732 patients with non-small-cell lung cancer or metastatic melanoma) in which ICIs were used as an adjunct to radiosurgery. Meta-analysis showed a lower incidence of out-of-treatment-field BMs with ICIs compared to controls at 1 year (RR 0.65, 95% CI 0.49-0.88, p = 0.005). The overall Grading of Recommendations, Assessment, Development and Evaluations score for the evidence evaluating the role of bevacizumab and ICIs was high and moderate, respectively.

DISCUSSION

VEGF and ICIs may have a role in prophylaxis against BM in patients with solid tumors.

Role of stereotactic radiosurgery for the treatment of brain metastasis in the era of immunotherapy: A systematic review on current evidences and predicting factors

Stereotactic radiosurgery (SRS) in combination with immunotherapy (IT) is increasingly used in the setting of melanoma and non-small cell lung cancer (NSCLC) brain metastases (BM). The synergistic properties of this treatment combination are still not deeply understood. IT-SRS appropriate combination has been envisioned as a strategic point in patients' management. Authors performed a systematic review on current evidences up to December 2020. The impact of SRS-IT and different IT schedules on survival, local/distant intracranial control and toxicity, as well as predictive factors for relevant oncological and radiological outcomes has been analyzed. Authors retrieved 23 pertinent studies. Combining SRS with IT resulted in a significant improvement in OS and lesion response with no increase in radionecrosis, hemorrhage or other complications. The present review suggests that combining IT to SRS is safe and effective in providing a significant improvement in relevant clinical and radiological outcomes in melanoma and NSCLC BMs patients.

Radiation Necrosis from Stereotactic Radiosurgery-How Do We Mitigate?

OPINION STATEMENT

Intracranial stereotactic radiosurgery (SRS) is an effective and convenient treatment for many brain conditions. Data regarding safety come mostly from retrospective single institutional studies and a small number of prospective studies. Variations in target delineation, treatment delivery, imaging follow-up protocols and dose prescription limit the interpretation of this data. There has been much clinical focus on radiation necrosis (RN) in particular, as it is being increasingly recognized on follow-up imaging. Symptomatic RN may be treated with medical therapy (such as corticosteroids and bevacizumab) with surgical resection being reserved for refractory patients. Nevertheless, RN remains a challenging condition to manage, and therefore upfront patient selection for SRS remains critical to provide complication-free control. Mitigation strategies need to be considered in situations where the baseline risk of RN is expected to be high-such as large target volume or re-irradiation. These may involve reduction in the prescribed dose or hypofractionated stereotactic radiation therapy (HSRT). Recently published guidelines and international meta-analysis report the benefit of HSRT in larger lesions, without compromising control rates. However, careful attention to planning parameters and SRS techniques still need to be adhered, even with HSRT. In cases where the risk is deemed to be high despite mitigation, a combination approach of surgery with or without post-operative radiation should be considered.

Emerging principles of brain immunology and immune checkpoint blockade in brain metastases

Brain metastases are the most common type of brain tumours, harbouring an immune microenvironment that can in principle be targeted via immunotherapy. Elucidating some of the immunological intricacies of brain metastases has opened a therapeutic window to explore the potential of immune checkpoint inhibitors in this globally lethal disease. Multiple lines of evidence suggest that tumour cells hijack the immune regulatory mechanisms in the brain for the benefit of their own survival and progression. Nonetheless, the role of the immune checkpoint in the complex interplays between cancers cells and T cells and in conferring resistance to therapy remains under investigation. Meanwhile, early phase trials with immune checkpoint inhibitors have reported clinical benefit in patients with brain metastases from melanoma and non-small cell lung cancer. In this review, we explore the workings of the immune system in the brain, the immunology of brain metastases, and the current status of immune checkpoint inhibitors in the treatment of brain metastases.

