Intracranial outcomes following neurosurgical resection in patients with brain metastases secondary to HER2-positive breast cancer versus other subtypes.

PURPOSE: Neurosurgical resection serves an important role in select patients with breast cancer and brain metastases but can delay systemic therapy and yield complications. Consequently, identification of patients most likely to benefit from surgery is important. Given the poorer long-term intracranial responses to radiotherapy sometimes observed in HER2-positive (HER2 +) patients, we investigated whether neurosurgical resection is differentially beneficial in this population. METHODS: We identified 633 patients with newly diagnosed brain metastases arising from breast cancer managed at Brigham and Women's Hospital/Dana-Farber Cancer Institute between 2010 and 2022. Patients were stratified by breast cancer subtype: HER2 + (N = 189), hormone receptor positive (HR +)/HER2- (N = 267), and triple negative (N = 177). Per-patient and per-metastasis outcomes were evaluated; interaction models assessing the impact of neurosurgical resection by subtype were constructed. RESULTS: Relative to HR + /HER2- subtype, omission of upfront neurosurgical resection in patients with HER2 + disease was associated with increased subsequent utilization of salvage stereotactic radiation, whole brain radiotherapy, and craniotomy (interaction HR 2.02 [95% CI, 1.04-3.93], p = 0.04; HR 3.92 [95% CI, 1.24-12.40], p = 0.02; HR 4.98 [95% CI, 1.34-18.58], p = 0.02, respectively). Tumors stemming from HER2 + versus HR + /HER2- primaries displayed increased local recurrence when upfront neurosurgical resection was omitted (interaction HR 3.62 [95% CI, 1.06-12.38], p = 0.04). No such associations were noted when comparing triple negative to HR + /HER2- subtype (p-interaction > 0.05 in all cases). CONCLUSION: Patients with HER2 + disease and brain metastases may disproportionately benefit from upfront neurosurgical resection relative to other subtypes. If validated, our results may suggest a lower threshold to consider surgery in brain metastases secondary to HER2 + breast cancer.

"Per protocol" practice patterns for Children's Oncology Group trials within the radiation oncology community.

Little is known about the prevalence of pediatric radiation oncologists treating patients off study according to Children's Oncology Group (COG) trials before data are available regarding toxicity and efficacy of novel radiotherapy regimens. We conducted a 12-question survey of 358 pediatric radiation oncologists to characterize practice patterns regarding ongoing and completed COG protocols off study. With 130 responses (40.3%), the prevalence of providing treatment per protocol, but off study, before data are available in abstract or peer-reviewed form varied from 9.1% (for ACNS1422) to 88.1% (for AHOD1331). Future studies are needed to understand the effects of these practice patterns on outcomes.

Radiotherapy for Primary Pediatric Central Nervous System Malignancies: Current Treatment Paradigms and Future Directions.

BACKGROUND: Central nervous system tumors are the most common solid tumors in childhood. Treatment paradigms for pediatric central nervous system malignancies depend on elements including tumor histology, age of patient, and stage of disease. Radiotherapy is an important modality of treatment for many pediatric central nervous system malignancies. SUMMARY: While radiation contributes to excellent overall survival rates for many patients, radiation also carries significant risks of long-term side effects including neurocognitive decline, hearing loss, growth impairment, neuroendocrine dysfunction, strokes, and secondary malignancies. In recent decades, clinical trials have demonstrated that with better imaging and staging along with more sophisticated radiation planning and treatment set-up verification, smaller treatment volumes can be utilized without decrement in survival. Furthermore, the development of intensity-modulated radiotherapy and proton-beam radiotherapy has greatly improved conformality of radiation. KEY MESSAGES: Recent changes in radiation treatment paradigms have decreased risks of short- and long-term toxicity for common histologies and in different age groups. Future studies will continue to develop novel radiation regimens to improve outcomes in aggressive central nervous system tumors, integrate molecular subtypes to tailor radiation treatment, and decrease radiation-associated toxicity for long-term survivors.

DICER1 mutations in primary central nervous system tumors: new insights into histologies, mutations, and prognosis.

