BACKGROUND
Thyroid cancer is a common cancer, especially among women. The vast majority of patients with the most common thyroid of thyroid cancer (papillary thyroid cancer) do very well as thyroid cancer generally tends to have very good outcomes. Many of the thyroid cancers identified are small cancers (<1 cm), called papillary thyroid microcarcinoma. These small cancers are considered low-risk and treatment options often recommend removal of only the lobe containing the cancer (thyroid lobectomy). Recently, the option of following these small cancers with serial thyroid ultrasounds and deferring initial surgery, called active surveillance, has become more common. With active surveillance, surgery is deferred until/unless the cancer grows bigger. Several studies have examined the factors that affect cancer growth during active surveillance.

Young age has been shown to be a predictor of cancer growth. However, other features to quantify this growth, including cancer doubling time (time for the cancer to increase twice the initialthe size) or even a decrease in size have not been evaluated. Using periodic ultrasound studies to determine cancer volume-doubling rate, this study was performed to examine the age-related cancer volume changes of papillary thyroid microcarcinomas under an active surveillance protocol.

THE FULL ARTICLE TITLE
Yamamoto M et al. Tumor volume-doubling rate is negatively associated with patient age in papillary thyroid microcarcinomas under active surveillance. Surgery 2023:S0039-6060(23)00887-5; doi: 10.1016/j. surg.2023.11.022. PMID: 38142143.

SUMMARY OF THE STUDY
Subjects 20 years of age and older, who did not have spread of the cancer outside the thyroid and were not receiving levothyroxine at the time of diagnosis were evaluated. They needed to be followed for more than 1 year and have at least 4 ultrasounds to be included in the study. There was a total of 2219 subjects and they were separated into 3 groups: young (>20 to <40 years), middle-aged (40–59 years), and elderly (>60 years) with 229, 888 and 1012 patients in each group respectively. Serum thyroglobulin antibodies and TSH were evaluated.

Ultrasounds were performed once or twice a year. Surgery was recommended if the primary cancer enlarged by > 3mm or the biopsy of a suspicious lymph node was positive, indicating spread of the cancer outside the thyroid.

Cancer size at diagnosis did not differ among groups. Positive antithyroglobulin antibody levels were significantly more common in the young group, while TSH levels were significantly higher in the elderly group. Surgery was performed in 8.3% of patients for varying reasons. The cancer volume doubling rate was measured as follows: ≥1.0 (rapid growth), ≥0.3 to <1.0 (moderate growth), ≥0 to <0.3 (marginal growth), ≥ –0.1 to <0 (marginal regression), and < –0.1 (clear regression). Rapid or moderate growth occurred in only 6.6% of subjects (140), but differed according to the patient’s age, occurring in 11.3% of young, 7.1% of middle-aged, and 5.0% of elderly patients. Cancer regression occurred in 56.4% of patients (1200) and was seen in 44.5% of young, 55.3% of middle-aged and 60% of elderly patients.

On statistical analysis, being in the middle-aged or elderly group was a negative predictor of cancer enlargement, while being in these groups, having positive anti-TgAb or cancer size 5-9 mm were positive predictors of cancer regression.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
In adult patients undergoing active surveillance of papillary thyroid microcarcinoma, those >40 years were much less likely to have cancer growth and more likely to have cancer regression over time. This study expands upon previous reports showing an overall low risk of cancer growth in patients with papillary thyroid microcarcinoma undergoing active surveillance as well as showing the age effect on growth. It does help patients and their physicians decide upon treatment options when papillary thyroid microcarcinoma is identified. Particularly in older patients with a lower risk of progression and higher rate of regression, active surveillance is an excellent choice. For younger patients, even with the low rate of cancer progression, lobectomy may be preferred to decrease the need for close follow up over the long term. Either way, this study expands upon the information we have to help patients make an informed choice for their care.

— Marjorie Safran, MD

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