日本内分泌・甲状腺外科学会雑誌
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Treatmentʼs Results of Papillary Thyroid Carcinoma in Belarusian Center of Thyroid Cancer
Victor Alexandrovich KondratovitchPavel Yevgenyevich KorotkevichYuriy Yevgenyevich DemidchikVladimir Stepanovich KaranikAliaksandr Gennadievich Zhukavets
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2018 年 35 巻 2 号 p. 90-103

詳細

Introduction

Thyroid cancer (TC) is the most wide-spread malignant tumour of the endocrine system, which accounts for 1-1.5% of all newly detected cases of malignant tumours[]. Over 15 years in Belarus, the annual number of the registered disease cases increased from 939 in 2000 up to 1,220 in 2014. Rough intensive morbidity rate in 2014 amounted to 12.9 : 100,000 people[].

Over the past few decades in the Republic of Belarus, no significant changes within the structure of morphological thyroid cancer forms have been observed. Thus, based on the data of the Belarusian Cancer Register, the overwhelming majority of malignant thyroid tumours are papillary (94%). Follicular and medullary cancer comprise 2.6% and 2.4%, respectively. Anaplastic cancer and other morphological forms comprise about 1% of all malignant thyroid tumours.

Recently, no increase in the rate of mortality due to TС has been observed despite a significant increase in its detectability[]. This fact can testify to the timely treatment of clinicaly insignificant thyroid tumours, which are primarily presented by papillary carcinoma of a small size[].

In papillary TC, the 10-year survical is at the level of 93%. Most commonly, the unfavourable outcome is possible in patients of a high risk group with histologically unfavourable variants of papillary cancer, as well as in cases of late diagnosing and presence of local tumour invasion. To the current moment, several systemic prognostic signs of the disease outcome have been proposed, which include the patientʼs age and gender, morphologic peculiarities, tumour size, vascular invasion, neoplasm extension to the surrounding thyroid tissues, presence of regional and distant metastasis, etc.

Study materials and methods

The study materials were 3,266 cases of morphologically verified papillary TC (3,230 - histologically verified, and 36 - cytologically verified), which were registered during the period from 01.01.1990 till 31.12.2005. The main evaluated parameters of the results were overall survival (OS), cause-specific survival (CSS), event-free survival (EFS), and cumulative relapse rate (CIR). The following types of events were set : relapse, continued tumour growth, death due to treatment complications. The variation statistics standard methods were used during the work. The monofactorial analysis included examination of the correlation relationship of the quantitative and qualitative parameters (Spearmanʼs correlation coefficient). The survival assessment included the calculations performed according to the Kaplan-Meier method. Comparison of the data in different groups was carried out using a long-rank test. To predict the risk of death due to TC, a multifactorial analysis of the parameters was used, which was carried out based on the Cox proportional hazards regression[]. To analyse the risk of relapse, a competing risks regression model was applied[]. The parameters, which had demonstrated the statistical significance within the monofactorial analysis, were included into the multifactorial analysis preliminary model as predictors. The results were considered as statistically significant if p<0.05. The matched-pair analysis was used for historical randomization. All calculations were performed within the R package; version R 3.1.1[].

Characterization of the observations

The median observation amounted to 122.43 months. Female patients prevailed in the study group in a ratio of 4.9 : 1. The patientsʼ mean age was 45.13 years.

In the majority of cases, the disease was asymptomatic and was found during the prophylactic examinations using neck ultrasonography (67.7%). Clinical manifestations were noted in 1022 cases. Mostly, patients complained of a node, which deformed the neck contour (n=435; 42.5%), or a compression sensation (442 ; 43.2%), and less often - of general symptoms typical for hypothyreosis or thyrotoxicosis (n=308 ; 30.1%). Hoarseness as the first sign of the disease occurred in 29 (2.8%) cases, and dysphagia - in 24 (2.3%) patients.

