The effects of the Union for International Cancer Control/American Joint Committee on Cancer Tumour, Node, Metastasis system version 8 on staging of differentiated thyroid cancer: a comparison to version 7

Abstract

Summary Objective To assess the changes resulting from the changes from UICC/AJCC TNM version 7 to version 8 and to subsequently determine whether TNM version 8 is an improvement compared to previous iterations of the TNM system and other staging systems for differentiated thyroid cancer (DTC) with regard to prognostic power. Design Database study of DTC patients treated in our centre between 1978 up to and including 1 July 2014. Results were compared to our previous comparison of prognostic systems using the same data set. Patients 2257 DTC patients. Measurements Staging in accordance with TNM 7 and TNM 8. Thyroid cancer‐specific mortality; comparison was based on p‐values of univariate Cox regression analyses as well as analysis of the proportion of variance explained (PVE). Results There is a redistribution from stage 3 to lower stages affecting 206 (9.1%) patients. DTC‐related mortality according to Kaplan‐Meier for younger and older patients in TNM 7 had a slightly lower prognostic power than that in accordance with TNM 8 (P = 8.0 10−16 and P = 1.5 10−21, respectively). Overall staging is lower in 627/2257 (27.8%) patients. PVE (TNM 7: 0.29; TNM 8: 0.28) and the P‐value of Cox regressions (TNM 7: P = 7.1*10−52; TNM 8: P = 3.9*10−49) for TNM version 8 are marginally lower than that for TNM version 7, but still better than for any other DTC staging system. Conclusion TNM 8 results in a marked downstaging of patients compared to TNM 7. Although some changes, like the change in age boundary, appear to be associated with an improvement in prognostic power, the overall effect of the changes does not improve the predictive power compared to TNM 7.

Changes in Stage Distribution and Disease-Specific Survival in Differentiated Thyroid Cancer with Transition to American Joint Committee on Cancer 8th Edition: A Systematic Review and Meta-Analysis

“…AJCC staging for thyroid cancer is used for both adult and pediatric populations, and studies were not limited to adults to allow inclusion of greater geographic diversity. Additionally, although some studies were limited to individuals aged 18 years or older [14,19], multiple published studies outside of the U.S. and Europe provided only interquartile range or standard deviation for age without specific age range, precluding determination of minimum included age [13,16,17], and one study reported an age range of 5.8 to 89.5 years [15]. Studies of medullary, poorly differentiated, or anaplastic thyroid cancer were excluded.…”

“…Studies reported staging assignment by clinicians and study authors, including surgeons, endocrinologists, and pathologists, with expertise in thyroid cancer. Review of primary data [13][14][15] and/or direct communication with original study authors [13][14][15][16][17]19] provided additional confirmation of staging completeness and process. All studies except for one included all information needed for assignment of both AJCC-7 and -8 stage for all patients, including data on tumor size, extrathyroidal extension, and nodal and metastatic spread.…”

“…For variables or outcomes with incomplete data, additional information was requested from the original study authors in writing to allow inclusion and optimize the completeness of data collection. Specifically, outcome data for hazard ratios and 10-year DSS were requested from authors of studies for which only a Kaplan-Meier curve for DSS was shown in the published literature [13][14][15][16][17][18][19]. Of such studies, one [18] was excluded because original study authors were unable to provide data for 10-year DSS and hazard ratios (HRs), and therefore data necessary for this meta-analysis could not be obtained.…”

“…Specifically, the summary disease-specific survival HRs in AJCC-8 increase progressively with higher clinical stage. For AJCC-8 classification, the summary HR for stage II was 10.6 (95% CI: 6.68- 15 . Across all stages, the summary HRs were higher in AJCC-8 compared with AJCC-7, although these differences were not statistically significant (Table 2 and Fig.…”

“…The goal of these changes was to improve diseasespecific mortality prediction in patients with DTC, incorporating new data about risk factors for worse survival to better target increased surveillance and adjuvant therapy to patients with higher mortality risk and limit the burden of unnecessary care in lower risk patients [5,7]. Since publication, several reports have compared the performance of the 7th edition of AJCC (AJCC-7) and 8th edition of AJCC (AJCC-8) [13][14][15][16][17][18][19]. Because thyroid cancer patient populations and practice patterns vary geographically and among institutions, we anticipated that this heterogeneity would be reflected in single-center studies evaluating the new staging criteria.…”