Recently, another well done study of vitamin D and cancer resulted in disappointing results. Vitamin D supplements showed no benefit in persons with metastatic colorectal cancer (CRC). It did not result in a difference in overall survival outcomes.
In the study, 455 patients with metastatic colorectal cancer were assigned randomly to either high daily vitamin D3 or standard dose vitamin D3, in addition to receiving standard chemotherapy. The high dose vitamin D group received a loading dose of 8000 IU per day for 2 weeks, followed by a maintenance dose of 4000 IU per day until the end of the study. The standard dose vitamin D group received 400 IU per day.
However, there was no difference in "significant progression-free survival benefit". There also was no significant difference in how long people survived in the 2 groups (a median of 25.6 months in the high-dose group, and 27.0 months in the standard dose group).
The study results were disappointing because in laboratory studies vitamin D has anticancer properties. Critics of this study pointed out that vitamin D supplementation may have a role in cancer prevention - but at this point, that is unknown.
From Medscape: High-Dose Vitamin D Disappoints in Metastatic CRC: SOLARIS
The addition of high-dose vitamin D supplementation to standard chemotherapy plus bevacizumab did not result in a significant progression-free survival benefit in patients with metastatic colorectal cancer (CRC) in the SOLARIS study.
The researchers did identify a small progression-free survival improvement in patients with left-sided primary tumors, but this should be considered "hypothesis-generating," according to lead investigator Kimmie Ng, MD, MPH, with Dana-Farber Cancer Institute, Boston. [Translation: may be a random, fluke result, rather than a real effect]
Ng reported results from the first phase 3 randomized controlled trial to test high-dose vitamin D in metastatic CRC at the European Society for Medical Oncology (ESMO) Annual Meeting 2024.
Vitamin D has demonstrated anticancer properties, including inhibiting tumor growth and inducing cell death, in preclinical studies, and the phase 2 SUNSHINE trial found higher vitamin D levels improved progression-free survival in patients with advanced or metastatic CRC.
The phase 3 SOLARIS trial aimed to confirm these findings.
The trial enrolled 455 patients with previously untreated, locally advanced or metastatic CRC. Patients had measurable disease and good performance status and had not been taking regular high-dose vitamin D over the past year. Patients had no preexisting hypercalcemia or any condition predisposing to hypercalcemia.
Participants were randomized to standard chemotherapy with FOLFOX or FOLFIRI plus bevacizumab with either high-dose vitamin D3 (a loading dose of 8000 IU/d for 2 weeks, followed by a maintenance dose of 4000 IU/d) or to a control receiving 400-IU/d vitamin D3 (standard-dose group).nThe two groups were well balanced, with no significant differences in demographics, tumor or treatment factors, or genomic alterations.
After a median follow-up of 20 months, Ng and colleagues observed no statistically significant difference in progression-free survival between the two groups — a median of 11.8 months in the high-dose vitamin D group vs 10.3 months in the standard-dose group (hazard ratio [HR], 0.92; P = .25).
The researchers also reported no significant difference between the two groups in overall survival outcomes — a median of 25.6 months for the high-dose group vs 27.0 months for the standard-dose group (HR, 1.05; P = .34) — or in objective response rate — 51% for the high-dose group vs 44% for the standard-dose group (P = .12).
The researchers also found no significant differences in grade 3 or higher adverse events between the two treatment groups, and compliance with vitamin D supplementation was high in both groups.
Given the positive results from SUNSHINE, SOLARIS was a "very good idea and it was well done," said the study discussant, Michel Ducreux, MD, PhD, with Gustave Roussy Cancer Center, Paris-Saclay University in France.
Unfortunately, it's a completely negative trial, which is disappointing but also important, said Ducreux, who also did not think a new trial in left-sided tumors would be worthwhile.