Cancer
Routine lipid measurements after breast cancer diagnosis and survival: A population-based longitudinal study of serial blood measures Shana J Kim* Shana J Kim Vasily Giannakeas Brendan T Smith Husam Abdel-Qadir Jennifer D Brooks
Background: Breast cancer survivors are at increased risk of mortality and require long-term surveillance. Lipid blood tests are routinely assessed in most women over the age of 40, and can provide additional information when monitoring cancer survivors. The study objective was to investigate the association between routine lipid measurements after breast cancer and mortality among survivors in Ontario to improve post-diagnostic survivorship care.
Methods: This retrospective population-based cohort study included breast cancer cases from the Ontario Cancer Registry (2007-2019). Lipids measured after breast cancer diagnosis recorded in the Ontario Laboratories Information System database were examined as a time-varying exposure. Cox proportional hazards models estimated the HR and 95%CI of all-cause mortality. Models were adjusted for tumor characteristics, treatment, sociodemographic factors, and comorbidities. Lipids were modelled as quintiles and continuously using restricted cubic splines.
Results: Among 70,728 breast cancer survivors 8,419 (11.9%) died over a mean follow-up of 5.9 years. Breast cancer survivors with total cholesterol levels in the lowest quintile (<3.78 mmol/L) had an increased risk of all-cause mortality (HR 1.64; 95%CI 1.53, 1.75), while those in the highest quintile (≥5.81 mmol/L) had a reduced risk of all-cause mortality (HR 0.85; 95%CI 0.78, 0.91), compared to those in the middle quintile (4.44–5.06 mmol/L). When total cholesterol was modelled continuously, a U-shaped relationship was evident; total cholesterol levels below the 5th percentile (<3.05 mmol/L) and above the 95th percentile (>6.84 mmol/L) were associated with an increased risk of all-cause mortality. Findings were similar for LDL and HDL.
Conclusions: Routine lipids measured after breast cancer diagnosis are associated with all-cause mortality in a U-shaped relationship. Breast cancer survivors with very low or very high lipid levels should receive enhanced survivorship care.