Lead author Thomas Churilla, a medical student at the Commonwealth Medical College, Scranton, Pa., said the study involved 160 patients with a median age of 64 -- half women, half men. The five most common primary diagnoses were breast, prostate, lung, thyroid and colorectal cancer.
The study found 77 percent of the patients had vitamin D concentrations either deficient -- less than 20 nanograms per milliliter, or sub-optimal 20 to 30 ng/mL.
The median serum vitamin D level was 23.5 ng/mL, but regardless of the age or sex of the patient, levels of vitamin D were below the median predicted for advanced stage disease in the patient group.
Patients found to be vitamin D deficient were administered replacement therapy, increasing serum D levels by an average of 14.9 ng/mL.
"The benefits of vitamin D outside of improving bone health are controversial, yet there are various levels of evidence to support that vitamin D has a role in either the prevention or the prediction of outcome of cancer," Churilla said in a statement.
The findings were presented at the 53rd annual meeting of the American Society for Radiation Oncology in Miami.