Photo courtesy of ESMO
Session at ESMO 2017
MADRID—New research suggests patients with well-differentiated thyroid cancer (WDTC) are more likely to develop acute myeloid leukemia (AML) if they receive radioactive iodine (RAI) after surgery.
Of the WDTC patients studied, those who only underwent surgery were less likely to develop AML.
WDTC patients who did develop AML had a far worse prognosis than WDTC patients without AML and patients with de novo AML.
These results were presented at the ESMO 2017 Congress (abstract 996O).
Researchers already knew that the risk of developing leukemia is increased after radiation and RAI treatment for WDTC.
However, the risk of AML following RAI treatment in WDTC survivors had not been fully characterized, according to Remco J. Molenaar, an MD/PhD candidate at Academic Medical Centre in Amsterdam, Netherlands.
Therefore, Molenaar and colleagues reviewed data from all 18 registries in the Surveillance Epidemiology and End Results database for WDTC cases treated solely with surgery or by surgery and RAI.
The researchers identified 148,215 patients who were diagnosed with WDTC from 1973 to 2014. Fifty-five percent were treated with surgery alone, and 45% were treated with surgery and RAI.
The median follow-up was 4.3 person-years. AML occurred in 44 patients in the surgery-only arm and 56 patients in the RAI arm.
A comparison to the background rates in the general population showed that patients receiving surgery plus RAI had an increased risk of developing AML (relative risk=5.6; 95% confidence interval [CI] 3.8, 8.1; P<0.0001), after correcting for age, sex, and year of WDTC diagnosis.
This risk peaked within the first 3 years following RAI and subsequently regressed to baseline rates.
In multivariate analysis that corrected for sex and WDTC tumor size, 3 variables emerged as independent predictors of AML development. There was an increased risk of AML associated with:
- Patient age (hazard ratio [HR]=1.03; 95% CI 1.02, 1.05; P<0.001)
- WDTC tumor stage (HR=1.36; 95% CI 1.04, 1.79; P=0.03)
- Receiving RAI after thyroidectomy vs thyroidectomy alone (HR=1.38; 95% CI 1.09, 1.75; P=0.007).
The researchers also found prognosis is significantly poorer in WDTC patients who develop AML following RAI and in patients with spontaneous AML development.
Case-control analyses revealed that WDTC patients who developed AML after surgery and RAI survived one-third as long as matched control patients who were successfully treated for WDTC but did not develop AML. The median overall survival was 7.4 years and 24.4 years, respectively (P<0.0001).
Patients who were diagnosed with AML after RAI treatment also had a significantly worse prognosis than patients with de novo AML. The median overall survival was 1.2 years and 3.5 years, respectively (P=0.004).
The researchers noted that rates of AML in WDTC survivors will likely continue to rise due to the increasing incidence of WDTC, the young ages at which most WDTC diagnoses are made, and the otherwise high survival rates of patients with WDTC.
