ERBB2 Status Updates Breast Cancer Prognostic Tool

Addition of ERBB2 status to the breast cancer staging system allows its application in ERRB2-positive women with breast cancer undergoing neoadjuvant chemotherapy

medwireNews: US researchers find that incorporation of the receptor tyrosine-protein kinase ERBB2 status further improves the previously validated CPS+EG staging system for evaluating the prognosis of breast cancer patients treated with neoadjuvant chemotherapy.

They explain that the original CPS+EG system, which incorporates the pretreatment clinical and post-treatment pathological stages, oestrogen receptor (ER) status and grade, “cannot be used for patients with ERBB2-positive breast cancer because its development predated the routine use of ERBB2-targeted therapy.”

Moreover, the staging system uses a cutoff of 10% to define ER positivity, whereas the current American Society of Clinical Oncology and College of American Pathologists guidelines recommend a cutoff of 1%.

The team from the University of Texas MD Anderson Cancer Center in Houston, USA, used data from 2377 women with breast cancer who received neoadjuvant chemotherapy, either with or without trastuzumab depending on their ERBB2 (also known as HER2) status, between 2005 and 2012.

In this contemporary cohort followed up for a median of 4.2 years, 5-year disease-specific survival (DSS) rates ranged from 98% to 0% for scores of 0–6 on the CPS+EG model with a 1% cutoff for ER-positive status.

And the Akaike Information Criterion score for the model using a 1% cutoff to define ER-positivity was “nearly identical” to that with a 10% cutoff, indicating that the staging system is “applicable regardless of whether a 1% or 10% cutoff is used to define ER positivity”, the authors write in JAMA Oncology.

Moreover, addition of the ERBB2 status to the CPS+EG model with a 1% cutoff significantly improved the fit of the model. Therefore, the CPS+EG system was refined to include the ERBB2 status, and this updated staging system – named Neo-Bioscore – classified patients into eight groups, with estimated 5-year DSS rates ranging from 99% to 0% for scores of 0 to 7.

Elizabeth Mittendorf and co-investigators say that the “Neo-Bioscore accounts for the favorable effect of trastuzumab on the prognosis of patients with ERBB2-positive disease by assigning an additional point to patients with ERBB2-negative breast cancer.”

And therefore, it “allows for prognostic stratification of patients with breast cancer of all subtypes who receive neoadjuvant chemotherapy.”

The researchers believe that the Neo-Bioscore could also be used “to identify high-risk patients for clinical trial participation or to stratify patients in such studies.”

Reference

Mittendorf EA, Vila J, Tucker SL, et al. The Neo-Bioscore update for staging breast cancer treated with neoadjuvant chemotherapy. Incorporation of prognostic biologic factors into staging after treatment.JAMA Oncol 2016; Advance online publication 17 March. doi:10.1001/jamaoncol.2015.6478

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