In the majority of patients, TC was diagnosed during the preoperative period by means of puncture-needle biopsy. However, in 25.62% of patients the malignant lesion was confirmed after the histologic diagnosis.

The multifocal growth of the tumour was observed in 23.8% of patients. Distant metastasis at the moment of diagnosing was found in 41 (1.3%) patients. Lungs were the primary target organ for distant metastasis (Table 1).

Table 1 .

Characterization of the clinical observations

Surgical treatment was performed in 3,230 (98.9%) patients. In 66.9% of cases, the surgery was performed within the thyroidectomy volume. In 66.3% of cases, the surgery on the thyroid gland was supplemented with lymph node dissection. The variants of primary surgical interventions are presented in Table 2.

Table 2 .

Variants of the primary surgical interventions

Treatment results.

The observed 5-, 10-, 15-, and 20-year survival appeared to be equal to 95.7±0.4%, 91.7±0.5%, 86.8±0.8%, and 79.1±1.7%. The values of the cause-specific survival were better and amounted to 98.4±0.2%, 98.1±0.3%, 97.3±0.4%, and 96.6±0.6% for the respective time periods.

To the moment of the study completion, 336 (11.2%) patients died: 141 (42%) - due to non-cancer diseases, 81 (24.1%) - due to primarily-multiple tumours, 61 (18.2%) - due to thyroid cancer, 6 (1.8%) - due to treatment complications; in 47 (14%) cases, causes of death were not established. More likely, they were non-cancer diseases, since no signs of thyroid cancer progression were observed in this group during the dispensary observation.

In the group of operated patients, 5-, 10-, 15-, and 20-year cause-specific survival amounted to 99.0±0.2%, 98.8±0.2%, 98.0±0.3%, 97.3±0.6%, respectively. 304 events associated with TC were established: 275 relapses, 6 cases of postoperative lethality, and 23 cases of continued tumour growth. The results of treatment of patients are presented in Figure 1, Table 3.

Figure 1 .

Results of treatment of patients with papillary TC.

1. Cause-specific survival; n=3,230; censored - 50; [95.8±1.6];

2. Observed survival; n=3,230; censored - 312; [73.6±3.5];

3. Event-free survival; n=3,230; censored - 304; [77.7%±6.9%];

4. Cumulative relapse rate; n=3,230; censored - 275; [21.3±7.2];

Table 3 .

Results of treatment of patients with papillary TC.

Independent prognostic factors

The prognostic factors, which have demonstrated statistical significance in monovariant analysis, are presented in Table 4.

Table 4 .

Impact of the independent prognostic factors on the results of treatment of patients with papillary thyroid cancer (monovariant analysis results)

In the female population, such signs as tumour size, clinical disease manifestations, and autoimmune thyroiditis have not revealed statistical significance after inclusion into the multivariant analysis. The model has been reduced with exclusion of the above-mentioned risk factors. The obtained data testify to the fact that the key prognostic factors defining death due to cancer in women are 55 years of age and over, presence of distant metastasis, and massive extrathyroidal extension of a tumour (Table 5).

Table 5 .

Risk of death due to cancer in female patients with papillary thyroid cancer

In men, the primary factors defining the cause-specific survival are distant metastasis, 35 years of age and over, and presence of massive extrathyroidal extension(Table 6). All other risk factors being included into the Cox proportional hazards regression model have not demonstrated statistical significance.

Table 6 .

Risk of death due to cancer in male patients with papillary thyroid cancer

The key independent prognostic factor defining the risk of disease recurrence is presence of metastasis in regional lymph nodes, which can testify to the insufficient volume of lymph node dissection in patients with regional metastasis(Table 7).

Table 7 .

Relapse risk in patients with papillary TC.

To define the risk of relapse depending on the affection of the lymph nodes of the central or lateral compartment, the above-mentioned prognostic factors are included into separate regression models(Tables 8, 9).

Table 8 .

