Sensitive Detection of Mono- and Polyclonal ESR1 Mutations in Primary Tumors, Metastatic Lesions, and Cell-Free DNA of Breast Cancer Patients.
OBJECTIVE
Given the clinical relevance of ESR1 mutations as potential drivers of resistance to endocrine therapy, this study used sensitive detection methods to determine the frequency of ESR1 mutations in primary and metastatic breast cancer, and in cell-free DNA (cfDNA).


METHODS
Six ESR1 mutations (K303R, S463P, Y537C, Y537N, Y537S, D538G) were assessed by digital droplet PCR (ddPCR), with lower limits of detection of 0.05% to 0.16%, in primary tumors (n = 43), bone (n = 12) and brain metastases (n = 38), and cfDNA (n = 29). Correlations between ESR1 mutations in metastatic lesions and single (1 patient) or serial blood draws (4 patients) were assessed.


RESULTS
ESR1 mutations were detected for D538G (n = 13), Y537S (n = 3), and Y537C (n = 1), and not for K303R, S463P, or Y537N. Mutation rates were 7.0% (3/43 primary tumors), 9.1% (1/11 bone metastases), 12.5% (3/24 brain metastases), and 24.1% (7/29 cfDNA). Two patients showed polyclonal disease with more than one ESR1 mutation. Mutation allele frequencies were 0.07% to 0.2% in primary tumors, 1.4% in bone metastases, 34.3% to 44.9% in brain metastases, and 0.2% to 13.7% in cfDNA. In cases with both cfDNA and metastatic samples (n = 5), mutations were detected in both (n = 3) or in cfDNA only (n = 2). Treatment was associated with changes in ESR1 mutation detection and allele frequency.


CONCLUSIONS
ESR1 mutations were detected at very low allele frequencies in some primary breast cancers, and at high allele frequency in metastases, suggesting that in some tumors rare ESR1-mutant clones are enriched by endocrine therapy. Further studies should address whether sensitive detection of ESR1 mutations in primary breast cancer and in serial blood draws may be predictive for development of resistant disease. See related commentary by Gu and Fuqua, p. 1034.
School of Medicine, Tsinghua University, Beijing, People's Republic of China. Womens Cancer Research Center, Magee-Women Research Institute, Pittsburgh, Pennsylvania.
Peilu
P
Wang
Womens Cancer Research Center, Magee-Women Research Institute, Pittsburgh, Pennsylvania. Department of Human Genetics, University of Pittsburgh, Pittsburgh, Pennsylvania.
Amir
A
Bahreini
Womens Cancer Research Center, Magee-Women Research Institute, Pittsburgh, Pennsylvania. Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania.
Rekha
R
Gyanchandani
Department of Pathology, University of Pittsburgh, Pittsburgh, Pennsylvania.
Peter C
PC
Lucas
Womens Cancer Research Center, Magee-Women Research Institute, Pittsburgh, Pennsylvania. Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania.
Ryan J
RJ
Hartmaier
Womens Cancer Research Center, Magee-Women Research Institute, Pittsburgh, Pennsylvania. Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania.
Rebecca J
RJ
Watters
Womens Cancer Research Center, Magee-Women Research Institute, Pittsburgh, Pennsylvania.
Amruth R
AR
Jonnalagadda
Department of Pathology, University of Pittsburgh, Pittsburgh, Pennsylvania.
Humberto E
HE
Trejo Bittar
Department of Pathology, University of Pittsburgh, Pittsburgh, Pennsylvania.
Aaron
A
Berg
Department of Pathology, University of Pittsburgh, Pittsburgh, Pennsylvania.
Ronald L
RL
Hamilton
Department of Biostatistics, University of Pittsburgh, Pittsburgh, Pennsylvania.
Brenda F
BF
Kurland
Department of Orthopedic Surgery, University of Pittsburgh Medical Center (UPMC) Pittsburgh, Pittsburgh, Pennsylvania.
Kurt R
KR
Weiss
Department of Medicine, Division of Hematology/Oncology, University of Pittsburgh Cancer Institute and UPMC Cancer Center, Pittsburgh, Pennsylvania.
Aju
A
Mathew
Department of Medicine, Division of Hematology/Oncology, University of Pittsburgh Cancer Institute and UPMC Cancer Center, Pittsburgh, Pennsylvania.
Jose Pablo
JP
Leone
Womens Cancer Research Center, Magee-Women Research Institute, Pittsburgh, Pennsylvania. Department of Medicine, Division of Hematology/Oncology, University of Pittsburgh Cancer Institute and UPMC Cancer Center, Pittsburgh, Pennsylvania.
Nancy E
NE
Davidson
Department of Pathology, University of Pittsburgh, Pittsburgh, Pennsylvania.
Marina N
MN
Nikiforova
Womens Cancer Research Center, Magee-Women Research Institute, Pittsburgh, Pennsylvania. Department of Medicine, Division of Hematology/Oncology, University of Pittsburgh Cancer Institute and UPMC Cancer Center, Pittsburgh, Pennsylvania.
Adam M
AM
Brufsky
Department of Medicine, Division of Hematology/Oncology, University of Pittsburgh Cancer Institute and UPMC Cancer Center, Pittsburgh, Pennsylvania.
Tadeu F
TF
Ambros
Drug Discovery Institute, University of Pittsburgh, Pittsburgh, Pennsylvania.
Andrew M
AM
Stern
Womens Cancer Research Center, Magee-Women Research Institute, Pittsburgh, Pennsylvania. Department of Medicine, Division of Hematology/Oncology, University of Pittsburgh Cancer Institute and UPMC Cancer Center, Pittsburgh, Pennsylvania.
Shannon L
SL
Puhalla
Womens Cancer Research Center, Magee-Women Research Institute, Pittsburgh, Pennsylvania. Department of Human Genetics, University of Pittsburgh, Pittsburgh, Pennsylvania. Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania. oesterreichs@upmc.edu leeav@upmc.edu.
Adrian V
AV
Lee
Womens Cancer Research Center, Magee-Women Research Institute, Pittsburgh, Pennsylvania. Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania. oesterreichs@upmc.edu leeav@upmc.edu.
Steffi
S
Oesterreich
D000328:Adult; D000368:Aged; D001859:Bone Neoplasms / Q000235:genetics* / Q000473:pathology / Q000556:secondary; D001932:Brain Neoplasms / Q000235:genetics* / Q000473:pathology / Q000556:secondary; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology; D060965:Clonal Evolution / Q000235:genetics; D004273:DNA, Neoplasm / Q000235:genetics; D047628:Estrogen Receptor alpha / Q000235:genetics*; D005260:Female; D005787:Gene Frequency; D006801:Humans; D008207:Lymphatic Metastasis / Q000235:genetics; D008875:Middle Aged; D009154:Mutation
D004273:DNA, Neoplasm; C506487:ESR1 protein, human; D047628:Estrogen Receptor alpha