Research from Canada suggests that women with breast cancer who were low in Vitamin D at the time of their diagnosis had a higher risk of the cancer spreading and poorer survival rates compared with women who had adequate levels of Vitamin D.

The study is to be presented in two weeks time at the 44th Annual Meeting of the American Society of Clinical Oncology (ASCO) by lead investigator Dr Pamela Goodwin of Mount Sinai Hospital in Toronto, and colleagues.

The ASCO meeting will be held in Chicago from 30th May to 3rd June 2008. An abstract of the study is also due to be published as a supplement to the 20th May issue of the Journal of Clinical Oncology.

For the study, Goodwin and colleagues examined diagnostic records of new breast cancer cases and the results of dietary questionnaires from 512 women aged around 40 to 60 years, who were enrolled at three University of Toronto hospitals from 1989 to 1995 and who were followed until 2006.

The women also gave blood samples when they were diagnosed; these had been kept at 80 degrees C and the researchers used radioimmunoassay to assess the Vitamin D levels at time of diagnosis.

The results showed that:

  • 288 women had T1 tumours, 164 of them had T2 tumours, and 24 had T3/T4 tumours (the higher the T number, the larger and more invasive the tumour).
  • 356 of the tumours were N0 (no lymph nodes involved) and 342 were estrogen receptor (ER) positive.
  • 73 tumours were grade 1, while 202 were grade 2 and 173 were grade 3 (higher grade means tumour cells are less “normal” and more likely to grow and spread).
  • 199 women received adjuvant chemotherapy (treatment given after the primary treatment) and 200 received tamoxifen.
  • The cancer spread in 22.7 per cent (116) of the women and 20.7 per cent (106) of them died during a median follow up of 11.6 years.
  • Only 24 per cent (123) of the women had adequate leves of Vitamin D in their blood samples.
  • Low Vitamin D levels were linked to a reasonable degree (p
  • Low Vitamin D levels were more strongly linked (p

The researchers concluded that:

“Vit D deficiency is common at BC [breast cancer] diagnosis and is associated with poor prognosis.”

Goodwin told the press that this was:

“The first time that vitamin D has been linked to breast cancer progression,” according to a report in the Los Angeles Times.

The results have been described as “provocative” by experts not involved in the study, which was sponsored by the National Breast Cancer Institute. One told the Times that there was some evidence that certain drugs for breast cancer are “activated” by vitamin D.

Vitamin D is known to regulate many aspects of cellular growth and differentiation. Previous research has linked Vitamin D deficiency with increased risk of breast cancer, but this is the first study to examine the prognostic effect of Vitamin D on a group of women who already had breast cancer.

Because this was a prospective study, as opposed to say a randomized clinical trial, it would be wrong to conclude from these findings that Vitamin D levels directly impacts cancer spread and survival rates, and therefore women should not use these results as a reason to start taking Vitamin D supplements to treat their breast cancer.

“Frequency of vitamin D (Vit D) deficiency at breast cancer (BC) diagnosis and association with risk of distant recurrence and death in a prospective cohort study of T1-3, N0-1, M0 BC.”
P. J. Goodwin, M. Ennis, K. I. Pritchard, J. Koo, N. Hood.
J Clin Oncol 26: 2008 (May 20 suppl; abstr 511)

Click here for Journal of Clinical Oncology

Source: ASCO, LA Times, National Cancer Institute.

Written by: Catharine Paddock, PhD