Risk of relapse in patients with papillary TC depending on the affection of the central compartment lymph nodes(N1a)

Table 9 .

Risk of relapse in patients with papillary TC depending on the affection of the lateral compartment lymph nodes(N1a)

The data of multivariant analysis testify that presence of metastasis in the cerviral lymph nodes significantly increases the risk of relapse (PR=2.81) compared to the affection of the central compartment lymph nodes (PR=1.68). Nevertheless, both factors statistically define the risk of the disease progression.

Characterization of the surgical approaches in 1990-2005.

For the period from 1990 till 2005, the surgical tactics was revised several times. Until 1998, more than 50% of surgeries on thyroid gland were organ preservation ones. In the majority of cases, the lymph node dissection was performed only in case of metastatic affection of lymph nodes of one or another compartment. The accumulated experience in treatment of patients with differentiated thyroid cancer necessitated the expansion of the surgical volume for both thyroid gland and lymphatic system. Since 1998, the treatment approaches for patients with such pathology had been unified. Extrafascial thyroidectomy with bilateral selective cervical dissection of levels III, IV, and VI is recommended to all patients, excluding the cases of microcarcinoma without any signs of metastatic affection of the cervical lymph nodes. The indicated tactics was necessitated by the peculiarities of the papillary thyroid cancer behaviour, and in particular by the tendency to multicentric growth, including bilobed affection, and high frequency of lymphangitic metastasis. Such surgical intervention volumes as subtotal thyroidectomy and thyroid resection in cancer had been refused of. These surgeries were perfomed predominantly in non-cancer institutions. Also, the approaches to selection of the lymph node dissection volume have been changed. Bilateral lateral lymph node dissection has ranked first. Their number has increased from 3.5% to 57.3% for the mentioned time periods(Tables 10, 11).

Table 10 .

Structure of surgeries on thyroid gland for the periods of 1990-1997 and 1998-2005.

Table 11 .

Structure of surgeries on lymphatic system for the periods of 1990-1997 and 1998-2005.

In a group of patients treated after 1998, better parameters of the cause-specific (p<0.0001) and event-free survival (p<0.001), as well as comulative relapse rate (p<0.0001) were achieved.

In order to understand the reason for improvement in survival, the matched-pair analysis was performed, which included matching of patientsʼ pairs from a group until 1998 and after 1998 with the established criteria. Pairs matching was performed based on the following attributes: men ≥ 35 / < 35 years old, women ≥ 55 / < 55 years old; presence/absence of massive extrathyroidal extension, N0/N1, M0/M1. Due to the above, 2 equal cohorts of patients identical in the tumour process extension and defining independent prognostic factors were obtained. Their comparison allowed to determine the genuine impact of the treatment factor on the long-term results. It was managed to match a pair to 987 patients. Subsequently, the survival calculation was performed (Figure 2,Table 12).

Figure 2 .

Treatment results of patients with papillary thyroid cancer operated in 1990-1997 and 1998-2005.

1. CSS of patients, who were operated in 1998-2005; n=987; censored - 9; [98.7±0.5];

2. CSS of patients, who were operated in 1990-1997; n=987; censored - 31; [94.7±1.7];

3. CIR in patients operated in 1998-2005; n=2,229; censored - 60; [12.2±5.5];

4. CIR in patients operated in 1990-1997; n=987; censored - 163; [27.3±7.3];

Table 12 .

Treatment results of patients with papillary thyroid cancer operated in 1990-1997 and 1998-2005.

Statistically better results of the cause-specific survival in the group of patients treated after 1998 (p=0.0273) were obtained. However, the most significant changes were noted in the relapse rate (p<0.0001).

Characterization of repeated surgeries.

