Abstract 183P
Background
Breast cancer (BC) accounts for 9.1% of all new cancer cases diagnosed in the Republic of Belarus in 2019. This study assessed germinal BRCA1 «founder» mutations frequency and a risk of the disease progression according to BRCA1 status in patients (pts) with different HER2-negative molecular subtypes of BC.
Methods
Pts clinical characteristics were collected from N.N. Alexandrov National Cancer Centre of Belarus registry. Ki-67 cut-off was 20%. The main criterias for referring pts with BC for BRCA-testing were young age (<40 yrs) and family history of BC. The statistical differences in genotypes distribution and clinical characteristics among the groups were compared using the chi-square, exact Fisher, Log Rank and U tests.
Results
496 records were provided from January 2018 through September 2022. Median follow up was 19 months; the mean age was 45 yrs.; TNBC – 37,1% (n=184), Luminal B – 30,0% (n=149) and Luminal A – 32,9% (n=163). There was no statistical difference in age and stage distribution between groups with different molecular subtypes of BC. BRCA1 «founder» mutations were detected in 20,4% cases (n=101) with a statistically significant prevalence in TNBC group (TNBC – 35,9%, Luminal B – 20,8%, Luminal A – 2,5%; p<0,001).). BRCA1-mut frequency in pts with early stages of the disease (I-II) was 43,7% in TNBC group and 18,1% in Luminal B (p<0,001). However, pts with advanced stages (III-IV) in both groups have similar frequency of BRCA1-mut (25,9% vs 24,2%). Pts with I-II stages of the disease and BRCA1-mut progressed less frequently during follow up period than BRCA1-WT (Luminal B: 13,3% vs 30,7%, p = 0,17; TNBC: 17,7% vs 36,2%, p<0,05). Pts with III stage of BC had similar tendency in risk of progression depending on BRCA1 status (mut vs WT) in both Luminal B (25,0% vs 45,5%) and TNBC (35,3% vs 48,7%), however non-significant. Also there were no statistical differences in PFS/OS between BRCA1-mut and BRCA1-WT pts with different molecular subtypes of BC.
Conclusions
Germinal BRCA1-mut in pts with Luminal A BC were rare even in selected cohort. BRCA1-mut TNBC more often diagnosed in pts with early stages and had lower risk of progression than BRCA1-WT. In pts with Luminal B HER2- molecular subtype this risk reduction effect was not significant.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.