Published online May 24, 2020. doi: 10.5306/wjco.v11.i5.283
Peer-review started: December 31, 2019
First decision: March 15, 2020
Revised: April 16, 2020
Accepted: May 16, 2020
Article in press: May 16, 2020
Published online: May 24, 2020
Processing time: 145 Days and 4.9 Hours
Invasive lobular carcinomas (ILC) represent about 5%-10% of breast cancer. Prevalence of overexpression of human epidermal growth factor receptor 2 (HER2) in breast cancer has been reported at 4.8%-5.1%. The clinicopathological characteristics of HER2 positive (HER2+) invasive ductal carcinomas are known to differ from that of HER2 negative (HER2-) invasive ductal carcinomas. However, there remains a paucity of research examining the characteristics of HER2+ as opposed to HER2- ILC, particularly in Asian populations.
This study compares the clinicopathological characteristics of HER2+ and HER2- ILC to assess the differences in survival probability between the two groups.
This study aims to investigate the prevalence and prognostic clinicopathological factors of HER2+ ILC in an Asian population.
A retrospective review of patients with ILC seen between January 1985 and March 2018 at various SingHealth medical institutions was conducted. Demographic and clinical data were collected from medical records. We examined clinicopathological characteristics and survival in relation to HER2 status. Differences between HER2+ and HER2- ILC were tested using chi-squared test for categorical variables and Mann-Whitney U test for continuous variables. Overall survival (OS), disease-free survival (DFS) and breast cancer-specific overall survival (BCSS) were analyzed for HER2+ and HER2- status using Kaplan-Meier survival analysis and were tested using log-rank test. All statistical tests were two-sided and P < 0.05 was considered statistically significant.
Interestingly, although most ILC patients have HER2- tumours, our cohort reports a higher prevalence of HER2+ ILC (10.1%) as compared to some previous studies. The median survival time was 2.95 (interquartile range: 1.89-8.87) years and 4.16 (interquartile range: 1.84-8.32) years respectively for HER2+ and HER2- ILC patients (P = 0.315). Based on the multivariate analysis, significant negative prognostic factors were HER2+, age, ethnicity and Stage. HER2+ and Luminal B molecular subtypes also had also notably poorer OS compared to Luminal A subtype. Additional univariate and multivariate Cox proportional hazard regression analyses of BCSS and DFS demonstrated that HER2 positivity remained a significant negative prognostic factor for BCSS and DFS on both the univariate and multivariate analysis.
In conclusion, our study demonstrates the prevalence of HER2+ ILC to be 10.1%. HER2+ ILC patients were more likely to have poorer prognostic features such as estrogen receptor negativity, progesterone receptor negativity and higher tumour grade. Lastly, patients with HER2+ ILC had poorer OS, BCSS and DFS compared to those with HER2- ILC.
The findings from our study warrant further prospective studies to validate observation and investigate the benefit of various treatment modalities to improve outcomes in HER2+ ILC.