*2.5. Postoperative Management and Follow-Up*

Serum calcium and (Parathyroid Hormone) PTH levels were assayed pre- and postoperatively. Postsurgical hypoparathyroidism was defined as PTH < 10 pg/mL following the operation (normal range = 10–65 pg/mL).

Postoperative fibrolaryngoscopy was performed in the case of loss of signal at IONM or in patients experiencing dysphonia after surgery, even in the case of normal signal at IONM.

Hypoparathyroidism and RLN injury were considered permanent if lasting for more than 12 months after surgery.

All patients were referred to an endocrinologist for postoperative management and were stratified in ATA groups for risk of disease recurrence, following the 2009 and then 2015 ATA Guidelines. Radioactive iodine was routinely administrated after total thyroidectomy in case of ATA intermediate and high risk tumors.

Serum thyroglobulin (Tg) and anti-Tg antibodies measurements and neck ultrasound (US) were used for postoperative evaluation. During initial follow-up, serum Tg and anti-Tg antibodies were measured every 6–12 months. More frequent Tg and anti-Tg antibody measurements were performed in ATA high risk patients. In ATA low and intermediate-risk patients that achieved an excellent response to treatment, Tg measurements were repeated every 12–24 months. ATA high risk patients (regardless of response to therapy) and all patients with biochemical incomplete, structural incomplete, or indeterminate response to treatment continued to execute Tg and anti-Tg antibodies measurements at least every 6–12 months for several years.

In patients with DTC of any risk level with significant comorbidity that precluded thyroid hormone withdrawal prior to RAI therapy, recombinant human TSH (rhTSH) preparation was done; these situations included medical or psychiatric conditions that could be acutely exacerbated in the case of hypothyroidism (leading to a serious adverse event) or inability to mount an adequate endogenous TSH response with thyroid hormone withdrawal.

Disease-free status was defined as a no evidence of disease (NED) and included the following features: no clinical evidence of tumor, no imaging evidence of disease by RAI imaging and/or neck US, and low serum Tg levels during TSH suppression (Tg < 0.2 ng/mL) or after stimulation (Tg < 1 ng/mL) in the absence of interfering antibodies.

Disease-free survival was defined as the time elapsed from surgery to the detection of recurrent disease.

For the purpose of this work, risk stratification for disease recurrence was reviewed for every patient that underwent surgery until 2015 and was eventually adapted to the latest ATA guidelines.
