Transaxillary Endoscopic Thyroidectomy versus Conventional Open Thyroidectomy for Papillary Thyroid Cancer: 5-year Surgical Outcomes

Thyroid cancer is the most common endocrine malignancy and has excellent prognosis.(1) Papillary thyroid cancer (PTC) is most frequent type of thyroid malignancy and its incidence is increasing worldwide and is higher in women.(1, 2) The overall survival rate has remained at 90% to 95% in recent decades according to a SEER (surveillance, epidemiology, and end results) report.(1) Conventional open thyroidectomy has been standard surgical treatment of PTC for more than a century due to it's low morbidity and mortality, but it leaves a noticeable scar in the anterior neck area.(3) Various endoscopic approaches have been adopted to eliminate visible neck scar of the conventional open thyroidectomy, and as a result, the patient's quality of life has improved with excellent cosmetic satisfaction.(1, 4, 5, 6, 7, 8)

The gasless transaxillary endoscopic thyroidectomy is an extra-cervical approach using axillary skin incision, and its early surgical outcomes in low risk PTC patients have shown comparable results to those of conventional open thyroidectomy.(6) However, there is little evidence on its surgical radicality, oncologic safety and long-term outcomes. Therefore, the aim of this study is to compare the 5-year surgical outcomes of endoscopic thyroidectomy and conventional open thyroidectomy.

We reviewed 804 patients with papillary carcinoma who underwent thyroidectomy with prophylactic central compartment neck dissection (CCND) between October 2008 and October 2010 in the Department of Surgery, Seoul St. Mary's hospital, College of Medicine, The Catholic University of Korea. The endoscopic thyroidectomy was considered ineligible for cases with definite extrathyroidal extension and/or clinical nodal metastasis and/or a tumor located in the thyroid dorsal area with posterior capsular invasion or extension to adjacent structures. For the patients who were eligible for endoscopic thyroidectomy, they were offered both options preoperatively and the decisions whether to perform conventional open or endoscopic thyroidectomy were made according to the patient's preference. The surgical procedure of endoscopic thyroidectomy was conducted as described in previous literatures.(7) A total of 703 patients were conventional open thyroidectomy group (OT) and 101patients were endoscopic thyroidectomy group (ET).

Extent of surgical resection was determined according to American Thyroid Association (ATA) guidelines.(9, 10) Prophylactic and/or therapeutic ipsilateral CCND was performed in all cases. The bilateral CCND was performed in a patient with preoperatively diagnosed bilateral cancer. All patients received levothyroxine for thyroid stimulating hormone suppression postoperatively. Radioactive iodine (RAI) ablation was performed according to ATA guidelines, after 6~8 weeks post-thyroidectomy. Serum levels of thyroglobulin (Tg) and neck ultrasonography were regularly checked during follow-up. Postoperative hypocalcemia was assessed in total thyroidectomy cases, transient hypocalcemia was defined as the presence of hypocalcemic symptoms or PTH levels below the normal range with serum total calcium ≤7.5 mg/dl. Hypocalcemia was considered to be permanent if a patient needed calcium supplementation and had PTH levels below normal after 6 months. The injury of recurrent laryngeal nerve (RLN) was assessed as the number of nerve palsy/the number of nerve at risk to adjust the discrepancy of total thyroidectomy/lobectomy in both groups. Transient RLN injury was defined as nerve paralysis confirmed by laryngoscopic examination at postoperative 1 week and considered to be permanent if the nerve paralysis remained after 6 months. The recurrent disease was confirmed by ultrasound-guided fine needle aspiration cytology.

We retrospectively compared the clinicopathological characteristics and surgical outcomes including operation time, complication, surgical completeness and oncologic safety between two groups. All statistical analyses were performed using SPSS ver. 18.0 software (SPSS; Chicago, IL).

The mean follow-up period was 58.3 months (range, 18~81 months). In regards to the patients' clinical characteristics, ET showed significant predominance of young patients and female patients (Table 1). Mean patient age was 48.6 years in OT and 38.7 years in ET, and patients in ET were significantly younger (P<0.001). The proportion of age younger than 45 years was significantly greater in ET (P<0.001). The male to female ratio was 3.8 in OT, however, there was no male patient in ET. Types of operation were significantly different in two groups. In terms of surgical extent, lobectomy and unilateral CCND was performed more frequently in ET. Radioactive iodine ablation after total thyroidectomy was significantly more frequent in OT (62.2% in OT and 41.9% in ET, P=0.010).

Table 1
Clinical and therapeutic characteristics of conventional open and endoscopic thyroidectomy groups

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The histopathological characteristics of the two groups were also compared (Table 2). The mean tumor size was smaller in ET (0.9 cm in OT and 0.6 cm in ET, P<0.001). The incidence of extrathyroidal extension, multiplicity/bilaterality, and intrathyroidal lymphatic invasion was more frequent in OT (P=0.002, P<0.001, and P=0.025, respectively). However, the incidence of vascular invasion and perineural invasion were similar in the two groups (P=0.999 and P=0.999). The T status and TNM stage were more advanced in OT (P=0.003 and P<0.001), whereas the N status was similar between two groups (P=0.053).

