hrvatski

TNM classification and other thyroid carcinoma prognostic systems

Pathohistological classification of the basic types of thyroid carcinoma (papillary, follicular, medullary and anaplastic) has proved to be the most important prognostic factor, which influences general survival, the length of the remission period and recidivation and metastasis occurrence [1]. Tumour size, stage of extension, differentiation, the presence of metastases and the method of carcinoma treatment are important prognostic factors. Age is also a very important prognostic factor. Old age is followed by lower relative survival in all histological types. Differentiated thyroid carcinoma prognosis is better in patients under the age of 40 and in the cases when carcinoma did not spread outside of the thyroid capsule or invaded the blood vessels [2]. In the cases of follicular and papillary carcinoma, the prognosis is determined more by the stage at diagnosis, age at the time of occurrence and how differentiated the tumour is, than by the follicular or papillary histology [1]. Age over 45, follicular histology, primary tumour larger than 4 cm (T2-3), extrathyroid extension (T4) and distant metastases are independent factors that increase the risk of death in patients with differentiated thyroid carcinoma [3]. Generally, the prognosis is much more favourable for women than for men [4]. Different systems of scoring for the prognosis of thyroid carcinoma have been developed. Some of them are: Tumour– Node– Metastasis (TNM) classification, prognostic system of the European Organization for Research and Treatment of Cancer (EORTC), Age– Metastases– Extent– Size system (AMES), Grade– Age– Metastases– Extent– Size system (GAMES), Age– Grade– Extent– Size system (AGES), Metastases– Age– Completeness of Resection– Invasion– Size system (MACIS), Age– Invasion of blood vessels– Metastases system (AIM), the Ohio State system for papillary or follicular carcinoma (OSU), University of Chicago system for papillary carcinoma, National Thyroid Cancer Treatment clinical system (NTCTCS), Noguchi thyroid clinic staging system, University of Münster staging system, University of Alabama and MD Anderson staging system (UAB&MDA), Cancer Institute of the Hospital of Tokyo staging system (CIH), Ankara Oncology Training and Research Hospital staging system and other [5]. All of them include pathohistological type of carcinoma as the main component. Most of the staging systems refer only to the papillary and follicular carcinoma (EORTC, AMES, GAMES, OSU) or just to the papillary carcinoma (AGES, MACIS, University of Chicago), and include the tumour size (except EORTC), age of the patients (except University of Chicago and OSU), gender (EORTC and AMES) and lymph nodes metastases presence (University of Chicago, OSU, NTCTCS and TNM, depending on age). Extrathyroid extension and distant metastases are considered in all of the scoring systems and the extent of the performed surgical resection only in MACIS system and TNM system with the application of "R" category [6]. To avoid the differences in the schemes of the prognostic systems, Union International Contre Cancer (UICC) and the American Joint Committee on Cancer (AJCC) [7] have accepted the TNM staging system. The differential capability of the existing systems was compared in studies on a larger number of patients, and none of the abovementioned systems showed clear advantage over the TNM system [8], which is less complex and easier to use. Therefore, TNM system is widely accepted, recommended for reports, disease outcome prognosis, and comparison of different methods of treatment among the groups of patients with similar cases of carcinoma and as a treatment guide for patients with thyroid carcinoma. However, up to this point, with all abovementioned, smaller number of studies contains the clinical data based on this classification [9]. In the latest, 6th edition of the UICC TNM classification, published in 2002 [10], new international standards, which describe and categorise the stages of carcinoma and its progression, were set. In classifying differentiated thyroid carcinoma, the 6th edition of the TNM system has especially altered the description of the primary tumour (T) and the extension to the regional lymph nodes (N), and is differed from the 5th edition, published in 1997 [10, 11]. While the 5th edition classifies primary tumours ≤ 1 cm in size as T1, and tumours >1≤ 4 cm in size as T2, the 6th edition defines tumours ≤ 2 cm in diameter as T1, and as T2 tumours >2≤ 4 cm in size [10]. In the 5th edition, tumours >4 cm in size, without the extrathyroid expansion are classified as T3, and all of the tumours with extrathyroid extension are classified as T4. In the 6th edition, tumours >4 cm in diameter or all of the tumours with minimal extrathyroid extension are defined as T3. T4 is divided on T4a (tumour with expansion outside of the thyroid capsule and with the invasion of the subcutaneous soft tissue, larynx, trachea, oesophagus or nervus recurens) and T4b (tumour which invades prevertebral fascia and mediastinal blood vessels, or spans to the arteria carotis). The N system has also been modified. While the 5th edition classifies the metastasis to the unilateral cervical lymph nodes as N1a, the 6th edition defines N1a as metastasis only to the VI. group of lymph nodes (pretracheal, paratracheal and prelaryngeal). In the group of tumour stages, all stages of thyroid carcinoma had been modified. In the beginning, the "occult papillary carcinoma" was defined as a tumour up to 1.5 cm in diameter. Later on, based on the definition of the WHO and the T1 stage of the 5th edition of the TNM classification was replaced by the term "papillary microcarcinoma" up to 1.0 cm in diameter [4]. According to research in different countries, the incidence of clinically manifested papillary carcinoma is in disproportion with the prevalence of the microcarcinoma, which supports the hypothesis that the papillary microcarcinoma is a separate clinical entity with a very low rate of morbidity and mortality [4, 12]. Therefore, the new TNM system of the UICC for the differentiated thyroid carcinoma simplifies and summarises the categorisation of the tumours ≤ 2 cm in size, including microcarcinomas, which results in the increase of the T1 group, due to the larger size of the tumours (up to 2 cm, instead of the 1 cm in the earlier edition). Due to the abovementioned, survival without recidivation in the new T1 classified differentiated thyroid carcinoma is slightly lower in relation to the older T1 cases [13]. In the recent studies, the effects of the 6th edition TNM classification usage for the differentiated thyroid carcinoma are evaluated in retrospective and survival rates without recidivation and they are compared to the earlier, 5th, edition, so the expansion of the T1 group on the papillary carcinoma up to 2 cm in size is considered unjustified [14]. The clinical staging system of medullar carcinoma (AJCC) compares the survival rate to the size of the primary tumour, metastasis to the lymph nodes and distant metastasis. The best prognosis is for the patients whose carcinoma is detected with provocative screening, before the palpable tumour appears [3]. There is no generally accepted staging system for anaplastic (non-differentiated) carcinoma. Therefore, independent on T (or N or M) category, every anaplastic carcinoma is classified as stage IV. of the tumour.

