Vitamin D Supplement May Make Chemo Before Breast Cancer Surgery More Effective

Women who took a vitamin D supplement got more benefits from chemotherapy before breast cancer surgery, according to a small study.

While more research is needed, the findings suggest that doctors may want to start measuring vitamin D levels before women start chemo for breast cancer and prescribe a supplement for women whose levels are low.

“Even with a small sample of participants, it was possible to observe a significant difference in the response to chemotherapy,” co-author Eduardo Carvalho-Pessoa, PhD, president of the São Paulo Regional Brazilian Society of Mastology, said in a statement.

The study included 80 women diagnosed with early-stage breast cancer with a high risk of recurrence. All the women were scheduled to receive chemotherapy before surgery, called neoadjuvant chemotherapy by doctors.

The chemotherapy regimens used were AC-T: Adriamycin, Cytoxan, and Taxol; AC-T plus Herceptin (chemical name: trastuzumab); or AC-T plus carboplatin.

The women’s average age was 55 and they all had what the researchers considered low vitamin D levels, about 20 nanograms per milliliter of blood (ng/mL). But the U.S. National Institutes of Health says that vitamin D levels of 20 ng/mL are adequate for most people and that levels of 12 ng/mL are considered too low.

Half the women took 2,000 IU (50 micrograms) of vitamin D per day while receiving chemotherapy. The other half took a placebo, pills that looked just like vitamin D but contained no vitamins.

After finishing chemotherapy, all the women had surgery to remove the cancer. One way doctors judge how well neoadjuvant chemotherapy works is to look for any actively growing cancer cells in tissue removed during surgery. If there aren’t any cancer cells in the tissue, doctors call it a pathologic complete response, or pCR. If there are cancer cells in the tissue, doctors call it residual cancer.

pCR rates were almost twice as high among women who took vitamin D supplements — 43% — compared to women who took the placebo —24%. The researchers also noted that the higher the women’s vitamin D levels, the higher the percentage of women who had a pCR.

The researchers said that vitamin D supplements may be an easy, safe way to improve pCR in women with breast cancer.

Still, there are some concerns about the study. The researchers didn’t say whether the two groups of women were evenly balanced by breast cancer subtype. So one group may have had more HER2-positive or hormone receptor-positive diagnoses than the other group, which could affect the study’s results.

The researchers also noted that Herceptin wasn’t available at times during the study. So it’s unclear if all the women in each group diagnosed with HER2-positive breast cancer received Herceptin. This also could affect the results because pCR rates are always better for people diagnosed with HER2-positive breast cancer who receive Herceptin.

However, a vitamin D supplement is simple, inexpensive, and safe. If chemotherapy before breast cancer surgery is recommended for you, you may want to talk to your doctor about checking your vitamin D levels and whether taking a supplement makes sense for you.