Table 2. Cox Regression for Factors Associated With Change in Tumor Diameter or Volume During Active Surveillance.
| Covariate | Cox Regression, OR (95% CI)a | |
|---|---|---|
| Univariate | Multivariableb | |
| Tumor Diameter Growth of ≥3 mm | ||
| Age, y | 0.93 (0.89-0.98) | 0.92 (0.87-0.98) |
| Appropriateness for AS | ||
| Appropriate | 1 [Reference] | 1 [Reference] |
| Ideal | 0 | 0 |
| Inappropriate | 37.68 (7.13-199.03)c | 55.17 (9.40-323.19)c |
| Sex | ||
| Male | 1 [Reference] | |
| Female | 1.62 (0.58-4.55) | |
| Cytology | ||
| Bethesda category V | 1 [Reference] | |
| Bethesda category VI | 0.81 (0.42- 0.91) | |
| Tumor maximal diameter (continuous) | 1.09 (0.88-1.35) | |
| Tumor maximal diameter (category) | ||
| <1.0 cm | 1 [Reference] | |
| 1.0-1.5 cm | 1.94 (0.41-9.23) | |
| Tumor Volume Growth of >50% During Observation | ||
| Age, y | 0.97 (0.94-0.99) | 0.97 (0.94-0.99) |
| Appropriateness for AS | ||
| Appropriate | 1 [Reference] | 1 [Reference] |
| Ideal | 0.41 (0.06-2.99) | 0.67 (0.08-5.39) |
| Inappropriate | 6.12 (1.45-25.75)c | 10.54 (2.39-46.53)c |
| Sex | ||
| Male | 1 [Reference] | |
| Female | 1.09 (0.74-1.62) | |
| Cytology | ||
| Bethesda category V | 1 [Reference] | |
| Bethesda category VI | 0.49 (0.24-0.99) | 0.43 (0.21-0.87) |
| Tumor maximal diameter (continuous) | 0.94 (0.82-1.07) | |
| Tumor maximal diameter (category) | ||
| <1.0 cm | 1 [Reference] | |
| 1.0-1.5 cm | 0.93 (0.36-2.41) | |
Abbreviation: AS, active surveillance.
a
Empty cells indicate measure was not applicable.
b
On multivariable Cox regression, both patient age at diagnosis and risk category at presentation were independently associated with the likelihood of tumor growth in either diameter or volume.
c
Patients initially classified as inappropriate for active surveillance, either owing to radiographic suspicion for invasion of tumor beyond the thyroid capsule or location of the tumor in close proximity to the trachea or recurrent laryngeal nerve, were more likely to experience an increase in tumor diameter of 3 mm or more and an increase in tumor volume of 50% or more than were patients classified as receiving appropriate surveillance.