A novel classification system for patients with PTC: addition of the new variables of large (3 cm or greater) nodal metastases and reclassification during the follow-up period.

BACKGROUND

Several factors have been proven to be useful for classifying patients with papillary thyroid carcinoma (PTC) into either low- or high-risk groups. However, the relative importance of prognostic factors, including lymph nodal metastasis, remains unclear.

METHODS

A total of 604 patients who underwent initial surgery for PTC (diameter of tumor>1 cm) were analyzed. The mean duration of follow-up was 10.7 years.

RESULTS

By multivariate analysis for disease-specific survival, distant metastasis was the only significant risk factor (risk ratio=65.1) for younger patients (age<50). For older patients (age> or =50), distant metastasis (risk ratio=6.7), extrathyroidal invasion (risk ratio=2.4), and large nodal metastasis (> or =3 cm; risk ratio=5.3) had relative importance. From the results, younger patients with distant metastasis and older patients with any of the 3 factors were defined as at high risk, whereas the other patients were defined as at low risk. Overall, 106 patients at high risk (18%) and 498 patients at low risk (83%) had 10-year survival rates of 69% and 99%, respectively. Only 3 patients of the low-risk group died from the disease. Among postoperative factors, recurrence within 3 years after initial surgery was the most important risk factor for cancer death. Of the high-risk group, patients with a disease-free interval of >3 years showed an excellent outcome (96% of a 10-year survival rate), similar to patients in the low-risk group.

CONCLUSIONS

A novel classification system, in which large nodal metastases and postoperative reclassification were added, was devised. This was useful for choosing proper therapeutic strategies, offering rational information, and determining adequate postoperative follow-up schemes for individual patients with PTC.