Pre‐diagnosis lipid levels and mortality after obesity‐related cancer diagnosis in the Women's Health Initiative cardiovascular disease biomarker cohort

BACKGROUND: Published studies have demonstrated inconclusive relationships between serum lipid levels and mortality after cancer. METHODS: The primary objective was to evaluate the relationship between fasting lipid levels and mortality after cancer. Data were obtained on baseline lipids and outcomes after cancer from 1263 postmenopausal women diagnosed with 13 obesity‐related cancers who were part of the Women's Health Initiative (WHI) lipid biomarkers cohort. Obesity‐related cancers included incident invasive cancers of the breast, colorectum, endometrium, esophagus (adenocarcinoma), kidney, liver, gallbladder, pancreas, ovaries, small intestine, thyroid, stomach, as well as multiple myeloma. Baseline lipid measurements included high‐density lipoprotein (HDL)‐cholesterol, low‐density lipoprotein (LDL)‐cholesterol, and non‐HDL‐cholesterol. Outcomes were all cause, cancer‐specific, and CVD mortality. Multivariable Cox proportional hazards models were used to measure associations between lipid levels and mortality (all cause, cancer, and CVD) after a cancer diagnosis, with lipids analyzed as continuous variables. RESULTS: Among women with obesity‐related cancer, there were 707 deaths, of which 379 (54%) were due to cancer and 113 (16%) were due to CVD. Mean time from blood draw to cancer diagnosis was 5.1 years (range: 0.05–10 years). LDL‐C values above the 95th percentile were associated with higher risk of all‐cause mortality (p < 0.001), and cancer‐specific mortality (p < 0.001), but not mortality due to CVD. Non‐HDL‐C values above the 65th percentile were associated with higher risk of all‐cause mortality (p = 0.01) and mortality due to CVD (p = 0.003), but not cancer‐specific mortality (p = 0.37). HDL‐C values above the 95th percentile were associated with lower all‐cause mortality (p = 0.002), and above the 65th percentile with lower cancer‐specific mortality (p = 0.003), but no significant relationship with mortality due to CVD was observed. CONCLUSIONS: The relationship between pre‐diagnosis fasting lipid levels and mortality after cancer diagnosis is complex. These results suggest that improved lipid control through lifestyle and anti‐lipid medications could have a meaningful impact on outcomes after cancer.