P13.13.B RADIONECROSIS VERSUS SECOND MALIGNANCY: BRAINSTEM LESION 19 YEARS AFTER PAEDIATRIC MEDULLOBLASTOMA TREATMENT

• Published in: Neuro-oncology (Charlottesville, Va.) Va.), 2024-10, Vol.26 (Supplement_5), p.v74-v74
• Main Authors: Turcas, A, Mihut, E, Homorozeanu, B, Avram, G, Roman, A, Fekete, Z
• Format: Article
• Language: English
• ISSN: 1522-8517; 1523-5866
• DOI: 10.1093/neuonc/noae144.246

Abstract BACKGROUND Brain radionecrosis is a rare, but severe complication of radiotherapy. In children, the incidence ranges around 2-4% of patients and peaks around 5-7 years after conventional radiotherapy, wherease in adults treated with stereotactic radiotherapy it can occur more often and sooner, usually between 6 monts up to 2 years. Other important late side effects of radiotherapy in paediatric patients are second malignancies, which usually occur in the irradiated region, around 15-20 years after treatment. CASE REPORT We present the case of a 36-year old patient treated at the age of 16 (in 2005) with surgery, followed by standard chemotherapy and cranio-spinal irradiation (36Gy) with a boost up to 54 Gy to the entire posterior fossa for a non-metastatic medulloblastoma. Complete remission was obtained and maintained until October 2023, when the patient developed new symptoms in terms of headache, balance issues and accentuated motor deficits in the lower limbs. The MRI showed a new infiltrative, enhancing lesion in the pontine region, with diffusion restriction and heterogenous hyper-intense T2. We raised the suspicion of a second, radiation-induced malignancy or a late radionecrosis. MRI spectroscopy showed high Lactate, low NAA, Choline and Creatinine, being suggestive of radionecrosis, thus the patient was offered corticosteroids (16mg Dexamethasone for 1 week with progressive reduction of doses and cessation after 4 weeks). Monthly follow-up MRI’s showed a progressive volume and enhancement reduction of the lesion, with significant improvement of the symptoms. The last MRI (April 2024) shows a major reduction of the lesion, from 3/2cm at diagnosis to 0.6/1cm at 6 months, with good clinical status. CONCLUSION The presented case is impressive in terms of the timing of radionecrosis, given that with standard-fractionated radiotherapy this toxicity occurs very rare and usually much sooner. Also, the radiologic and clinical response to steroids was impressive. This report aims to raise awareness on the importance of long-term follow-up in paediatric brain tumour patients and underlies the importance of advanced imaging techniques for differentiating between tumour relapse, radio-necrosis and second malignancies.