Vitamin D may aid late-stage colorectal cancer treatment but which dosage is best?

• If detected early, colorectal cancer is a curable disease, with about 90% of those diagnosed with stage 1 cancer surviving 5 years from diagnosis.
• However, later stage, or metastatic colorectal cancer has much poorer outlook.
• Studies have shown that vitamin D supplements may help treat metastic colorectal cancer.
• A new phase 3 trial, testing high dose vitamin D3, has found that it is no better than lower doses in improving survival rates, but may benefit people whose primary tumor is in the left colon.

Early stage colorectal cancer can usually be treated with surgery, with or without chemotherapy, and has a 5-year survival rate of about 90%.

But when colorectal cancer has spread, or metastasized beyond the bowel, only around 14% of people with this diagnosis survive longer than 5 years from diagnosis.

Early research has shown that vitamin D3 supplementation, alongside chemotherapy, may help prevent the disease from progressing, and enhance survival rates from metastatic colorectal cancer.

Following these encouraging results, the SOLARIS randomized clinical trial, published in JAMA, tested whether higher doses of vitamin D3 would improve progression-free survival in these patients.

Although the higher dose enhanced survival in people with tumors on the left colon, overall there was no significant difference in survival between those on the higher and lower D3 doses.

Kimmie Ng, MD, MPH, professor of medicine at Harvard Medical School, Associate Chief of the Division of Gastrointestinal Oncology at the Dana-Farber Cancer Institute in Boston, MA, lead author of the study, told Medical News Today:

“Unfortunately, the primary results of the study did not show statistically significant differences in progression-free survival between patients randomized to high-dose vitamin D compared to low-dose vitamin D. There were also no statistically significant differences in the response rates of these patients’ cancers or in overall survival.”