PURPOSE: We sought to characterize clinical outcomes for adult and pediatric patients with primary CNS tumors harboring DICER1 mutations or loss of DICER1. METHODS: We conducted a retrospective cohort study of 98 patients who were treated between 1995 and 2020 for primary CNS tumors containing DICER1 mutations or loss of DICER1 on chromosome 14q, identified by targeted next generation sequencing. Kaplan-Meier plots and log rank tests were used to analyze survival. Cox proportional-hazards model was used for univariate and multivariable analyses for all-cause mortality (ACM). RESULTS: Within our cohort, the most common malignancies were grade 3/4 glioma (61%), grade 1/2 glioma (17%), and CNS sarcoma (6%). Sarcoma and non-glioma histologies, and tumors with biallelic DICER1 mutations or deletions were common in the pediatric population. Mutations occurred throughout DICER1, including missense mutations in the DexD/H-box helicase, DUF283, RNaseIIIa, and RNaseIIIb domains. For patients with grade 3/4 glioma, MGMT methylation (Hazard ratio [HR] 0.35, 95% Confidence Interval [CI] 0.16-0.73, p = 0.005), IDH1 R132 mutation (HR 0.11, 95% CI 0.03-0.41, p = 0.001), and missense mutation in the DexD/H-box helicase domain (HR 0.06, 95% CI 0.01-0.38, p = 0.003) were independently associated with longer time to ACM on multivariable analyses. CONCLUSION: DICER1 mutations or loss of DICER1 occur in diverse primary CNS tumors, including previously unrecognized grade 3/4 gliomas as the most common histology. While prior studies have described RNaseIIIb hotspot mutations, we document novel mutations in additional DICER1 functional domains. Within the grade 3/4 glioma cohort, missense mutation in the DexD/H-box helicase domain was associated with prolonged survival.

Anatomic patterns of relapse and progression following treatment with 131 I-MIBG in relapsed or refractory neuroblastoma.

OBJECTIVES: Patients with metaiodobenzylguanidine (MIBG)-avid relapsed or refractory neuroblastoma after initial therapy may exhibit transient responses to salvage treatment with iodine-131 metaiodobenzylguanidine (131 I-MIBG). It is unclear whether disease progression following 131 I-MIBG treatment occurs in previously involved versus new anatomic sites of disease. Understanding this pattern of relapse will inform the use of consolidation therapy following 131 I-MIBG administration. METHODS: Patients with relapsed or refractory metastatic MIBG-avid neuroblastoma or ganglioneuroblastoma, who received single-agent 131 I-MIBG, had stable or responding disease 6-8 weeks following 131 I-MIBG, but subsequently experienced disease progression were included. MIBG scans were reviewed to establish anatomic and temporal evolution of MIBG-avid disease. RESULTS: A total of 84 MIBG-avid metastatic sites were identified immediately prior to MIBG therapy in a cohort of 12 patients. At first progression, a total of 101 MIBG-avid sites were identified, of which 69 (68%) overlapped with pre-treatment disease sites, while 32 (32%) represented anatomically new disease areas. Eight of 12 patients had one or more new MIBG-avid sites at first progression. Of the 69 involved sites at progression that overlapped with pre-treatment disease, 11 represented relapsed sites that had cleared following MIBG therapy, two were persistent but increasingly MIBG-avid, and 56 were stably persistent. CONCLUSIONS: Previously involved anatomic disease sites predominate at disease progression following 131 I-MIBG treatment. Nevertheless, the majority of patients progressed in at least one new anatomic disease site. This suggests that consolidation focal therapies targeting residual disease sites may be of limited benefit in preventing systemic disease progression following 131 I-MIBG treatment of relapsed or refractory neuroblastoma.

Clinical outcomes for pediatric patients receiving radiotherapy for solid tumor central nervous system metastases.

Central nervous system (CNS) metastases are rare, but devastating complications of pediatric solid tumors. Radiotherapy alone or postresection serves as an important treatment; however, data on the use of whole-brain radiotherapy (WBRT) versus focal radiotherapy, including stereotactic radiosurgery or stereotactic radiotherapy, for these indications are limited. We report a single institution experience of 26 pediatric patients treated with radiotherapy for solid tumor CNS metastases without leptomeningeal disease. Focal radiotherapy (n = 10) was well tolerated and survival outcomes did not differ between patients treated with WBRT (n = 16) versus focal radiation, suggesting that focal radiotherapy may be considered for patients with limited CNS metastases.

