Ajcc 8th edition head and neck pdf

New AJCC/UICC staging system for head and neck, and thyroid cancerNuevo sistema de etapificación AJCC/UICC de los cánceres de cabeza y cuello, y tiroides

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Abstract

The AJCC/UICC staging system is a major tool in oncology, currently used worldwide for clinical, pathological and recurrent disease staging. Squamous cell carcinomas (SCC) of the head and neck are a heterogeneous disease. The TNM classification offers a reliable method for estimating the prognosis of patients with cancer based on certain characteristics of the tumor. It is also used in planning treatment, and has helped to standardize the way cancer is staged and treatment results are reported around the world. Although the original TNM system was based solely on the anatomic extent of the tumor, other non-anatomic parameters have found their way into the staging paradigm. The objective of this communication is to present the characteristics of the TNM staging system and review the current modification in the 8th version of the head and neck cancer staging. The objective of this article is to describe the characteristics of the TNM staging system and review the changes made to head and neck cancer staging in the most recent (8th) edition.

RESUMEN

El sistema de etapificación de la AJCC/UICC es una herramienta de gran utilidad en oncología y es actualmente utilizado en todo el mundo para la etapificación clínica, patológica y de la enfermedad recurrente. El cáncer de células escamosas de la cabeza y el cuello es una enfermedad heterogénea. La clasificación de TNM ofrece un método confiable para estimar el pronóstico de pacientes con cáncer basado en ciertas características del tumor. Sin embargo, también se utiliza en la planificación y selección de tratamiento y ha contribuido a estandarizar la forma de cáncer se etapifica y los resultados del tratamiento son registrados y reportados alrededor del mundo. Aunque el sistema TNM se basó inicialmente únicamente en la extensión anatómica del tumor, otros parámetros no anatómicos han ido encontrado su lugar en este sistema de etapificación. El objetivo de esta comunicación es describir las características del sistema de etapificación y revisar la actual modificación en la 8va versión de la etapificación del cáncer de cabeza y cuello.

Keywords

TNM Staging

head and neck cancer

squamous cell carcinoma

thyroid cancer.

Palabras clave

Etapificación TNM

cáncer de cabeza y cuello

cáncer escamoso

cáncer de tiroides.

Curr Oncol Rep. Author manuscript; available in PMC 2020 Apr 17.

Published in final edited form as:

PMCID: PMC6528815

NIHMSID: NIHMS1025119

Abstract

Purpose of review

The objectives of this article are to review the major changes in the staging of head and neck cancers and the rationale for the modifications.

Recent findings

Information gathered from various institutional reports lead to a better understanding of the clinical and biological behavior of head and neck tumors, resulting in distinct outcomes, which were used to update the staging system.

Summary

This article reviews the changes in the staging of head and neck cancers published in the 8th edition of the AJCC/UICC TNM staging system.

Keywords: TNM staging, head and neck cancer, squamous cell carcinoma, thyroid cancer, HPV related oropharyngeal cancer

Introduction

The American Joint Committee on Cancer (AJCC)/International Union Against Cancer (UICC) staging system is a tool which provides clinicians across the world with the ability to stage cancer prior to any treatment (cTNM), after surgical resection (pTNM), and at recurrence (rTNM). Staging stratifies patients into various prognostic groups and, based on the stage of the disease, it is possible to select best treatment option, plan the treatment, and estimate prognosis.

In 1944, Pierre Denoix proposed a staging system for solid tumors based on tumor characteristics (T), nodal spread (N) and distant metastasis (M)[1]. The UICC adopted this system in 1954. The AJCC was established in 1958. The UICC and AJCC worked independently for nearly 25 years and had separate staging systems for classification of cancer. The first edition of the AJCC/UICC TNM classification was published in 1987. Since then, the TNM classification has been widely used not only to plan treatment and to reliably estimate the prognosis of patients but also to evaluate treatment results and to compare outcomes between institutions in different parts of the world [1, 2].

The simplicity of TNM staging makes it the most accepted and used system in clinical practice. In order to increase acceptance and compliance, by design the TNM staging system has to be kept simple and user-friendly. A highly complex staging system may be most accurate, but may not be easy to accept in clinical practice, and thus will have poor compliance. Therefore, some important prognostic information (tumor and host factors) are often not included in the staging system to keep it simple and increase compliance. Each new edition of the AJCC / UICC staging manual incorporates changes and improves the prognostic accuracy and predictability. The major modifications in the 8th edition were changes in the T category for oral cavity cancer by incorporating depth of invasion of the primary tumor; inclusion of extranodal extension in N staging except in p16+ oropharynx cancer and nasopharynx cancer; the division of the pharynx chapter into one chapter for oropharynx (p16-) and hypopharynx, a separate chapter describing the staging system for human papilloma virus-related (p16+) oropharyngeal cancer, and a third separate chapter for nasopharynx; new head-and-neck-specific cutaneous malignancy and soft tissue sarcoma chapters; and changes in the age cutoff and N categories for staging of thyroid cancer. These modifications were based on information gathered from various institutional reports leading to a better understanding of the clinical and biological behavior of these tumors, resulting in distinct outcomes [3].

