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ORIGINAL ARTICLE
Year : 2017  |  Volume : 13  |  Issue : 1  |  Page : 102-106

Morbidity of central compartment clearance: Comparison of lesser versus complete clearance in patients with thyroid cancer


Department of Head and Neck Surgery, Tata Memorial Hospital, Mumbai, Maharashtra, India

Date of Web Publication03-Feb-2017

Correspondence Address:
Gouri Pantvaidya
Department of Head and Neck Oncosurgery, Tata Memorial Hospital, Parel, Mumbai, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0973-1482.199378

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 > Abstract 

Background: Extent of central compartment neck dissection (CCND) in thyroid cancers has been a debate because of associated morbidity. There have been attempts to reduce the extent of surgery in an attempt to decrease morbidity.
Patients and Methods: We analyzed the morbidity of CCND from our prospectively maintained surgical morbidity database. CCND was divided into bilateral complete clearance (BCC) and less than complete clearance (LCC). LCC was performed for clinicoradiologically node negative patients. Rates of hypocalcemia and recurrent laryngeal nerve (RLN) palsy rates were compared for LCC versus BCC. We also classified procedures performed in the central neck according to the extent of dissection.
Results: Of 153 evaluable patients, BCC was performed in 43.8% and LCC in 56.2%. Rate of postoperative hypocalcemia was 40.2% in BCC group versus 17.4% in LCC group. We had an overall RLN palsy rate of 7.4%. There was no significant difference in RLN palsy rates between the groups.
Conclusion: Lesser extent of dissection in central compartment reduces postoperative hypocalcemia but has no influence on RLN palsy rates.

Keywords: Central compartment clearance, neck dissection, papillary thyroid cancer, thyroid cancer


How to cite this article:
Pantvaidya G, Katna R, Deshmukh A, Nair D, D'Cruz A. Morbidity of central compartment clearance: Comparison of lesser versus complete clearance in patients with thyroid cancer. J Can Res Ther 2017;13:102-6

How to cite this URL:
Pantvaidya G, Katna R, Deshmukh A, Nair D, D'Cruz A. Morbidity of central compartment clearance: Comparison of lesser versus complete clearance in patients with thyroid cancer. J Can Res Ther [serial online] 2017 [cited 2019 Nov 21];13:102-6. Available from: http://www.cancerjournal.net/text.asp?2017/13/1/102/199378


 > Introduction Top


Differentiated thyroid cancers (DTC) constitute 90% of all thyroid cancers and carry an excellent long-term prognosis.[1] The long survival rates mandate that the quality of life in these patients is optimal with minimum morbidity of treatment. The incidence of lymph node metastases is high in patients with papillary thyroid cancers (PTCs) ranging from 45% to 60%. Clinical examination will detect metastases in approximately 10%–15% of these patients.[2] However, occult central compartment nodal disease is seen in a much higher number of patients. Central compartment disease has been consistently shown to be associated with increased incidence of locoregional recurrences.[3],[4],[5] Current standard of care for central compartment disease is “central compartment clearance (CCC) from the hyoid superiorly to innominate artery inferiorly and from carotid to carotid”. However, the need for such extensive nodal clearance in all patients with DTC is a matter of debate, because of the need to balance the associated morbidity and better disease control.

The main morbidity associated with CCC is hypocalcemia (postoperative and permanent) and recurrent laryngeal nerve (RLN) paralysis. Attempts have been made to decrease the extent of surgical procedures in the central compartment. These have been mainly in the form of avoiding prophylactic CCC in low risk, node negative patients or performing unilateral procedures for lateralized lesions.[6],[7] However, there is a dearth of prospective data evaluating morbidity after lesser surgical procedures. Does performing lesser procedures in the central compartment actually translate into lesser morbidity, is not known. We therefore decided to evaluate the morbidity of CCC when a “less than complete clearance” (LCC) was done as compared to a “bilateral complete clearance” (BCC) in patients with DTC.


 > Patients and Methods Top


A 30 days morbidity database of all patients undergoing thyroid surgery was prospectively maintained from January 2012 to December 2012. We retrospectively analyzed the morbidity associated with thyroid surgery and central compartment dissection from this prospective database.

During surgery, all central compartments were divided into ipsilateral and contralateral compartments depending upon the laterality of the cancer in the two lobes of the thyroid and using the trachea as a midline to divide these compartments. The pretracheal and prelaryngeal nodes were included in the ipsilateral central compartment. We classified the different surgical procedures in each central compartment as follows:

  • Clearance was defined as “Complete nodal and soft tissue clearance from carotid artery laterally till trachea in midline with pretracheal and prelaryngeal clearance and superiorly from hyoid to innominate artery inferiorly”
  • Sampling was defined as “Nodal tissue clearance along RLNs (paratracheal tissue)”
  • Inspection was defined as “Visual inspection and palpation of central compartment for any enlarged nodes.”


