Clarity Needed on Which Patients with PTC Can Be Safely Observed

Can localized papillary thyroid cancer (PTC) forgo surgery and be observed?

Background: Recent epidemiologic trends have documented a dramatic increase in the incidence of PTC, much of it due to the overdiagnosis of subclinical PTC. In 2006, the authors published a landmark study demonstrating this increase and raised the question of whether the definition or treatment approach deserves revision.

Study design: Retrospective cohort of incident localized papillary thyroid cancer with comparison of a selected subgroup without treatment (<1.5 percent of the overall cohort) to the cohort overall

Setting: National Cancer Institute’s Surveillance, Epidemiology and End Results (SEER) cancer registry program with data on cause of death from the National Vital Statistics System

Synopsis: Over 35,000 patients with localized PTC undergoing surgery were compared in outcome to a selected subgroup of 440 patients who were observed. While there was a significant difference (2 percent at 20 years) in cancer-specific survival in favor of the treatment group (P<0.001), the authors concluded that this was not clinically significant.

The central limitation is that the conclusion, “Papillary thyroid cancers of any size that are limited to the thyroid gland (no extraglandular extension or lymph node metastases at presentation) have favorable outcomes whether or not they are treated in the first year after diagnosis and whether they are treated by hemithyroidectomy or total thyroidectomy,” is not substantiated by the data and ignores significant existing literature. Namely, the study did not specifically analyze by size, age, sex, family history, radiation exposure or the specific timing or type of treatment. The conclusion seems to suggest that patients may be observed regardless of the presence of numerous well-documented adverse prognostic factors. The registry lacked sufficient medical history, stage, histology and treatment details to allow multivariate adjustment. Additionally, the conclusion, justifying a relatively unselected approach to PTC observation, is based upon a highly selected subset out of a huge national registry. Furthermore, while the differences were statistically significant, the authors interpreted the findings to lack clinical significance.

Bottom line: While it is likely that highly selected patients with PTC can be safely observed, the conclusions of this paper cannot be taken literally because the authors are unable to specify in which patients with localized PTC observation is safe. Surgeons, endocrinologists and ultrasonographers should adhere to national guidelines specifying that most nodules less than 1 centimeter should not be biopsied unless otherwise indicated.

Citation: Davies L, Welch HG. Thyroid cancer survival in the United States: observational data from 1973 to 2005. Arch Otolaryngol Head Neck Surg. 2010;136(5):440-444.