High-dose vitamin D3 does not provide benefit for metastatic colorectal cancer, clinical trial shows

SOLARIS (Alliance A021703), a multicenter, double-blind, randomized Phase III clinical trial led by Dana-Farber Cancer Institute researchers and conducted across several hundred cancer centers in the U.S. tested the addition of high-dose vitamin D3 to standard treatment for patients with untreated metastatic colorectal cancer. More than 450 patients received standard chemotherapy plus bevacizumab and were randomized to high-dose or standard dose vitamin D3.

The results were presented at the European Society for Medical Oncology 2024 congress.

The team observed no additional concerning side-effects or toxicities with the addition of high-dose vitamin D3. However, the addition of high-dose vitamin D3 to standard treatment did not delay the progression of cancer more so than standard-dose vitamin D3, according to the team’s analysis after a median 20-month follow up.

A potential benefit for high-dose vitamin D3 was observed for patients with left-sided disease (i.e., primary tumors that arise in the descending colon, sigmoid colon, or rectum) and requires further investigation.

The SOLARIS trial was inspired by previous research suggesting that higher levels of vitamin D in the blood are associated with improved survival for metastatic colorectal cancer and that the addition of high-dose vitamin D3 to standard therapy could potentially improve progression free survival.

The SOLARIS results suggest, however, that high-dose vitamin D3 cannot be recommended as a treatment for patients with untreated metastatic colon cancer.