2482 - Clinical Efficacy and Adverse Effects of Radiotherapy in Pediatric Medulloblastoma with Residual or Disseminated Disease - A Single Center Experience

Purpose/Objective(s): This study aimed to explore the clinical efficacy and acute adverse effects of radiotherapy (RT) in pediatric medulloblastoma (MB) with residual or disseminated disease.

Materials/Methods: Data from 170 pediatric patients with MB and residual disease or metastases prior to RT were analyzed.

Results: The median follow-up period was 5.2 years, multivariate Cox analysis revealed that radiation response and large cell/anaplastic subtype were independent prognostic factors for survival (P<0.05). A total of 74 (43.5%) patients achieved CR, 85 (50.0%) patients achieved PR, 8 (4.7%) patients had SD and 3 (1.8%) patients developed PD after RT. Five year post-radiotherapy progression-free (prtPFS) and overall survival (prtOS) were superior in patients who achieved CR compared to those who had non-CR (prtPFS: 67% ± 6% vs. 42% ± 6%, P<0.001; prtOS: 82% ± 5% vs. 44% ± 6%, P<0.001). Multivariable logistic regression analysis showed that residual disease site was the predictive factor for radiation response, patients who had residual diseases in both the brain and spinal cord before RT had higher non-CR rate (OR: 7.312, 95%CI 3.375-15.845, P<0.001). Hematologic toxicity is the well documented adverse effect of craniospinal irradiation, most patients exhibited grade 3 leukopenia, grade 3 neutropenia, grade 1 anemia, grade 0 thrombocytopenia and no patients died because of hematologic toxicity during RT.

Conclusion: Response to RT was an independent prognostic factor for survival in patients with MB and residual disease prior to RT. Patients who did not achieve CR after RT should have intensified adjuvant chemotherapy to improve survival. Hematologic toxicity is the main acute adverse effect of RT and is well tolerated.