Is tumor size the best predictor of outcome for papillary thyroid cancer?

There are many risk classification schemes that determine both treatment and outcome for patients with papillary thyroid cancer. Most of these formulas often utilize tumor size as the key predictor of outcome. Furthermore, there is no clear consensus regarding the treatment of small papillary cancers. Therefore, we reviewed our experience in order to determine which factors best predict outcome for papillary thyroid cancer. In addition, we sought to establish a tumor size threshold beyond which papillary cancers require treatment.

From May 1994 to October 2004, 174 patients underwent surgery for papillary thyroid cancer (PTC) at our institution. These patients were divided into five groups based on tumor size. The data from these groups were analyzed utilizing ANOVA, Chi-square and linear regression analysis.

The mean age of the patients was 42 +/- 1 years and 126 (72%) were female. Mean tumor size was 17.2 +/- 1.1 mm. The overall outcome was quite good with a survival rate of 97% and a recurrence rate of 12%. On univariate analysis, there was no difference amongst the groups in regards to age or gender. However, there was a significantly higher incidence of lymph node metastasis amongst those with the largest tumors. Consequently, those patients with the largest tumors were treated more aggressively, with 75% undergoing total thyroidectomies and 85% receiving radioactive iodine therapy. However, on univariate and multivariate analysis, tumor size was not shown to correlate with higher recurrence. Rather, the only factor associated with a greater recurrence rate was the presence of lymph node metastases.

At our institution, the recurrence rates for PTC were similar for all sizes of tumors. Furthermore, presence of metastatic disease at the time of diagnosis, rather than tumor size, seems to be a better predictor of recurrence and outcome.