The association of modifiable breast cancer risk factors and somatic genomic alterations in breast tumors: The cancer genome atlas network

Background: The link between modifiable breast cancer risk factors and tumor genomic alterations remains largely unexplored. We evaluated the association of prediagnostic body mass index (BMI), cigarette smoking, and alcohol consumption with somatic copy number variation (SCNV), total somatic mutation burden (TSMB), seven single base substitution (SBS) signatures (SBS1, SBS2, SBS3, SBS5, SBS13, SBS29, and SBS30), and nine driver mutations (CDH1, GATA3, KMT2C, MAP2K4, MAP3K1, NCOR1, PIK3CA, RUNX1, and TP53) in a subset of The Cancer Genome Atlas (TCGA). Methods: Clinical and genomic data were retrieved from the TCGA database. Risk factor information was collected from four TCGA sites (n = 219 women), including BMI (1 year before diagnosis), cigarette smoking (smokers/nonsmokers), and alcohol consumption (current drinkers/nondrinkers). Multivariable regression analyses were conducted in all tumors and stratified according to estrogen receptor (ER) status. Results: Increasing BMI was associated with increasing SCNV in all women (P = 0.039) and among women with ER- tumors (P = 0.031). Smokers had higher SCNV and TSMB versus nonsmokers (P < 0.05 all women). Alcohol drinkers had higher SCNV versus nondrinkers (P < 0.05 all women and among women with ER^þ tumors). SBS3 (defective homologous recombination-based repair) was exclusively found in alcohol drinkers with ER- disease. GATA3 mutation was more likely to occur in women with higher BMI. No association was significant after multiple testing correction. Conclusions: This study provides preliminary evidence that BMI, cigarette smoking, and alcohol consumption can influence breast tumor biology, in particular, DNA alterations. Impact: This study demonstrates a link between modifiable breast cancer risk factors and tumor genomic alterations.