Abstract 1991P
Background
This study evaluated the relationship between circulating tumor DNA (ctDNA), and tumor features and prognosis in breast cancer patients.
Methods
We determined E542K, E545K, H1047R PIK3CA mutations in 183 plasma samples preserved at biobank from the Instituto Nacional de Enfermedades Neoplasicas and 140 paired paraffin samples as well as pathological features including TIL levels and CD63 staining (Epithelial-Mesenchymal-Transition marker), and clinical characteristics including outcome data were collected. Overall survival (OS) was calculated from date of blood sample drawn.
Results
We analyzed plasma samples from 183 breast cancer patients. Median age was 54 years, most frequent histology was ductal (90%), Luminal-B phenotype (44.8%) and clinical stage (CS) II (50.8%). PIK3CA hotspot mutations in plasma was found in 35% cases (most with E545K). Paraffin tumor samples were evaluated in 140 paired cases, and PIK3CA mutation rate was 46% and was not related to detection in plasma samples (p=0.62). Median TIL was 20% and CD63 was positive in 70.5%. Mutation of PIK3CA in tumor was found in 46% and was associated to (p=0.019) and ctDNA had a trend (p=0.069) to be associated to TIL level of ≤20%. The median follow-up from the plasma drawn was 29.3 months (range 1.4– 44.4 months). Shorter survival was associated to TNBC phenotype (p=0.004) and advanced stages (p<0.001). Presence of PIK3CA in plasma was associated with shorter survival (73.4 vs. 84.9% at 3 years, p=0.049). This association kept in advance stages (III and IV/Recurrent) (72.0% vs. 51.6% at 3 years, p=0.030) but not in I-II (p=0.994) clinical stages. However, the analysis of the 154 early cases without metastasis at the drawn time found a total of 21 recurrence events which was associated to shorter overall survival (p<0.001), however not differences in DFS in those with or without PIK3CA in plasma (87.5% vs. 85.8% at 3 years, p=0.729).
Conclusions
Presence of PIK3CA hotspot mutations in plasma was found in 35% of the cases and was associated to shorter survival. This work was supported by CONCYTEC (contract No. 198-2015-CONCYTEC).
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
CONCYTEC.
Disclosure
All authors have declared no conflicts of interest.