Toxicity and time lapse between immunotherapy and stereotactic radiotherapy of brain metastases

PURPOSE

Stereotactic radiotherapy (SRT) is the standard treatment for brain metastases of non-small-cell lung cancer (NSCLC) and melanoma, mostly in combination with immunotherapy. The objective was to retrospectively evaluate the influence of the time-lapse between immunotherapy and stereotactic radiotherapy on toxicity.

PATIENTS AND METHODS

From 2016 to 2019, 59 patients treated with SRT for 103 brain metastases of NSCLC (60%) and melanoma (40%) in combination with concomitant immunotherapy (≤30 days) were included. The prescribed dose was 20Gy/1f or 33Gy/3f at the isocentre and 14Gy or 23.1Gy (70%) respectively at the PTV envelope (PTV=GTV+2mm). The mean tumour diameter was 14mm (4-52mm). The immunotherapies used were anti-PD1 and anti-PDL1. The 103 metastases were classified into 3 groups according to the time-lapse between instatement of immunotherapy and instatement of SRT for the patient concerned: 7 (7%) in group A (≤7 days), 38 (37%) in group B (7 to 14 days) and 58 (56%) in group C (14 to 30 days).

RESULTS

The mean follow-up was 10.1 months. The median overall survival was 11.5 months for NSCLC and 12.5 months for melanoma. The percentage of local control (LC) at one year was 65.1% (93.6% for NSCLC and 26.5% for melanoma). The time-lapse between immunotherapy and SRT was not a significant predictor of LC (P=0.86), while the histology was (P<0.001). The proportion of grade≥3 toxicities was 5.1%, and that of radionecrosis was 9.7% (among these patients, 80% were non-symptomatic): 0%, 13.1% and 8.6% for groups A, B and C respectively. The time-lapse between immunotherapy and SRT was not a significant predictor of toxicity. Only tumour volume was a significant predictive factor (P=0.03).

CONCLUSION

The time lapse between immunotherapy and SRT does not influence brain toxicity. The tumour volume remains the main factor.

Imaging challenges of immunotherapy and targeted therapy in patients with brain metastases: response, progression, and pseudoprogression

The advent of immunotherapy using immune checkpoint inhibitors (ICIs) and targeted therapy (TT) has dramatically improved the prognosis of various cancer types. However, following ICI therapy or TT-either alone (especially ICI) or in combination with radiotherapy-imaging findings on anatomical contrast-enhanced MRI can be unpredictable and highly variable, and are often difficult to interpret regarding treatment response and outcome. This review aims at summarizing the imaging challenges related to TT and ICI monotherapy as well as combined with radiotherapy in patients with brain metastases, and to give an overview on advanced imaging techniques which potentially overcome some of these imaging challenges. Currently, major evidence suggests that imaging parameters especially derived from amino acid PET, perfusion-/diffusion-weighted MRI, or MR spectroscopy may provide valuable additional information for the differentiation of treatment-induced changes from brain metastases recurrence and the evaluation of treatment response.

Safety of radiosurgery concurrent with systemic therapy (chemotherapy, targeted therapy, and/or immunotherapy) in brain metastases: a systematic review

Stereotactic radiosurgery (SRS) is a standard option for brain metastases (BM). There is lack of consensus when patients have a systemic treatment, if a washout is necessary. The aim of this review is to analyze the toxicity of SRS when it is concurrent with chemotherapies, immunotherapy, and/or targeted therapies. From Medline and Embase databases, we searched for English literature published up to April 2020 according to the PRISMA guidelines, using for key words the list of the main systemic therapies currently in use And "radiosurgery," "SRS," "GKRS," "Gamma Knife," "toxicity," "ARE," "radiation necrosis," "safety," "brain metastases." Studies reporting safety or toxicity with SRS concurrent with systemic treatment for BM were included. Of 852 abstracts recorded, 77 were included. The main cancers were melanoma, lung, breast, and renal carcinoma. These studies cumulate 6384 patients. The median SRS dose prescription was 20 Gy [12-30] .For some, they compared a concurrent arm with a non-concurrent or a SRS-alone arm. There were no skin toxicities, no clearly increased rate of bleeding, or radiation necrosis with significant clinical impact. SRS combined with systemic therapy appears to be safe, allowing the continuation of treatment when brain SRS is considered.

