Abstract
Purpose
Little is known regarding the mutation profiles of ctDNA in the older adult breast cancer population. The objective of this study is to assess differences in mutation profiles in the older adult breast cancer population using a ctDNA assay as well as assess utilization of testing results.
Methods
Patients with advanced breast cancer underwent molecular profiling using a plasma-based ctDNA NGS assay (Guardant360) between 5/2015 and 10/2019 at Siteman Cancer Center. The profiling results of a multi-institutional database of patients with advanced breast cancer who had undergone molecular profiling were obtained. Associations between mutations and age group (≥ 65 vs. < 65) were examined using a Fisher’s exact test.
Results
In the single-institutional cohort, 148 patients (69.2%) were < 65 years old and 66 patients (30.8%) ≥ 65 years old.
ATM, BRAF
, and
PIK3CA
mutations were found more frequently in older patients with ER + HER2- breast cancers (
p
< 0.01). In the multi-institutional cohort, 5367 (61.1%) were < 65 years old and 3417 (38.9%) ≥ 65 years old.
ATM, PIK3CA,
and
TP53
mutations were more common in the older cohort (
p
< 0.0001) and
MYC
and
GATA3
mutations were less common in the older cohort (
p
< 0.0001). CtDNA testing influenced next-line treatment management in 40 (19.8%) patients in the single-institutional cohort.
Conclusion
When controlling for subtype, results from a single institution were similar to the multi-institutional cohort showing that
ATM
and
PIK3CA
were more common in older adults. These data suggest there may be additional molecular differences in older adults with advanced breast cancers.
