Staging is considered the universal language that describes the extent to which a cancer has developed or spread. The TNM system, which assigns a letter and number to describe a Tumor, Nodal involvement, and presence or absence of Metastases, has been used for decades to stage the majority of cancer types. Although this system is primarily an anatomic approach, it is used throughout the world to guide cancer treatment and predict prognosis.
Technological advances in cancer detection and identification have made biologic markers, such as genomic profiles and molecular targets, increasingly important in the understanding of how different types of cancer present themselves and respond to treatment. These advances have spawned “prognostic staging,” which incorporates and supersedes anatomic staging. It is anticipated that starting next year, the prognostic stage of a cancer will be the primary stage that is recorded in cancer registries in the United States.
The forthcoming 8th edition of the American Joint Committee on Cancer (AJCC) Cancer Staging Manual (which will be effective for all cases diagnosed as of January 1, 2018, and onward) includes cancer staging changes that incorporate biologic information. For example, the prognostic staging of breast cancer will include TNM staging and grade along with HER2, estrogen receptor (ER), and progesterone receptor (PR) status.
When appropriate, it also will include genomic profiles, such as Oncotype DX and MammaPrint results. Information from multigene panels is incorporated for patients with T1-2N0M0, ER-positive, HER2-negative tumors.
With these 8 variables (tumor, nodal involvement, metastases, grade, ER, PR, HER-2, and multigene panel score), the complexity of staging has increased. The result is the creation of several hundred possible combinations of variables.
Other noteworthy changes include the elimination of lobular carcinoma in situ as a breast cancer diagnosis. It is estimated that with the new AJCC staging system there will be more cases of stage I disease diagnosed in the United States and fewer cases of stage IIA, IIB, and IIIA breast cancer.
All disease sites in the updated staging manual will incorporate nonanatomic prognostic factors when relevant and include prognostic risk-calculating models for cancers of the breast, colon, prostate, lung, and head and neck; melanoma; soft tissue sarcoma; and select hematolymphoid malignancies.
Oropharyngeal cancer staging systems will include human papillomavirus status; there is a separate staging system for patients receiving neoadjuvant therapy for various cancers, and the staging system for bone and soft tissue sarcomas is further delineated.
The updated AJCC staging system includes the anatomy- and histology-based original TNM staging system and uses the addition of various biomarkers to refine prognostic information. The ultimate goal is better treatment and improved treatment outcomes. For example, using the new staging system, it is now possible to identify women with invasive breast cancer with a prognosis so favorable that they may forgo systemic chemotherapy. This ability to predict benefit from or resistance to specific treatments is of major clinical relevance.
The new staging system creates a bridge between a population-based approach to cancer staging and a more personalized approach. The system will continue to be refined and updated as new information on the biology and genomics of different types of cancer emerges.