Active Surveillance for T1bN0M0 Papillary Thyroid Carcinoma

Abstract

Background: Prospective trials of active surveillance for asymptomatic papillary microcarcinoma (T1aN0M0) since the 1990s have shown progression rates of only 5-10%. Late rescue surgery after progression had no deleterious effects on mortality and morbidity. The 2015 American Thyroid Association guidelines approved active surveillance for very low-risk papillary thyroid carcinoma (PTC) as an alternative method to immediate surgery. However, there is no study that evaluates long-term active surveillance for T1b tumors. Methods: A prospective trial of active surveillance with 360 very low-risk PTC (T1aN0M0) patients has been conducted since 1995. Of the 392 T1bN0M0 patients, 61 selected active surveillance over surgery and eventually participated in this trial, while the remaining 331 patients underwent surgery. To find an appropriate management strategy for patients with T1bN0M0 PTC, the outcomes of active surveillance for T1bN0M0 to T1aN0M0 PTC were investigated and compared, and the outcomes of surgery for T1bN0M0 PTC were studied. Results: After a mean of 7.4 years of active surveillance, 29 (8%) T1aN0M0 tumors and four (7%) T1bN0M0 tumors had increased in size ( p = 0.69). Development of lymph node metastasis was seen in three (0.8%) patients and two (3%) patients, respectively ( p = 0.10). No significant difference in progression rate was seen between groups. Among T1bN0M0 tumors, weak calcification and rich vascularity were risk factors for tumorsize increase, and younger age was a predictor for the development of lymph node metastasis. Mean initial tumor size was significantly greater in T1bN0M0 patients who underwent immediate surgery (14.5 -2.8 mm) than it was in patients who chose observation (11.7 -1.1 mm; p < 0.0001). No postoperative recurrence was seen in patients with tumor <15 mm in diameter. Conclusions: Active surveillance is an option for selected patients with T1bN0M0 PTC.

Overdiagnosis of Juvenile Thyroid Cancer

“…The main difference between these 2 models is whether PTMs, once stopping growth, resume proliferation in the elderly. Although data from long-term observation trials of PTMs have been presented, there is no report of a PTM turning into a lethal cancer, or showing anaplastic transformation [19,20]. Furthermore, recent experiences in Korea have shown that surgery to remove PTMs does not result in decreased cause-specific mortality [6].…”

“…In addition, in the young, it is difficult to perform active surveillance, which is now recommended for some PTMs in adults [19,20]. In the case of children, such an observation may last for more than half a century.…”

Low-risk papillary thyroid carcinoma

“…Sakai et al 7 observed three groups in his study. Two of them were active surveillance groups, however the third received surgery at diagnosis.…”

“…The third group was compound of 331 patients with lowrisk T1b PTC that underwent immediate surgery rather than active surveillance management, 84% (279/331) were women, mean age was 51.9 years (SD 12.6; range 17-82), and mean tumor size was 14.5 mm (SD 2.8; range 11-20). Exclusion criteria were based on the low-risk definition as well 3,7 . It is important to note that mean tumor size of T1b immediate surgery group is significantly bigger when compared to T1b active surveillance group.…”

“…All studies followed their patients with clinical examination (e.g., palpation) and medical imaging (e.g., neck US) every 6 or 12 months in order to check for tumor enlargement, development of LNM or distant metastasis. Also, the studies defined "tumor enlargement" as a 3 mm increase or more when compared to the tumor size at diagnosis 5,6,7 .…”