Pleomorphic Xanthoastrocytoma: Multi-Institutional Evaluation of Stereotactic Radiosurgery

BACKGROUND AND OBJECTIVES

Pleomorphic xanthoastrocytoma (PXA) is a rare low-grade glial tumor primarily affecting young individuals. Surgery is the primary treatment option; however, managing residual/recurrent tumors remains uncertain. This international multi-institutional study retrospectively assessed the use of stereotactic radiosurgery (SRS) for PXA.

METHODS

A total of 36 PXA patients (53 tumors) treated at 11 institutions between 1996 and 2023 were analyzed. Data included demographics, clinical variables, SRS parameters, tumor control, and clinical outcomes. Kaplan-Meier estimates summarized the local control (LC), progression-free survival, and overall survival (OS). Secondary end points addressed adverse radiation effects and the risk of malignant transformation. Cox regression analysis was used.

RESULTS

A total of 38 tumors were grade 2, and 15 tumors were grade 3. Nine patients underwent initial gross total resection, and 10 received adjuvant therapy. The main reason for SRS was residual tumors (41.5%). The median follow-up was 34 months (range, 2-324 months). LC was achieved in 77.4% of tumors, with 6-month, 1-year, and 2-year LC estimates at 86.7%, 82.3%, and 77.8%, respectively. Younger age at SRS (hazard ratios [HR] 3.164), absence of peritumoral edema (HR 4.685), and higher marginal dose (HR 6.190) were significantly associated with better LC. OS estimates at 1, 2, and 5 years were 86%, 74%, and 49.3%, respectively, with a median OS of 44 months. Four patients died due to disease progression. Radiological adverse radiation effects included edema (n = 8) and hemorrhagic change (n = 1). One grade 3 PXA transformed into glioblastoma 13 months after SRS.

CONCLUSION

SRS offers promising outcomes for PXA management, providing effective LC, reasonable progression-free survival, and minimal adverse events.

Brain and Brain Stem Necrosis After Reirradiation for Recurrent Childhood Primary Central Nervous System Tumors: A PENTEC Comprehensive Review

PURPOSE

Reirradiation is increasingly used in children and adolescents/young adults (AYA) with recurrent primary central nervous system tumors. The Pediatric Normal Tissue Effects in the Clinic (PENTEC) reirradiation task force aimed to quantify risks of brain and brain stem necrosis after reirradiation.

METHODS AND MATERIALS

A systematic literature search using the PubMed and Cochrane databases for peer-reviewed articles from 1975 to 2021 identified 92 studies on reirradiation for recurrent tumors in children/AYA. Seventeen studies representing 449 patients who reported brain and brain stem necrosis after reirradiation contained sufficient data for analysis. While all 17 studies described techniques and doses used for reirradiation, they lacked essential details on clinically significant dose-volume metrics necessary for dose-response modeling on late effects. We, therefore, estimated incidences of necrosis with an exact 95% CI and qualitatively described data. Results from multiple studies were pooled by taking the weighted average of the reported crude rates from individual studies.

RESULTS

Treated cancers included ependymoma (n = 279 patients; 7 studies), medulloblastoma (n = 98 patients; 6 studies), any CNS tumors (n = 62 patients; 3 studies), and supratentorial high-grade gliomas (n = 10 patients; 1 study). The median interval between initial and reirradiation was 2.3 years (range, 1.2-4.75 years). The median cumulative prescription dose in equivalent dose in 2-Gy fractions (EQD22; assuming α/β value = 2 Gy) was 103.8 Gy (range, 55.8-141.3 Gy). Among 449 reirradiated children/AYA, 22 (4.9%; 95% CI, 3.1%-7.3%) developed brain necrosis and 14 (3.1%; 95% CI, 1.7%-5.2%) developed brain stem necrosis with a weighted median follow-up of 1.6 years (range, 0.5-7.4 years). The median cumulative prescription EQD22 was 111.4 Gy (range, 55.8-141.3 Gy) for development of any necrosis, 107.7 Gy (range, 55.8-141.3 Gy) for brain necrosis, and 112.1 Gy (range, 100.2-117 Gy) for brain stem necrosis. The median latent period between reirradiation and the development of necrosis was 5.7 months (range, 4.3-24 months). Though there were more events among children/AYA undergoing hypofractionated versus conventionally fractionated reirradiation, the differences were not statistically significant (P = .46).

