Despite an overall increase in the use of radioactive iodine following total thyroidectomy for primary thyroid cancer, there are still significant variations in use among institutions and across demographically different populations.
That variation, however, doesn’t appear to have had much of an impact on disease severity, according to a study published online Aug. 16 in JAMA.
"The recent increase in the incidence of small, low-risk thyroid cancer mandates an understanding of patterns of care in thyroid cancer," wrote lead author Dr. Megan R. Haymart and her colleagues (JAMA 2011;306:721-8).
Moreover, "the significant between-hospital variation in radioactive iodine use suggests clinical uncertainty about the role of radioactive iodine in thyroid cancer management."
Dr. Haymart, of the University of Michigan, Ann Arbor, and her coauthors analyzed the cases of 189,219 patients with primary thyroid cancer who underwent total thyroidectomy between 1990 and 2008. Data were culled from the National Cancer Database, which captures close to 85% of all thyroid cancers in the United States, according to the investigators.
They found that in 1990, 1,373 of 3,397 patients with the diagnosis received radioactive iodine (40%).
By 2008, that number had jumped to 11,539 of 20,620 cases (56%) – a significant increase (P less than .001).
The authors then conducted a subgroup analysis involving 85,948 patients diagnosed between 2004 and 2008, in order to "define the most contemporary practice patterns." They found that "younger age and absence of comorbidity were associated with a small but significantly greater likelihood of receiving radioactive iodine after total thyroidectomy."
Younger patients (aged 44 years and less) had an odds ratio of 2.15 for receiving the treatment compared with patients aged 60 years and older (95% confidence interval, 2.04-2.26).
Similarly, patients with a Charlson-Deyo comorbidity index score of 0 registered an OR of 1.19 for receiving radioactive iodine following thyroidectomy, compared to patients with scores of 2 or greater (95% CI, 1.07-1.35).
Factors significantly associated with a lower rate of radioactive iodine use were female sex (OR, 0.87; 95% CI, 0.84-0.91), African American race (OR, 0.83; 95% CI, 0.77-0.89), and the absence of private/government insurance (OR, 0.84; 95% CI, 0.81-0.88).
By comparison, disease severity appeared to play less of a role in treatment patterns. There was a significant difference between radioactive iodine use between American Joint Committee on Cancer designation stage I and stage IV (OR for stage I vs. stage IV, 0.34; 95% CI, 0.31-0.37). However, no difference in use existed between stage II and stage IV (OR for stage II vs. stage IV, 0.97; 95% CI, 0.88-1.07). Nor was there a significant difference in use between stage III and stage IV (OR, 1.06; 95% CI, 0.95-1.17).
The number of cases of post-thyroidectomy thyroid cancers seen at a particular institution per year also affected the use of radioactive treatment. Compared with high-volume institutions, defined as treating 35 or more cases per year, there was significantly less use of radioactive iodine at low-volume centers, treating 6 or fewer cases per year (OR, 0.44; 95% CI, 0.33-0.58) and medium-volume centers, treating 7-11 cases per year (OR, 0.62; 95% CI, 0.48-0.80).
According to Dr. Haymart and her colleagues, the conflicting use patterns are not easily explained, although some uncertainty may be due to a lack of clinical trials, as well as previous conflicting, single-institution studies. "Because of limited clinical evidence, clinical guidelines have left radioactive iodine use to physician discretion in many cases," they wrote.
"In the interest of curbing the increasing health care costs and preventing both overtreatment and undertreatment of disease, indications for radioactive iodine should be clearly defined and disease severity should become the primary driver of radioactive iodine use," they said.
The authors reported no potential conflicts of interest. The study was funded by a grant to Dr. Haymart from the National Institutes of Health.