Long-term outcomes of pediatric and young adult patients receiving radiotherapy for nonmalignant vascular anomalies.

BACKGROUND: Nonmalignant vascular anomalies (VA) comprise a heterogeneous spectrum of conditions characterized by aberrant growth or development of blood and/or lymphatic vessels and can cause significant morbidity. Little is known about outcomes after radiotherapy in pediatric and young adult patients with nonmalignant VA. METHODS: Thirty patients who were diagnosed with nonmalignant VA and treated with radiotherapy prior to 2017 and before the age of 30 were identified. Clinical and treatment characteristics and outcomes were recorded. RESULTS: Median age at first radiotherapy was 15 years (range 0.02-27). Median follow-up from completion of first radiotherapy was 9.8 years (range 0.02-67.4). Lymphatic malformations (33%), kaposiform hemangioendothelioma (17%), and venous malformations (17%) were the most common diagnoses. The most common indication for first radiotherapy was progression despite standard therapy and/or urgent palliation for symptoms (57%). After first radiotherapy, 14 patients (47%) had a complete response or partial response, defined as decrease in size of treated lesion or symptomatic improvement. After first radiotherapy, 27 (90%) required additional treatment for progression or recurrence. Long-term complications included telangiectasias, fibrosis, xerophthalmia, radiation pneumonitis, ovarian failure, and central hypothyroidism. No patient developed secondary malignancies. At last follow-up, three patients (10%) were without evidence of disease, 26 (87%) with disease, and one died of complications (3.3%). CONCLUSIONS: A small group of pediatric and young adult patients with nonmalignant, high-risk VA experienced clinical benefit from radiotherapy with expected toxicity; however, most experienced progression. Prospective studies are needed to characterize indications for radiotherapy in VA refractory to medical therapy, including targeted inhibitors.

Response rate and local recurrence after concurrent immune checkpoint therapy and radiotherapy for non-small cell lung cancer and melanoma brain metastases.

BACKGROUND: Prior literature has suggested synergy between immune checkpoint therapy (ICT) and radiotherapy (RT) for the treatment of brain metastases (BrM), but to the authors' knowledge the optimal timing of therapy to maximize this synergy is unclear. METHODS: A total of 199 patients with melanoma and non-small cell lung cancer with BrM received ICT and RT between 2007 and 2016 at the study institution. To reduce selection biases, individual metastases were included only if they were treated with RT within 90 days of ICT. Concurrent treatment was defined as RT delivered on the same day as or in between doses of an ICT course; all other treatment was considered to be nonconcurrent. Multivariable Cox proportional hazards models were used to assess time to response and local disease recurrence on a per-metastasis basis, using a sandwich estimator to account for intrapatient correlation. RESULTS: The final cohort included 110 patients with 340 BrM, with 102 BrM treated concurrently and 238 BrM treated nonconcurrently. Response rates were higher with the use of concurrent treatment (70% vs 47%; P < .001), with correspondingly lower rates of progressive disease (5% vs 26%; P < .001). On multivariable analysis, concurrent treatment was found to be associated with improved time to response (hazard ratio, 1.76; 95% CI, 1.18-2.63 [P = .006]) and decreased local recurrence (hazard ratio, 0.42; 95% CI, 0.23-0.78 [P = .006]). This effect appeared to be greater for melanoma than for non-small cell lung cancer, although interaction tests were not statistically significant. Only 1 of 103 metastases which had a complete response later developed disease progression. CONCLUSIONS: Concurrent RT and ICT may improve response rates and decrease local recurrence of brain metastases compared with treatment that was nonconcurrent but delivered within 90 days. Further study of this combination in prospective, randomized trials is warranted.

Treating the SARS-CoV-2-positive patient with cancer: A proposal for a pragmatic and transparent ethical process.

The treatment of patients with cancer who test positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) poses unique challenges. In this commentary, the authors describe the ethical rationale and implementation details for the creation of a novel, multidisciplinary treatment prioritization committee, including physicians, frontline staff, an ethicist, and an infectious disease expert. Organizational obligations to health care workers also are discussed. The treatment prioritization committee sets a threshold of acceptable harm to patients from decreased cancer control that is justified to reduce risk to staff. The creation of an ethical, consistent, and transparent decision-making process involving such frontline stakeholders is essential as departments across the country are faced with decisions regarding the treatment of SARS-CoV-2-positive patients with cancer.

