OP47 – Active surveillance for T1bN0M0 papillary thyroid carcinoma

      Sakai, Toshihiko1; Sugitani, Iwao1, 2; Ebina, Aya1; Fukuoka, Osamu3; Toda, Kazuhisa1; Mitani, Hiroki1; Keiko, Yamada4 1 Division of Head and Neck, Cancer Institute Hospital, Tokyo, Japan 2 Department of Endocrine Surgery, Nippon Medical School, Tokyo, Japan 3 Department of Otolaryngology, University of Tokyo Hospital, Tokyo, Japan 4 Department of Ultrasonography, Cancer Institute Hospital, Tokyo, Japan   Background/Purpose: Prospective trials of active surveillance (AS) for asymptomatic papillary microcarcinoma (T1aN0M0) since the 1990s have shown progression rates of only 5-10%. Late salvage surgery after progression had no deleterious effects on mortality and morbidity. The 2015 American Thyroid Association guidelines approved AS for very low-risk papillary thyroid carcinoma (PTC) as an alternative to immediate surgery. However, no studies published to date have evaluated AS for T1b tumors. Methods: We have been conducting a prospective trial of AS for 421 patients with very-low-risk PTC since 1995. This trial included 61 patients with T1bN0M0 tumor who selected observation over surgery. During the same period, 331 patients underwent surgery for T1bN0M0 PTC. Results: After a mean of 7.4 years of AS, 29 T1aN0M0 tumors (8%) and 4 T1bN0M0 tumors (7%) had increased in size (p=0.69). Development of lymph node metastasis (LNM) was seen in 3 patients (0.8%) and 2 patients (3%), respectively (p=0.10). No significant difference in progression rate was seen between groups. Among T1bN0M0 tumors, weak calcification and rich vascularity were significant risk factors for tumor size increase and younger age was a significant predictor for LNM. Mean initial tumor size was significantly greater in T1bN0M0 patients who underwent immediate surgery (14.5±2.8 mm) than 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. Discussion & Conclusion: AS would be admitted for selected T1bN0M0 PTC <15 mm in diameter. References:
    1. Fukuoka O, Sugitani I, Ebina A, et al(2016) Natural History of Asymptomatic Papillary Thyroid Microcarcinoma: Time-Dependent Changes in Calcification and Vascularity During Active Surveillance. World J Surg 40:529-537 doi: 10.1007/s00268-015-3349-1
    2. Ebina A, Sugitani I, Fujimoto Y et al (2014) Risk-adapted management of papillary thyroid carcinoma according to our own risk-group classification system: Is thyroid lobectomy the treatment of choice for low-risk patients? Surgery 156:1579–1589
    3. Sugitani I, Toda K, Yamada K et al (2010) Three distinctly different kinds of papillary thyroid microcarcinoma should be recognized: our treatment strategies and outcomes. World J Surg 44:1222–1231. doi:10.1007/s00268-009-0359-x
    4. Ito Y, Miyauchi A, Kihara M et al (2014) Patient age is significantly related to the progression of papillary microcarcinoma of the thyroid under observation. Thyroid 24:27–34
    5. Ito Y, Miyauchi A, Inoue H et al (2010) An observational trial for papillary thyroid microcarcinoma in Japanese patients. World J Surg 34:28–35. doi:10.1007/s00268-009-0303-0


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