Abstract 138P
Background
The role of HER2 status as possible predictor of pathological complete response (pCR) and disease-free survival (DFS) in Luminal-HER2-negative EBC patients undergoing NACT is currently unclear. In this regard, a retrospective analysis evaluating the correlation between HER2 status (low vs score 0) and pCR/DFS was conducted.
Methods
Data of EBC patients undergoing NACT and surgery were collected. HER2 low breast cancer (BC) was defined as IHC score of 1+ or 2+ with negative FISH. Concordance of HER2 status at biopsy and residual disease (RD) was analyzed. Logistic regression model and Cox proportional hazard model were adopted to investigate the putative independent role of HER2 status and outcomes of interest (pCR, CPS-EG and DFS).
Results
566 patients were included: 340 (60%) were HER2 low and 226 (40%) were HER2 0; 294 (61%) and 186 (39%) of non-pCR patients had HER2 low and HER2 0 expression on biopsy, respectively. 281 (63%) had HER2 low expression on RD. The HER2 discordance rate was 35% (158/452), with 17% (78/452) converting from HER2 0 to HER2 low and 17% (76/452) from HER2 low to HER2 0. The concordance rate of HER2 low BCs between pre- and post-NACT was significantly higher than that of HER2 0 BCs (71% vs 55%, p<0.001). pCR was achieved in 13% (n=45) of HER2 low vs 18% (n=40) of HER2 0 (p=0.21). There was no correlation between baseline HER2 status and CPS-EG score (p=0.13). With a median follow-up of 53.6 months, a trend toward improved DFS for HER2 low BC was observed (HR 0.72; 95% CI 0.51-1.03, p=0.07), with 5-year DFS of 78.5% (95% CI 72.7%-84.6%) vs 68.8% (95% CI 61.7%-76.7%) for HER2 low and HER2 0 BCs, respectively. While in the HER2 0 cohort, there was a relapse peak at 24-36 months after surgery, in the HER2 low cohort the relapse rate showed a steady increase after surgery. No DFS difference was found between concordance vs discordance (p=0.30), concordant HER 0 vs gain of HER2 low (p=0.85) or concordant HER2 low vs loss of HER2 low (p=0.17).
Conclusions
Among Luminal-HER2-negative EBCs, our results do not support a clear predictive and prognostic effect of HER2 status, although a trend of worse pCR and better survival for HER2 low BCs cannot be ruled out.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.