Prescription of memantine during non-stereotactic, brain-directed radiation among patients with brain metastases: a population-based study.

PURPOSE: Whole brain radiation therapy (WBRT) remains an important component of treatment for patients with multiple brain metastases (BrM) but is associated with significant neurotoxicity and memory impairment. Although RTOG 0614 demonstrated that administration of memantine to patients receiving WBRT may reduce radiation-associated cognitive decline, prior literature has suggested that radiation oncologists are hesitant to prescribe memantine. We sought to assess the frequency of memantine prescription in patients managed with non-stereotactic, brain-directed radiation for BrM. METHODS: Patients > 65 years old with newly diagnosed BrM between 2007 and 2016 receiving non-stereotactic, brain-directed radiation (including WBRT) were identified using the SEER-Medicare database. Receipt of memantine with non-stereotactic, brain-directed radiation was defined as any Part D claim for memantine 30 days before or after initiation of non-stereotactic, brain-directed radiation. Clinical and demographic variables among patients who did and did not receive memantine were compared. RESULTS: Between 2007 and 2016, we identified 6220 patients with BrM receiving non-stereotactic, brain-directed radiation. Only 2.20% of patients (n = 137) received memantine with radiation. Rates were 1.10% versus 5.14% in the period preceding (2007-2013) and following (2014-2016) the publication of RTOG 0614, respectively. Overall utilization of memantine remained low across several clinical, demographic, and prognostic variables. CONCLUSION: Despite phase 3 evidence supporting memantine utilization among patients receiving WBRT, our population-based study indicates that rates of memantine prescription are strikingly low, although memantine utilization seems to be increasing since publication of RTOG 0614. Further investigation is needed to identify provider and practice-related barriers preventing incorporation of memantine into management paradigms.

Practice patterns and recommendations for pediatric image-guided radiotherapy: A Children's Oncology Group report.

This report by the Radiation Oncology Discipline of Children's Oncology Group (COG) describes the practice patterns of pediatric image-guided radiotherapy (IGRT) based on a member survey and provides practice recommendations accordingly. The survey comprised of 11 vignettes asking clinicians about their recommended treatment modalities, IGRT preferences, and frequency of in-room verification. Technical questions asked physicists about imaging protocols, dose reduction, setup correction, and adaptive therapy. In this report, the COG Radiation Oncology Discipline provides an IGRT modality/frequency decision tree and the expert guidelines for the practice of ionizing image guidance in pediatric radiotherapy patients.

Germline MUTYH Mutation in a Pediatric Cancer Survivor Developing a Secondary Malignancy.

Radiotherapy-induced second malignant neoplasms (SMNs) are a severe late complication in pediatric cancer survivors. Germline mutations in tumor suppressor genes contribute to SMNs; however, the most relevant germline variants mediating susceptibility are not fully defined. The authors performed matched whole-exome sequencing analyses of germline and tumor DNA from 4 pediatric solid tumor survivors who subsequently developed radiation-associated SMNs. Pathogenic and predicted deleterious germline variants were identified for each patient and validated with Sanger sequencing. These germline variants were compared with germline variants in a cohort of 59 pediatric patients diagnosed with primary sarcomas. Pathway analysis was performed to test for similarities in the germline variant profiles between individuals diagnosed with SMNs or primary sarcomas. One index patient was found to have a pathogenic germline monoallelic mutation in the MUTYH gene, which encodes the base excision repair enzyme adenine DNA glycosylase. This specific germline mutation is associated with a form of familial adenomatous polyposis, a new diagnosis in the patient. Germline-level genetic similarity exists between SMN-developing patients and patients developing primary sarcomas, with relevant genes involved in signal transduction and DNA repair mechanisms. The authors identify a germline MUTYH mutation in a pediatric cancer survivor developing an SMN. Germline mutations involving specific pathways such as base excision repair may identify individuals at risk for developing SMNs. The composition of germline variants in individual patients may enable estimates of patient-specific risk for developing SMNs. The authors anticipate that further analyses of germline genomes and epigenomes will reveal diverse genes and mechanisms influencing cancer risk.

Risk stratification by somatic mutation burden in Ewing sarcoma.

