ASPO Abstracts
Dietary acid load, serum polychlorinated biphenyl (PCB) levels, and mortality following breast cancer in the Long Island Breast Cancer Study Project
Category: Lifestyles Behavior, Energy Balance & Chemoprevention
Conference Year: 2021
Abstract Body:
Purpose: To examine the associations between dietary acid load (DAL) and risk of all-cause and
breast cancer-specific mortality, overall and by serum total PCB levels, among women who
participated in a population-based study of breast cancer.
Methods: Participants included 1479 women who were diagnosed with first primary invasive or in
situ breast cancer in 1996-1997 and were followed through 2014. After a median follow-up of 17
years, we identified 585 deaths (230 breast cancer-specific deaths). DAL was estimated by
calculating the Potential Renal Acid Load (PRAL) and the Net Endogenous Acid Production
(NEAP) scores using nutrient estimates derived from the baseline Food Frequency Questionnaire
completed within 3 months of diagnosis. PCBs and lipids (used to correct PCB levels) were
measured in serum samples in a subsample (n=591) of women. We used Cox regression to
estimate covariate-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for the
associations between PRAL/NEAP quartiles and all-cause and breast cancer-specific mortality.
Effect measure modification was evaluated by conducting stratified analyses (≤median versus
>median PCBs) for PRAL/NEAP median splits, and by including interaction terms between
PRAL/NEAP and PCBs in fully-adjusted models.
Results: The highest (vs. lowest) quartiles of PRAL and NEAP were not associated with all-cause
or breast cancer-specific mortality among women overall. In the upper median of PCBs, we
observed elevated rates of all-cause mortality for the upper (vs. lower) median of PRAL (HR=1.40,
95%CI=0.94-2.08) and NEAP (HR=1.37, 95%CI=0.93-2.03) in fully-adjusted models; however,
confidence intervals included the null and the multiplicative interactions were not statistically
significant (PInteraction>0.10). In the lower median of PCBs, we observed an inverse association
for the upper (vs. lower) median of NEAP and breast cancer-specific mortality (HR=0.45,
95%CI=0.21-0.96), and a null association for the upper (vs. lower) median of NEAP and breast
cancer-specific mortality in the upper median of PCBs (HR=1.01, 95%CI=0.49-2.07).
Conclusions: Our findings suggest that DAL may be associated with increased risk of all-cause
mortality following breast cancer among women with high serum total PCB levels.
Keywords: Dietary Acid Load, Breast Cancer Mortality, Polychlorinated Biphenyls, Potential Renal Acid Load, Net Endogenous Acid Production