CONCLUSIONS

Existing reports suggest that in children/AYA with recurrent brain tumors, reirradiation with a total EQD22 of about 112 Gy is associated with an approximate 5% to 7% incidence of brain/brain stem necrosis after a median follow-up of 1.6 years (with the initial course of radiation therapy being given with conventional prescription doses of ≤2 Gy per fraction and the second course with variable fractionations). We recommend a uniform approach for reporting dosimetric endpoints to derive robust predictive models of late toxicities following reirradiation.

Stereotactic Radiosurgery for Ependymoma in Pediatric and Adult Patients: A Single-Institution Experience

BACKGROUND AND OBJECTIVES

Ependymoma is commonly classified as World Health Organization grade 2 with the anaplastic variant categorized as grade 3. Incomplete resection or anaplastic features can result in unfavorable outcomes. Stereotactic radiosurgery (SRS) provides a minimally invasive approach for recurrent ependymomas. Our study investigates the efficacy and safety of SRS for grade 2 and 3 ependymomas in pediatric and adult populations.

METHODS

We conducted a retrospective analysis on 34 patients with 75 ependymomas after CyberKnife SRS between 1998 and 2023. Fourteen were pediatric (3-18 years), and 20 were adult (19-75 years) patients. The median age was 21 years, and the median tumor volume was 0.64 cc. The median single-fraction equivalent dose was 16.6 Gy, with SRS administered at 77% of the median isodose line.

RESULTS

After a median follow-up of 42.7 months (range: 3.8-438.3), 22.7% of ependymomas progressed. The 5-year local tumor control rate was 78.1%, varying between 59.6% and 90.2% for children and adults, with grade 2 at 85.9% compared with 58.5% for grade 3 tumors. The 5-year overall survival rate was 73.6%, notably higher in adults (94.7%) than in children (41%), and 100% for grade 2 but decreased to 35.9% for grade 3 patients. The 5-year progression-free survival rate was 68.5%, with 78.3% and 49.2% for adults and children, respectively, and a favorable 88.8% for grade 2, contrasting with 32.6% for grade 3 patients. Symptom improvement was observed in 85.3% of patients. Adverse radiation effects occurred in 21.4% of pediatric patients.

CONCLUSION

Our study supports SRS as a viable modality for pediatric and adult patients with grade 2 and 3 ependymomas. Despite lower local tumor control in pediatric and grade 3 cases, integrating SRS holds promise for improved outcomes. Emphasizing careful patient selection, personalized treatment planning, and long-term follow-up is crucial for optimal neurosurgical outcomes.

Less common intraparenchymal tumors

The chapter outlines the management of a great variety of rare intraparenchymal tumors. For some like medulloblastomas or ependymomas, GKNS has little to offer. For others like neurocytomas, primary central nervous system lymphomas, and papillary pineal tumors the current findings look most hopeful. For choroid plexus papillomas there is currently not enough information to define the role of GKNS in their treatment. Pineal region tumors are a complex and varied group of neoplasms. Their complexity, variety and ethnic variability means that defining the role of GKNS will require continuing research before a consensus about management can be reached.

Evaluation of dose, volume and outcome in children with localized, intracranial ependymoma treated with proton therapy within the prospective KiProReg Study

Background

Radiotherapy (RT) of ependymoma in children is an important part of the interdisciplinary treatment concept. However, feasibility and dose concepts are still under investigation, particularly in very young children. The aim of this study was to evaluate the standard dose and volume of proton therapy (PT) in children with ependymoma.

Methods

In this analysis, 105 patients with localized, intracranial ependymoma under the age of 18 years treated with PT between 2013 and 2018 were included. Patient characteristics, treatment, outcome, and follow-up data were analyzed using descriptive statistics, Kaplan-Meier, and Cox regression analysis.