Immune Checkpoint Inhibitors and Survival Outcomes in Brain Metastasis: A Time Series-Based Meta-Analysis

Immune checkpoint inhibitors (ICIs) have shown potential to improve the prognosis of patients with brain metastasis (BM) caused by advanced cancers. However, controversies still exist in regard to its survival benefits. In the present work, a time series-based meta-analysis based on the phase I/II/III trials and observational studies were performed to investigate the differences in mortality of ICI-treated BM patients. A number of public library databases, including MEDLINE, EMBASE, OVID, and COCHRANE, were systemically searched by March 2019. The quality of included studies was evaluated by the Newcastle-Ottawa Scale (NOS) scoring. Outcome measures here established were mortality and progression-free survival (PFS) at different follow-up endpoints. Survival rates and curve data were pooled for further analysis. To detect the data heterogeneity, subgroup analyses were conducted according to tumor and ICI types. Eighteen studies, 6 trials, and 12 controlled cohorts were assessed, involving a total of 1330 ICI-treated BM patients. The 6-month survival rate and PFS were 0.67 (95%CI: 0.59–0.74) and 0.36 (95%CI: 0.24–0.49), respectively. According to the tumor type (melanoma, NSCLC, and RCC), subgroup analyses indicated that melanoma presented the lowest survival rates among the three groups here selected. In regard to the type of ICIs, the anti-CTLA-4 combined with the anti-PD-1/PD-L1 showed the best survival outcome among these groups. The 12-month survival rate and PFS showed a consistent pattern of findings. In the long-term, the 24-month survival rate and PFS were 0.20 (95%CI: 0.12–0.31) and 0.18 (0.05–0.46) in BM patients. Hence, ICI therapy may be associated with an improved prognosis of BM patients. Nevertheless, current research presented a limited study design. Multicenter randomized trials may later assist in validating ICI-based therapies for a better outcome of BM patients.

Quantification of Scheduling Impact on Safety and Efficacy Outcomes of Brain Metastasis Radio- and Immuno-Therapies: A Systematic Review and Meta-Analysis

Objectives: The goal of this quantitative research was to evaluate the impact of various factors (e.g., scheduling or radiotherapy (RT) type) on outcomes for RT vs. RT in combination with immune checkpoint inhibitors (ICI), in the treatment of brain metastases, via a meta-analysis. Methods: Clinical studies with at least one ICI+RT treatment combination arm with brain metastasis patients were identified via a systematic literature search. Data on 1-year overall survival (OS), 1-year local control (LC) and radionecrosis rate (RNR) were extracted; for combination studies which included an RT monotherapy arm, odds ratios (OR) for the aforementioned endpoints were additionally calculated and analyzed. Mixed-effects meta-analysis models were tested to evaluate impact on outcome, for different factors such as combination treatment scheduling and the type of ICI or RT used. Results: 40 studies representing a total of 4,359 patients were identified. Higher 1-year OS was observed in ICI and RT combination vs. RT alone, with corresponding incidence rates of 59% [95% CI: 54-63%] vs. 32% [95% CI: 25-39%] (P < 0.001). Concurrent ICI and RT treatment was associated with significantly higher 1-year OS vs. sequential combinations: 68% [95% CI: 60-75%] vs. 54% [95% CI: 47-61%]. No statistically significant differences were observed in 1-year LC and RNR, when comparing combinations vs. RT monotherapies, with 1-year LC rates of 68% [95% CI: 40-90%] vs. 72% [95% CI: 63-80%] (P = 0.73) and RNR rates of 6% [95% CI: 2-13%] vs. 9% [95% CI: 5-14%] (P = 0.37). Conclusions: A comprehensive, study-level meta-analysis of brain metastasis disease treatments suggest that combinations of RT and ICI result in higher OS, yet comparable neurotoxicity profiles vs. RT alone, with a superiority of concurrent vs. sequential combination regimens. A similar meta-analysis using patient-level data from past trials, as well as future prospective randomized trials would help confirming these findings.

