Having clinically sufficient vitamin D levels at the time of breast cancer diagnosis is associated with better outcomes.

USA: Higher vitamin D levels at the time of diagnosis may improve outcomes in breast cancer patients, finds a recent study.

The findings of the study were presented at the American Society of Clinical Oncology (ASCO) 2021 virtual annual meeting by the first author Song Yao, a molecular epidemiologist and Professor of Oncology with the Department of Cancer Prevention and Control at Roswell Park.

The study is based on Kaiser Permanente Northern California's Pathways Study — a large prospective study in breast cancer patients that has been underway since 2006 under the direction of Larry Kushi, ScD, who is Senior Author on the new study.

"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 breast cancer patients, particularly among Black women and patients with more advanced stage disease," notes Dr. Yao, a molecular epidemiologist and Professor of Oncology with the Department of Cancer Prevention and Control at Roswell Park.

"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," says study Senior Author Lawrence Kushi, ScD, Director of Scientific Policy at the Kaiser Permanente Northern California Division of Research.

The research team measured 25-hydroxyvitamin D (25OHD) 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 25OHD levels, including polygenic score. Vitamin D supplement intake, BMI, and race/ethnicity were the most influential factors on serum 25OHD levels, while genetic variants had only a limited impact, notes 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 (OS), breast cancer-specific survival (BCSS), recurrence-free survival (RFS), and invasive disease-free survival (IDFS) after a median follow-up time of 9.6 years. The researchers built Cox proportional hazards models adjusting for non-clinical, clinical and treatment factors that were further stratified by stage, estrogen receptor (ER) status and body mass index (BMI).

"Having clinically sufficient vitamin D levels at the time of breast cancer diagnosis is associated with better outcomes," Dr. Yao notes. "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 ER 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 body mass index. 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," says 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.

Reference:

"Clinically sufficient vitamin D levels at breast cancer diagnosis and survival outcomes in a prospective cohort of 3,995 patients after a median follow-up of 10 years," (abstract 10510) was presented as a poster discussion session at the American Society of Clinical Oncology (ASCO) 2021 virtual annual meeting.

DOI: https://meetinglibrary.asco.org/record/196871/abstract