Dr Ng on the Addition of Vitamin D to Bevacizumab Plus Chemotherapy in mCRC

Kimmie Ng, MD, MPH, associate chief, Division of Gastrointestinal Oncology, director, Young-Onset Colorectal Cancer Center, co-director, Colon and Rectal Cancer Center, physician, Dana-Farber Cancer Institute; associate professor, medicine, Harvard Medical School, discusses the findings from the phase 3 SOLARIS trial (NCT04094688) of vitamin D combined with standard chemotherapy plus bevacizumab (Avastin) in patients with previously untreated metastatic colorectal cancer (mCRC). Notably, data from the investigation were shared at the 2024 ESMO Congress.

To be eligible for the multicenter, double-blind, randomized study, patients must have had mCRC with no prior therapy and an ECOG performance status of 0 to 1; patients were not permitted to enroll if they were already taking vitamin D in doses exceeding 2000 IU daily. Patients were randomly assigned 1:1 to receive either high-dose vitamin D or standard-dose vitamin D alongside chemotherapy plus bevacizumab. Patients continued treatment until disease progression, unacceptable toxicity, or withdrawal of consent.

Investigators found that adding high-dose vitamin D to standard treatment did not lead to any clinically relevant or additional toxicity, Ng begins. There were no adverse effects specifically associated with the vitamin D. However, regarding the primary end point of progression-free survival (PFS), there was no significant difference between patients receiving high-dose vitamin D and those receiving the standard dose, she reports. Similarly, Ng says investigators observed no significant differences in secondary end points, including overall survival and overallresponse rate.

Despite these overall findings, investigators saw an interesting signal in prespecified subgroup analyses, she continues. Among patients with left-sided primary tumors, high-dose vitamin D appeared to provide some prolongation of PFS compared with the standard dose. Although this observation is not statistically significant and does not change the overall outcome of the trial, it is hypothesis-generating and indicates a potential area for future research, Ng emphasizes.

Further studies will be necessary to confirm whether this subgroup may indeed benefit from higher doses of vitamin D, according to Ng. Although the overall results did not meet expectations, the potential benefit of vitamin D in a specific patient population warrants additional exploration, she concludes.