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).

Brain metastasis formation and irradiation by stereotactic radiation therapy combined with immunotherapy: A systematic review

INTRODUCTION

Brain metastasis (BM) is a complex process that implies immune cells and microglia. Stereotactic radiation therapy (SRT) and immunotherapy (IT) are established to increase the immune response; but their association has never been prospectively studied.

MATERIALS AND METHODS

Two reviewers performed a systematic review in original papers published up to September 2019. We analysed OS, local (mLRF) and regional (mBRF) median disease-free survival in patients with BMs after SRT with and without IT.

RESULTS

Upon 14 studies, eleven concerned melanoma, three concerned lung cancers. SRT-IT showed better OS, mLRF and mBRF than SRT. mBRF was better if SRT was performed with short delay from IT. No higher rates of radionecrosis and haemorrhage were found among groups.

CONCLUSION

This review suggests SRT combined to IT in melanoma is safe and could provide better BRF, suggesting a lymphocytic immune reaction in brain. No improvement trend was found in lung cancer BM.

Stereotactic radiosurgery combined with targeted/ immunotherapy in patients with melanoma brain metastasis

BACKGROUND

There is limited data on the use of targeted or immunotherapy (TT/IT) in combination with single fraction stereotactic radiosurgery (SRS) in patients with melanoma brain metastasis (MBM). Therefore, we analyzed the outcome and toxicity of SRS alone compared to SRS in combination with TT/IT.

METHODS

Patients with MBM treated with single session SRS at our department between 2014 and 2017 with a minimum follow-up of 3 months after first SRS were included. The primary endpoint of this study was local control (LC). Secondary endpoints were distant intracranial control, radiation necrosis-free survival (RNFS), and overall survival (OS). The local/ distant intracranial control rates, RNFS and OS were analyzed using the Kaplan-Meier method. The log-rank test was used to test differences between groups. Cox proportional hazard model was performed for univariate continuous variables and multivariate analyses.

RESULTS

Twenty-eight patients (17 male and 11 female) with 52 SRS-lesions were included. The median follow-up was 19 months (range 14-24 months) after first SRS. Thirty-six lesions (69.2%) were treated with TT/IT simultaneously (4 weeks before and 4 weeks after SRS), while 16 lesions (30.8%) were treated with SRS alone or with sequential TT/IT. The 1-year local control rate was 100 and 83.3% for SRS with TT/IT and SRS alone (p = 0.023), respectively. The estimated 1-year RNFS was 90.0 and 82.1% for SRS in combination with TT/IT and SRS alone (p = 0.935). The distant intracranial control rate after 1 year was 47.7 and 50% for SRS in combination with TT/IT and SRS alone (p = 0.933). On univariate analysis, the diagnosis-specific Graded Prognostic Assessment including the BRAF status (Melanoma-molGPA) was associated with a significantly improved LC. Neither gender nor SRS-PTV margin had a prognostic impact on LC. V10 and V12 were significantly associated with RNFS (p < 0.001 and p = 0.004).

CONCLUSION

SRS with simultaneous TT/IT significantly improved LC with no significant difference in radiation necrosis rate. The therapy combination appears to be effective and safe. However, prospective studies on SRS with simultaneous TT/IT are necessary and ongoing.

TRIAL REGISTRATION

The institutional review board approved this analysis on 10th of February 2015 and all patients signed informed consent (UE nr. 128-14).