“Berry picking” is not practiced at our institute for central compartment disease. The indications for the various surgical procedures in the central compartment are detailed in [Table 1].
Table 1: Tata Memorial Hospital classification of procedures in the central compartment with their respective indications

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Patients with histology other than DTC, those who underwent hemithyroidectomy and patients in whom the central compartment was not addressed, were excluded from the analysis. Patients who underwent unilateral central compartment dissection were also excluded from final analysis as morbidity in these patients would be minimal and not comparable to patients having bilateral procedures. Hypocalcemia and RLN paralysis within 30 days postsurgery was documented. For hypocalcemia, symptomatology in the form of tingling numbness and a positive Chovstek's sign was considered as clinical hypocalcemia.[8] The serum calcium levels were done 48–72 h postsurgery. Patients with serum calcium levels <8.5 mg/dl were considered as having biochemical hypocalcemia. Patients were classified as having clinical (C), biochemical (B), or a combination of clinical and biochemical (C + B) hypocalcemia. For assessing recurrent laryngeal dysfunction, patients underwent indirect laryngoscopy to assess cord mobility in the 30 days postoperative period.

Clinicopathological parameters documented were as follows; age, sex, previous surgery for thyroid, type of surgery, tumor histology, pathological central compartment node positivity, and nodal yield in central compartment.

Parathyroid glands were saved whenever possible and auto transplanted as and when required.

Analysis

We broadly classified central compartment neck dissection (CCND) into two groups for analysis according to the extent of surgical dissection in each central compartment. The two groups which were formed were “Bilateral Complete Clearance (BCC)” and “Less than Complete Clearance (LCC)” [Figure 1]. The BCC group had clearance done on both sides of the trachea i.e., from hyoid to innominate and from carotid to carotid. The LCC group had both central compartments addressed in one of the ways described in [Figure 1]. The two groups were compared for nodal yield and pathological node positivity on final histology. The morbidity with regard to hypocalcemia and RLN injury was compared between the two groups.
Figure 1: Classification of central compartment neck dissection for analysis

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Statistical analysis was performed using SPSS 19.0 software (SPSS, Inc., Chicago, IL, USA). Categorical data was compared using Chi-square analysis. Univariate analysis was performed and any value of P< 0.05 was considered to be statistically significant.


 > Results Top


Demographic details

Two hundred sixty-two patients underwent thyroid surgery at our institute in year 2012. Of these, 57 patients were excluded because they underwent a hemithyroidectomy or had benign/other histology. Fifty-two patients who had either bilateral central compartment inspection alone or unilateral central compartment dissection performed were excluded and finally 153 patients were analyzed. The selection of patients according to the inclusion and exclusion criteria is shown in [Figure 2]. As mentioned previously, each patient had a unilateral and contralateral central compartment which was addressed. Therefore, 306 central compartments were addressed in 153 patients in the study. Of these, 66 central compartments were inspected, 37 were sampled and 203 were cleared. The demographic and treatment details for the patients are shown in [Table 2].
Figure 2: Flow chart depicting selection of patients

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Table 2: Demographic details of the patient population

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Central compartment neck dissection: Bilateral complete clearance versus less than complete clearance

BCC was performed in 43.8% patients and LCC in 56.2% patients. Mean number of nodes retrieved in BCC group was 6.2 (range 1–29), whereas in LCC group, it was 3.4 (range 1–14). Central compartment nodes were positive in 56.2% patients on final histology. Nodes positive on histology (pN+) in BCC group were seen in 46/67 (68.6%) patients and in 40/86 (46.5%) patients in the LCC group. Seventeen patients did not have a clearance in bilateral compartments i.e., only inspection or sampling was done in bilateral central compartments. Only one of 17 such patients had a positive node, indicating that inspection and sampling was done for node negative patients only. However, among the patients who underwent bilateral clearance, 31% were node negative on histology and may not have required such extensive clearance.

Morbidity of central compartment neck dissection

Overall 27.4% patients had postoperative hypocalcemia. Clinical hypocalcemia was documented in 7 patients, biochemical hypocalcemia in 9 patients, and combined clinical and biochemical hypocalcemia in 26 patients. In the BCC group, rate of postoperative hypocalcemia was 40.2% compared to 17.4% in the LCC group, which was significant on univariate analysis (P = 0.002).

Five RLNs were sacrificed intraoperatively because of gross involvement by disease. These five patients have not been included in the analysis of postoperative RLN paralysis. Eleven patients had postoperative RLN palsy (7.4%). The RLN palsy rate was 3.4% if RLNs at risk were considered for the analysis.

Among these 11 patients with RLN paralysis, 10 patients had multiple nodes positive in the central compartment. In two of these patients, the nodal disease was shaved off the nerve, and in another three patients, there was documented excess handling of the RLN to remove the nodal disease.

On comparing the two groups; The BCC group had RLN palsy rate of 4.4% compared to 9.3% in LCC group (P = 0.21). The LCC group had higher number of recurrent surgical explorations as compared with the BCC group, i.e., 36 (42%) versus 17 (25%); (P = 0.01). To explain the higher incidence of RLN palsy in the LCC group, we evaluated only per primum cases. However, even with the exclusion of cases undergoing redo surgeries, the RLN palsy rate was higher in the LCC group as compared to the BCC group (14.5% vs. 2%).


