P14.65 Anaplastic pleomorphic xanthoastrocytoma: literature review& case report

Pleomorphic xanthoastrocytoma (PXA) is a rare glial brain tumor. 9% to 30% cases have anaplastic features which determine poor prognosis. Anaplastic features may be found either in primary tumor or in recurrent PXA in any time frame. According to WHO 2016 Brain Tumor Classification, anaplastic pleomorphic xanthoastrocytoma (aPXA) was reclassified as grade III tumor (previously grade II). Characteristic features for aPXA are mitotic index of 5% or higher and worse 5-year survival rates in comparison with PXA: 57.1% and 90.4%, respectively. About 6% cases have TP53 gene mutation. About 60–78% tumors are BRAF-mutated, which is a potential target for therapy. Currently there are ongoing clinical trials to determine efficacy of BRAF and MEK inhibitors in pediatric patients with high-grade glioma with BRAF mutation. There is a number of publications showing positive outcome of targeted therapy both in children and adults. Treatment protocol for aPXA has not been defined. Case report Patient N. 14-y.o. female. MRI showed tumor of left occipital lobe. 02.03.2016 stereotactic biopsy was performed. Histological examination revealed diffuse astrocytic glioma WHO grade III-IV. Radiation therapy was performed, after which patient’s condition abruptly deteriorated with back pain, patient became almost unable to walk, however control MRI showed no signs of spinal dissemination. 01.12.2016 surgery to remove left occipital lobe tumor was performed. 07.12.2016 MRI showed contrast enhancing lesions throughout entire length of the spinal cord. Histological examination revealed aPXA gr. III, Ki-67 up to 8%. From December to June 2017 patient received 6 cycles of chemotherapy with temozolomide. Molecular testing discovered BRAF V600 mutation in exon 15. Chemotherapy regimen was thereby changed to vemurafenib 1920 mg/day from July 2017. After a month of treatment patient developed cutaneous toxicity and the dose was lowered to 960 mg/day. Patient’s condition improved: back pain syndrome regressed, lower extremity muscle strength increased, patient became able to walk. MRI 03.12.2017 revealed an increase of contrast enhancing lesion and T2-FLAIR hyperintense signal area in left occipital lobe, no progression in spinal cord. Methionine PET/CT was performed, the findings were evaluated as a combination of radiation necrosis and glioma growth. In view of MRI and PET/CT findings, amount of time passed after radiation therapy, we decided to include bevacizumab 400 mg every 2 weeks in the regimen. Since January 2018 patient is receiving vemurafenib 960 mg/day and bevacizumab 400 mg every 2 weeks. There is a marked positive dynamic in clinical findings and imaging data (MRI and PET/CT). We report the patient with aPXA and prolonged response to targeted therapy. The presence of the BRAF V600E mutation was possibility of treatment which led to successful results.

P14.15 Benefit of Bevacizumab for recurrent glioblastoma. Results of 81 patients from a single institution

BACKGROUND

No standard of care has been established for patients with progressive glioblastoma (rGBM). Previous studies suggested that bevacizumab (BEV) is safe and produces responses that result in a decreased use of glucocorticoids and increased progression-free survival (PFS) with an unclear effect on overall survival (OS). Crossover to BEV in the control arm is the possible reason why the advantage of BEV has not been proven in Phase III trials. We retrospectively analyzed own results of BEV treatment in rGBM.

MATERIAL AND METHODS

81 patients progressed after radiotherapy plus concomitant and maintenance temozolomide (TMZ) and undergo BEV as monotherapy (BevMo, 11 patients) or in combinations (Irinotecan (BevI) - 53, lomustine (BevL)- 11, TMZ (BevT) - 6. Median age 54 years. Among them 33 patients were re-irradiated: 11 - radiosurgery (RS), 20 fractionated irradiation (RT), 2 - RS+RT. 33 patients continued BEV after progression with changing or adding cytostatic. PFS was calculated from the date of verification, PFS1 - from the date of 1-st progression, PFS2 - from the date of 2-nd progression.