BACKGROUND: Up to one-third of patients with localized Ewing sarcoma (ES) develop recurrent disease, but current biomarkers do not accurately identify this high-risk group. Therefore, the objective of this study was to determine the utility of mutational burden in predicting outcomes in patients with localized ES. METHODS: Clinical and genomic data from 99 patients with ES, of whom 63 had localized disease at diagnosis, were obtained from the cBioPortal for Cancer Genomics. Genomic data included the type and number of somatic mutations using cBioPortal mutation calling. Primary endpoints were overall survival (OS) and the time to progression (TTP). RESULTS: Patients had a median number of 11 somatic mutations. Patients were stratified according to whether they had a lower or higher mutational burden if they had ≤11 or >11 mutations, respectively. Higher mutational burden was significantly associated with inferior OS and TTP, a finding that was confirmed by univariate and multivariable analyses. In patients who had localized disease at diagnosis, higher mutational burden was the only variable significantly associated with inferior OS and TTP. The presence of a mutation in either stromal antigen 2 (STAG2) or tumor protein 53 (TP53), both of which were correlated previously with shorter OS in patients with ES, were significantly associated with higher mutational burden. Upon stratifying patients who had localized disease based on a standard panel of cancer genes, higher risk stratification was correlated significantly with inferior TTP and trended toward significance with inferior OS. CONCLUSIONS: Patients who have localized ES and a higher mutational burden have inferior OS and TTP compared with those who have lower mutation burden. The current findings suggest that the somatic mutation burden can be used to better risk stratify these patients and to guide clinical decision making.

Breast cancer subtype and intracranial recurrence patterns after brain-directed radiation for brain metastases.

PURPOSE: Brain metastases from breast cancer are frequently managed with brain-directed radiation but the impact of subtype on intracranial recurrence patterns after radiation has not been well-described. We investigated intracranial recurrence patterns of brain metastases from breast cancer after brain-directed radiation to facilitate subtype-specific management paradigms. METHODS: We retrospectively analyzed 349 patients with newly diagnosed brain metastases from breast cancer treated with brain-directed radiation at Brigham and Women's Hospital/Dana-Farber Cancer Institute between 2000 and 2015. Patients were stratified by subtype: hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-), HER2+ positive (HER2+), or triple-negative breast cancer (TNBC). A per-metastasis assessment was conducted. Time-to-event analyses were conducted using multivariable Cox regression. RESULTS: Of the 349 patients, 116 had HR+/HER2- subtype, 164 had HER2+ subtype, and 69 harbored TNBC. Relative to HR+/HER2- subtype, local recurrence was greater in HER2+ metastases (HR 3.20, 95% CI 1.78-5.75, p < 0.001), while patients with TNBC demonstrated higher rates of new brain metastases after initial treatment (HR 3.16, 95% CI 1.99-5.02, p < 0.001) and shorter time to salvage whole brain radiation (WBRT) (HR 3.79, 95% CI 1.36-10.56, p = 0.01) and salvage stereotactic radiation (HR 1.86, 95% CI 1.11-3.10, p = 0.02). CONCLUSIONS: We identified a strong association between breast cancer subtype and intracranial recurrence patterns after brain-directed radiation, particularly local progression for HER2+ and distant progression for TNBC patients. If validated, the poorer local control in HER2+ brain metastases may support evaluation of novel local therapy-based approaches, while the increased distant recurrence in TNBC suggests the need for improved systemic therapy and earlier utilization of WBRT.

Local control after brain-directed radiation in patients with cystic versus solid brain metastases.

