Taking vitamin D supplements may help to slow or even reverse the progression of low-grade prostate tumors, according to a new study presented at the 249th American Chemical Society (ACS) National Meeting & Exposition.

“Vitamin D is very important in the development and control of various neoplasms. Whether you give it alone or with chemotherapy you need to make sure your patients are getting adequate levels,” said study investigator Bruce Hollis, PhD, of the Medical University of South Carolina in Charleston, SC.

Currently, a man must wait 60 days from the time of his biopsy before he can undergo a prostatectomy so that inflammation from the biopsy can subside. Dr. Hollis and his team wondered if giving these men vitamin D supplements during the 60-day waiting period would affect their tumors.

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His previous research had shown that when men with low-grade prostate cancer took vitamin D supplements for a year, 55% of them showed decreased Gleason scores or even complete disappearance of their tumors compared to their biopsies a year before.1

In a new randomized controlled clinical trial, 37 men undergoing elective radical prostatectomies (RP) received either 4,000 international units of vitamin D per day or a placebo. Following RP, the researchers examined tumor specimens.

The researchers found that many of the men who received vitamin D showed improvements in their prostate tumors, whereas the tumors in the placebo group either stayed the same or got worse.

Also, vitamin D caused dramatic changes in the expression levels of many cell lipids and proteins, particularly those involved in inflammation. The protein most strongly induced by vitamin D was one called growth differentiation factor 15 (GDF15).

RELATED: Vitamin D Levels Not Linked with Aggressive Prostate Cancer

The new research suggests that vitamin D supplementation may improve low-grade prostate cancers by reducing inflammation, perhaps lessening the need for eventual surgery or radiation treatment. Dr. Hollis noted that the dosage of vitamin D administered in the study (4,000 international units) is well below the 10,000 to 20,000 that the human body can make from daily sun exposure. “Our urology team is using it. They were very skeptical at first, but after they saw the results they made clinical changes,” Dr. Hollis said in an interview with Cancer Therapy Advisor.

Song Yao, PhD, an Associate Professor of Oncology, Department of Cancer Prevention and Control, Roswell Park Cancer Institute in Buffalo, NY, said this is a provocative study that may provide a crucial piece of justification for the initiation of a randomized clinical trial with adequate sample size and long-term follow-up to answer definitively whether vitamin D supplementation can prevent low-grade prostate cancer from progressing.

“With this small sample size, the study lacks the statistical power to assess how large the effect of vitamin D supplementation is and whether the observed effect is due to random chance or not. With only 60 days between the start of supplementation and evaluation of tumor changes, this study lacks the time scale to assess long-term tumor changes in response to vitamin D supplementation and, more importantly, whether the observed reduction in tumor grade can be translated into a clinical endpoint,” Dr. Yao told Cancer Therapy Advisor.

Tomasz Beer, MD, a professor of Medicine, Hematology, and Medical Oncology at Oregon Health & Science University in Portland, OR, agrees with Dr. Yao and said it is far too soon for clinicians to start prescribing vitamin D to patients with prostate cancer.

“There has been so much tantalizing data, but nothing definitive. The possibility that there is a biological effect is exciting. We can’t just yet tell men to take vitamin D and it is going to help with your prostate cancer. However, we need to make sure patients are not vitamin D deficient and it is a very common vitamin deficiency,” Dr. Beer said in an interview with Cancer Therapy Advisor.