title: Complete blood counts are frequently abnormal 1 year after dosimetry-guided radioactive iodine therapy for metastatic thyroid cancer.
abstract: OBJECTIVE
  Radioactive iodine (RAI) has been associated with hematologic abnormalities. Previous research has shown that even a single dose of RAI can cause changes in the peripheral complete blood count (CBC). It is unclear if the use of dosimetry guidance would prevent the effects of high doses of RAI on bone marrow suppression.
  
  
  METHODS
  CBC at baseline was compared to a CBC obtained 1 year after the last RAI treatment in 50 thyroid cancer patients that received ≥250 mCi RAI during the course of their disease. Cumulative dose, number of treatments, patients' age, and the use of external beam radiation therapy (EBRT) were considered in the analysis.
  
  
  RESULTS
  We observed a small but statistically significant decrease in hemoglobin (Hb), hematocrit (Hct), and platelet (Plt) counts at 1 year in 50 patients who had received ≥250 mCi RAI. We did not find a significant change in white blood cell count (WBC). Approximately 60% of patients who developed anemia had concomitant WBC and Plt abnormalities. RAI dose, number of treatments, and age at diagnosis did not confer a higher risk of bone marrow suppression.
  
  
  CONCLUSIONS
  High cumulative activities of RAI administered under dosimetric guidance are associated with a small but statistically significant decreases in Hb, Hct, and Plt counts. The clinical implications of these changes, if any, are unclear. The benefits obtained with high doses of RAI, when indicated, are likely to outweigh the minimal hematologic risks observed in the present study.
authors.affiliation: Endocrinology Service, Federal University of Sao Paulo, Brazil.
authors.forename: Rosalia P
authors.initials: RP
authors.lastname: Padovani
authors.affiliation: Endocrinology, Memorial Sloan-Kettering Cancer Center, New York, New York.
authors.forename: R Michael
authors.initials: RM
authors.lastname: Tuttle
authors.affiliation: Nuclear Medicine Services, Memorial Sloan-Kettering Cancer Center, New York, New York.
authors.forename: Ravinder
authors.initials: R
authors.lastname: Grewal
authors.affiliation: Nuclear Medicine Services, Memorial Sloan-Kettering Cancer Center, New York, New York.
authors.forename: Steve M
authors.initials: SM
authors.lastname: Larson
authors.affiliation: Endocrinology, Memorial Sloan-Kettering Cancer Center, New York, New York.
authors.forename: Laura
authors.initials: L
authors.lastname: Boucai
mesh_terms: D000328:Adult; D001772:Blood Cell Count; D005260:Female; D006400:Hematocrit; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D011874:Radiometry; D013964:Thyroid Neoplasms / Q000097:blood / Q000473:pathology / Q000532:radiotherapy*
chemical_list: D007457:Iodine Radioisotopes