Results

The median age of patients at PT was 2.8 years (0.9-17.0 years). The molecular subgroup analysis was performed in a subset of 50 patients (37 EP-PFA, 2 EP-PFB, 7 EP-RELA, 2 EP-YAP, 2 NEC [not elsewhere classified]). The median total dose was 59.4 Gy (54.0-62.0 Gy). The median follow-up time was 1.9 years. The estimated 3-year overall survival (OS), local control (LC), and progression-free survival (PFS) rates were 93.7%, 74.1%, and 55.6%, respectively. Within univariable analysis, female gender and lower dose had a positive impact on OS, whereas age ≥4 years had a negative impact on OS and PT given after progression had a negative impact on PFS. In the multivariable analysis, multiple tumor surgeries were associated with lower PFS. New ≥3° late toxicities occurred in 11 patients.

Conclusion

For children with localized ependymoma, PT was effective and well tolerable. Multiple surgeries showed a negative impact on PFS.

Hypofractionated stereotactic body radiation therapy (SBRT) in pediatric patients: preliminary toxicity results of a national prospective multicenter study

OBJECTIVES

While hypofractionated stereotactic body radiotherapy (SBRT) has been largely adopted in the adult setting, its use remains limited in pediatric patients. This is due, among other factors, to fear of potential toxicities of hypofractionated regimens at a young age. In this context, we report the preliminary acute (<3 months from SBRT) and middle-term (3-24 months) toxicity results of a national prospective study investigating SBRT in pediatric patients.

METHODS

Between 2013 and 2019, 61 patients were included. The first 40 patients (median age: 12 y, range: 3-20) who completed a 2-year-follow-up were included in the present analysis. SBRT was used for treating lung, brain or (para)spinal lesions, either as first irradiation (35%) or in the reirradiation setting (65%).

RESULTS

Acute and middle-term grade ≥2 toxicities occurred in 12.5 and 7.5% of the patients, respectively. No grade ≥4 toxicities occurred. Almost all toxicities occurred in the reirradiation setting.

CONCLUSION

SBRT showed a favorable safety profile in young patients treated for lung, brain, and (para)spinal lesions.

ADVANCES IN KNOWLEDGE

SBRT appeared to be safe in pediatric patients treated for multiple oncology indications. These results support further evaluation of SBRT, which may have a role to play in this patient population in the future.

Image-Guided Robotic Radiosurgery for the Management of Spinal Ependymomas

Background

Ependymomas are rare neoplasms of the central nervous system (CNS), usually localized intracranially and most commonly diagnosed in children. Spinal ependymomas are more frequent in young adults. They are either primary lesions or manifest as disseminated seeding of cranial tumors. Data on the management of spinal ependymoma lesions remain scarce, especially concerning stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT). The purpose of this study is to report the treatment outcomes of two institutions using robotic radiosurgery (RRS) for the treatment of spinal ependymomas.

Materials and Methods

All patients with a histopathologically confirmed diagnosis of an ependymoma WHO grade II or III who were treated with RRS for one or more spinal lesions were included in this analysis.

Results

Twelve patients underwent RRS for the treatment of 32 spinal ependymoma lesions between 2005 and 2020. Two patients were below the age of 18 when treated, whereas nine patients (75%) suffered from a primary spinal ependymoma. The median dose was 15 Gy prescribed to a median isodose of 70%, with 27 lesions (84%) receiving a single-session treatment. The local control (LC) after a median follow-up of 56.7 months was 84%. LC rates at 1, 3, and 5 years were 92, 85, and 77%, respectively. The Kaplan-Meier estimated overall survival after 1, 3, and 5 years were 75, 75, and 64%, respectively. Five patients died, all of them suffering from an anaplastic ependymoma, with widespread CNS tumor progression being the reason for death in four patients. The majority of patients (58%) showed a stable neurological status at the last available follow-up. Overall, the treatment was well tolerated.

Conclusion

RRS appears to be a safe and efficient treatment modality for managing primary and secondary spinal ependymal tumors in patients with multiple lesions and local recurrences.

Repeated gamma knife radiosurgery enables longer tumor control in cases of highly-recurrent intracranial ependymoma

PURPOSE

Stereotactic radiosurgery (SRS) is a potential re-irradiation treatment for recurrent intracranial ependymoma after prior radiation therapy. The purpose of this study was to examine the efficacy and safety of repeated SRS in the treatment of recurrent intracranial ependymomas.

