Prospective multicenter cohort study of estrogen and insulin-like growth factor system in BRCA mutation carriers.

PURPOSE

Major clinical characteristics of BRCA1/2-related cancers include association with estrogen and metabolic consequences. We aimed to evaluate serum estradiol (E2) and insulin-like growth factor 1 (IGF-1) levels as a marker of insulin resistance in BRCA1/2 mutation carriers and high-risk, BRCA-negative controls.

METHODS

Eligible cancer-free women (age 18-42 with regular menstrual cycles) who had been screened for BRCA1/2 mutations between 2005 and 2013 completed a questionnaire and underwent a single blood draw. E2 was measured with radioimmunoassay, and IGF-1 was measured with enzyme-linked immunosorbent assay.

RESULTS

Eighty-six women participated (44 carriers and 42 non-carriers) in this study. BRCA mutation carriers were significantly younger than non-carriers (p = 0.0002). Age-adjusted basal (menstrual cycle days 2-5) serum E2 level was not significantly different between BRCA mutation carriers and non-carriers (30.4 vs. 24.7 pg/mL, p = 0.07). BRCA mutation carriers have significantly lower age-adjusted serum IGF-1 levels compared to non-carriers (89.7 vs. 112.6 ng/mL, p < 0.001). In women with BRCA mutations, the risk of having low serum IGF-1 level (IGF-1: ≤85 ng/mL) was 10.7 times as great as that of women without BRCA mutations (95 % CI 2.5, 46.2). There was a significant inverse association between basal E2 and IGF-1 levels in BRCA mutation carriers after adjusting age and BMI (p = 0.03).

CONCLUSIONS

IGF-1 level is significantly lower in cancer-free BRCA mutation carriers versus BRCA-negative controls, and there is a potential association between E2 and IGF-1 in cancer-free BRCA mutation carriers. Our findings may instigate future studies evaluating the role of both E2 and IGF-1 in BRCA mutation carriers.