Abstract
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Objectives Toxicity limits for I-131 NaI therapy are known, but acute hematologic toxicity using standardized National Cancer Institute Common Toxicity Criteria for Adverse Events (NCI CTCAE v4) has not been formally studied.
Methods IRB approved retrospective study of 95 patients who underwent treatment with I-131 following dosimetry studies. All patients had baseline Complete Blood Count <2 weeks prior to, and within 3-7 weeks after treatment. The association of administered activity (dosage) and predicted radiation dose to blood (blood dose) with follow-up White Blood Cells (WBC), Platelets (Plts) and Hemoglobin (Hgb) were evaluated by linear regression models. Measurements included absolute counts and toxicity Grades, which were evaluated using CTCAE. Model fit was measured using Bayesian Information Criterion (BIC).
Results Both the dosage (Range 1.21-22.2 GBq, Mean 9.9 GBq, Median 10.03 GBq) and blood dose (Range 0.19-3.02 Gy, Mean 1.50 Gy, Median 1.51 Gy) were significantly associated with both WBC measures (p<0.0001 - 0.01). The only statistical association was with blood dose for absolute counts (p=0.005) in Plts, and CTCAE grades (p=0.01) in Hgb. Although correlation coefficients were not strong for either type of model, BIC values (>2) showed blood dose fit the data better than using dosage for all models except for WBC absolute counts, where the 2 fit similarly (BIC=1.8).
Conclusions Blood dose predicts acute hematologic toxicities following I-131 therapies slightly better than dosage. This may result in improved management and dosage selection in patients undergoing treatment, and could be used to extrapolate hematologic toxicities for patients undergoing other systemic radionuclide therapies.