METHODS

This is a retrospective study of consecutive patients with residual or recurrent intracranial ependymomas who were treated with SRS between 1993 and 2018. Tumor progression was defined as a ≥ 10% increase in tumor volume. Tumor regression was defined as a ≥ 10% reduction in tumor volume. A tumor that remained within 10% of its original volume was defined as stable. Tumor control comprised tumor regression and stability. Time-dependent analyses were performed using two treatment failure endpoint definitions: (1) evidence of local tumor progression or distant metastasis (single SRS analysis), and (2) lack of tumor response to SRS (repeated SRS analysis). These analyses were adjusted for the competing risk of death.

RESULTS

The study comprised 37 patients (65 intracranial ependymomas) who underwent multiple SRS sessions (range: 1-7). Median age was 10.2 years (range: 0.8-53.8 years), and median tumor volume was 1.5 mL (range: 0.01-22.5 mL). The median radiation dose was 13.3 Gy (range: 7.9-22.0 Gy) at a median isodose line of 57% (range: 50-90%). Overall tumor control rates in the single SRS analysis adjusting for the competing risk of death were 53.6%, 30.5%, and 23.6% at 1, 3, and 5 years, respectively. Overall tumor control rates in the repeated SRS analysis adjusting for the competing risk of death were 70.6%, 50.4%, and 43.1% at 1, 3, and 5 years, respectively. Prior gross total resection was the only independent predictor of overall tumor control after SRS (aHR = 25.62 (1.55-422.1), p = 0.02).

CONCLUSIONS

Repeated GKRS appeared to be an effective treatment strategy for recurrent or residual intracranial ependymomas, with acceptable complication rates.

Two-Session Radiosurgery for Large Primary Tumors Affecting the Brain

Introduction Surgery is an option for patients with large, symptomatic primary tumors affecting the brain. However, surgery might not be suitable for all tumors, especially those located in sensitive areas such as the pineal region and the hypothalamus. Single-session stereotactic radiosurgery (SRS) might not provide an adequate dose for long-term local control due to the initial tumor volume and the involvement of radiation sensitive organs at risk (OARs). Two-session radiosurgery has been described as a feasible strategy for dose escalation in large secondary brain tumors. This report describes a series of patients treated upfront with two-session radiosurgery for primary tumors affecting the brain. Materials and methods From May 2017 to January 2020, eight patients with primary tumors affecting the brain were treated with two-session radiosurgery due to either an initial large tumor volume or tumor localization and the involvement of OARs. The response was assessed by imaging and clinical evaluations. Results A total of eight patients were treated, nine tumors were treated with two-session radiosurgery, four patients had tumors in the pineal region (50%), and the rest were in the hypothalamic region (25%) or elsewhere. The mean tumor volume for the first SRS session was 15 mL (range 5.2 to 51.6 mL), the mean prescription dose was 13 Gy, and the timespan between both sessions was 30 days (range, 30 to 42 days). During the second session, tumor volume was reduced to 73.6% (range, -20% to 98.7%) of the original dimension, mean tumor volume was 5 mL (range, 0.1 to 17.8 ml), mean prescription dose for the second session was 16.2 Gy estimated by time, dose, and fractionation and by bioequivalent dose under alpha-beta values often to be equivalent to a single dose of 15.8 Gy. Doses to the OARs for the optic pathway were equivalent to a single maximum dose of 9.75 Gy (range, 7.12 to 10.92), and to the brainstem, the equivalent was a maximum dose of 12.3 Gy (range, 5.6 to 15.07). At last follow-up, at a mean of 336.5 days (range, 65 to 962 days), seven patients were alive, five tumors had a partial response (PR), and three had stable disease in accordance to Response Evaluation Criteria in Solid Tumors (RECIST) criteria. One patient died 435 days after treatment, the Karnofsky Performance Status (KPS) was 90 at the first session, 90 at the second session, and was maintained at last follow-up. No adverse radiation effects were reported. Conclusions Two-stage SRS proved to be a safe method to escalate dose in proportionately large volume primary brain tumors whose histology is expected to have a quick biological response to radiation. Longer follow-up is needed to determine the long-term effectiveness by tumor subtypes of two-stage SRS in the same manner as it has been proven in single session SRS series in smaller tumor volumes.