Given the excellent prognosis for low-risk papillary thyroid carcinoma (PTC) and, in particular, papillary microcarcinoma (≤1 cm in maximal diameter) confined to the thyroid, active surveillance (AS) is sometimes considered as a disease management option. Initial reports on the association between age at diagnosis and risk of PTC progression in individuals undergoing AS were conflicting. The aim of this review was to evaluate whether age is associated with disease progression in individuals undergoing AS.
A total of 1658 unique citations were screened, and 62 full-text articles were reviewed, including 5 studies. Three studies included exclusively microcarcinomas and 2 included tumors up to 2 cm in maximal diameter. The mean age of participants was 51.0 to 55.2 years in 4 studies reporting this value. The mean or median follow-up was 5 years or more in 3 studies and approximately 2 years in 2 studies.
The pooled risk ratio for tumor growth of 3 mm or more in maximal diameter in individuals aged 40 to 50 years compared with younger individuals was 0.51 when adjusted for confounders (95% CI, 0.29-0.89; 1619 patients, 2 studies), and the unadjusted risk ratio of this outcome for individuals 40 years or older was 0.55 (95% CI, 0.36-0.82; 2097 patients, 4 studies). In adults aged 40 to 45 years, the unadjusted risk ratio for any tumor volume increase compared with younger individuals was 0.65 (95% CI, 0.51-0.83; 1232 patients, 4 studies). The pooled risk ratio for incident nodal metastases in individuals 40 years or older was 0.22 (95% CI, 0.10-0.47; 1806 patients, 3 studies). However, in a secondary analysis, the risk difference was not significantly different. There were no thyroid cancer–related deaths nor incident distant metastases.
This study suggests that older age may be associated with a reduced risk of primary papillary thyroid carcinoma tumor growth under active surveillance. Incident metastatic disease is uncommon during active surveillance.