TNM classification; thyroid carcinoma; prognostic systems

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engleski

TNM classification and other thyroid carcinoma prognostic systems

Pathohistological classification of the basic types of thyroid carcinoma (papillary, follicular, medullary and anaplastic) has proved to be the most important prognostic factor, which influences general survival, the length of the remission period and recidivation and metastasis occurrence [1]. Tumour size, stage of extension, differentiation, the presence of metastases and the method of carcinoma treatment are important prognostic factors. Age is also a very important prognostic factor. Old age is followed by lower relative survival in all histological types. Differentiated thyroid carcinoma prognosis is better in patients under the age of 40 and in the cases when carcinoma did not spread outside of the thyroid capsule or invaded the blood vessels [2]. In the cases of follicular and papillary carcinoma, the prognosis is determined more by the stage at diagnosis, age at the time of occurrence and how differentiated the tumour is, than by the follicular or papillary histology [1]. Age over 45, follicular histology, primary tumour larger than 4 cm (T2-3), extrathyroid extension (T4) and distant metastases are independent factors that increase the risk of death in patients with differentiated thyroid carcinoma [3]. Generally, the prognosis is much more favourable for women than for men [4]. Different systems of scoring for the prognosis of thyroid carcinoma have been developed. Some of them are: Tumour– Node– Metastasis (TNM) classification, prognostic system of the European Organization for Research and Treatment of Cancer (EORTC), Age– Metastases– Extent– Size system (AMES), Grade– Age– Metastases– Extent– Size system (GAMES), Age– Grade– Extent– Size system (AGES), Metastases– Age– Completeness of Resection– Invasion– Size system (MACIS), Age– Invasion of blood vessels– Metastases system (AIM), the Ohio State system for papillary or follicular carcinoma (OSU), University of Chicago system for papillary carcinoma, National Thyroid Cancer Treatment clinical system (NTCTCS), Noguchi thyroid clinic staging system, University of Münster staging system, University of Alabama and MD Anderson staging system (UAB&MDA), Cancer Institute of the Hospital of Tokyo staging system (CIH), Ankara Oncology Training and Research Hospital staging system and other [5]. All of them include pathohistological type of carcinoma as the main component. Most of the staging systems refer only to the papillary and follicular carcinoma (EORTC, AMES, GAMES, OSU) or just to the papillary carcinoma (AGES, MACIS, University of Chicago), and include the tumour size (except EORTC), age of the patients (except University of Chicago and OSU), gender (EORTC and AMES) and lymph nodes metastases presence (University of Chicago, OSU, NTCTCS and TNM, depending on age). Extrathyroid extension and distant metastases are considered in all of the scoring systems and the extent of the performed surgical resection only in MACIS system and TNM system with the application of "R" category [6]. To avoid the differences in the schemes of the prognostic systems, Union International Contre Cancer (UICC) and the American Joint Committee on Cancer (AJCC) [7] have accepted the TNM staging system. The differential capability of the existing systems was compared in studies on a larger number of patients, and none of the abovementioned systems showed clear advantage over the TNM system [8], which is less complex and easier to use. Therefore, TNM system is widely accepted, recommended for reports, disease outcome prognosis, and comparison of different methods of treatment among the groups of patients with similar cases of carcinoma and as a treatment