Due to the requirements of the treatment protocols and non-radicality of the initial surgical intervention, 238 (7,4%) patients were operated repeatedly during 6 months following the first surgery. Based on the examination data, no residual tumour and regional metastasis were found in this group of patients. Residual cancer diagnosed during the repeated surgery was not considered as a relapse, and consequently, it did not influence the event-free survival and cumulative relapse rate. In patients of this group, the first and second surgeries had been combined, and during the assessment of the surgical treatment, the intervention volume following the repeated surgery was taken into account. The majority of the initial surgical interventions was performed in the non-cancer institutions, and thyroid cancer was diagnosed only after the morphological examination of the surgical materials. As a consequence, the surgical allowance did not correspond to the principles of radical surgeries in case of malignant neoplasms. The organ preservation surgeries were performed in 97.9% of cases, while in 64.7% of cases, the surgical allowance volume was limited to resection or enucleation of a tumour, and the indications for lymph node dissection were only in 11 patients(Table 13).

Table 13 .

Variants of the initial surgical interventions in the group of repeatedly operated patients

All repeated surgeries were performed in the Belarusian center of thyroid cancer. In all cases, the restaging following the repeated surgical intervention was carried out.

In 137 (57.6%) patients after the repeated surgery, no signs of residual cancer were found. In 35 (14.7%) cases, the morphological examination revealed the tumour growth in the residual thyroid tissue; in 40 (16.8%) cases, metastases in regional lymph nodes were found; in 26 (10.9%) cases - papillary cancer growth was diagnosed both in the residual thyroid gland and lymph nodes. Therefore, the residual cancer was found in 40% of supposedly radically operated patients. The repeated surgery in such patients allowed to carry out the accurate staging of the tumour process, ensured the adequate further treatment with radioactive iodine and suppressive hormone therapy.

Surgical treatment results

At the first stage, the analysis of the cause-specific survival was performed in the groups of patients, who underwent surgical treatment within the thyroidectomy volume compared to the group of organ preservation surgeries, and it was established, whether lymph node dissection influenced life expectancy of patients with papillary thyroid cancer(Table 14). No statistically significant differences were found in the analysis of the cause-specific survival of all cohort of patients depending on the initial surgery volume. In the group of patients, who underwent thyroidectomy, the risk of relapse was significantly less (p<0.0001)(Figure 3). Lymph node dissection also statistically decrease the possibility of relapse (p=0.0003)(Figure 4).

Table 14 .

Treatment results of patients with papillary thyroid cancer depending on the volume of the surgery on thyroid gland and lymphatic system.

Figure 3 .

EFS and CIR depending on the volume of surgery on thyroid gland

1. EFS of patients operated within the volume of thyroidectomy; n=2,376; censored - 164;

2. EFS of patients, who underwent the organ preservation surgeries; n=854; censored - 140;

3. CIR of patients operated within the volume of thyroidectomy; n=2,376; censored - 138;

4. CIR of patients, who underwent the organ preservation surgeries; n=854; censored - 137;

Figure 4 .

Treatment results depending on the volume of surgery on lymphatic system

1. EFS of patients, who underwent lymph node dissection; n=2,341; censored - 187;

2. EFS of patients, who did not undergo lymph node dissection; n=889; censored - 117;

3. CIR of patients, who underwent lymph node dissection; n=2,341; censored - 165;

4. CIR of patients, who did not undergo lymph node dissection; n=889; censored - 110;

For detailed analysis of the surgical treatment, all operated patients were divided in 4 groups depending on the type of surgery on thyroid gland(Table 15). The obtained data testify that the volume of the surgery on thyroid gland does not influence the patientsʼ life expectancy, but statistically impacts the relapse rate(Figure 5). The greater is the resected part of thyroid gland, the better treatment long-term results have been achieved. Thus, in case of thyroid gland resection, during 20 years the relapse occured in every third operated patient, and in case of thyroidectomy - the disease relapse was diagnosed in every tenth subject.

Table 15 .

Treatment results of patients with papillary thyroid cancer depending on the volume of the surgery on thyroid gland

Figure 5 .

