Patients with papillary thyroid cancers that are limited to that gland are likely to have a favorable outcome regardless of whether they undergo rapid definitive treatment or are simply observed for disease progression, researchers reported.
In an epidemiologic study using Surveillance, Epidemiology, and End Results (SEER) data on more than 35,000 papillary thyroid cancers (PTCs) diagnosed in 1973–2005, 20-year survival was 97% in patients who did not receive definitive treatment within 1 year, compared with 99%—“only 2% better”—in those who did, wrote Dr. Louise Davies of Veterans Affairs Medical Center, White River Junction, Vt., and her associates.
“Papillary thyroid cancers of any size that are confined to the thyroid gland, have no lymph node metastases at presentation, and do not show extraglandular extension are unlikely to result in death due to the cancer. Thus, clinicians and patients should feel comfortable considering the option to observe for a year or longer cancers that fall into this category,” the investigators said.
In an editorial, Dr. Erich M. Sturgis and Dr. Steven I. Sherman of the University of Texas M.D. Anderson Cancer Center, Houston, strongly disagreed with this conclusion, emphasizing that observation “should only be cautiously considered in the most carefully selected cases.” They added, “We would wonder whether the six people who died of their thyroid cancer in this real yet very selected … 'no treatment' group would have agreed that a statistically significant 2% difference in survival was not clinically relevant.”
Dr. Davies and her associates examined the natural history of untreated PTC using SEER data because the number of thyroid cancers detected using new technologies has tripled in the past 30 years, and there is still great uncertainty about whether and how to treat these mostly subclinical lesions.
They identified 35,663 cases of microscopically confirmed, localized PTC diagnosed during the 32-year study period. Only 440 patients (1.2%) did not undergo hemithyroidectomy or total thyroidectomy, with or without irradiation, within 1 year of diagnosis.
The reasons for the decision to forgo treatment were not available. In 216 of the 440 patients, definitive treatment was recommended but not done, and in 165 it was not recommended and not done. Treatment recommendations were not documented for the remaining 59 patients.
After mean follow-up of approximately 8 years for the treated group and 6 years for the untreated group, there was no significant difference between the proportion of thyroid cancer deaths that occurred in the treated group (161 of 35,223 patients, or 0.5%) and the untreated group (6 of 440 patients, or 1.4%). Long-term thyroid cancer–specific survival rates “were nearly identical” at 99% and 97%, respectively, the investigators said.
Survival was not affected by whether treatment had been recommended or not, Dr. Davies and her colleagues said (Arch. Otolaryngol. Head Neck Surg. 2010;136:440–4). In addition, cancer-specific survival was essentially the same whether patients underwent hemithyroidectomy or total thyroidectomy.
For patients with this form of cancer, “survival is so good that it is appropriate to consider whether the risk of complications outweighs the benefits of treatment during discussions about when and how to treat the disease. The risk of permanent hypoparathyroidism and significant damage to laryngeal function have been reported to range from 3% to 5% in large case series,” they noted.
In their invited commentary, Dr. Sturgis and Dr. Sherman disputed these conclusions, noting that readers will be “poorly informed and perhaps misinformed” by the authors' interpretation of their data (Arch. Otolaryngol. Head Neck Surg. 2010;136:444–6).
Disclosures: This study was supported in part by the Department of Veterans Affairs and the Robert Wood Johnson Faculty Scholars Program. No financial conflicts of interest were reported.