TNM Tumor Staging Revisited: A Look at Updated AJCC Guidelines

Cancer Network had the opportunity to speak with Chelsea Backler, MSN, APRN, AGCNS-BC, AOCNS, and an Oncology Clinical Specialist with the Oncology Nursing Society, during the 2018 ONS Congress, held in Washington, DC, May 17–20. Ms. Backler’s presentation, "American Joint Committee on Cancer Staging Guidelines: TNM Revisited," highlighted recent changes to the guidelines and their impact on patients.

- Interviewed by Lori Smith, BSN, MSN, CRNP

Cancer Network:Can you briefly discuss your presentation?

Chelsea Backler: The American Joint Committee on Cancer (AJCC) published the most recent edition (8th) of the staging manual in 2016, with the guidelines applying to any patient diagnosed January 1, 2018 or after. These guidelines apply to solid tumors with the exception of brain tumors and hematologic malignancies which have separate staging guidelines.

With this newest edition of the manual come some significant changes to the landscape of cancer staging as we’ve known it for the last 80 years. These changes may certainly impact oncology nursing practice, and ONS is dedicated to providing nurses with the most up-to-date information in cancer care. My presentation during the 43rd annual ONS Congress was intended to provide an overview of the fundamentals of cancer staging, highlight the changes in the 8th edition, and identify relevant nursing implications for the audience to take back to practice.

Cancer Network: Can you elaborate on some of the major changes made to the 8th edition of the AJCC Cancer Staging Manual?

Chelsea Backler: The 8th edition contains some major changes to staging in relation to nonanatomic prognostic factors. Historically, the staging of cancer has been based on an assessment of the anatomic extent of a patient’s cancer at the time of diagnosis. The elements of anatomic staging include the size of the primary tumor (T), the presence or absence of any lymph node involvement (N), and the presence or absence of distant metastases (M).

Staging not only assists the provider in determining appropriate treatment, but it also defines prognosis. Anatomic staging has been the basis for cancer staging for decades, but it is now considered less clinically relevant due to the rapid evolution of knowledge surrounding cancer biology. Research such as the Human Genome Project and the Cancer Genome Project has advanced our understanding of the molecular basis of cancer, and as a result, therapies to treat cancer have become more sophisticated and targeted. Nonanatomic or biologic factors of cancer (eg, HER2 status) have been found, in some cases, to better predict prognosis and response to treatment with more accuracy than anatomic staging alone.

Anatomic staging does not take into account these biologic data, and thus only tells part of the story for many cancer patients. The 8th edition of the AJCC Staging Manual is changing that. In the previous two editions of the manual, there was judicious addition of nonanatomic factors to staging for a few types of cancer, but staging remained primarily anatomic. The 8th edition is the first time we are seeing incorporation of nonanatomic factors in the staging of cancer patients on such a large scale, with the addition of multiple nonanatomic factors required to stage a patient across a multitude of cancer types. This edition also established four levels of evidence which guide the addition of current and future content to the manual. All of these changes were made in a 6-year span between the publishing of the 7th edition and 8th edition, making it a very large undertaking involving hundreds of multidisciplinary contributors.

Cancer Network: You discussed updated prognostic factors during your presentation. Can you please elaborate a bit on the new cancer-specific HER2, HPV, and PSA status recommendations? 

Chelsea Backler: HER2, HPV, and PSA are just a few of the nonanatomic prognostic factors that are now required to stage different types of cancers in the 8th edition. The nonanatomic prognostic factors required to stage a patient are those which are known to affect prognosis with sufficient evidence to support incorporation into staging. For example, we now understand HPV-positive oropharynx cancers are more radiosensitive; have fewer genetic alterations, which lead to better response to therapy; and occur in patients who are younger, have fewer co-morbidities, and a better performance status than patients with HPV-negative cancers.

As a result, HPV-positive patients tend to have better prognosis and treatment outcomes than HPV-negative patients. However, this would not be reflected in anatomic staging alone. The addition of nonanatomic prognostic factors, such as HPV status, allows for better personalization of treatment and a more accurate prognosis. There are two other categories of prognostic factors in the 8th edition in addition to those which are required: recommended factors and emerging factors.

Recommended prognostic factors are those which are considered clinically significant at this time but are not included as requirements for staging. An example is carcinoembryonic antigen for colon cancer. While these factors are not yet required, AJCC recommends collecting this information for cancer registries, when able, as it will help in the measurement of impact on prognosis and development of future clinical tools. Lastly, emerging factors are those which do not have enough supporting evidence to include them routinely in practice but will be re-evaluated as the evidence base grows. 

Cancer Network: Blood-based liquid biopsies were discussed during your talk. Can you explain how this tool could potentially be incorporated into the TNM system?

Chelsea Backler: Blood-based liquid biopsies and their ability to detect alterations in the cellular composition of a patient’s cancer better than a standard tissue biopsy of the primary tumor is an emerging discussion with the potential to impact cancer staging in the future. Some researchers have argued that the genetic alterations of a cancer are not well represented in a tissue biopsy of the primary tumor, because of the cellular variability within the primary tumor itself and in any distant metastases.

Circulating tumor DNA (ctDNA) present in the patient’s blood may provide additional information to better identify cancer mutations on a more systemic level, not just in the primary tumor. Because collection of this DNA is less invasive than a tissue biopsy, re-sampling over time to monitor for further changes in the cellular composition of the cancer is more feasible. If mutations can be better detected via ctDNA, this information would allow for even more accurate staging and prognosis, while also targeting treatment with a greater degree of personalization to the patient’s cancer.

The hope is this will ultimately lead to improved patient outcomes. Researchers have proposed the addition of blood-based liquid biopsies to the TNM staging system, to create the TNMB system, with “B” standing for blood-based biopsy.