EFS and CIR depending on the volume of surgery on thyroid gland

1.EFS of patients operated within the volume of thyroidectomy; n=2,376; censored - 164;

2.EFS of patients operated within the volume of hemithyroidectomy; n=518; censored - 66;

3.EFS of patients operated within the volume of subtotal thyroidectomy; n=162; censored - 24;

4.EFS of patients operated within the volume of thyroid gland resection; n=174; censored - 50;

5.CIR of patients operated within the volume of thyroidectomy; n=2,376; censored - 138;

6.CIR of patients operated within the volume of hemithyroidectomy; n=518; censored - 64;

7.CIR of patients operated within the volume of subtotal thyroidectomy; n=162; censored - 23;

8.CIR of patients operated within the volume of thyroid gland resection; n=174; censored - 50;

The best treatment results were achieved in the group of patients, who underwent the surgery on lymphatic system within the volume of bilateral lateral lymph node dissection(Table 16).

Table 16 .

Treatment results depending on the type of surgery on lymphatic system

To determine the risk of relapse, a competing risks model was created, which apart from the independent prognostic factors included the treatment factors, which demonstrated statistical significance in monovariant analysis(Table 17).

Table 17 .

Relapse risk in patients with papillary thyroid cancer

Metastatic involvement of regional lymph nodes 7.26-fold increases the risk of relapse and is a key prognostic factor. This fact testifies to the inadequate lymph node dissection in patients with regional metastasis. Additionally, the variant of initial surgery both on thyroid gland and lymphatic system is of great importance. The organ preservation surgeries without lymph node dissection often lead to the relapse, and require repeated surgical interventions.

Variants of papillary thyroid cancer progression.Characterization of the repeated surgeries

Progression of the tumour process was diagnosed in 272 (8.4%) operated patients. Median time to progression amounted to 28.7 months (min - 1 month, max - 21.7 years). The most common relapse variant was locoregional recurrence, which was responsible for 76.5% of all cases. At the same time, metastasis was found in regional lymph nodes. The progression variants are presented in Table 18.

Table 18 .

Variants of papillary thyroid cancer progression

Repeated surgery was performed in 278 patients. In the majority of patients, relapse was the indication for surgical treatment (215, 77.4%). The repeated surgery due to the continued growth after the non-radical (R2) surgery was performed in 3 (1.0%) cases. 60 patients (22.6%) underwent surgical treatment due to suspected progressing or a goiter in the residual thyroid tissue.

Completing thyroidectomy (removal of the residuals) was performed in 172 (60.6%) patients. In the majority of cases, the surgery was supplemented with the lymphatic system surgeries, which were various in volume(Table 4, 15).

Selection of a surgery in papillary thyroid cancer (discussion)

The objective of primary treatment is to improve the overall and cause-specific survival, to decrease the risk of relapse and continued tumour growth, to exclude the unnecessary treatment, i.e. recure, along with minimal complications and side effects. For risk stratification, it is important to accurately establish the tumour process stage[]. According to the majority of recommendations for treatment of differentiated TC, thyroidectomy is indicated to all patients, excluding the cases of intrathyroid tumours sized to less than 1 cm in diameter without any sings of multifocal growth, as well as regional and distant metastasis[10]. However, a tendency to extension of the indications for organ preservation surgeries has appeared recently. In the 2015 recommendations of the American Thyroid Association, lobectomy is an acceptable surgical option for patients with a tumour diameter of more than 1 cm and less than 4 cm without extrathyroidal extension, sings of metastatic affection of regional lymph nodes and distant organs[]. A change in the approaches was preconditioned by the results of new large retrospective studies, which had demonstrated similar distant results in both groups[1114]. In Japan, thyroidectomy is recommended in case of T1N0M0 tumours. All other patients are allocated by the investigators to the so called “grey zone”, the optimal treatment tactics in which has not been developed due to the lack of randomized studies data and the ambiguous retrospective data. Nevertheless, thyroidectomy is recommended to this group of patients only if the tumour diameter is >4cm, and there are regional metastases. To all other patients, lobectomy is indicated[15]. To a large extent, this phenomenon is conditioned by the low accessibility of radioiodine therapy in the region.