 > Discussion Top


CCND in DTC has been a matter of controversy because of associated morbidity, especially in the clinically node negative (cN0) patient. American Thyroid Association (ATA) recommendations for CCND are not based on level I evidence but on large retrospective studies or nonrandomized prospective data.[9] The extent of surgical clearance within the central compartment is not yet standardized and often based on the surgeon's discretion.

The controversy on the extent of neck dissection stems from many issues such as division of a anatomically single central compartment into an ipsilateral and contralateral compartment, need for complete dissection from carotid to carotid and hyoid to innominate in all cases. The ATA guidelines define CCND as clearance of at least one paratracheal region with the prelaryngeal, pretracheal nodes.[9] Most surgeons use a combination of procedures depending on preoperative node positivity, intraoperative findings after inspection of the central compartment and poor prognostic features of the thyroid malignancy.

At our institute, we have tried to define the various extents of surgical procedures in the central compartment along with their indications. We defined sampling as removal of the nodes and fibrofatty tissue medial to the RLN. This would potentially prevent the injury and vascular compromise to the parathyroid glands as the inferior thyroid artery would provide blood supply to the lower parathyroid gland from the lateral aspect of the gland.

We prospectively documented the morbidity with regard to RLN paralysis and hypocalcemia when these procedures were performed. The main hypothesis behind performing less than a complete bilateral clearance is to decrease morbidity associated with extensive bilateral dissections. To the best of our knowledge, there are no studies in literature, which have prospectively tested this hypothesis. Whether performing less surgery in the central compartment really reduces complications of RLN paralysis and hypocalcemia is unknown.

In our study, inspection and sampling were only performed on patients who were clinicoradiologically node negative. Only one of the17 patients who underwent these procedures had a positive node on histopathology. Needless to say, this cannot be applied to patients who underwent inspection alone as no tissue was submitted for histopathology and a true node negative status in these central compartments can only be confirmed on long-term follow-up.

Central compartment nodes were positive in 56.2% patients on final histopathology which is similar to the reports in literature.[10] The nodal positivity rates varied in the two groups (BCC - 68.6% vs. LCC - 46.5%) expectedly so, as more patients with positive lymph nodes underwent a BCC. Nodal yield may act as an indirect marker of adequacy of CCC though this has not been very well validated. There are few studies which have reported nodal yield in CCND to around 5–6 nodes.[11],[12] Similarly, in a large retrospective series of PTC, CCND was defined as adequate if there were a minimum number of 5 nodes on histology.[13] When we looked at the nodal yield in our two defined groups, we found that mean number of nodes retrieved in BCC group was 6.2 compared to 3.4 in LCC group.

Incidence of postoperative hypocalcemia in our cohort was 27.4%, which is in range reported in literature across various studies.[14],[15],[16] The incidence of postoperative hypocalcemia was significantly lower in LCC group (P = 0.002). However the impact of this on the permanent hypocalcemia rate is not known from this study as we have not included long term follow up of these patients. It may therefore not be justified to use lower rates of temporary hypocalcemia as a reason to perform lesser CCCs. Similar findings of lower hypocalcemia have also been documented by Moo et al. in a study looking at results of ipsilateral versus bilateral CCC.[17] In another study by Giordano et al., both temporary and permanent hypoparathyroidism was significantly higher in the bilateral clearance group as compared to the ipsilateral clearance group.[18]

Incidence of permanent RLN paralysis in total thyroidectomy with CCND has been documented to be 1%–12% by various authors.[11],[18],[19],[20] Most of these studies are retrospective in nature and may underreport RLN paralysis if routine postoperative evaluation in all patients, irrespective of symptomatology, is not done. We report a RLN paralysis rate of 7.4% in our series. When we compared performing lesser central clearances to a complete bilateral clearance, we found that there was no difference in the RLN palsy. In a metanalysis by Zhu et al., there were no significant differences in temporary or permanent vocal cord paralysis rates when comparing no central compartment dissection versus prophylactic node dissection in node negative patients.[21] A similar finding was noted in a study by Giordano et al., where they retrospectively evaluated RLN palsy rates comparing ipsilateral clearance versus bilateral clearance. They too found no difference in their palsy rates.[18] Contrary to the hypothesis that lesser surgery would result in lesser morbidity, we found no difference in RLN palsy rates.


 > Conclusion Top


Lesser surgery or avoidance of prophylactic surgery in the central compartment is being advocated in an attempt to decrease the morbidity in a cancer where survival outcomes are extremely favorable. However, this hypothesis has not been adequately studied. There appears to be a definite decrease in the rates of temporary hypoparathyroidism when lesser procedures are performed in the central compartment. However, its effect on permanent hypoparathyroidism is not known. RLN palsy rates do not seem to be any different when lesser procedures are performed. Good technique of dissection of the RLN is probably of utmost importance, irrespective of whether unilateral or bilateral procedures are being performed. To help standardize reporting of central compartment procedures, we recommend reporting unilateral versus bilateral procedures and classifying each of these procedures as per our classification system.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
 > References Top

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