Comparison of different metrics for estimating kidney radiation exposure during treatment for childhood cancer: A report from the St. Jude Lifetime Cohort Study.

10047 Background: Risk for impaired kidney function varies with radiation therapy (RT). We compared different methods for quantifying RT. Methods: Kidney function was graded in 2753 survivors (>10 years post-diagnosis, age ≥18 years) and 806 community controls (CC) per the Kidney Disease International Global Outcomes 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease (CKD). Multivariable logistic regression was used to evaluate the associations between grades 3-5 CKD and demographics and treatment exposures. RT was expressed as percentage of total kidney volume treated with 5 Gray (Gy) or more (V5), 10 Gy or more (V10) Gray, Children’s Oncology Group (COG) abdominal RT, or total body irradiation (TBI)/whole abdomen RT (WA). Model discrimination was assessed using area under the receiver operating characteristic curve (AUC). Results: 2.1% of survivors had stages 3 to 5 CKD, compared to 0.12% of CC (Odds Ratio (OR): 17.0 (95% confidence interval (CI) 2.9, 682.8), p < 0.001). Significant associations between higher risks of grades 3-5 CKD and demographic and treatment exposures were identified in separate regression models (Table). AUCs were 0.891, 0.888 and 0.896 for V5, V10, and TBI/WA, models respectively. Conclusions: TBI/WA is a more readily available exposure designation than V5 or V10. These results inform identification of survivors at highest risk for CKD. V5 V10 COG TBI/WA Predictors OR (95%CI) p OR (95%CI) p OR (95%CI) p OR (95%CI) p Race (White vs non-White) 1.68(0.81 – 3.30) 0.144 1.71(0.82 – 3.35) 0.133 1.80(0.89 – 3.44) 0.086 1.71(0.85 – 3.28) 0.116 Age at evaluation 1.09(1.04 – 1.13) <0.001 1.09(1.05 – 1.13) <0.001 1.09(1.05 – 1.13) <0.001 1.10(1.05 – 1.14) <0.001 Hypertension 8.21(4.12 – 17.61) <0.001 8.27(4.15 – 17.71) <0.001 8.61(4.41 – 18.02) <0.001 8.61(4.42 – 17.97) <0.001 Nephrectomy (yes/no) 2.44(0.88 – 6.12) 0.069 2.68(0.97 – 6.72) 0.044 4.23(1.81 – 9.48) 0.001 3.42(1.36 – 8.01) 0.006 Ifosfamide (per 1000 mg/m 2 ) 1.04(1.02 – 1.06) <0.001 1.04(1.02 – 1.05) <0.001 1.04(1.03 – 1.06) <0.001 1.04(1.03 – 1.06) <0.001