Although radioiodine therapy can lower levels of platelets, white blood cells and hemoglobin in some older adults with differentiated thyroid cancer, the therapy does not suppress marrow to a clinically significant degree, according to findings published in Thyroid.
“Management of elderly patients with differentiated thyroid cancer poses a unique challenge,” Eyal Robenshtok, MD, an endocrinologist at the Endocrinology Institute of Rabin Medical Center in Petah-Tikva, Israel, and colleagues wrote. “While advanced age is an adverse prognostic factor requiring a more aggressive therapeutic approach, treatment of the elderly is often complicated by comorbidities, which increase the risk of surgery, radioiodine treatment and local or systemic therapies.”
In a retrospective study, Robenshtok and colleagues examined electronic medical records of 122 adults (mean age, 76 years; 75% women) aged at least 70 years with differentiated thyroid cancer. From these records, which were from Rabin Medical Center, the researchers confirmed that each patient had a total thyroidectomy and received at least 30 mCi during radioiodine treatment. Complete blood counts in the year before and after radioiodine therapy were identified as well.
Among the cohort, 88% of patients received a dose of at least 100 mCi across 153 total radioiodine treatments, and the average dose was 183.6 mCi, according to the researchers. Compared with before treatment, hemoglobin in women fell 3% (P = .01) whereas among all patients, white blood cells fell 13% (P < .001) and platelets fell 10% (P < .001) in the first 3 months after radioiodine treatment. The researchers noted that after at least 1 year, these measures still met reference ranges despite continuing to be lower than at baseline. In addition, there was a 16% drop in platelets, a 17% drop in white blood cells and a 2.3% drop in hemoglobin compared with baseline for patients who received a dose of at least 150 mCi (P < .01 for all). However, no association was observed between treatment frequency or radioiodine dose and marrow suppression, the researchers reported.
“The results were surprising, as previous safety thresholds (which were determined based on calculated bone marrow exposure) proved to be too low, and in patients who received high activities and high cumulative dose, no clinically significant bone marrow suppression was noted,” Robenshtok told Endocrine Today, noting in the study that the American Thyroid Association previously recommended avoiding radioiodine doses of more than 150 mCi in patients aged 70 years and older. “The results of the study may benefit patients by allowing a more aggressive therapeutic approach in elderly patients with advanced disease.” – by Phil Neuffer
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Eyal Robenshtok, MD, can be reached at email@example.com.
Disclosures: The authors report no relevant financial disclosures.