NEW YORK (GenomeWeb) – Researchers at the University of Texas MD Anderson Cancer Center have developed a new breast cancer staging system that incorporates tumor biology as a critical prognostic indicator for women who undergo neoadjuvant therapy.
Published this week in JAMA Oncology, the Neo-Bioscore staging system incorporates HER2/ERBB2 status, which allows for more precise prognostic stratification of all breast cancer subtypes.
To date, breast cancer patient staging involved considering the size of the primary tumor, metastasis, or disease in the lymph nodes at the time of presentation as the primary factors.However, this fails to take into account the biology of the tumor, which has shown to be critically important, Elizabeth Mittendorf, associate professor of Breast Surgical Oncology at MD Anderson and corresponding author on the study, said in a statement.
The new system builds on the development of an earlier breast cancer staging system developed by MD Anderson, CPS+EG, that incorporates preclinical stage, estrogen receptor status, grade, and post-treatment pathologic stage. While it was an improvement from previous methods, it is no longer a sufficient staging system because it predates the routine use of trastuzumab in the neoadjuvant setting and therefore had a limited ability to provide prognostic information for HER2/ERBB2-positive patients, Mittendorf said.
To develop the staging system, the researchers conducted a retrospective study that evaluated 2,377 MD Anderson breast cancer patients who all had non-metastatic invasive breast cancer and were treated with neoadjuvant chemotherapy.
Each patient's clinicopathologic data were recorded, including age, clinical and pathological stage, ER status, HER2/ERBB2 status, and nuclear grade. Patients' ER status was recorded as a percentage of cells staining positive under immunohistochemical analysis. Their ERBB2 status was defined as positive at a reading of 3+ on immunohistochemical analysis or when gene amplification was shown on fluorescence in situ hybridization.
All patients received an anthracycline and/or taxane-based neoadjuvant chemotherapy regimen. Patients with HER2/ERBB2-positive disease routinely completed one year of trastuzumab therapy. After completing chemotherapy, patients underwent either breast-conserving therapy or mastectomy with axillary evaluation with or without post-mastectomy irradiation.
Patients' CPS+EG score was determined according to the previously published staging system and was calculated twice (once using 1 percent or higher as the cutoff for ER positivity and again using 10 percent or higher as the cutoff).
Their disease-specific survival (DSS) was also calculated using multiple staging systems: AJCC clinical stage, AJCC pathologic stage, CPS+EG (1 percent cutoff), and CPS+EG (10 percent cutoff). Within each staging system, DSS among subgroups was compared using the log-rank test.
After the researchers determined a CPS+EG score for each patient, they added the patient's respective HER2/ERBB2 status to the model. They then constructed the novel staging system by adding a point to the CPS+EG score for HER2-negative tumors. In the study cohort, 591 patients were HER2/ERBB2 positive.
The researchers found that in addition to validating previous findings that CPS+EG score improved prognostication of patients, the Neo-Bioscore created a more refined stratification in approximately 75 percent of the study cohort. This shift reflects the number of HER2/ERBB2-negative tumors in the study and demonstrated that adding HER2/ERBB2 standards created a highly significant improvement.
"With this tool, I can give my patients the precise information they are looking for: a more refined prognosis. Also, with this data, we will know which patients are in greatest need of additional therapy," Mittendorf said. "Hopefully these findings will result in more informed conversations between doctor and patient."