Hadar Daskin-Bitan1,2; Eyal Robenshtok1,2, Anat Leibner1; Oren Amitai1; Dania Hirsch1,2; Carlos Benbassat2,3
1 Endocrinology Institute, Rabin Medical Center, Israel
2 Sackler School of Medicine, Tel-Aviv University, Israel
3 Endocrine Institute, Assaf Harofeh Medical Center, Israel
Background: Elderly patients with differentiated thyroid cancer (DTC) tend to have more advanced disease at presentation, for which high activities of radioiodine (RAI) are often recommended. However, the 2015 ATA guidelines recommend caution in administering activities higher than 100-150mCi in elderly patients, based on calculated bone-marrow exposure from two dosimetry-based studies.
Objectives: To evaluate real-life effect of RAI treatment on bone marrow function in elderly DTC patients. Levels of hematologic cell lines before/after RAI administration were compared.
Methods: DTC patients >70 y/o who received RAI treatment and performed complete blood count (CBC) before and after treatment were included from the Rabin Medical Center registry.
Results: We included 123 RAI treatments in 106 patients. Mean±SD age was 76.6±4.4, and 64.2% were females. Most patients had advanced disease: 17% stage I, 7% stage II, 39% stage III and 38% stage IV. Median RAI activity was 150mCi (range 30-244, 87%?100mCi, 63%?150mCi) with mean cumulative activity of 180mCi (range 30-844). At 0-3 months there was a small but significant decrease in Hb (13.2±1.4 vs. 12.9±1.3, p=0.001), WBC (6.7±2 vs. 5.9±2, p<0.001), Platelets (234±65 vs. 210±66, p<0.001), and lymphocytes (1.7±0.7 vs. 1.4±0.7, p<0.001). Hemoglobin, WBC, Platelets, and lymphocytes remained decreased at 3-6 months. All cell lines recovered after ?12 months of follow-up. Subgroup analysis demonstrated no bone marrow suppression with activities ?50mCi. There were no clinically-significant cytopenia events during follow-up.
Conclusions: Empiric RAI treatment in elderly patients causes mild, clinically-insignificant bone marrow suppression. Activities higher than 100-150mCi can be safely used when clinically indicated.