Twenty-eight specialists from various disciplines with expertise and knowledge in head and neck cancer biology and staging formed the AJCC Head and Neck Task Force. The group analyzed in detail chapters from the 7th edition and proposed changes to incorporate new information. When the task force recommended changes, additional analyses were performed to confirm if there is available data to support the modifications [4]. The aim of this article is to review some of the major changes in the staging of head and neck cancers and the rationale for the modifications that were published in the 8th edition of the AJCC/UICC TNM staging system.

Oral Cavity Cancer

Traditionally, the greatest dimension of the tumor was the most important characteristic for the T stage categories in oral cancer. Since depth of invasion (DOI) has been shown to have prognostic implications, with deeper tumors showing an increased risk of nodal metastases and decreased disease-specific survival, this parameter was included in the categorization of T stages in the AJCC 8th edition (Table 1) [5]. Clinical assessment of accurate DOI can be challenging but differentiation among thin (≤ 5 mm), intermediate (> 5 mm and ≤ 10 mm) and thick (> 10 mm) lesions is usually possible in the hands of experienced head and neck surgeons.

Table 1.

Primary tumor (T) definition for oral cavity cancers.

In the past, lip was included in oral cavity primary sites. Lip is now divided into mucosal and cutaneous lip. Mucosal lip is included in oral cavity.

The N category was also modified in the 8th edition. Extranodal extension (ENE) has been shown to have a profound effect on prognosis of most head and neck cancers, except for tumors associated with HPV, and therefore, it was incorporated in the N category [6]. In order to clinically classify the disease as ENE+, unambiguous evidence of ENE in clinical examination supported by strong radiological evidence ENE must be present. Note that once clinical ENE is detected, the disease is cN3b. In case of doubt, the lower category should be assigned (ENE-) [3]. Clinical and pathological N stage categories for squamous cell carcinomas of the oral cavity and all other head and neck sites (except for HPV-related oropharynx, nasopharynx, melanoma, thyroid, and sarcoma) are described in Tables 2 and ​3, respectively.

Table 2.

Clinical assessment of regional lymph nodes (cN).

Table 3.

Pathological assessment of regional lymph nodes (pN).

Nasopharyngeal Cancer

Nasopharyngeal cancers (NPC) have a unique biology and was given a separate chapter in the AJCC 8th edition. The major changes are the inclusion of a T0 category for patients with Epstein-Barr virus (EBV) positive metastatic cervical lymph nodes with unknown primary, clarification to avoid ambiguity for the other T categories, and changes in the regional lymph node definition. Unlike the other head and neck cancer sites for which surgery plays an important role in primary treatment, NPC is treated primarily with radiotherapy with or without chemotherapy. For this reason, pathological classification is not relevant in this disease. Tables 4, ​5 and ​6 describe the tumor, node and overall stage classification of NPC, respectively [3].

Table 4.

Primary tumor (T) definition for nasopharyngeal cancers.

Table 5.

Assessment of regional lymph nodes (N) in nasopharyngeal cancers.

Table 6.

AJCC prognostic stage groups for nasopharyngeal cancers.

Oropharyngeal Cancer

Human papillomavirus (HPV) related or p16-positive oropharyngeal cancer (OPC) is a different entity that occurs more frequently in younger individuals, with little or no tobacco exposure, and that usually shows excellent response to treatment even in patients with advanced stage disease. The incidence of OPC associated with HPV has been rising since 1990 and the observation of the diverse clinical and biological behavior of p16-positive OPC versus p16-negative OPC has been reported by many authors [7, 8]. Because it behaves as a completely different disease when compared to p16-negative OPC, a separate staging system was developed for HPV-related (p16-positive) OPC [9]. However, the T categories for both p16-positive and p16-negative OPC remain similar. The main differences are: Tis is not included in p16-positive OPC, T0 (unknown primary in patients with metastatic nodes tested positive for p16) category is only used in p16-positive metastatic nodes, where the primary is presumed to be OPC, and the T4b category has been removed from p16-positive OPC. Table 7 describes the T categories for p16-positive OPC. The clinical N staging categories for p16-positive disease are shown in Table 8. Ipsilateral nodes (one or multiple), none larger than 6 cm are staged N1. Contralateral or bilateral nodes are classified as N2, as long as none of them is larger than 6 cm. Nodes that are greater than 6 cm are included in N3 category. Pathological staging is only applicable to patients who are treated with surgery. For HPV-related (p16-positive) OPC treated with surgery, an important change in behavior is observed when the number of positive nodes was between 1 and 4 versus 5 or more [3]. This was incorporated in pN staging for p16-positive tumors. The pathological N categories for HPV-related (p16-positive) OPC are shown in Table 9. The clinical and pathological prognostic stage groups are described in Tables 10 and ​11.

