CORONADO, CALIF. – Patients with differentiated thyroid cancer who were younger than age 45 years were more likely to undergo total or near-total thyroidectomy and to receive radioactive iodine, compared with their older counterparts, a large registry analysis demonstrated.
In addition, younger patients were more likely to be Hispanic and female and to have papillary carcinoma, lead study author Dr. Thomas J. Semrad reported during the annual meeting of the American Thyroid Association.
“Not much is known about how treatment administration differs between younger and older patients with thyroid cancer,” Dr. Semrad of the division of hematology/oncology at the University of California, Davis, Comprehensive Cancer Center, Sacramento, said in an interview. “Some data suggest that perhaps patients younger than age 15 years may respond better to radioactive iodine and may present with more advanced disease. But not much is known about how they’re treated.”
To find out, Dr. Semrad and his associates used the California Cancer Registry to identify 23,629 patients who were diagnosed with differentiated thyroid cancer between 2004 and 2011. They divided the patients into two cohorts: younger (defined as those younger than 45 years) and older (those 45 years or older). Treatment variables of interest included total or near-total thyroidectomy, other types of thyroid surgery, and the administration of radioactive iodine (RAI). The researchers compared the descriptive statistics between the two groups and used univariate and multivariate logistic regression to identify predictors of the treatment administered.
Compared with older patients, younger patients were significantly more likely to be Hispanic (33% vs. 22%), to be female (83% vs. 75%), to have papillary carcinoma (93% vs. 91%), and to have lymph node involvement (32% vs. 20%, all P < .0001).
Overall, the majority of patients (86%) underwent total or near-total thyroidectomy, but the surgery was slightly and significantly more common in younger patients, compared with their older counterparts (88% vs. 85%, P < .0001). Younger patients also were significantly more likely to receive RAI (55% vs. 49%, P < .0001).
On multivariate analysis, statistically significant predictors of total thyroidectomy, compared with other thyroid surgery, included younger age (odds ratio, 1.193); higher socioeconomic status (OR, 1.263, for higher-middle SES and OR, 1.325, for highest SES); higher T stage (OR, 1.848, for T2; OR, 2.473, for T3; and OR, 2.908, for T4); and papillary histology (OR, 0.349).
At the same time, statistically significant predictors of RAI administration included younger age (OR, 1.116); higher SES (OR, 1.410, for higher-middle SES and OR, 1.307, for highest SES); more advanced T stage (OR, 2.194 for T2; OR, 2.084, for T3; and OR, 1.527, for T4); node positivity (OR, 0.481), and total thyroidectomy (OR, 3.76).
“As we expected, the younger population was more likely to be female, but we did find that the younger population was also more likely to be Hispanic,” Dr. Semrad said. “We don’t know if they were native Hispanics or if it has something to do with immigration rates.”
Dr. Semrad acknowledged certain limitations of the study, including the risk of misclassification bias in registry data, the lack of details about surgical procedures performed, and the fact that the radioiodine dose was not captured.
“We have data regarding the T stage, the nodal stage, and the number of lymph nodes examined, but we don’t have some of the finer histology data,” he said.
Even so, he characterized the findings as “provocative in suggesting that perhaps our treatment patterns in younger patients are different. With more aggressive surgery and more use of radioactive iodine, that can have potential implications in terms of long-term side effects and follow-up.”
The researchers said they plan to use linked administrative data to analyze initial and subsequent thyroid surgical procedures in this patient population.
The study was supported by a grant from the National Institutes of Health. Dr. Semrad reported having no relevant financial disclosures.
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