RONC-11. Permanent alopecia in pediatric patients with medulloblastoma treated by craniospinal irradiation: looking for a threshold dose

BACKGROUND: Permanent alopecia in adult survivors of childhood cancer is a late effect that has a negative impact on vitality and social function, and it is not clear if it is only associated with radiotherapy or also with high-dose chemotherapy. In this study, we analysed a cohort of medulloblastoma survivors treated with craniospinal irradiation (CSI) with long follow-up looking for radiotherapy parameters associated with permanent hair loss. METHODS: We retrospectively analysed 42 patients with medulloblastoma with median follow up of 10 years. In 27 pts, Eclipse subgroup, the scalp was accurately re-contoured and were estimated specifics dosimetric parameters. Any relationship between presence of alopecia and other characteristics was investigated by univariate and multivariate analysis, in both groups. For each significant predictor variable, a Receiver Operating Characteristic curve was drawn for calculating the Area Under the Curve and identifying the optimal dose discriminatory cut-off value for prediction of alopecia. RESULTS: The best predictor for the occurrence of permanent alopecia was the dose of CSI (OR: 1.002; 95%CI: 1.001-1.003; p=0.003), with a cut-off value of 30.9 Gy. In Eclipse subgroup median Dose hair skin was statistically significant, (OR: 1.216; 95%CI: 1.030-1.435; p=0.021), with a cut-off value of 28.7 Gy. If the median dose of each Gy unit of D median is exceeded, the probability of alopecia increases by 21.6% (3.0% - 43.5%), with a specificity of 90.9%. None of the other variables was statistically significant. CONCLUSIONS: Pediatric Medulloblastoma survivors have a high risk of developing permanent alopecia.Our study supports the finding that permanent hair loss is dose-dependent and identified a threshold dose, the median dose of 28.7 Gy, to prevent the occurrence of permanent alopecia in paediatric patients undergoing radiotherapy. Therefore, we suggest that this dosimetric parameter should be evaluated when planning radiation treatment, especially when planning CSI in low- and standard-risk medulloblastoma.