Calcium/Vitamin D May Be Protective Against Blood Cancers

Calcium and vitamin D supplementation had a protective effect against hematologic malignancies, according to a post-hoc analysis of data from the Women’s Health Initiative (WHI) Calcium/Vitamin D study.

Women assigned to modest supplementation had a 20% decreased risk of incident hematologic malignancy, the study found.

“Considered in absolute terms, the size of the effect is not likely to be clinically significant, but may have public health relevance when considered at the population level,” wrote researcher Eric M. Ammann, PhD, of the University of Iowa, and colleagues in Cancer. “Given the substantial associations between vitamin D insufficiency and inferior outcomes in patients with hematologic malignancies and the current interest in evaluating the role of vitamin D treatment of patients with these diseases, clinical trials investigating vitamin D supplementation currently are underway.”

Current evidence linking vitamin D deficiency to hematologic malignancies is from observational data. In this study, Ammann and colleagues conducted a secondary analysis of data from the WHI trial, which randomly assigned 36,282 older women to calcium/vitamin D supplementation or placebo.

“Several biologic observations support a role for vitamin D as protective against hematologic malignancies,” the researchers wrote.

The trial was initially designed to look at skeletal fractures and incidence of colorectal and breast cancer. In this analysis, the researchers examined association between supplementation and hematologic malignancies and hematologic cancer–specific mortality.

“Vitamin D has effects on T cells, B cells, natural killer cells, and dendritic cells in the lymphoid compartment, in which it may impact the malignant transformation of these cells or affect their ability to mitigate the emergence of other malignant hematologic clones,” they wrote. “Vitamin D also decreases Janus-associated kinase-signal transducer and activator of transcription (JAK-STAT) pathway activation in vitro, providing a potential rationale for protective effects against myeloid malignancies.”

During the 10-year follow-up period, 349 cases of hematologic malignancy were diagnosed. These included 44 myeloid malignancies, 70 plasma cell dyscrasias, and 235 lymphoid malignancies. Risk for malignancy was significantly lower in women assigned to supplementation (hazard ratio [HR], 0.80; 95% CI, 0.65–0.99).

Death from hematologic cancer occurred in 117 participants; however, there was no significant association between supplementation and cancer-specific mortality (HR, 0.77; 95% CI, 0.53–1.11) for the entire cohort.

The protective association seen with supplementation appeared to be most consistent for lymphoid malignancies with a trend toward reduced incident cancer (HR, 0.77) and cancer-specific mortality (HR, 0.46).

Looking at patients diagnosed with a hematologic malignancy, the researchers found no association between supplementation and cancer-specific mortality during the 5 years after diagnosis (HR, 1.03).

“Although the current study lacked power to detect 5-year survival among cases after diagnosis, the findings for lymphoid malignancies (HR, 0.66; 95% CI, 0.32–1.37) indicate that further research is warranted,” the researchers wrote.