While other studies have shown an association between vitamin D levels and aggressive prostate cancer, they were based on blood drawn well before treatment. The new study provides a more direct correlation because it measured D levels within a couple of months before the tumor was visually identified as aggressive during surgery to remove the prostate (radical prostatectomy).
The finding can offer guidance to men and their doctors who may be considering active surveillance, in which they monitor the cancer rather than remove the prostate.
“Men with dark skin, low vitamin D intake, or low sun exposure should be tested for vitamin D deficiency when they are diagnosed with an elevated PSA or prostate cancer. Then a deficiency should be corrected with supplements,” says Adam Murphy, an assistant professor of urology at Northwestern University and lead investigator.
The relationship between vitamin D and prostate cancer may explain some disparities seen in prostate cancer, especially among African-American men. Prior research by Murphy and colleagues showed African-American men who live in low sunlight locations are up to 1½ times more likely to have vitamin D deficiency than Caucasian men.
But because vitamin D is a biomarker for bone health and aggressiveness of other diseases, all men should check their levels, Murphy says.
“All men should be replenishing their vitamin D to normal levels,” Murphy adds. “It’s smart preventive health care.”
Aggressive prostate cancer is defined by whether the cancer has migrated outside of the prostate and by a high Gleason score. A low Gleason score means the cancer tissue is similar to normal prostate tissue and less likely to spread; a high one means the cancer tissue is very different from normal and more likely to spread.
The study was part of a larger ongoing study of 1,760 men in the Chicago area examining vitamin D and prostate cancer. The current study included 190 men, average age of 64, who underwent a radical prostatectomy to remove their prostate from 2009 to 2014.
Of that group, 87 men had aggressive prostate cancer. Those with aggressive cancer had a median level of 22.7 nanograms per milliliter of vitamin D, significantly below the normal level of more than 30 nanograms/milliliter. The average D level in Chicago during the winter is about 25 nanograms/milliliter, Murphy notes.
“It’s very hard to have normal levels when you work in an office every day and because of our long winter,” he says.
The study was published in the Journal of Clinical Oncology. Murphy collaborated on the study with Rick Kittles, associate director of cancer disparities at the University of Arizona Cancer Center.
The National Institutes of Health, the Veterans Health Administration, and the US Department of Defense funded the study.