Integration of stereotactic radiosurgery or whole brain radiation therapy with immunotherapy for treatment of brain metastases

The prognosis of brain metastases (BM) is traditionally poor. BM are mainly treated by local radiotherapy, including stereotactic radiosurgery (SRS) or whole brain radiation therapy (WBRT). Recently, immunotherapy (i.e., immune checkpoint inhibitors, ICI) has demonstrated a survival advantage in multiple malignancies commonly associated with BM. Individually, radiotherapy and ICI both treat BM efficiently; hence, their combination seems logical. In this review, we summarize the existing preclinical and clinical evidence that supports the applicability of radiotherapy as a sensitizer of ICI for BM. Further, we discuss the optimal timing at which radiotherapy and ICI should be administered and review the safety of the combination therapy. Data from a few clinical studies suggest that combining SRS or WBRT with ICI simultaneously rather than consecutively potentially enhances brain abscopal-like responses and survival. However, there is a lack of conclusion about the definition of "simultaneous"; the cumulative toxic effect of the combined therapies also requires further study. Thus, ongoing and planned prospective trials are needed to further explore and validate the effect, safety, and optimal timing of the combination of immunotherapy with radiotherapy for patients with BM.

The impact of current treatment modalities on the outcomes of patients with melanoma brain metastases: A systematic review

Patients with melanoma brain metastases (MBM) still have a very poor prognosis. Several treatment modalities have been investigated in an attempt to improve the management of MBM. This review aimed to evaluate the impact of current treatments for MBM on patient‐ and tumor‐related outcomes, and to provide treatment recommendations for this patient population. A literature search in the databases PubMed, Embase, Web of Science and Cochrane was conducted up to January 8, 2019. Original articles published since 2010 describing patient‐ and tumor‐related outcomes of adult MBM patients treated with clearly defined systemic therapy were included. Information on basic trial demographics, treatment under investigation and outcomes (overall and progression‐free survival, local and distant control and toxicity) were extracted. We identified 96 eligible articles, comprising 95 studies. A large variety of treatment options for MBM were investigated, either used alone or as combined modality therapy. Combined modality therapy was investigated in 71% of the studies and resulted in increased survival and better distant/local control than monotherapy, especially with targeted therapy or immunotherapy. However, neurotoxic side‐effects also occurred more frequently. Timing appeared to be an important determinant, with the best results when radiotherapy was given before or during systemic therapy. Improved tumor control and prolonged survival can be achieved by combining radiotherapy with immunotherapy or targeted therapy. However, more randomized controlled trials or prospective studies are warranted to generate proper evidence that can be used to change the standard of care for patients with MBM.

Concurrent Radiosurgery and Systemic Therapies for Melanoma Brain Metastases: A Systematic Review

Intracranial metastatic melanoma is a major challenge for neuro-oncological teams. Historically, treatment has focused on surgical or radiosurgical treatment of appropriate lesions, mostly for palliative purposes. Immunotherapies and other targeted therapies (BRAF/mitogen-activated protein kinase kinase inhibitors (BRAFi/MEKi)) are mainstays of advanced melanoma therapy, yet the optimal timing and synergistic properties of concurrent combinations of these systemic therapies and stereotactic radiosurgery (SRS) are poorly understood. We performed a systematic review of the MEDLINE and Scopus databases focused on outcomes after therapy using SRS and either immunotherapies or targeted therapies in an effort to define the optimal timing. We defined concurrent therapy as SRS within three months of treatment with any systemic therapy. End points included local control, distant control, overall survival, and toxicities. We identified five retrospective cohort studies from the literature. These studies found that concurrent SRS plus immunotherapy or BRAFi/MEKi is well tolerated by most patients and generally improved local control, distant control, and overall survival. Importantly, no significant increases in toxicities were noted with concurrent therapy. Combining concurrent SRS with immunotherapy or BRAFi/MEKi may offer important advances for patients with intracranial metastatic melanoma. To address interstudy heterogeneity, we propose reporting two major time intervals defining “concurrent treatment”: concurrent-SRS (≤4 weeks) and peri-SRS (≤3 months). Future large-scale, prospective trials considering truly concurrent SRS therapies with systemic therapies are desperately needed.

