BACKGROUND
Papillary thyroid cancer is the most common cause of thyroid cancer. There is some uncertainty about the clinical importance and treatment implications of having multiple cancers in the thyroid (multifocal papillary thyroid cancer) as opposed to a single cancer (unifocal papillary thyroid cancer). In additional, there have been some conflicting reports examining whether multifocal papillary thyroid cancer is a risk factor for thyroid cancer recurrence (i.e. disease coming back after treatment).

This study was performed to examine the independent risk of multifocal papillary thyroid cancer in predicting thyroid cancer outcomes, including cancer recurrence and death. In order to account for potential differences in the characteristics of the patients that could also impact risk of disease outcomes, the authors performed a study in which statistical techniques were used to adjust for differences between groups.

THE FULL ARTICLE TITLE:
Geron Y et al 2019 Multifocality Is not an Independent Prognostic Factor in Papillary Thyroid Cancer: A Propensity Score–Matching Analysis Thyroid 29:513–522.

SUMMARY OF THE STUDY
The authors reviewed the medical records of patients with classical or follicular variant papillary thyroid cancer who were treated at the Assaf Harofeh and Rabin Medical Centers in Israel and registered in a study database since 2005. About half of the patients were followed more than 10 years after thyroid cancer treatment. There were 1039 eligible patients identified, including 51% (534) with multifocal papillary thyroid cancer. There were 690 patients who were included in the statistical analysis who had sufficient data available on clinical features and outcomes. Relevant clinical features accounted for in the analysis included: age, sex, radiation exposure, family history of thyroid cancer, primary cancer size, stage of cancer, blood vessel invasion, American Thyroid Association risk of recurrence level, and the presence of extrathyroidal extension (the cancer invading outside the thyroid into adjacent tissues).

The authors reported that patients with multifocal papillary thyroid cancer were older, more frequently male, had a higher rate of extrathyroidal extension, more lymph node metastases, more advanced disease (stage III/IV), and a higher American Thyroid Association recurrence risk level, compared to those with unifocal papillary thyroid cancer. Furthermore, patients with multifocal papillary thyroid cancer received more aggressive treatment (higher rates of more extensive surgery, radioactive iodine use [and dose], and external beam radiation treatment). By the end of study follow-up, about 13% of patients in the entire study population died (from all causes) and 2% died from thyroid cancer. After the statistical analysis, the presence of multifocal papillary thyroid cancer did not significantly predict papillary thyroid cancer recurrence or death from all cause, but was associated with having persistent thyroid cancer at one year following treatment (detected on imaging or suspected on bloodwork).

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
The authors concluded that the presence of multifocal papillary thyroid cancer is associated with other higher risk disease features at baseline, but is not necessarily a significant independent predictor of long-term thyroid cancer outcomes. Patients diagnosed with papillary thyroid cancer should discuss the features of their disease with their thyroid cancer specialist, to fully understand any potential implications for treatment decision-making.

— Anna M. Sawka, MD, PhD

Table of Contents | PDF File for Saving and Printing