Researchers have again found that higher levels of circulating vitamin D on diagnosis of cancer are associated with significantly better survival and remission rates. The new findings come from a comprehensive meta-analysis involving more than 17,000 cancer patients, published online in the April 29 issue of the Journal of Clinical Endocrinology and Metabolism.

Mian Li, PhD, graduate student, University of the Chinese Academy of Sciences, Shanghai, China, and multicenter colleagues found that overall survival for colorectal and breast cancer patients in the highest quartile of circulating 25-hydroxyvitamin D [25(OH)D] levels was significantly better than it was for those in the lowest quartile of 25(OH)D levels.

Overall survival was also significantly better for lymphoma patients in the highest 25(OH)D quartile compared with those in the lowest quartile.

Higher circulating levels of vitamin D were also significantly associated with lower cancer-specific mortality rates among patients with both colorectal cancer and lymphoma, and disease-free survival rates were also significantly improved for patients with breast cancer and those with lymphoma.

“This study could be considered as the most confirmatory evidence to date supporting an association between circulating 25(OH)D levels and cancer outcomes,” senior author Hui Wang, MD, PhD, professor at the Institute for Nutritional Sciences, Chinese Academy of Sciences, told Medscape Medical News.

“Considering that vitamin D deficiency is widespread around the world, our suggestion is to ensure everyone has sufficient levels of this important nutrient — that is, circulating 25(OH)D levels — greater than 75 nmol/L.”

Robust Evidence

For the meta-analysis, the authors included 25 studies involving a total of 17,732 patients with cancer.

The evidence supporting a protective effect from high circulating 25(OH)D levels on diagnosis was most robust for colorectal cancer, breast cancer, and lymphoma.

Table. Cancer Outcomes Between Those in the Highest vs the Lowest 25(OH)D Quintiles

Limited — but favorable — evidence for a protective effect from high circulating 25(OH)D levels on diagnosis was also observed for patients with lung cancer, gastric cancer, prostate cancer, leukemia, melanoma, and Merkel cell carcinoma.

Indeed, when investigators compared 25(OH)D levels in the range of 40 to 70 nmol/L to levels <19 nmol/L, they found that a 10-nmol/L increase in circulating vitamin D levels upon cancer diagnosis was associated with a 4% reduction in all-cause mortality among all cancer patients in whom a dose-response relationship was assessed.

Chemopreventive Agent

As Dr. Wang told Medscape Medical News, researchers tend to consider vitamin D as a cancer chemopreventive agent.

“A lot of laboratory studies have suggested that vitamin D might inhibit the progression of cancers by acting on tumor cells and modulating the tumor microenvironment,” he explained.

In addition, the biological effects of vitamin D on both bone health and the immune system may help cancer patients better weather difficult treatment regimens and help alleviate adverse reactions.

More Aggressive Prostate Cancer

In a separate study published in Clinical Cancer Research, vitamin D deficiency was associated with more aggressive prostate cancer in both European American and African American men. These men were undergoing their first biopsy because of an abnormal prostate-specific antigen (PSA) or digital rectal examination (DRE) test.

Results showed that a 25(OH)D level of <12 ng/ml was positively associated with a higher Gleason grade (≥ 4 + 4) and a higher clinical stage (tumor stage ≥ cT2b) in both groups of men but that the association between more aggressive prostate cancer and vitamin D deficiency was stronger among African Americans.

This study also found an association between lower 25(OH)D levels and men at high and very high risk for prostate cancer according to National Comprehensive Cancer Network (NCCN) criteria.

“In our study, vitamin D deficiency seemed to be a predictor of aggressive forms of prostate cancer diagnosis in European American and African American men,” lead author Adam B. Murphy, MD, assistant professor in the Department of Urology at the Northwestern University Feinberg School of Medicine in Chicago, commented in a statement.

“The stronger associations in African American men imply that vitamin D deficiency is a bigger contributor to prostate cancer in African American men compared with European American men,” Dr. Murphy added. “Vitamin D supplementation may be a relevant strategy for preventing prostate cancer incidence and/or tumor progression in prostate cancer patients,” he suggested.

The study by Dr. Li and colleagues was supported by a number of grants, including a grant from the Ministry of Science and Technology of China, the National Nature Science Foundation, and the Science and Technology Commission of Shanghai Municipality. The study by Dr. Murphy and colleagues was funded by the National Institutes of Health and the US Department of Defense. The authors of both studies have disclosed no relevant financial relationships.

Clin Endocrinol Metab. Published online April 29, 2014. Abstract

Clin Cancer Res. 2014;20:2289-2299.