The surgical intervention volume and a prognostic group, to which the patient will be allocated, are primarily determined according to the quality of the preoperative ultrasound examination. Sensitivity and specificity of the ultrasound examination in diagnostics of metastases in the central compartment lymph nodes are very low. The efficacy of the ultrasound diagnostics is significantly higher in revealing pathologically changed lymph nodes of the lateral compartment. The method sensitivity is more than 90%[16]. However, such ultrasound examination quality is achievable only in large centres specialized in treatment of patients with thyroid disorders. During the ultrasound examination, the most accurately defined parameter is the tumour size, and it is the neoplasm size, which is a basis for planning the surgical intervention volume.

With an increase of the tumour size, the frequency of the metastatic affection of regional lymph nodes also grows up. Even if the tumour diameter is less than 10mm (microcarcinoma), metastases in regional lymph nodes were revealed in 25.1% of patients. In 46% of cases the involvement was limited to the central compartment, and in 54% of cases, the cervical lymph nodes were affected. If the tumour is more than 1cm, the possibility of lymph nodes involvement increased almost twice. With the further tumour growth, the possibility of lymph nodes involvement increased, but not so fast(Table 19).

Table 19 .

Frequency of metastatic involvement of regional lymph nodes depending on the primary tumour size

In patients with metastatic affection of regional lymph nodes, the median diameter of the primary tumour was 16mm, and in 75% of cases, the size did not exceed 24 mm(Figure 6).

Figure 6 .

Frequency of metastatic involvement of regional lymph nodes depending on the primary tumour size

The presented data testify to the fact that the tumour size is a weak predictor for choosing an optimal surgery, especially for the lymph node dissection. Even the neoplasms with a diameter of less than 1cm have a high metastatic potential. While planning the surgery volume reduction, it is necessary to perform the repeated ultrasound examination by a highly qualified physician, who specializes in the thyroid pathologies.

Papillary thyroid cancer is distinguished by the tendency to multicentric growth, including bilobed affection, and characterized by a high lymphangitic metastasis potential. Metastases in regional lymph nodes following the primary surgical interventions are diagnosed in 38.71% of patients.

Locoregional control primarily depends on the radicality of the surgical intervention. Although the patientsʼ life expectancy is primarily defined by the independent prognostic factors, the event-free survival and cumulative relapse rate directly depend on the adequacy of the performed surgery. One should remember that these parameters of the long-term treatment results rank second in terms of relevance in oncology. Great caution should be exercised while reducing the volume of surgery on thyroid gland, since it statistically worsens the parameters of the event-free survival, and as a consequence, it increases the number of repeated surgeries.

Although the metastatic affection of lymph nodes can be associated with higher incidence of relapses and decreased survival rate (especially in elderly patients, as well as in cases of multricentric growth and extrathyroidal extension), it is unclear up to now, whether the prophylactic central cervical lymph node dissection decreases the risk of locoregional recurrence[1718]. Thus in the USA, the prophylactic central lymph node dissection is recommended only in case of locally advanced papillary cancer (T3 or T4), as well as in case of metastatic affection of the lateral compartment lymph nodes[]. In Great Britain, the central lymph node dissection is indicated only in case of metastatic affection of the lymph nodes of this level or such suspected affection, i.e. the issue of the prophylactic dissection is not discussed at all[19]. In Japan, the central lymph node dissection is recommended to all patients, since repeated surgeries in this region are associated with a high risk of complications[15].

