Clinical behaviors of rare variants of papillary thyroid carcinoma are associated with survival: a population-level analysis

Abstract

Objective

This study was to evaluate the risk factors of survival in patients with columnar cell variant (CCV) and encapsulated variant (ECV).

Materials and methods

The Surveillance, Epidemiology, and End Results database (1988–2013) was used to compare the characteristics of CCV and ECV with those of classic papillary thyroid carcinoma (PTC). Survival was analyzed by the Kaplan–Meier method, the log-rank test, and Cox multivariate regression. Multivariate logistic regression was used to further analyze lymph node metastases and distant metastasis. There were 765 CCV, 529 ECV, and 39,035 PTC patients. ECV tumors were similar to PTC in terms of overall survival, disease-specific survival, age, sex, and distant metastasis.

Results

Compared with PTC, CCV tumors tended to be larger, with a higher incidence rate among males and in patients ≥65 years of age. CCV was associated with higher rates of extrathyroidal extension, multifocality, lymph node examinations, and lymph node and distant metastases (p<0.0001). Significant differences were found in 10-year overall survival (97.14% vs 89.15%, p<0.0001) and disease-specific survival (99.08% vs 93.07%, p<0.0001) between PTC and CCV. In CCV, distant metastasis (hazard ratio 5.125, p<0.0001) and lymph nodal metastasis (hazard ratio 2.152, p=0.032) predicted a poor prognosis. After adjustment, distant metastasis was independently associated with age ≥65 years, and lymph nodal metastasis was independently associated with female sex (odds ratio [OR] 0.341 [0.234–0.496]), extrathyroidal extension (OR 2.453 [1.368–4.397]), multifocality (OR 2.168 [1.318–3.569]), size >20 mm, ≤40 mm (OR 1.851 [1.170–2.928]), and size >40 mm (OR 1.847 [1.088–3.136]).

Conclusion

ECV appears to have a similar prognosis to PTC, while CCV has a worse prognosis than classic PTC. Treatment with external beam radiotherapy and radioactive implants should be conducted carefully in patients with CCV.

Keywords:

• columnar cell
• encapsulated variant
• disease-specific survival
• external beam radiotherapy
• distant metastasis
• SEER

Acknowledgments

This study used the SEER database. The interpretation and reporting of these data are the sole responsibilities of the authors. The authors acknowledge the efforts of the applied Research Program, NCI; the Office of Research, Development and Information, and the Surveillance, Epidemiology and End Results (SEER) Program tumor registries in the creation of this database.

Author contributions

SW conceived and designed the study, CJ performed data collection and analysis, TC helped with construction and manuscript writing, JL contributed to the discussion, XZ supervised this data, SH contributed to the discussion, SL interpreted the data, and JW participated in the design of the study. All authors contributed toward data analysis, drafting and revising the paper and agree to be accountable for all aspects of the work.

Disclosure

The authors report no conflicts of interest in this work.