HER2-low status may not affect survival outcomes of patients with MBC receiving palbociclib plus ET as frontline therapy.

[Hazelgreen]

A retrospective study was conducted with "252 consecutive HR+/HER2- MBC patients who received first-line ET plus palbociclib at six Italian Oncology Units between March 2016 and June 2021".

The researchers were interested in "the prognostic significance of HER2-low status in HR+/HER2- metastatic BC (MBC) patients treated with endocrine therapy (ET) plus palbociclib as first line"...."The authors found no statistically significant differences in the progression-free survival or overall survival between the HER2-low and HER2-0 subgroups."

"Approximately 45–50% of breast cancers (BCs) have a HER2 immunohistochemical score of 1+ or 2+ with negative in situ hybridization, defining the “HER2-low BC” subtype. No anti-HER2 agents are currently approved for this subgroup in Europe, where treatment is still determined by HR expression status."

"A total of 165 patients were included in the analysis: 94 (57%) and 71 (43%) patients had HER2-0 and HER2-low disease, respectively. The median age at treatment start was 64 years. No correlation between patients and tumor characteristics and HER2 status was found."

"Median PFS (mPFS) for the entire study cohort was 20 months (95% CI,18–25 months), while median OS (mOS) was not reached at the time of analysis. No statistically significant differences, in terms of PFS (p = 0.20) and OS (p = 0.1), were observed between HER2-low and HER2-0 subgroups."

"Conclusions: In our analysis, HR+ MBC patients with low HER2 expression who received first-line treatment with ET plus Palbociclib reported no statistically different survival outcomes compared to HER2-0 patients."

[Bettybuckets]

thanks hazel!

[hurricaneheather]

thank you for sharing this.

[Gingerann1]

Hi Hazelgreen! Guess this was a little too clinical for me…low status, etc. I am on Ibrance and Fulvestrant as first line treatment for 2 years next month. Can you break this down a little so I can understand the study?

[Hazelgreen in reply to Gingerann1]

Hi Ann,

The study is particularly relevant to you if you have been diagnosed as HER2- low.

Since you are on Ibrance and Fulvestrant, your cancer was probably diagnosed as ER+ HER2- (negative, not low). If that is indeed the case, the findings of the study will not matter to you.

It is true though that sometimes cancer cells mutate, and HER2- becomes HER2-low. If that happens, it is good to know, from the findings of this study, that may not make a difference to your treatment. We all hope to remain on each treatment as long as possible.

I hope this helps, Cheers, Cindy

[Gingerann1 in reply to Hazelgreen]

Thanks for the clarification!

[Bestbird]

Hazelgreen, thank you for your reply. One small clarification: HER2 negative encompasses patients with HER2 low (HER2 +1 and HER2 +2) and HER2 zero (HER2 0) as per test results. HER2 low patients have HER2 +1 or HER2 +2 but not HER2 zero.