Combination of radiotherapy and immunotherapy for brain metastases: A systematic review and meta-analysis

Radiotherapy (RT) represents a mainstay in the treatment of brain metastases (BMs) from solid tumors. Immunotherapy (IT) has improved survival of metastatic cancer patients across many tumor types. The combination of RT and IT for the treatment of BMs has a strong rationale, but data on efficacy and safety of this combination is still limited. A systematic search of PubMed, the Cochrane Central Register of Controlled Trials, and EMBASE was conducted. 33 studies were included for a total of 1520 patients, most of them with melanoma (87%). Median pooled OS was 15.9 months (95%CI 13.9-18.1). One- and 2-year OS rates were 55.2% (95% CI 49.3-60.9) and 35.7% (95% CI 30.4-41.3), respectively. Addition of IT to RT was associated with improved OS (HR = 0.54, 95%CI 0.44-0.67; P < 0.001). For patients with BMs from solid tumors, addition of concurrent IT to brain RT is able to increase survival and provide long term control.

Stereotactic Radiosurgery and Immune Checkpoint Inhibitors in the Management of Brain Metastases

Brain metastases traditionally carried a poor prognosis with an overall survival of weeks to months in the absence of treatment. Radiation therapy modalities include whole brain radiation therapy (WBRT) and stereotactic radiosurgery (SRS). WBRT delivers a relatively low dose of radiation, has neurocognitive sequelae, and has not been investigated for its immunostimulatory effects. Furthermore, WBRT exposes the entire intracranial tumor immune microenvironment to radiation. SRS delivers a high dose of conformal radiation with image guidance to minimize dose to surrounding normal brain tissue, and appears to promote anti-tumor immunity. In parallel with many of these discoveries, immune checkpoint inhibitors (ICIs) have demonstrated a survival advantage in multiple malignancies commonly associated with brain metastases (e.g., melanoma). Combination SRS and ICI are theorized to be synergistic in anti-tumor immunity directed to brain metastases. The purpose of this review is to explore the synergy of SRS and ICIs, including pre-clinical data, existing clinical data, and ongoing prospective trials.

Robotic Stereotactic Radiosurgery in Melanoma Patients with Brain Metastases under Simultaneous Anti-PD-1 Treatment

Combination concepts of radiotherapy and immune checkpoint inhibition are currently of high interest. We examined imaging findings, acute toxicity, and local control in patients with melanoma brain metastases receiving programmed death 1 (PD-1) inhibitors and/or robotic stereotactic radiosurgery (SRS). Twenty-six patients treated with SRS alone (n = 13; 20 lesions) or in combination with anti-PD-1 therapy (n = 13; 28 lesions) were analyzed. Lesion size was evaluated three and six months after SRS using a volumetric assessment based on cranial magnetic resonance imaging (cMRI) and acute toxicity after 12 weeks according to the Common Terminology Criteria for Adverse Events (CTCAE). Local control after six months was comparable (86%, SRS + anti-PD-1, and 80%, SRS). All toxicities reported were less than or equal to grade 2. One metastasis (5%) in the SRS group and six (21%) in the SRS + anti-PD-1 group increased after three months, whereas four (14%) of the six regressed during further follow-ups. This was rated as pseudoprogression (PsP). Three patients (23%) in the SRS + anti-PD-1 group showed characteristics of PsP. Treatment with SRS and anti-PD-1 antibodies can be combined safely in melanoma patients with cerebral metastases. Early volumetric progression of lesions under simultaneous treatment may be related to PsP; thus, the evaluation of combined radioimmunotherapy remains challenging and requires experienced teams.