Table 2
Histologic characteristics of conventional open and endoscopic thyroidectomy groups

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The early and long-term surgical outcomes were compared between two groups (Table 3). The mean operation time of ET was significantly longer than OT in both lobectomy and total thyroidectomy (89.8 vs 114.0 minutes, P=0.012 and 104.2 vs 141.1 minutes, P<0.001, respectively). In terms of surgical completeness, the total number of retrieved central lymph nodes was greater in OT in unilateral CCND (7.6 vs 5.7, P<0.001). However, there was no statistical difference in bilateral CCND between two groups (13.2 vs 8.2, P=0.154). The serum levels of stimulated thyroglobulin (Tg) at 1st RAI ablation was similar in both groups (3.03 vs 4.27 ng/ml, P=0.339). The total amounts of RAI administration were not significantly different between the two groups (132.5 vs 147.2 mci, P=0.179). The five-year recurrence rate was not significantly different between two groups (P=0.380). The ET had no recurrence during follow-up, but the OT had 12 local recurrences (1.7%), and the mean recurrence time was 57.5±11.3 months. Of 12 patients who showed recurrent disease, 3 were recurrence in operation bed and nine were recurrence in lateral neck node. In terms of surgical complications, the incidence of transient hypocalcemia was significantly lower in ET than OT (23.3% vs 42.7%, P=0.016). However, other major complications including the incidence of permanent hypocalcemia and transient/permanent RLN injury were similar in both groups (P=0.999, P=0.217, and P=0.125, respectively). Seven patients with vocal cord palsy and 4 patients with transient hypocalcemia patient in OT was loss to follow-up and excluded in assessing permanent complications.

Table 3
Surgical outcomes of conventional open and endoscopic thyroidectomy groups

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The incidence of PTC, especially, papillary thyroid microcarcinoma is increasing explosively worldwide, and the proportion of young female patient shows a sequential rapid increase.(1, 2) PTC has an excellent prognosis, and the guideline has changed to treat conservatively and emphasis on the patient quality of life is brought to light.(11) In this study, young female patients show preference on ET over OT. Young females show more body image concern than the older females and male patients, and they prefer a more aesthetic procedure than others. A conspicuous scar on a neck may affect patient's self-esteem and the cosmetic benefit of endoscopic thyroidectomy resulted in a faster recovery of emotional function.(8) Furthermore, transaxillary endoscopic procedure showed less sensory change on anterior neck area and decreased swallowing discomfort by preservation of anterior neck area.(12, 13) Due to previously mentioned various benefits, the efforts of minimizing or eliminating neck scar are in the limelight.(1, 2, 4, 6, 12, 14, 15, 16)

Neck is a confined area without a natural body cavity, transaxillary endoscopic thyroidectomy had several obstacles including a narrow, limited working space, unsophisticated instruments and a gradual learning curve.(13, 17, 18) Despite these shortcomings, the early surgical outcomes of gasless transaxillary endoscopic thyroidectomy were comparable with those of conventional open thyroidectomy in many reports.(1, 2, 4, 6, 12, 14, 15, 16) However, long-term follow-up data including oncological safety were less available.

In this study, the early surgical outcomes including major complications related to parathyroid gland and RLN injury showed no significant difference between two groups except the incidence of transient hypocalcemia. The total operation times for ET were significantly longer in both lobectomy and total thyroidectomy than OT and these results were from the additional time for tunneling from axilla to neck and making working space.

The surgical radicality of two groups was compared by the completeness of thyroid gland removal and the extent of CCND. The stimulated serum Tg at 1st RAI ablation and total amount of RAI dosage were not significantly different between two groups. These revealed that the amount of thyroid remnants after total thyroidectomy in both procedures was similar. In regarding nodal dissection, the total numbers of retrieved lymph nodes of ET were smaller than OT in unilateral CCND. These may be becasue that the cases with clinical nodal metastasis preoperatively are excluded from eligible criteria of ET. This may result in higher incidence of transient hypocalcemia in OT.

Oncological safety was assessed by 5-year follow-up data including recurrence and mortality. There was no disease related death in both groups and 12 patients who showed a local/regional recurrence was only found in OT. The aggressive tumor including larger tumor, clinical nodal metastasis and definite extrathyroidal extension were all excluded in ET, and the histologic characteristic of OT were significantly advanced than ET. Accordingly, total thyroidectomy with RAI ablation was performed more frequently in OT. Therefore, the oncological safety of the two groups are not directly comparable. However, endoscopic thyroidectomy show acceptable long-term surgical outcomes in patients who is eligible for the endoscopic procedure.

According to 2015 ATA guidelines, the management of well differentiated thyroid cancer has changed to a more conservative treatment, thyroid lobectomy is suggested as sufficient unless there are clear indications to remove the contralateral lobe.(11) Central neck dissection is recommended as therapeutic intend in clinically involved central nodes.(11) Furthermore, prophylactic CCND is not appropriate for T1/T2, noninvasive, clinically node-negative PTC.(11) We suggest indication of endoscopic thyroidectomy might be expanded according to new ATA guideline and applied more PTC patients who concern of neck scar and it can improve their quality of life with acceptable surgical outcomes.

This study had some limitations in that the study was conducted by a single institute, retrospectively and the two study groups differed regarding the patient's demographics. Therefore, we suggest a study which matches the inter-group differences in risk factors, such as, age and tumor characteristics with similar inclusion criteria be undertaken to confirm the definite long-term outcomes of endoscopic thyroidectomy.

We suggest that, in experienced hand, endoscopic thyroidectomy for well selected patient groups matches conventional thyroidectomy in terms of surgical outcomes.