Table 7.

Primary tumor (T) definition for HPV-related (p16-positive) oropharyngeal cancers.

Table 8.

Clinical assessment of regional lymph nodes (cN) in HPV-related (p16-positive) oropharyngeal cancers.

Table 9.

Pathological assessment of regional lymph nodes (pN) in HPV-related (p16-positive) oropharyngeal cancers.

Table 10.

AJCC prognostic clinical stage groups for HPV-related (p16-positive) oropharyngeal cancers.

Table 11.

AJCC prognostic pathological stage groups for HPV-related (p16-positive) oropharyngeal cancers.

Cutaneous Carcinoma of the Head and Neck

Staging of skin cancers was developed by a multidisciplinary team to create a system for nonmelanoma skin cancers of the head and neck. It encompasses 82 different types of skin cancers excluding melanoma and Merkel cell carcinoma. The cutaneous lip consisting of the keratinizing epithelium of the vermilion border is included in this classification. In spite of expected diversity among skin cancers that are included in this group, basal cell carcinomas and squamous cell carcinomas are the most common varieties in the head and neck area. A decision was made for a common staging system because it would not be feasible to have a meaningful system for each of the individual histologic types. This new chapter was created to emphasize the importance of staging these tumors in the head and neck area. T categories are based on independent risk factors for poor prognosis [10]. Table 12 describes the T categories for cutaneous carcinomas of the head and neck.

Table 12.

Primary tumor (T) definition for cutaneous carcinomas of the head and neck.

Head and Neck Soft Tissue Sarcoma

Sarcomas of the head and neck are separately staged from the general soft tissue sarcomas of the trunk and extremities because that staging system did not suit this anatomic region. The size cutoffs for T are changed to 2 and 4 cm (T1 ≤ 2 cm, T2 > 2 cm and ≤ 4 cm, T3 > 4 cm, T4 tumor invades adjoining structures). Nodal disease is uncommon and is staged as N0 (when no regional lymph node metastases are present or if the lymph node status is unknown) or N1 (lymph node metastasis is present) [3].

Thyroid

Significant changes were made in thyroid cancer staging. Modifying the age cutoff from 45 to 55 years of age [11] and excluding microscopic extrathyroidal extension from the definition of T3 resulted in downstaging a significant number of patients. Downstaging these patients correctly fitted them in the right group according to their risk for dying from thyroid cancer [12]. Table 13 describes the definition of the primary tumor (T). The definition of nodal metastases is also revised. Metastatic lymph nodes in the central neck (levels VI and VII) are now staged as N1a. Lymph nodes in the lateral neck are staged N1b (table 14). In the previous editions, all anaplastic thyroid cancers were staged as T4. In this new edition, anaplastic thyroid cancers are classified using the same definitions for T category as differentiated thyroid cancer. Tables 15 and ​16 describe the prognostic stage groups for differentiated and anaplastic thyroid cancers, respectively.

Table 13.

Primary tumor (T) definition for papillary, follicular, poorly differentiated, Hurthle cell and anaplastic thyroid carcinoma.

Table 14.

Assessment of regional lymph node (N).

Table 15.

AJCC prognostic stage groups for differentiated thyroid cancer.

Table 16.

AJCC prognostic stage groups for anaplastic thyroid cancer.

Improving the TNM staging system

The goal of updating the staging system is to use new knowledge about the disease to develop a model to predict outcomes better than the previous editions. Advances in understanding the behavior of the disease and risk factors, as well as new imaging technologies and emerging new therapies can improve outcomes. For this reason, periodically revising the outcome prediction capability of the system is needed. Keeping the staging system as simple as possible is important to make it universally used and to standardize the way head and neck oncologists present and discuss their results. A simple system, however, will not allow for an accurate personalized prognostic tool. Nomograms are calculation devices that have been widely tested in a variety of cancers, including in the head and neck [13–19]. This prediction tool is dynamic, personalized, and can predict prognosis individually with a higher accuracy. Therefore, nomograms will likely be widely used in the near future.

Conclusions

Since the 1940s when it was first described, the TNM staging system has been continuously used for cancer prognostication. Its user-friendliness has allowed it to be implemented and used worldwide. With the understanding of many other tumor and host factors that can influence outcomes, it will be challenging to create a tool as simple as the TNM that can incorporate all these factors

Acknowledgements

This work was funded in part through the NIH/NCI Cancer Center Support Grant P30 CA008748.

References

Papers of particular interest, published recently, have been highlighted as: of importance.

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