P26: Applying 8th edition AJCC guidelines to differentiated thyroid cancer: Stage migration and impact on overall survival

Friday, March 24, 2023

11:36 AM – 11:41 AM

Location: SSO HUB: Breast & Endocrine Zone

Poster Presenter(s)

Heming H. Zhao, MD

Resident Physician
University Hospitals Cleveland Medical Center
Cleveland, Ohio, United States

Disclosure information not submitted.

Author(s)

Heming H. Zhao, MD

Resident Physician
University Hospitals Cleveland Medical Center
Cleveland, Ohio, United States

Disclosure information not submitted.
Lauren M. Drapalik, MD

General Surgery Resident
University Hospitals / Case Western University School of Medicine
Cleveland, Ohio, United States

Disclosure information not submitted.
Richard S. Hoehn, MD

Assistant Professor of Surgery
University Hospitals, Cleveland Medical Center
Cleveland, Ohio, United States

Disclosure(s): No financial relationships to disclose
SW

Scott Wilhelm, MD

Professor of Surgery
Division of Surgical Oncology, University Hospitals Cleveland Medical Center, United States

Disclosure information not submitted.

Disclosure(s):

Richard S. Hoehn, MD: No financial relationships to disclose

Introduction: Papillary and Follicular thyroid cancer (PTC/FTC) also known as well-differentiated thyroid cancer (DTC), make up about 95% of all thyroid cancer. The American Joint Committee of Cancer (AJCC) TNM staging system has been used to predict the prognosis of DTC. In 2016, the AJCC published the 8^th edition staging system that went into effect on January 1, 2018. We aimed to quantify how the 8^th edition affected stage migration patterns and survival prognostic.

Methods: PTC, aggressive variant PTC (aPTC), and FTC patients were selected from NCDB (2004-2017). Staging criteria for the 7^th and 8^th editions were applied to the same cohort to create two groups for comparison of overall survival (OS) by stage. Five- and ten-year OS were estimated using the Kaplan-Meier method. Multivariable Cox proportional hazard models were used to identify prognostic factors associated with OS.

Results: For PTC, aPTC, and FTC, 30%, 33% and 48% of the patients were downstaged in the 8^th compared to the 7^th edition. Five- and 10-year OS were significantly related to stage for both editions (p < 0.05). In all three cohorts, the 8^th edition showed worse stage-specific survival compared to the 7^th edition for most stages (see Table). Unexpectedly, for aPTC, those classified into stage IVb showed better 5-year OS (34.7%) than IVa (21.7%) under the 8^th edition. For FTC, stage IVb showed better 5- and 10-year OS than IVa under the 8^th edition (38.7 vs 12.7% and 13.4 vs 6.4%, respectively). For the PTC cohort, older patients with higher T-stage at diagnosis, Black race, higher Charlson-Deyo score, and positive surgical margins had a worse prognosis that may require more aggressive treatments. For aPTC, older patients with higher T-stage, Black and Hispanic races, and positive margin had a worse prognosis. For FTC, only older age, higher T-stage, and positive margin were predictive of a worse prognosis.

Conclusions: The AJCC 8^th edition staging for DTC resulted in downstaging for 1/3 of cases. For aPTC and FTC in particular, our study indicated that modified staging systems may be warranted to improve the prognostic values of higher stages due to their different disease behaviors.

Learning Objectives:

Summarize the key changes in the 8th edition AJCC TNM staging system.
Verbalize clinical factors found to be associated with worse prognosis for each type of thyroid cancer.
interpret the implications of overall survival analysis for each type of thyroid cancer.