New and important changes in breast cancer TNM: incorporation of biologic factors into staging

ABSTRACT

Introduction: Cancer staging has historically been based solely on the anatomic extent of the tumor (T), spread to lymph nodes (N), and the presence of distant metastases (M). More recently biologic factors have been added to modify TNM stage groups to provide more accurate prognosis for patients.

Areas covered: The American Joint Committee on Cancer (AJCC) updated breast cancer staging in 2016 to include T, N, M, tumor grade and expression of estrogen and progesterone receptors and HER2. Addition of these factors changed the stage group for a large fraction of cases compared to prior TNM stage groupings. This updated ‘prognostic stage’ provides more robust and precise prognosis information.

Expert opinion: Inclusion of biological information in staging changes the meaning and the use of stage in clinical practice. This paper reviews the evidence supporting these changes, limitations affecting staging, and discusses the implications for clinical practice and the future of breast cancer staging.

KEYWORDS:

• Breast cancer
• cancer staging
• biomarkers
• prognosis
• AJCC

Article Highlights

• Breast cancer staging using the TNM system historically used only information on the extent of the primary cancer (T), involvement of regional lymph nodes (N) and the presence of distant metastases (M).

• Defining the prognosis and treatment of breast cancer requires information on biomarkers including the tumor grade, the status of estrogen and progesterone receptors and HER2 and in some cases genomic profiles.

• In 2016, the American Joint Committee on Cancer (AJCC) updated TNM staging to base stage groups on T, N, M, grade, ER, PR and HER2; and in select cases genomic profiling.

• This results in more precise prognostic information than the prior staging system.

• The use of this changes the meaning and use of stage – it provides prognosis based on the expectation of receiving therapy and cannot be used to define treatment as in the past.

• Future revisions of staging to include other biologic or genomic information will likely require fundamental changes in staging to use predictive models in place of the current ‘bins’ system of stage groups.

Declaration of interest

The authors are all members of the AJCC Breast Expert Panel. The work of the panel is funded by the AJCC. None of the authors receive any remuneration from the AJCC or other entities for this work. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

This manuscript was not funded.