Vol.:(0123456789) 1 3 Annals of Nuclear Medicine https://doi.org/10.1007/s12149-020-01467-6 ORIGINAL ARTICLE An impact of microscopic positive margin on incomplete response after I‑131 treatment in diferentiated thyroid cancer Yutapong Raruenrom 1  · Katanyoo Sawangsri 2  · Charoonsak Somboonporn 1,3  · Daris Theerakulpisut 1  · Nantaporn Wongsurawat 1  · Teeraporn Ratanaanekchai 4 Received: 16 February 2020 / Accepted: 7 April 2020 © The Japanese Society of Nuclear Medicine 2020 Abstract Objective To fnd an impact of microscopic positive margin on incomplete response after initial I-131 therapy in diferenti- ated thyroid cancer. Methods We retrospectively recruited patients with diferentiated thyroid cancer who underwent total thyroidectomy and received the frst dose of radioiodine during January 2014–February 2018. Patients with grossly incomplete tumor resection or distant metastasis at the time of radioiodine therapy were excluded. Thyroid specimens were re-evaluated by one patholo- gist who was blinded to clinical information to determine microscopic margin status. Treatment response was evaluated at 6–12 months after therapy and was categorized according to the 2015 American Thyroid Association guidelines. Univariable and multivariable analyses were used to fnd an association between microscopic positive margin and incomplete response. Results A total of 101 patients (78 females; mean age 50.3 years) were enrolled. Ninety-four patients (93.1%) had papil- lary thyroid carcinoma. Microscopic positive margin was found in 27 patients (26.7%). After the median follow-up time of 10.3 months, incomplete response was observed in 13 patients (48.5%) and 17 patients (23.0%) with positive and negative margins, respectively. Multivariable analysis showed a signifcant association between microscopic positive margin and incomplete response after adjusting for tumor size, ETE, and cervical lymph node metastasis with adjusted odds ratio of 3.04 (95% CI 1.05–8.75, p value = 0.04). Moreover, after adding pre-ablative Tg as a covariate in 69 patients with negative TgAb, positive margin had a trend toward being associated with incomplete response with adjusted odds ratio of 3.43 (95% CI 0.73–16.07, p value = 0.118). Conclusions Microscopic positive margin was found to be signifcantly associated with incomplete response after I-131 therapy in patients with diferentiated thyroid cancer after adjusting for tumor size, ETE, and cervical lymph node metastasis and also had a trend toward being associated with incomplete response after adjusting for pre-ablative Tg. Keywords Thyroid cancer · Microscopic margin · Radioactive iodine treatment · Treatment response Introduction Total thyroidectomy is considered the standard surgical procedure and the mainstay treatment for diferentiated thyroid cancer (DTC). The most important aim of primary thyroid surgery is to eradicate all macroscopic disease [1, 2]. Grossly incomplete primary tumor resection is associ- ated with poor disease-specifc survival in papillary thyroid cancer [3, 4]. Furthermore, patients with macroscopic posi- tive margin after surgery have high risk of recurrent disease and more than half of them have persistent disease following the initial therapy [5–7]. According to the latest American Thyroid Association (ATA) guidelines, persistent disease after total thyroidectomy and radioiodine remnant ablation * Yutapong Raruenrom yutara@kku.ac.th 1 Division of Nuclear Medicine, Department of Radiology, Faculty of Medicine, Khon Kaen University, 123 Mittraphap Highway, Muang, Khon Kaen 40002, Thailand 2 Department of Pathology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand 3 Clinical Epidemiology Unit, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand 4 Department of Otorhinolaryngology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand