Predicting outcome in papillary thyroid carcinoma: development of a reliable prognostic scoring system in a cohort of 1779 patients surgically treated at one institution during 1940 through 1989.

BACKGROUND: Multivariate analyses in papillary thyroid carcinoma (PTC) have shown that age, tumor size, local invasion and distant metastasis are independent predictive variables. This study attempted to define a reliable prognostic scoring system for predicting PTC mortality rates with 15 candidate variables that included completeness of primary tumor resection but excluded histologic grade and DNA ploidy.
METHODS: The study group comprised 1779 patients with PTC (followed up for > 26,000 patient-years), divided by treatment dates into 1940 to 1964 (n = 764) and 1965 to 1989 (n = 1015). Cox model analysis and stepwise variable selection led to a prognostic model initially derived from the training set (n = 764). The initial prognostic score was thereafter validated externally with the later (1965 to 1989) "test" data set.
RESULTS: The final model included five variables abbreviated by metastasis, age, completeness of resection, invasion, and size (MACIS). The final prognostic score was defined as MACIS = 3.1 (if aged < or = 39 years) or 0.08 x age (if aged > or = 40 years), + 0.3 x tumor size (in centimeters), +1 (if incompletely resected), +1 (if locally invasive), +3 (if distant metastases present). Twenty-year cause-specific survival rates for patients with MACIS less than 6, 6 to 6.99, 7 to 7.99, and 8+ were 99%, 89%, 56%, and 24%, respectively (p < 0.0001).
CONCLUSIONS: Because the five variables needed for MACIS scoring are readily available after primary operation, such a prognostic system could have widespread applicability in assessment of PTC.