Development of a Prognostic Score for Papillary Thyroid Carcinoma Incorporating Ki‐67 Labeling Index: MASSIN‐K
Yasuhiro Ito, Masashi Yamamoto, Mitsuyoshi Hirokawa, Hiroo Masuoka, Minoru Kihara, Akihiro Miya, Akira Miyauchi, Takashi AkamizuABSTRACT
Background
We previously demonstrated that the Ki‐67 labeling index (LI), a marker of cell proliferation, strongly predicts prognosis in patients with papillary thyroid carcinoma (PTC). We subsequently developed a prognostic scoring system incorporating Ki‐67 LI.
Methods
We enrolled 8540 patients with PTC who underwent curative surgery (median follow‐up, 8.7 years). Multivariate Cox regression analysis identified prognostic factors, and regression coefficients from the final models were rounded to generate integer‐based scores.
Results
To date, 368, 125, and 22 patients experienced local recurrence (LR), distant recurrence (DR), and carcinoma‐related death, respectively. Scores were assigned for age, tumor size, N factor, M factor, Ki‐67 LI, and extrathyroidal/extranodal invasion (Ex). The LR score comprised sex (0 or 1), age (0, 1, or 2), T (0 or 2), N (0, 2, or 4), Ki‐67 (0 or 4), and Ex (0, 1, or 2). Ten‐year LR‐free survival rates for low (≤ 2), intermediate (3–4), and high (≥ 5) scores were 98.1%, 95.2%, and 84.5%, respectively ( p < 0.001). The DR score comprised sex (0 or 1), age (0 or 3), T (0 or 3), N (0, 2, or 4), Ki‐67 (0 or 5), and Ex (0, 3, or 6). Ten‐year DR‐free survival rates for low (≤ 5), intermediate (6–9), and high (≥ 10) scores were 99.6%, 97.9%, and 85.8%, respectively ( p < 0.01). The cause‐specific survival (CSS) score for the entire series comprised sex (0 or 2), age (0 or 4), N (0, 1, or 2), M (0 or 4), Ki‐67 (0 or 3), and Ex (0, 1, or 2). Ten‐year CSS rates for low (≤ 3), intermediate (4–5), and high (≥ 6) scores were 100%, 99.8%, and 97.1%, respectively ( p < 0.01). In M‐negative patients, the CSS score comprised sex (0 or 1), age (0 or 3), N (0, 1, or 2), Ki‐67 (0 or 3), and Ex (0, 1, or 2). The 10‐year CSS rate for high‐score (≥ 6) patients was 96.9%, significantly lower than those for low‐ and intermediate‐score patients (100% and 99.8%, respectively; p < 0.01).
Conclusions
MASSIN‐K, a prognostic scoring system incorporating Ki‐67 LI, showed good prognostic discrimination in patients with PTC. External validation is required as a further study.