guide for patients with thyroid carcinoma. However, up to this point, with all abovementioned, smaller number of studies contains the clinical data based on this classification [9]. In the latest, 6th edition of the UICC TNM classification, published in 2002 [10], new international standards, which describe and categorise the stages of carcinoma and its progression, were set. In classifying differentiated thyroid carcinoma, the 6th edition of the TNM system has especially altered the description of the primary tumour (T) and the extension to the regional lymph nodes (N), and is differed from the 5th edition, published in 1997 [10, 11]. While the 5th edition classifies primary tumours ≤ 1 cm in size as T1, and tumours >1≤ 4 cm in size as T2, the 6th edition defines tumours ≤ 2 cm in diameter as T1, and as T2 tumours >2≤ 4 cm in size [10]. In the 5th edition, tumours >4 cm in size, without the extrathyroid expansion are classified as T3, and all of the tumours with extrathyroid extension are classified as T4. In the 6th edition, tumours >4 cm in diameter or all of the tumours with minimal extrathyroid extension are defined as T3. T4 is divided on T4a (tumour with expansion outside of the thyroid capsule and with the invasion of the subcutaneous soft tissue, larynx, trachea, oesophagus or nervus recurens) and T4b (tumour which invades prevertebral fascia and mediastinal blood vessels, or spans to the arteria carotis). The N system has also been modified. While the 5th edition classifies the metastasis to the unilateral cervical lymph nodes as N1a, the 6th edition defines N1a as metastasis only to the VI. group of lymph nodes (pretracheal, paratracheal and prelaryngeal). In the group of tumour stages, all stages of thyroid carcinoma had been modified. In the beginning, the "occult papillary carcinoma" was defined as a tumour up to 1.5 cm in diameter. Later on, based on the definition of the WHO and the T1 stage of the 5th edition of the TNM classification was replaced by the term "papillary microcarcinoma" up to 1.0 cm in diameter [4]. According to research in different countries, the incidence of clinically manifested papillary carcinoma is in disproportion with the prevalence of the microcarcinoma, which supports the hypothesis that the papillary microcarcinoma is a separate clinical entity with a very low rate of morbidity and mortality [4, 12]. Therefore, the new TNM system of the UICC for the differentiated thyroid carcinoma simplifies and summarises the categorisation of the tumours ≤ 2 cm in size, including microcarcinomas, which results in the increase of the T1 group, due to the larger size of the tumours (up to 2 cm, instead of the 1 cm in the earlier edition). Due to the abovementioned, survival without recidivation in the new T1 classified differentiated thyroid carcinoma is slightly lower in relation to the older T1 cases [13]. In the recent studies, the effects of the 6th edition TNM classification usage for the differentiated thyroid carcinoma are evaluated in retrospective and survival rates without recidivation and they are compared to the earlier, 5th, edition, so the expansion of the T1 group on the papillary carcinoma up to 2 cm in size is considered unjustified [14]. The clinical staging system of medullar carcinoma (AJCC) compares the survival rate to the size of the primary tumour, metastasis to the lymph nodes and distant metastasis. The best prognosis is for the patients whose carcinoma is detected with provocative screening, before the palpable tumour appears [3]. There is no generally accepted staging system for anaplastic (non-differentiated) carcinoma. Therefore, independent on T (or N or M) category, every anaplastic carcinoma is classified as stage IV. of the tumour.

TNM classification; thyroid carcinoma; prognostic systems

nije evidentirano