A COMPARISON OF DIFFERENT STAGING SYSTEMS PREDICTABILITY OF PATIENT OUTCOME - THYROID-CARCINOMA AS AN EXAMPLE

BACKGROUND. There is no consensus regarding the comparison of staging classifications. Recently, numerous staging classifications for thyroi d carcinoma have been described. This study was performed to evaluate the relative discriminating ability of these different staging systems . METHODS. A literature review was conducted to identify the available staging classifications used for thyroid carcinoma. To compare the va rious staging classifications, cause specific survival data from a ret rospective review of 382 patients with papillary and follicular thyroi d carcinoma treated at Princess Margaret Hospital were applied to the various staging classifications. The ability of these classifications to distinguish the stage groupings were compared in the following ways : 1) tabulating the numbers of patients within each stage group; 2) co llapsing stage groupings into high and low risk groups and calculating mortality rates at 10 and 15 years; 3) summing observed deviations at 5, 10, and 15 years; and 4) calculating the proportion of variance ex plained (PVE) for each staging classification, using each classificati on separately as a prognostic factor in a Cox regression model. RESULT S. The application of the PVE model, the only method of the four that used statistical inference, showed no statistically significant superi ority of any system over the TNM classification of the American Joint Committee on Cancer (AJCC) and the International Union Against Cancer (UICC) in their ability to discriminate stage groupings. CONCLUSIONS. Because the TNM classification of the AJCC and UICC is universally ava ilable and widely accepted for other disease sites, the authors recomm end it for all reports of the treatment and outcome of patients with t hyroid carcinoma. Individual research groups also may use an alternati ve, validated classification to report results, provided that the outc omes are also reported using the TNM classification to facilitate comp arison between different centers. (C) 1997 American Cancer Society.