Tuttle RM, et al. - This study entailed the elucidation of the kinetics of papillary thyroid cancer (PTC) tumor growth during active surveillance. The findings unveiled low rates of tumor growth during active surveillance in a US cohort, with PTCs measuring 1.5 cm or less. Serial measurement of tumor volumes could enable early detection of tumors, persistently growing and thereby informing the timing of surveillance imaging and therapeutic interventions.

Methods

• The eligible candidates included 291 patients undergoing active surveillance for low-risk PTC (intrathyroidal tumors ≤1.5 cm) with serial tumor measurements via ultrasonography.
• It was conducted at a tertiary referral center in the United States.
• Active surveillance was included as the intervention.
• The main measure consisted of the cumulative incidence, rate, and magnitude of the change in tumor diameter or volume, along with the inter-relations with patient and tumor characteristics.

Results

• 219 (75.3%) enrollees were women; mean (SD) age was 52 (15) years, among the 291 patients.
• During a median (range) active surveillance of 25 (6-166) months, growth in tumor diameter of 3 mm or more was observed in 11 of 291 (3.8%) patients, with a cumulative incidence of 2.5% (2 years) and 12.1% (5 years).
• There were no regional or distant metastases during active surveillance.
• 3-dimensional measurements of tumor volume aided in earlier identification of growth (median, 8.2 months; range, 3-46 months before increase in tumor diameter), in all the cases.
• Both younger age at diagnosis (hazard ratio per year, 0.92; 95% CI, 0.87-0.98; P=.006) and risk category at presentation (hazard ratio for inappropriate, 55.17; 95% CI, 9.4-323.19; P < .001) dispalyed an independent link with the tendency of tumor growth, in multivariable analysis.
• Among those tumors experiencing volume growth, kinetics exhibited a classic exponential growth pattern, with a median doubling time of 2.2 years (range, 0.5-4.8 years; median r²=0.75; range, 0.42-0.99).