Assess Risk, not Just Stage, for Thyroid Cancer Treatment Planning

Thyroid cancer is one of the fastest growing cancers in the United States, especially in women, according to Bryan Haugen, MD, from the University of Colorado at Denver School of Medicine. The most common form is micropapillary thyroid cancer (MPTC), which has a low death rate when it is treated before it becomes regionalized. Haugen presented this information as part of “Controversies in the Management of Low-risk Thyroid Cancer,” a satellite symposium at the 19th Annual Meeting and Clinical Congress of the American Association of Clinical Endocrinologists.

Staging systems, of which there are several, “are set up for survival only,” he said. Risk stratification is done in the context of staging, but goes beyond it to consider multiple factors, including age, tumor size, histology, extent of resection, involvement of lymph nodes, and distant metastases. “The goal of risk stratification is to improve cancer-related survival, and minimize recurrence, and to minimize morbidity.”

“Not all lymph nodes are created equal,” he continued. Larger nodes or extranodal extensions greatly worsen outcome. A pre-operative neck ultrasound should be done in all patients undergoing thyroidectomy, according to guidelines.

Post-operative serum thyroglobin is also an important aspect of risk assessment. The level of thyroglobin reaches a nadir at six weeks, and then may stabilize. Worsening is a sign that there may be disease recurrence.

Surgeons disagree at times about criteria for determining the degree of resection, according to Greg Randolph, MD, of Harvard Medical School. His bottom line is that, if the tumor is one centimeter or larger, “you get total thyroidectomy. There is a significant improvement in survival and recurrence” with that cutoff.

The vexing problem is what to do about microcarcinomas found in the resected tissue. Almost 10% of patients undergoing thyroidectomy have these identified in their lesion. Many studies suggest that five millimeters provides an important threshold. Morbidity “seems to kick in at the five millimeter or greater size range,” he said. When Randolph sees that, he opts for completion surgery—removal of the remaining thyroid.

“Remnant ablation” refers to the use of radioactive iodine, and is used to treat what the surgeon does not remove. Stephanie Lee, MD, PhD, Associate Professor of Medicine at the Boston University School of Medicine, reviewed decision-making regarding this therapy.

“Management is based on risk assessment, not just staging,” she said. According to standard staging criteria, in which age plays a very large role, “if you are under age 45, you can have distant metastases and still be at stage 2, and that is clearly wrong.” She added, “We can't use just the [American Joint Committee on Cancer] guidelines to tell us if someone should get radioactive iodine or not.”

Newer guidelines, published in the journal Thyroid in 2009, recommend remnant ablation for a wider group of patients. “Bigger tumors, multifocality, invasion, adverse histology, and adverse risks all increase the likelihood of giving radioactive iodine,” Lee said. Ablation is not recommended when all foci are less than 1 cm and the patient has no high risk features.

The benefits of including risk stratification in decision-making are a possible reduction in morbidity and mortality, a reduction in recurrence in some patients, and an improvement in long-term surveillance of significant risk recurrence in most patients, she said.

This satellite symposium was sponsored by Genzyme and presented at the 19th Annual Meeting and Clinical Congress of the American Association of Clinical Endocrinologists