RESULTS

Median PFS was 9.0 ([CI] 7.0–10.9) months. Median PFS1 was 10.5 ([CI] 8.1–12.9) months. In the BevMo, BevI, BevL, BevT group PFS1 was 15.7, 10.1, 10.5, 13.2 months, respectively, p=0.7. Objective response (OR) was reached in 34%, stable disease (SD) in 28%, progression (PD) in 37% patients. 16 patients stopped BEV without progression (4-patient`s decision, 7- doctor`s decision, 2 - adverse event, 3 - concomitant disease). Median time of BEV treatment was 11.6 months. Median BEV-free interval till progression was 3.7 months. 33 patients continued or restarted BEV after progression. Median PFS2 was 8.0 ([CI] 4.9–11.1) months. The median OS from the date of 1-st progression was 23.5 months ([CI] 18.7–27.4). In groups with RT, RS, RS+RT and no re-irradiarion OS was 24.6 ([CI] 17.6–31.5), 35.4 ([CI] 35.0–35.8), 17.8, 20.6 ([CI] 15.2–26.0), respectively, p=0.2.

CONCLUSION

OS in our group is outrageously high. Maintaining BEV after progression was effective. In our group BEV discontinuation led to rapid progression. The resumption of Bev with progression was effective, which indicates the advisability of its continuous application.

P14.03 Adult medulloblastoma: Influence of risk stratification and molecular subtypes on chemotherapy efficacy

BACKGROUND

Incidence of medulloblastoma (MB) in adults is about 1%. Optimal treatment for adult medulloblastoma has not been defined. Published datasets were acquired over a long period of time, during which there were changes in surgical technique, radiotherapy, chemotherapy regimens; often disease stage was not considered in the analyses. Recently discovered molecular subgroups are not taken into account in studies concerning treatment of medulloblastoma in adults.

MATERIAL AND METHODS

Study includes 64 patients with medulloblastoma (median age 26.5 years (15–62)), who were first admitted to Burdenko Neurosurgery Institute for surgery from 2000 to 2017. 100 % patients included in the study received radiotherapy - craniospinal irradiation, 36 Gy (20 x 1.8 Gy) with boost to primary site (2 cm around tumor bed) up to 55 Gy total dose. 41 patients (64%) received chemotherapy (ChT). Chemotherapy was started 4–6 weeks after finishing craniospinal irradiation, the regimen included cisplatin 25 mg/m2 days 1–4+etoposide 100 mg/m2 days 1–4+cyclophosphamide 600 mg/m2 days 1–4; the cycles repeating every 28 days, 6 cycles in total. Treatment volume didn’t correspond with risk group and/or molecular genetic subgroup (these parameters were determined retrospectively). Median follow-up time is 4.45 years.

RESULTS

53% patients had classic histology MB, 27% - desmoplastic, 20% - large cell/anaplastic. High risk (HR), standard risk (SR) and unspecified risk (UR) groups included 23, 16 and 25 patients respectively. Molecular subgroup testing was performed in 39 cases: SHH-activated - 59%, WNT-activated - 18%, GROUP4 - 23%. Median time to tumor progression (MTTP) in patients who received radio-chemotherapy versus radiotherapy alone was 4.3 and 2.64 years, respectively (p=0.264). The differences in MTTP were the most pronounced in SR and UR patients who received radio-chemotherapy (5.5 and 6.0 months, respectively) versus radiotherapy alone (1.5 and 2.0 months, respectively). HR patients showed the least difference in MTTP for radiotherapy (2.0 years) versus radio-chemotherapy (2.5 years), p=0.093. The SHH-subgroup patients had MTTP of 3.1 years (3.1 and 3.0 years for ChT+ and ChT-, respectively). GROUP4 patients had MTTP of 4.3 years (4.3 and 1.5 years for ChT+ and ChT-, respectively). All WNT-subgroup patients received chemotherapy, MTTP was 9.0 years. Median overall survival cannot be defined in any of the subgroups.

CONCLUSION

Chemotherapy in adult medulloblastoma patients increases MTTP in SR and UR patients. Low efficacy of chemotherapy for high risk medulloblastoma urges search for more efficacious treatment protocols. WNT-activated adult medulloblastoma has the highest MTTP among other molecular subgroups.