SAN FRANCISCO – Thyroid cancer recurs in almost 40% of elderly patients, and while recurrence is accompanied by an increased mortality risk, this seems to be confined to the subset of patients with papillary thyroid cancer, according to researchers from Penn State Milton S. Hershey Medical Center in Hershey, Pa.
"Elderly patients with follicular disease and recurrence did not have a significantly different risk of death compared to patients without recurrences," said lead author Melissa M. Boltz, D.O., who presented the findings at the annual clinical congress of the American College of Surgeons.
About half of patients who develop recurrent disease will die from this, but little is known about the risk of recurrence. "We questioned whether the implications could be different for the elderly population," she said.
The researchers focused on recurrent well-differentiated thyroid cancer (WDTC) in patients aged 65 years or older and assessed its impact on 1-year and 5-year survival, controlling for patient-, disease-, and treatment-related variables.
From the SEER (Surveillance Epidemiology and End Results), Medicare-linked database, they identified 2,883 patients with primary WDTC treated between 1995 and 2007. They documented recurrence through billing codes, evidence of I-131 treatment, thyroid imaging, or the performance of additional thyroid procedures beyond 6 months of diagnosis. Of these, 1,126 patients (39%) developed recurrent disease, and the recurrent group was not demographically different from the group of patients without recurrence. The majority recurred within the first 2 years of initial treatment, after which the probability of developing recurrence was never more than 45% over 10 years, Dr. Boltz said.
Risk factors associated with recurrence included older age, advanced stage, lack of surgical treatment, and regional disease, she reported.
Regional disease was present in 44% of the recurrent group, vs. only 24% of the nonrecurrent group, and thyroidectomy was performed on 33% vs. 60%, respectively.
At 10 years, of the total thyroid cancer population, 662 (23%) died of some form of cancer with thyroid cancer as the cause of death in 273 (41%).
"In the 1-year landmark analysis, patients with recurrence had a higher risk for cancer-specific mortality within 10 years, versus those without recurrence, and the trend was similar at the 5-year landmark," Dr. Boltz noted.
By histology, patients who recurred with papillary thyroid cancer were significantly more likely to die of thyroid cancer as compared to papillary thyroid cancer patients not experiencing recurrence. Papillary patients who were older, had regional or distant disease, and who did not undergo surgery were also at increased risk for cancer-specific death.
The hazard ratios for thyroid cancer death for papillary thyroid cancer patients were as follows:
• Recurrence: HR, 1.96 (P less than .001).
• Age, 5-year increases: HR, 1.46 (P less than .001).
• Regional disease: HR, 4.90 (P less than .001).
• Distant disease: HR, 16.97 (P less than .001).
• No surgery: HR, 7.98 (P less than .001).
• Treatment other than surgery: HR, 3.47 (P less than 0.001).
In contrast, patients with follicular thyroid cancer had an increase in cancer-specific mortality only in relation to the presence of distant disease (HR, 17.78; P less than 0.001). Older age was also associated with an increase in cancer-specific mortality (HR, 1.24; P = 0.04), but disease recurrence was not (HR 0.58; P = 0.16).
"Unlike papillary cancer, follicular cancer recurrence did not contribute to cancer-specific mortality. The only risks were related to older age and advanced stage," Dr. Boltz reported.
Dr. Boltz cautioned that this study pertained to elderly Medicare patients, and the results should not be generalized to a younger population, in which thyroid cancer is more prevalent.
Dr. Boltz reported no relevant conflicts of interest.
