A research team has found that sufficient vitamin D levels at the time of diagnosis may be associated with improved outcomes among people with breast cancer. These findings were presented by Yao et al during the 2021 ASCO Annual Meeting (Abstract 10510).
These findings are based on Kaiser Permanente Northern California’s Pathways Study—a large prospective study in patients with breast cancer that has been underway since 2006.
“Consistent with results from randomized trials and meta-analyses, our findings from this large, observational cohort of breast cancer survivors with long follow-up provide the strongest evidence to date for maintaining sufficient vitamin D levels in [patients with] breast cancer, particularly among Black women and patients with more advanced-stage disease,” noted first study author Song Yao, MD, a molecular epidemiologist and Professor of Oncology in the Department of Cancer Prevention and Control at Roswell Park Comprehensive Cancer Center.
“These findings highlight not just the role of vitamin D in breast cancer prognosis, but also the contribution of and need for prospective studies in cancer survivors to complement clinical trials," added senior study author Lawrence Kushi, ScD, Director of Scientific Policy at the Kaiser Permanente Northern California Division of Research.
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Measuring Levels of Vitamin D and Their Effects
The research team measured 25-hydroxyvitamin D (25[OH]D) levels from 3,995 women with breast cancer who were enrolled in the Pathways Study, using blood serum samples collected at the time of diagnosis. They examined potential determinants of 25(OH)D levels, including polygenic score. Vitamin D supplement intake, body mass index (BMI), and race/ethnicity were the most influential factors on serum 25(OH)D levels, while genetic variants had only a limited impact, noted Dr. Yao.
The study categorized vitamin D levels based on clinical cutoffs: deficient (< 20 ng/mL), insufficient (20 to < 30 ng/mL), or sufficient (≥ 30 ng/mL). Dr. Yao and colleagues then evaluated these levels in relation to overall survival, breast cancer–specific survival, recurrence-free survival, and invasive disease–free survival after a median follow-up of 9.6 years. The researchers built Cox proportional hazards models adjusting for nonclinical, clinical, and treatment factors that were further stratified by stage, estrogen receptor status, and BMI.
“Having clinically sufficient vitamin D levels at the time of breast cancer diagnosis is associated with better outcomes,” Dr. Yao stated. “While these results are consistent with our earlier analysis based on a subset of the study population, it’s significant that we saw the same trends in this much larger, longer-term data set—suggesting an ongoing benefit for patients who maintain sufficient levels through and beyond breast cancer treatment.”
The team also observed that associations were similar by estrogen receptor status and found that the association between vitamin D levels and breast cancer outcomes appeared to be stronger among study participants diagnosed at more advanced stages or with lower BMI. Black women had the lowest vitamin D levels, which might contribute to their generally poorer outcomes after breast cancer diagnosis.
“In the context of supportive data from recent randomized trials and meta-analyses, our findings support the use of daily vitamin D supplementation to maintain sufficient vitamin D levels after breast cancer diagnosis, particularly among Black women and patients diagnosed with later-stage disease,” said senior author Christine Ambrosone, PhD, Co-Principal Investigator of the Pathways Study and Senior Vice President of Population Sciences and Chair of Cancer Prevention and Control at Roswell Park.
Disclosure: For full disclosures of the study authors, visit coi.asco.org.
