5327 - Response to neoadjuvant chemotherapy in HER2 non-overexpressing breast cancer subtypes

Background

Pathologic complete response (pCR) is a surrogate marker of a better relapse-free (RFS) and overall survival (OS), particularly in HER2 overexpressing and triple-negative breast cancer (TNBC) subtypes. Our aim is to assess the impact of HER2 expression level on pCR, in patients with luminal or TNBC treated with neoadjuvant chemotherapy (NAC).

Methods

We conducted a retrospective analysis in luminal and TN non-metastatic breast cancer patients, addressed to cancer center Georges François Leclerc in Dijon for NAC. Hormone receptor and HER2 expression were centrally assessed according to CAP/ASCO criteria. The pathologic response was dichotomized in pCR and non-pCR and evaluated according to Chevalier classification.

Results

Between 2007 and 2018, 761 patients (pts) were recorded, of which 263 (34.5%) had TNBC and 498 (65.5%) luminal-HER2 negative BC. Among TNBC, 189 pts (70.8%), 54 pts (20.2%) and 24 pts (8.9%) had respectively score 0, 1 and 2, and negative FISH. In luminal tumors these results were respectively 246 (49.3%), 181 (36.3%) and 21 (4.2%). Median age, size of primary tumour and lymph node involvement were similar in both subpopulations. Regarding NAC, 20.9% received only taxanes, 22.1% only anthracyclines and 55.1% both agents. The combination was more often recommended in TNBC 74.2% vs 59.3% (p = 0.03). pCR rate in the primary tumour and lymph nodes was 29% (157 pts) in the whole cohort. This rate varied according to HER2 expression (0, 1+, 2+) from respectively 48.6% (51pts), 36.4% (8pts) and 28.6% (4pts) (p = 0.256) in TNBC and from 8.5% (7pts), 5.3% (5pts) and 4.1% (2pts) (p = 0.532) among luminal tumors. Both OS and RFS were associated with a good Chevalier pathologic response (p < 0.001) in TNBC but not in luminal tumours (p = 0.5257 and p = 0.9845). Neither pCR, nor the Chevalier response was statistically correlated with HER2 score.

Conclusions

No correlation between pCR and the level of HER 2 expression was found neither in luminal nor in TNBC patients. In TNBC patients, differences in terms of pCR were noticed between the 3 HER expression groups. The predictive role of HER2 expression should be further explored in early localized TNBC in a larger population.

Clinical trial identification

Editorial acknowledgement

Isabel Gregoire, medical writer, Department of Biostatistics Georges Francois Leclerc Cancer Center, Dijon, France.

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.