Hemithyroidectomy Versus Total Thyroidectomy for Sporadic Medullary Thyroid Cancer: A Chinese Nationwide Large-Scale Cohort Study

Background: Medullary thyroid cancer (MTC) is a rare thyroid malignancy, with 70% to 80% of cases being sporadic (sMTC). Current guidelines recommend total thyroidectomy (TT) for all preoperatively suspicious sMTC, though there has been increasing support for reducing the surgical extent in recent years. However, relevant data are limited. This study aimed to comprehensively evaluate the safety of hemithyroidectomy (HT) in sMTC. Patients and Methods: This study included 797 patients with MTC who received curative-intent initial surgery at 19 participating referral centers. Genetic testing was performed to identify disease heredity. We evaluated the safety of HT in sMTC across 5 aspects: (1) prevalence of occult bilateral foci, (2) prevalence of contralateral lobe recurrence, (3) biochemical response, (4) structural recurrence-free survival (SRFS), and (5) overall survival (OS). Results: Of the 797 patients, 648 were genetically confirmed as having sMTC. HT and TT were performed as the index surgery in 232 (35.8%) and 416 (64.2%) patients, respectively. In the TT group, bilateral foci were found in 34 (8.2%) patients, of whom only 10 (2.4%) had sonographically occult foci, and of these, only 3 (0.72%) had a maximal tumor size ≤2 cm. In the HT group, only 1.7% (4/232) had recurrence in the preserved lobe, with only 1 (0.43%) having a maximal tumor size ≤2 cm. After propensity score matching, 230 pairs of patients were included in further analysis. No significant differences were found in OS (log-rank: P=.484; Cox regression: P=.380), SRFS (log-rank: P=.914; Cox regression: P=.309), or biochemical response (chi-square: P=.744; logistic regression: P=.818) between the 2 groups. Subgroup analyses showed that HT conferred comparable structural and biochemical outcomes with TT in small (≤2 cm) sMTCs, even for patients with high-risk factors such as high preoperative calcitonin, multifocal disease, lymph node metastases, RET^M918T mutation, and desmoplasia. Conclusions: For small unilateral sMTCs, HT may be considered an alternative treatment that does not compromise prognosis while avoiding additional complications associated with TT.