PV QA 2 - Poster Viewing Q&A 2
Purpose/Objective(s): Total Body Irradiation (TBI) is an integral part of the conditioning regimen for patients with Acute Lymphoblastic Leukemia (ALL) undergoing allogeneic hematopoietic cell transplantation (allo-HCT). There is conflicting data in the literature regarding the utility of pre-transplant cranial irradiation in adult ALL patients without central nervous system involvement. The goal of this study is to investigate the post-transplant clinical outcomes of high-risk adult ALL patients undergoing allo-HCT with TBI conditioning with, or without, pre-transplant whole brain boost.
Materials/Methods: A retrospective cohort study was conducted utilizing medical record analysis. We identified 58 patients treated from January, 1998, to December, 2016, meeting our pre-set inclusion criteria of adults (age >18 years old) who carried a pathologically confirmed diagnosis of high-risk ALL (WBC >50,000 at diagnosis, T-cell ALL subtype, or high risk cytogenetic features), who underwent HCT with TBI conditioning. 26 patient had undergone TBI alone, and 32 patients had undergone a cranial boost in addition to TBI. Additional data was collected including patient age, gender, TBI dose, Whole brain radiation dose, depth of response, previous SCT, WBC count at diagnosis, CNS relapse-free survival, progression-free survival, and overall survival. Multivariate analysis of correlation between categorical variables was assessed with Chi squared (χ2) analysis of independence. Survival analyses were assessed using Kaplan-Meier technique with a log rank test.
Results: Median follow up was 5.3 years. TBI dose consisted of 12Gy delivered in 6 fractions administered twice daily. Cranial boost consisted of an additional 6-14Gy administered to the whole brain. There was a statistically significant improvement in 5-year CNS relapse-free survival (100% vs. 77%; p=0.043) in favor of patients undergoing cranial boost. There was a trend towards a statistically significant improvement in 5-year progression-free survival (83.3% vs 65.4%; p=0.076) in favor of patients undergoing cranial boost. There was no difference in 5-year overall survival (50.0% vs 69.2%; p=0.921) with, versus without a cranial boost. On multivariate analysis, there was no statistically significant relationship between patient age, patient gender, TBI dose, cranial boost dose, depth of response to transplant, previous SCT, WBC count at diagnosis, and the survival endpoints. The presence of cranial boost was the only identified variable with an independent relationship to CNS relapse-free survival.
Conclusion: Adult patients with high-risk, CNS negative, ALL have a statistically significant improvement in CNS relapse-free survival, and may have an improvement in progression-free survival with the inclusion of a cranial boost with TBI pre-transplant conditioning. Our data suggest that the addition of a cranial boost may reduce the risk of CNS relapse in this high risk patient population.
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