Table 1.

Six Most Common Tumor Volume Kinetic Growth Patterns Observed in Patients on Active Surveillance for Papillary Thyroid Cancer or Suspicious for Papillary Thyroid Cancer

Tumor volume kinetic growth pattern	Description	Definition	Implications for clinical management
I	Stable	Tumor volume measurements on observation remain stable (up to ±72% change in tumor volume from baseline)	Continue active surveillance
II	Early increase in tumor volume	Steady exponential growth from time of diagnosis, with a TVDT of <5 years	Consider (1) transition to a therapeutic intervention or (2) continue observation depending on tumor size, location, rate of change, and patient preference
III	Later increase in tumor volume	Steady exponential growth from the time of diagnosis, with a TVDT of ≥5 years	Consider (1) transition to a therapeutic intervention or (2) continue observation depending on tumor size, location, rate of change, and patient preference
IV	Early increase in tumor volume followed by stability	Steady exponential growth from the time of diagnosis followed by transition to stability (tumor volume remains up to ±72% of size after exponential growth window)	Continue active surveillance
V	Stability followed by increase in tumor volume	Initial stability (tumor volume remains up to ±72% of baseline) with a subsequent transition to steady exponential growth	Transition to therapeutic intervention
VI	Decrease in tumor volume	Tumor volume decreases >72% from baseline	Continue active surveillance

TVDT, tumor volume doubling time.