Study design: evaluating gene-environment interactions in the etiology of breast cancer - the WECARE study.
BACKGROUND
Deficiencies in cellular responses to DNA damage can predispose to cancer. Ionizing radiation can cause cluster damage and double-strand breaks (DSBs) that pose problems for cellular repair processes. Three genes (ATM, BRCA1, and BRCA2) encode products that are essential for the normal cellular response to DSBs, but predispose to breast cancer when mutated.


METHODS
To examine the joint roles of radiation exposure and genetic susceptibility in the etiology of breast cancer, we designed a case-control study nested within five population-based cancer registries. We hypothesized that a woman carrying a mutant allele in one of these genes is more susceptible to radiation-induced breast cancer than is a non-carrier. In our study, 700 women with asynchronous bilateral breast cancer were individually matched to 1400 controls with unilateral breast cancer on date and age at diagnosis of the first breast cancer, race, and registry region, and counter-matched on radiation therapy. Each triplet comprised two women who received radiation therapy and one woman who did not. Radiation absorbed dose to the contralateral breast after initial treatment was estimated with a comprehensive dose reconstruction approach that included experimental measurements in anthropomorphic and water phantoms applying patient treatment parameters. Blood samples were collected from all participants for genetic analyses.


CONCLUSIONS
Our study design improves the potential for detecting gene-environment interactions for diseases when both gene mutations and the environmental exposures of interest are rare in the general population. This is particularly applicable to the study of bilateral breast cancer because both radiation dose and genetic susceptibility have important etiologic roles, possibly by interactive mechanisms. By using counter-matching, we optimized the informativeness of the collected dosimetry data by increasing the variability of radiation dose within the case-control sets and enhanced our ability to detect radiation-genotype interactions.
Bernstein
Jonine L
JL
Department of Community and Preventive Medicine, Mount Sinai School of Medicine, New York, NY, USA. jonine.bernstein@mssm.edu
Langholz
Bryan
B
Haile
Robert W
RW
Bernstein
Leslie
L
Thomas
Duncan C
DC
Stovall
Marilyn
M
Malone
Kathleen E
KE
Lynch
Charles F
CF
Olsen
Jørgen H
JH
Anton-Culver
Hoda
H
Shore
Roy E
RE
Boice
John D
JD
Berkowitz
Gertrud S
GS
Gatti
Richard A
RA
Teitelbaum
Susan L
SL
Smith
Susan A
SA
Rosenstein
Barry S
BS
Børresen-Dale
Anne-Lise
AL
Concannon
Patrick
P
Thompson
W Douglas
WD
D000328:Adult; D000483:Alleles; D064007:Ataxia Telangiectasia Mutated Proteins; D001943:Breast Neoplasms / Q000453:epidemiology / Q000209:etiology* / Q000235:genetics / Q000532:radiotherapy; D016022:Case-Control Studies; D018797:Cell Cycle Proteins; D003043:Cocarcinogenesis; D004268:DNA-Binding Proteins; D005260:Female; D019398:Genes, BRCA1; D024522:Genes, BRCA2; D016147:Genes, Tumor Suppressor; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006801:Humans; D016013:Likelihood Functions; D008875:Middle Aged; D009381:Neoplasms, Radiation-Induced / Q000453:epidemiology / Q000209:etiology* / Q000235:genetics; D016609:Neoplasms, Second Primary / Q000453:epidemiology / Q000209:etiology* / Q000235:genetics; D019047:Phantoms, Imaging; D017346:Protein Serine-Threonine Kinases / Q000235:genetics; D011878:Radiotherapy / Q000009:adverse effects*; D011879:Radiotherapy Dosage; D012042:Registries / Q000706:statistics & numerical data; D012107:Research Design; D016037:Single-Blind Method; D025521:Tumor Suppressor Proteins
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases