鄭學謙 吳哲維 王凌峰 江豐裕 高雄醫學大學附設醫院 耳鼻喉部 Does concomitant central neck dissection increase the risk of postoperative hypocalcemia in thyroid cancer patients after total thyroidectomy? 鄭學謙 吳哲維 王凌峰 江豐裕 高雄醫學大學附設醫院 耳鼻喉部

Background Hypocalcaemia is one of the most common complications after total thyroidectomy. Concomitant central neck dissection is often performed in patients with thyroid cancer. This study aimed to compare the risk of post-operative hypocalcemia (PH) between the patients with and without concomitant central neck dissection (CND).

Materials and Methods: Patients From January 2011 to April 2018, consecutive 368 thyroid cancer patients with total thyroidectomy were performed by a single surgeon (Chiang, FY) and divided into 2 groups. Group 1 included 158 patients who received total thyroidectomy with concomitant CND. Group 2 included 210 patients who received total thyroidectomy only.

Materials and Methods: Technique of CND Central neck dissection: Removal of the prelaryngeal nodes superiorly, pretracheal nodes inferiorly to the innominate artery, and uni- or bilateral paratracheal nodes inferiorly from the cricoid cartilage to the innominate artery level [1]. Parathyroid glands: Preservation of all parathyroid glands was anticipated. Parathyroid autotransplantation was only performed if the gland was accidentally resected or evaluated to be devascularized. American Thyroid Association Surgery Working Group, American Association of Endocrine Surgeons, American Academy of Otolaryngology- Head and Neck Surgery, et al., Consensus statement on the terminology and classification of central neck dissection for thyroid cancer, Thyroid 19 (11) (2009) 1153-1158.

Total thyroidectomy

CT m was a little bit injured.

Materials and Methods: Measurements Free calcium levels (FCL) were measured at the time points of pre- operation and post-operative 12, 24, 48, and 72 hours. The mean ± 2SD of preoperative FCL was used as normal range (4.2- 5.2 mg/dL). PH was defined as FCL under 4.2 mg/dL on at least two measurements. FCL would be measured at the time points of 2 weeks, 2, 4, 6 and 12 months if PH occurred.

Materials and Methods: Statistical Analysis Proportions were compared using the Chi2 test (Fisher's exact test, two-tailed analysis). Medians were compared using the independent sample t-test (Welch's t-test). P value of <0.05 was considered statistically significant.

Results Of the total 368 patients, hypocalcemia occurred in 92 patients (25%). Temporary hypocalcemia occurred in 88 patients (23.9%). Permanent hypocalcemia occurred in 4 patients (1.1%).

Results Group 1: total thyroidectomy with concomittent CND (n=158) Group 2: total thyroidectomy without concomittent CND (n=210) P value Age, yr, mean ± SD (range) 46.6 ± 13.0 (16-75) 52.9 ± 12.9 (18-85) <.001 Gender, % female 77% 73% .292 Pre-OP FCL, mg/dL, mean ± SD (range) 4.8 ± 0.3 (3.8-6.04) 4.8 ± 0.3 (4.0-5.9) .323 Hypocalcemia, n (%) 49 (31%) 43 (20%) .014 Temporary PH, n (%) 45 (28%) .049 Permanent PH, n (%) 4 (3%) 0 (0%) .033 CND = central neck dissection; SD = standard deviation; OP = operation; FCL = free calcium level Hypocalcemia occurred in 49 patients (31%) in group 1 and 43 patients (20%) in group 2. It showed significant difference of PH rates between the two groups (31% vs. 20%, p value <0.05). No permanent PH occurred in the patients without performing CND.

Group 1: total thyroidectomy with concomittent CND (n=158) Results Group 1: total thyroidectomy with concomittent CND (n=158) Unilateral CND (n=124) Bilateral CND (n=34) P value Age, yr, mean ± SD (range) 47.8 ± 13.9 (16-75) 42.1 ± 12.2 (22-71) .021 Gender, % female 80% 64% .147 Pre-OP FCL, mg/dL, mean ± SD (range) 4.8 ± 0.3 (3.8-6.0) 4.7 ± 0.3 (4.5-5.9) .624 Hypocalcemia, n (%) 37 (29.8%) 16 (47%) .048 Temporary PH, n (%) 36 (29%) 13 (38.2%) .21 Permanent PH, n (%) 1 (0.8%) 3 (8.8%) .032 CND = central neck dissection; SD = standard deviation; OP = operation; FCL = free calcium level; PH = hypocalcemia

Discussion Recent retrospective studies showed that temporary and permanent PH rate after total thyroidectomy were 22.8-28.2% and 2.6-6.8% respectively [2,3]. Cho JN et al. concluded that female gender (P=0.001) and CND (P=0.017) were significant risk factors for post-OP PH [2]. Cho JN, Park WS, Min SY (2016) Predictors and risk factors of hypoparathyroidism after total thyroidectomy. Int J Surg 34:47–52 Falch C, Hornig J, Senne M (2018) Factors predicting hypocalcemia after total thyroidectomy – A retrospective cohort analysis. Int J Surg 55:46-50

Discussion Post-OP PH rate after total thyroidectomy with and without CND was 52% and 21%, respectively [2]. In our study, there was no significant difference in gender between two groups. PH rate after total thyroidectomy was significantly higher in patient received concomitant CND (31% vs. 20%). Cho JN, Park WS, Min SY (2016) Predictors and risk factors of hypoparathyroidism after total thyroidectomy. Int J Surg 34:47–52

Conclusion Concomitant central neck dissection increases the risk postoperative hypocalcemia in thyroid cancer patients after total thyroidectomy. Bilateral CND has higher risk of permanent hypocalcemia. Prophylactic CND is not recommended.

Reference [1] American Thyroid Association Surgery Working Group, American Association of Endocrine Surgeons, American Academy of Otolaryngology- Head and Neck Surgery, et al., Consensus statement on the terminology and classification of central neck dissection for thyroid cancer, Thyroid 19 (11) (2009) 1153-1158. [2] Cho JN, Park WS, Min SY (2016) Predictors and risk factors of hypoparathyroidism after total thyroidectomy. Int J Surg 34:47–52 [3] Falch C, Hornig J, Senne M (2018) Factors predicting hypocalcemia after total thyroidectomy – A retrospective cohort analysis. Int J Surg 55:46-50