The results of our study indicated that presence of metastasis in the central compartment lymph nodes statistically increase the risk of relapse. As the frequency of affection of the lymph nodes of this compartment is very high, the ultrasound examination sensitivity is low, and repeated surgeries are associated with a higher frequency of postoperative complications, in our opinion the central lymph node dissection is indicated to all patients.

Lateral lymph node dissection is indicated to all patients with morphologically verified tumour involvement of the lymph nodes of this compartment[1015].

Large cohort studies in the USA, Canada, and Germany demonstrated that metastatic affection of lymph nodes should be considered as an independent factor defining the survival of patients with papillary TC[2022]. In the Republic of Belarus, bilateral lateral lymph node dissection with removal of level III and IV lymph nodes is recommended to all patients with papillary thyroid cancer. At the same time, the volume of prophylactic and therapeutic lymph node dissection has not been stipulated. The American Thyroid Association recommends radical modified cervical dissection of levels IIa, III, IV, and Vb for patients with morphologically verified metastatic affection[23]. The meta-analysis, which included 18 studies performed from 2002 till 2012 and 1,145 patients with cervical dissection, demonstrated that levels IIa, IIb, II, III, IV, and V were involved in the tumour process in 53%, 16%, 53%, 71%, 66%, and 25% of cases, respectively. Levels Va and Vb were reviewed separately only in 3 studies. Their metastatic affection was revealed in 8% and 22% of cases, respectively. Therefore, the authors recommend lateral lymph node dissection within the volume of levels IIa, IIb, III, IV, Vb, if the lateral group of lymph nodes is involved in the tumor process[24].

Based on the results of our study, presence of metastases in regional lymph nodes more than 7-fold increases the risk of relapse and is a decisive factor for the disease recurrence. It testifies to insufficiently removed level III, IV, and IV lymph nodes in case of any signs of their metastatic affection, and requires an extension of the lymph node dissection volume in such patients.

Despite the high frequency of metastatic involvement of lymph nodes in papillary TC, the prophylactic lymph node dissection is not recommended in the majority of countries, since: there are no evidence that it improves survival and influences the disease prognosis. The sensitivity of ultrasound diagnostics used in order to find pathologically changed lateral compartment lymph nodes is a lot better compared to the diagnostics of metastatic affection of the level VI-VII lymph nodes, and it amounts to 94%. During the surgery on thyroid gland, the lateral compartment remains intact, and due to it the risk of complications during the repeated surgeries in this region does not increase compared to the central compartment; the prophylactic lymph node dissection is associated with such complications as bleeding, lymphorrhea, damage of vagus, accessory, hypoglossal nerves, and brachiplex nerves, and it increases the length of a cut thus creating a huge cosmetic defect[1625].

Nevertheless, the results of our study testify that bilateral cervical lymph node dissection decreases cumulative relapse rate, and consequently it is recommended to all patients except for the cases of solitary microcarcinoma. While planning the reduction of the surgery volume, it is recommended to perform the expert ultrasound examination by a highly qualified specialist. To assess the role of lateral lymph node dissection in the disease outcome prognosis, to determine the optimal volume and indications both for prophylactic and lateral dissection, it is necessary to perform large randomized studies. For the purpose of the differentiated approach to the surgical intervention volume in papillary thyroid cancer, the first thing to do is to improve the quality of preoperative diagnostics, and the ultrasonic examination in particular.

Conclusions

1. Life expectancy of patients with papillary thyroid cancer is mainly established by the independent prognostic factors, and not by the volume of surgical intervention, which is related to the early diagnosing of a relapse and timely performed repeated surgery.

2. Thyroidectomy and bilateral lymph node dissection significantly reduce the risk of relapse, but statistically do not influence the cause-specific survival.

3. Presence of metastasis in the regional lymph nodes is a decisive factor of relapse. It testifies to insufficiently removed level III, IV, and IV lymph nodes in case of any signs of their metastatic affection, and requires an extension of the lymph node dissection volume in such patients.

References.
 

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