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A novel prognostic staging system for patients with de novo metastatic breast cancer (dnMBC) reflects improved outcomes for this disease, accurately summarizes prognosis, and facilitates patient-provider communication, researchers reported in the .

Although the American Joint Commission on Cancer (AJCC) revised staging guidelines for breast cancer in 2016, "this did not include any refinement for patients with dnMBC in that all patients, regardless of disease features, remained grouped into one stage IV category," explained Jennifer Plichta, MD, director of the Breast Risk Assessment Clinic at Duke Cancer Institute in Durham, North Carolina. "Our data confirm that the outcomes in this patient population are heterogeneous."

Writing about the approach, she and her co-authors said that using large population data sets and including estrogen receptor, progesterone receptor, and HER2, and grade, they identified four unique subgroups of patients with dnMBC with "distinctly different survival."

Those subgroups and the corresponding 3-year overall survival rates are as follows (P for between-group difference <0.001):

• A: 73.2%

• B: 61.9%

• C: 40.1%

• D: 17%

"In conclusion, we recommend that the AJCC expands the prognostic stage groups for patients with dnMBC to include four subgroups termed stages IVA, IVB, IVC, and IVD on the basis of 3-year OS rates," the researchers wrote. "This proposed system acknowledges and more accurately communicates the heterogeneous outcomes observed for those with dnMBC and will provide patients, caregivers, and providers useful information in treatment planning, patient understanding of their options, and focused discussions of patient values and end-of-life goals."

In the following interview, Plichta offered further details:

Why is a better prognostic staging system needed for patients with de novo metastatic breast cancer?

Plichta: Prior to the routine use of contemporary systemic therapies, survival outcomes for patients with dnMBC were dismal, and thus it probably made sense at the time to include all patients in the same category (stage IV). However, as our treatments have improved, so have survival outcomes, and our staging guidelines should reflect these advancements in treatments and improvements in outcomes.

How is your system different from other currently proposed nomograms, online tools, and staging models for patients with dnMBC?

Plichta: To our knowledge, we are one of the first groups to specifically propose a classification system for patients with dnMBC. Most other available tools yield prognostic information, but that information is not taken to the next step of placing patients into subgroups.

Our work parallels that of the current AJCC staging system, in that our proposal assigns patients a subgroup based on their estimated prognosis, which is based on their clinical information. In addition, we used a unique analytic approach -- recursive partitioning -- to create our subgroups, which allowed us to group patients with similar survival outcomes based on the variables found to be the most significant in a regression model.

Is your staging system available to clinicians who want to use it? How can they access it?

Plichta: Our work is currently being submitted to the AJCC for review and consideration for the next version of the breast cancer staging guidelines. If accepted, the staging system will be widely available to clinicians through the same resources as all other AJCC staging guidelines.

Your system does not incorporate information from genetic assays or circulating tumor DNA. Why did you not include these?

Plichta: In order to create these staging guidelines, a massive data set was needed, because there were so many variables to consider. After reviewing the available data sets, we elected to use the National Cancer Data Base, because it has the most patients with dnMBC and most of the clinical information needed, including survival. However, it does not reliably have information from genomic assays or circulating tumor DNA at this time. When this type of data becomes available in larger numbers, we hope to update the staging guidelines and include this likely significant variable.

How has the medical community responded to this proposed staging system so far?

Plichta: I began this work in 2018 and was fortunate to connect with colleagues through the AJCC in 2020 who shared a similar interest. However, our initial work that was first published in the in 2020 did not receive much attention, although it did serve as the basis for the work that we subsequently performed for this project. I think many clinicians are interested in having accurate prognostic information for their patients, and if our staging guidelines are able to reflect this, I believe practitioners will find it useful, but it will likely take some more time before it is widely accepted.

Read the study here.