PURPOSE: Brain metastases can be radiographically cystic or solid. Cystic metastases are associated with a greater intracranial disease burden and poorer oncologic outcomes, but the impact of cystic versus solid appearance on local control after radiation remains unknown. We investigated whether cystic versus solid nature is predictive of local control after management with stereotactic or whole brain radiation (WBRT) and whether the radiation modality utilized is an effect modifier. METHODS: We identified 859 patients with 2211 newly-diagnosed brain metastases managed with upfront stereotactic radiation or WBRT without preceding resection/aspiration at Brigham and Women's Hospital/Dana-Farber Cancer Institute between 2000 and 2015. Multivariable Cox regression with an interaction term and sandwich covariance matrix was used to quantify local failure. RESULTS: Cystic lesions were more likely to recur than solid ones when managed with stereotactic radiation (HR 2.33, 95% CI 1.32-4.10, p = 0.004) but not WBRT (HR 0.92, 95% CI 0.62-1.36, p = 0.67), p-interaction = 0.007. 1 year local control rates for cystic versus solid metastases treated with stereotactic radiation were 75% versus 88%, respectively; estimates with WBRT were 76% versus 76%, respectively. However, no significant differences were noted between the two cohorts in post-radiation outcomes including all-cause mortality and neurologic death (p > 0.05). CONCLUSIONS: Among patients with brain metastases, stereotactic radiation yields improved local control and less morbidity than WBRT, and consequently for many patients the cystic versus solid designation does not impact treatment selection. However, our results suggest that in patients with a large number of cystic brain metastases, a lower threshold to consider WBRT, as opposed to stereotactic radiation, should be employed. If our results can be confirmed, further investigation into the underlying mechanism(s) would be warranted.

Role of the extent of prophylactic regional lymph node radiotherapy on survival in high-risk neuroblastoma: A report from the COG A3973 study.

PURPOSE: Neuroblastoma is the most common extracranial solid pediatric malignancy, with poor outcomes in high-risk disease. Standard treatment approaches employ an increasing array of aggressive multimodal therapies, of which local control with surgery and radiotherapy remains a backbone; however, the benefit of broad regional nodal irradiation remains controversial. We analyzed centrally reviewed radiation therapy data from patients enrolled on COG A3973 to evaluate the impact of primary site irradiation and the extent of regional nodal coverage stratified by extent of surgical resection. METHODS: Three hundred thirty high-risk neuroblastoma patients with centrally reviewed radiotherapy plans were analyzed. Outcome was evaluated by the extent of nodal irradiation. For the 171 patients who also underwent surgery (centrally reviewed), outcome was likewise analyzed according to the extent of resection. Overall survival (OS), event-free survival (EFS), and cumulative incidence of local progression (CILP) were examined by Kaplan-Meier, log-rank test (EFS, OS), and Grey test (CILP). RESULTS: The five-year CILP, EFS, and OS for all 330 patients receiving radiotherapy on A3973 were 8.5% ± 1.5%, 47.2% ± 3.0%, and 59.7% ± 3.0%, respectively. There were no significant differences in outcomes based on the extent of lymph node irradiation regardless of the degree of surgical resection (< 90% or ≥90%). CONCLUSION: Although local control remains a significant component of treatment of high-risk neuroblastoma, our results suggest there is no benefit of extensive lymph node irradiation, irrespective of the extent of surgical resection preceding stem cell transplant.

Phase I study of vorinostat in combination with isotretinoin in patients with refractory/recurrent neuroblastoma: A new approaches to Neuroblastoma Therapy (NANT) trial.

BACKGROUND: Vorinostat combined with retinoids produces additive antitumor effects in preclinical studies of neuroblastoma. Higher systemic exposures of vorinostat than achieved in pediatric phase I trials with continuous daily dosing are necessary for in vivo increased histone acetylation and cytotoxic activity. We conducted a phase I trial in children with relapsed/refractory neuroblastoma to determine the maximum tolerated dose (MTD) of vorinostat on an interrupted schedule, escalating beyond the previously identified pediatric MTD. METHODS: Isotretinoin (cis-13-retinoic acid) 80 mg/m2 /dose was administered by mouth twice daily on days 1-14 in combination with escalating doses of daily vorinostat up to 430 mg/m2 /dose (days 1-4; 8-11) in each 28-day cycle using the standard 3 + 3 design. Vorinostat pharmacokinetic testing and histone acetylation assays were performed. RESULTS: Twenty-nine patients with refractory or relapsed neuroblastoma were enrolled and 28 were evaluable for dose escalation decisions. Median number of cycles completed was two (range 1-15); 11 patients received four or more cycles. Three patients experienced cycle 1 dose-limiting toxicities. A total of 18 patients experienced grade 3/4 toxicities related to study therapy. The maximum intended dose of vorinostat (430 mg/m2 /day, days 1-4; 8-11) was tolerable and led to increased histone acetylation in surrogate tissues when compared to lower doses of vorinostat (P = 0.009). No objective responses were seen. CONCLUSIONS: Increased dose vorinostat (430 mg/m2 /day) on an interrupted schedule is tolerable in combination with isotretinoin. This dose led to increased vorinostat exposures and demonstrated increased histone acetylation. Prolonged stable disease in patients with minimal residual disease warrants further investigation.

