Active surveillance using ultrasonography could be a key to delaying surgical treatment for low-risk papillary thyroid cancer (PTC)—the most common type of thyroid cancer.

A group of researchers, led by Michael Tuttle MD, an endocrinologist at New York's Memorial Sloan Kettering Cancer Center, recently published findings in JAMA Otolaryngology-Head & Neck Surgery confirming active surveillance of PTC prevents the overtreatment of tumors that would otherwise remain indolent and asymptomatic.

“Because PTCs appear to follow predictable growth kinetics under active surveillance, serial measurements of tumor volume hold significant promise in triaging patients to observation versus surgery,” the authors wrote.

The study established that incorporating 3D measurements of tumor volume allowed for earlier identification of growth in all cases studied. Information gathered from 3D images allowed for more precise readings in patients undergoing active surveillance and, if needed, intervention.

Over the course of 25 months, researchers studied PTC in 291 patients whose tumors were considered low risk. Patients with tumors that grew more than three millimeters were recommended for surgery.

The study marked a tumor diameter growth of three millimeters or more in 11 patients. After two years of active surveillance, 2.5 percent of tumors grew to three millimeters—making surgery a possibility. And after five years, 12 percent of patients’ tumors increased to three millimeters. All tumors experiencing three millimeters or more growth revealed a volume increase greater than 50 percent.

None of the patients’ tumors spread outside the thyroid. The volume of the tumor increased by more than 50 percent in 36 patients, remained unchanged in 229 patients and decreased by more than 50 percent in 19 patients. The change in volume could not be determined in seven of the remaining patients.

The findings confirmed that only 10 to 15 percent of small PTCs will increase in tumor diameter by three millimeters during the first five years of active surveillance and that increase in tumor size is more likely in younger patients.

For now, evident active surveillance is necessary to prevent the overtreatment of PTC tumors; however, the authors believe additional studies will help to determine the clinical significance of mild growth in PTC diameter and volume, which will further refine the thresholds for intervention.