Abstract 850P
Background
Acute lymphoblastic leukemia is one among the common paediatric malignancies. CNS relapse is the major concern in treatment of ALL because of inability of chemotherapy to cross the blood-brain barrier. CNS directed treatments include prophylactic cranial irradiation (PCI), intrathecal methotrexate (ITMTX) and high dose systemic therapy. A combination of PCI and IT MTX is the most commonly used CNS directed therapy. PCI is associated with neurocognitive side effects, memory and attention deficits. Radiation induced hippocampal damage is one of the causes for the side effects. The purpose of this to deliver PCI with hippocampal sparing using VMAT and also do a dosimetric analysis of the dose volume data generated.
Methods
25 patients were treated with hippocampal sparing PCI using VMAT. Dose of PCI was used according to the treatment protocol of the patient.18Gy and 12Gy dose schedules were used for most of the patients.
Results
For patients treated with 18Gy the mean dose to PTV was 18.9 Gy ± 0.3 Gy and hippocampus received a mean dose of 8.9 Gy ± 0.3 Gy. Conformity index and homogeneity index were 0.9 and 0.1 respectively. For patients treated with 12Gy the mean dose to PTV was 13.3 Gy ± 0.3 Gy and hippocampus received a mean dose of 7Gy ± 1 Gy. Conformity index and homogeneity index were 0.9 and 0.1 respectively.
Conclusions
Our study showed that PCI with hippocampal sparing through VMAT can achieve 100% dose coverage to PTV while keeping the dose to hippocampus to less than 9Gy which is less than the threshold dose causing neurocognitive effects. By achieving this low dose to the hippocampus, there is possibility avoid neurocognitive side effects in lonterm survivors.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
JIPMER.
Disclosure
All authors have declared no conflicts of interest.