Published in:
01-09-2020 | Obesity | Epidemiology
Obesity and related conditions and risk of inflammatory breast cancer: a nested case–control study
Published in: Breast Cancer Research and Treatment | Issue 2/2020
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Purpose
Inflammatory breast cancer (IBC) is a rare, poorly understood and aggressive tumor. We extended prior findings linking high body mass index (BMI) to substantial increased IBC risk by examining BMI associations before and after adjustment for well-characterized comorbidities using medical record data for diabetes, insulin resistance, and disturbances of cholesterol metabolism in a general community healthcare setting.
Methods
We identified 247 incident IBC cases diagnosed at Kaiser Permanente Northern California between 2005 and 2017 and 2470 controls matched 10:1 on birth year and geographic area and with ≥ 13 months of continuous enrollment prior to diagnosis/index date. We assessed exposures from 6 years up to one year prior to the diagnosis/index date, using logistic regression to calculate odds ratios (ORs) with 95% confidence intervals (CIs).
Results
Before adjustment for comorbidities, ORs (95% CIs) for BMI of 25–< 30, 30–< 35, and ≥ 35 compared to < 25 kg/m2 were 1.5 (0.9–2.3), 2.0 (1.2–3.1), and 2.5 (1.4–4.4), respectively. After adjustment for pre-diabetes/diabetes, HDL-C and triglyceride levels, and dyslipidemia, corresponding ORs were 1.3 (0.8–2.1), 1.6 (0.9–2.9), and 1.9 (1.0–3.5). The OR for HDL-C levels < 50 mg/dL compared to ≥ 65 mg/dL was 2.0 (1.2–3.3) in the adjusted model. In a separate model the OR for a triglyceride/HDL-C ratio ≥ 2.50 compared to < 1.62 was 1.7 (1.1–2.8) after adjustment for BMI, pre-diabetes/diabetes, and dyslipidemia. Results did not differ significantly by estrogen receptor status.
Conclusions
Obesity and measures of insulin resistance independently increased IBC risk as did obesity and low HDL-C levels. These findings, if confirmed, have implications for IBC prevention.