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Bone marrow toxicity limited in most patients after radioiodine therapy for DTC
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Long-term bone marrow function is not compromised after radioiodine treatment for thyroid cancer, according to research in The Journal of Clinical Endocrinology & Metabolism.
In a longitudinal study focusing on the short- and long-term effects of radioiodine therapy on blood count parameters, researchers found significant decreases in both platelet and leukocyte counts in the first year after radioiodine treatment; however, those counts were comparable to baseline measurements 5 years after treatment.
Hest e r T. Prinsen , PhD, of the University of Groningen and University Medical Center Groningen in the Netherlands, and colleagues analyzed data from 331 adults with differentiated thyroid carcinoma (DTC; mean age, 48 years; 74% women; 75% papillary-type tumors) treated with radioiodine therapy (median administered cumulative radioiodine dose, 150 mCi) between 1989 and 2013. Within the cohort, 221 patients received no further radioiodine therapy after ablation while 100 patients underwent subsequent treatment.
Researchers compared platelet, leukocyte and hemoglobin counts at baseline, 3 and 6 months, and at 1 and 5 years after treatment. Researchers excluded patients who received therapies that could have influenced blood count parameters.
Researchers found that patients’ platelets were decreased compared with baseline 6 months after the last radioiodine treatment (P = .022) and remained depressed after 1 year (P = .002), but had rebounded 5 years after treatment (P = .343). Leukocyte counts also were lower 3 months after treatment (P < .001) and remained decreased at both 6 months (P < .001) and 1 year (P = .006) after radioiodine treatment, but were similar to baseline 5 years after treatment (P = .412), according to researchers. Researchers found no decreases in hemoglobin levels.
“Surprisingly, we found a significant increase of [hemoglobin] in both men and women 3 months post-treatment,” the researchers wrote. “A possible explanation for this phenomenon could be that the short-term hypothyroid state prior to the [radioiodine] treatment may have caused a relatively anemic state ... which in turn recovered after administration of thyroid hormone treatment following the [radioiodine] therapy.”
Within the cohort, 14 patients (4.2%) developed thrombocytopenia within 1 year of completing radioiodine therapy; these patients were older, presented with a greater tumor size and received a higher cumulative dose of radioiodine treatment.
“Although the prognosis of DTC patients is favorable, it is important to determine the toxic hematological effects of [radioiodine] in these patients,” the researchers wrote. “Especially for patients with extensive disease, it is vital to maintain bone marrow reserves of sufficient quality for the next stage of treatment. These patients may benefit from the new and promising targeted approach using tyrosine kinase inhibitors that may also cause hematological toxicity.” – by Regina Schaffer
Disclosure: The researchers report no relevant financial disclosures.
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