Prediagnostic Calcium Intake and Lung Cancer Survival: A Pooled Analysis of 12 Cohort Studies

Abstract

Background: Lung cancer is the leading cause of cancer death. Little is known about whether prediagnostic nutritional factors may affect survival. We examined the associations of prediagnostic calcium intake from foods and/or supplements with lung cancer survival.Methods: The present analysis included 23,882 incident, primary lung cancer patients from 12 prospective cohort studies. Dietary calcium intake was assessed using food-frequency questionnaires at baseline in each cohort and standardized to caloric intake of 2,000 kcal/d for women and 2,500 kcal/d for men. Stratified, multivariable-adjusted Cox regression was applied to compute hazard ratios (HR) and 95% confidence intervals (CI).Results: The 5-year survival rates were 56%, 21%, and 5.7% for localized, regional, and distant stage lung cancer, respectively. Low prediagnostic dietary calcium intake (<500-600 mg/d, less than half of the recommendation) was associated with a small increase in risk of death compared with recommended calcium intakes (800-1,200 mg/d); HR (95% CI) was 1.07 (1.01-1.13) after adjusting for age, stage, histology, grade, smoking status, pack-years, and other potential prognostic factors. The association between low calcium intake and higher lung cancer mortality was evident primarily among localized/regional stage patients, with HR (95% CI) of 1.15 (1.04-1.27). No association was found for supplemental calcium with survival in the multivariable-adjusted model.Conclusions: This large pooled analysis is the first, to our knowledge, to indicate that low prediagnostic dietary calcium intake may be associated with poorer survival among early-stage lung cancer patients.Impact: This multinational prospective study linked low calcium intake to lung cancer prognosis. Cancer Epidemiol Biomarkers Prev; 26(7); 1060-70. ©2017 AACR.

Figure 1

Risk of death by prediagnostic dietary calcium intake (low vs. recommended intake) in subgroups of the Calcium and Lung Cancer Pooling Project. Low intake was defined as calcium intake less than half of the recommended dietary allowance (RDA), which is less than 500 mg/d for men ≤70 y and women ≤50 y, or less than 600 mg/d for men >70 y and women >50 y. Recommended intake was defined as calcium intake between the estimated average requirement (EAR) and RDA, which is 800–1000 mg/d for men ≤70 y and women ≤50 y, or 1000–1200 mg/d for men >70 y and women >50 y. The same stratified, multivariable-adjusted Cox model was used as shown in Table 2 footnote.

Figure 2

Risk of death by prediagnostic dietary calcium intake in the Calcium and Lung Cancer Pooling Project (solid line: hazard ratio, dashed line: 95% confidence interval) among: a. early-stage lung cancer patients (P = 0.03); b. early-stage male patients (P = 0.02); and c. early-stage female patients (P = 0.39). The same stratified, multivariable-adjusted Cox model was used as shown in Table 2 footnote.