Purpose: Our main aim was to explore whether pre-diagnostic circulating levels of 25-hydroxyvitamin D (25(OH)D) among older individuals with cancer were associated with overall and cancer-specific survival after diagnosis.
Design: We used data from the Reykjavik-AGES Study on participants (n = 4,619) without cancer at entry, when blood samples were taken for 25(OH)D standardized measurements. The association with cancer risk, all-cause- and cancer-specific mortality was assessed among those later diagnosed with cancer, comparing four 25(OH)D categories, using 50-69.9 nmol/L as the reference category.
Results: Cancer was diagnosed in 919 participants on average 8.3 years after blood draw. No association was observed between the reference group and other 25(OH)D groups and total cancer incidence. Mean age at diagnosis was 80.9 (± 5.7) years. Of those diagnosed, 552 died during follow-up, 67% from cancer. Low pre-diagnostic levels of 25(OH)D < 30 nmol/L were significantly associated with increased total mortality (HR: 1.39, 95% CI 1.03, 1.88) and non-significantly with cancer-specific mortality (HR: 1.33, 95% CI 0.93, 1.90). Among patients surviving more than 2 years after diagnosis, higher pre-diagnostic 25(OH)D levels (≥ 70 nmol/L) were associated with lower risk of overall (HR: 0.68, 95% CI 0.46, 0.99) and cancer-specific mortality (HR: 0.47, 95% CI 0.26, 0.99).
Conclusions: Among elderly cancer patients, low pre-diagnostic serum 25(OH)D levels (< 30 nmol/L) were associated with increased overall mortality.
Keywords: Cancer; Nutrition; Older individuals; Survival; Vitamin D.