Miriam E. Tucker

April 19, 2013

CHICAGO — Although survival following papillary thyroid cancer (PTC) is high, a small but significant number of recurrences and deaths occur decades after diagnosis, a long-term study has found.

The 3 most commonly cited studies on PTC have median follow-up times of 11, 15, and 15.7 years. In contrast, the new research reports on a median of 27 years of follow-up in a cohort of 269 PTC patients, said Raymon H. Grogan, MD, assistant professor of surgery and director of the endocrine surgery research program at the University of Chicago Medicine, Illinois. He presented the findings this week here at the American Association of Endocrine Surgeons 2013 Annual Meeting.

"Papillary thyroid cancer in general has a very good prognosis… Also, papillary thyroid cancer rates have been rising steadily for several decades worldwide. The combination of these 2 factors means that more and more people will be living with [the diagnosis] for several decades. This is why we think our study is important," Dr. Grogan told Medscape Medical News.

Indeed, added session moderator Dr. Elizabeth G. Grubbs, from the University of Texas MD Anderson Cancer Center, Houston, "what's important from the study in my mind is that some of these recurrences and events happen many years out, so there isn't a time frame where you say you don't need to follow people or worry any more. This helps us in our understanding of how we need to follow these patients as clinicians and how we need to counsel patients."

Majority of Recurrences and Deaths Occur in First Decade

Dr. Grogan reported on patients diagnosed at his institution between 1968 and 1988 and noted that data on these individuals were first published in 1990 with a median of 11 years of follow-up (J Clin Endocrinol Metab. 1990; 71:414-424).

Overall survival among the 269 patients was 95% at 5 years postdiagnosis, 94.7% at 10 years, 92% at 20 years, 91% at 30 years, and 86% at 40 years.

After about 10 years, the risk of dying from causes other than the cancer begin to surpass the cancer-related deaths, "showing again that survival rates for PTC are pretty good," Dr. Grogan commented.

The reason for the drop in survival between 30 and 40 years isn't entirely clear but might have to do with the PTC gaining additional genetic mutations and becoming more aggressive, he suggested, adding, however, "We do not have any proof of that, so at this point it is just speculation."

Recurrence rates were 16% at 5 years, 20% at 10 years, 27% at 20 years, 30% at 30 years, and 33% at 40 years.

Although the majority of recurrences and PTC-related deaths occurred in the first decade (68% and 58%, respectively),11% of all recurrences and 17% of all PTC-related deaths occurred more than 20 years after the initial diagnosis, with 4% and 13%, respectively, occurring more than 30 years out.

On multivariate analysis, factors associated with reduced survival were the presence of metastases and of positive lymph nodes and older age of diagnosis. Factors increasing the risk for recurrence were metastases, positive lymph nodes, tumor size, age, and follicular-variant as opposed to classic PTC.

Total thyroidectomy had no effect on survival in univariate or multivariate analysis, while it was associated with decreased recurrence on univariate but not multivariate analysis. Radioactive iodine had no impact on survival or recurrence on either analysis.

Gender also had no impact on outcomes, Dr. Grogan said.

Follow patients for the remainder of their lives…

Dr. Grogan told Medscape Medical News: "I think the biggest message from our data for physicians is the idea that currently we cannot accurately predict which PTC patients will survive or who will [suffer from recurrence]. Because of this uncertainty, the physicians who primarily care for these patients should have a mechanism in place to allow these patients to be followed for the rest of their life so that recurrences can be identified early and treated appropriately."

Dr. Grubbs praised the study. "Being able to capture those important outcomes, which are relatively rare, takes a diligent long-term study… It's valuable information."

Neither Dr. Grogan nor Dr. Grubbs has reported relevant financial relationships.

American Association of Endocrine Surgeons 2013 Annual Meeting. Abstract 38, presented April 16, 2013.