Survival after chemotherapy and stem cell transplant followed by delayed craniospinal irradiation is comparable to upfront craniospinal irradiation in pediatric embryonal brain tumor patients.

Pediatric embryonal brain tumor patients treated with craniospinal irradiation (CSI) are at risk for adverse effects, with greater severity in younger patients. Here we compare outcomes of CSI vs. high-dose chemotherapy (HD), stem cell transplant (SCT) and delayed CSI in newly diagnosed patients. Two hundred one consecutive patients treated for medulloblastoma (72 %), supratentorial primitive neuroectodermal tumor (sPNET; 18 %) or pineoblastoma (10 %) at two institutions between 1988 and 2014 were retrospectively identified. Progression free survival (PFS) and overall survival (OS) were estimated using the Kaplan-Meier method and compared by log-rank tests. Adjuvant CSI regimens were used for 56 % of patients (upfront-CSI), and HD/SCT regimens were used in 32 % of patients. HD/SCT patients were significantly younger than those receiving upfront-CSI (2.9 vs. 7.8 years; P < 0.0001). There were no differences in metastases, extent of resection, or CSI dose between upfront-CSI and HD/SCT patients, but median follow-up was shorter in the HD/SCT group (6.2 vs. 3.9 years; P = 0.007). There were no significant outcome differences between upfront-CSI and HD/SCT patients who received CSI as a prophylaxis or following relapse (OS 66 % vs. 61 %, P = 0.13; PFS 67 % vs. 62 %, P = 0.12). Outcomes were equivalent when restricting analyses to HD/SCT patients who received prophylactic CSI prior to relapse (OS 66 % vs. 65 %, P = 0.5; PFS 67 % vs. 74 %, P = 0.8). At last follow-up, 48 % of HD/SCT patients had received neither definitive nor salvage radiotherapy. In this retrospective cohort, outcomes with adjuvant HD/SCT followed by delayed CSI are comparable to upfront-CSI for carefully surveyed pediatric embryonal brain tumor patients. Future prospective studies are required to validate this finding, and also to assess the impact of delayed CSI on neurocognitive outcomes.

Survival advantage combining a BRAF inhibitor and radiation in BRAF V600E-mutant glioma.

Radiation (RT) is critical to the treatment of high-grade gliomas (HGGs) but cures remain elusive. The BRAF mutation V600E is critical to the pathogenesis of 10-20% of pediatric gliomas, and a small proportion of adult HGGs. Here we aim to determine whether PLX4720, a specific BRAF V600E inhibitor, enhances the activity of RT in human HGGs in vitro and in vivo. Patient-derived HGG lines harboring wild-type BRAF or BRAF V600E were assessed in vitro to determine IC50 values, cell cycle arrest, apoptosis and senescence and elucidate mechanisms of combinatorial activity. A BRAF V600E HGG intracranial xenograft mouse model was used to evaluate in vivo combinatorial efficacy of PLX4720+RT. Tumors were harvested for immunohistochemistry to quantify cell cycle arrest and apoptosis. RT+PLX4720 exhibited greater anti-tumor effects than either monotherapy in BRAF V600E but not in BRAF WT lines. In vitro studies showed increased Annexin V and decreased S phase cells in BRAF V600E gliomas treated with PLX4720+RT, but no significant changes in ß-galactosidase levels. In vivo, concurrent and sequential PLX4720+RT each significantly prolonged survival compared to monotherapies, in the BRAF V600E HGG model. Immunohistochemistry of in vivo tumors demonstrated that PLX4720+RT decreased Ki-67 and phospho-MAPK, and increased γH2AX and p21 compared to control mice. BRAF V600E inhibition enhances radiation-induced cytotoxicity in BRAF V600E-mutated HGGs, in vitro and in vivo, effects likely mediated by apoptosis and cell cycle, but not senescence. These studies provide the pre-clinical rationale for clinical trials of concurrent radiotherapy and BRAF V600E inhibitors.