Vitamin D and breast cancer survival
March 8, 2014
Jacob Schor ND, FABNO
Vitamin D may lower risk of dying from breast cancer. A newly published meta-analysis suggests having high levels of vitamin D may lower mortality rates by half. That’s enough to give one pause.
Up until now most of the studies on vitamin D and breast cancer have looked at incidence while only a few have looked for an association between vitamin D levels and cancer survival. This paper pooled data from other prior studies together achieving greater statistical power. Five studies were identified which measured similar variables so that the data could be combined: Villasenor (2012) , Hatse (2012)  , Tretli (2012)  , Vrieling (2012)  , and Goodwin (2009)  .
In the combined pool of data, 471 of the 4443 patients died of breast cancer. A pooled hazard ratio comparing the lowest with the highest quintile of serum vitamin D concentrations was calculated for each study and for the combined data. This is a statistical way to say they compared those patients in the upper 20% of the group with those in the lowest 20% when ranked by serum vitamin D levels.
Of the five studies analyzed, three found a statistically significant reduction in mortality with increasing vitamin D levels (Hatse, Tretli, and Vrieling). One study found a beneficial effect that did not reach statistical significance (Goodwin) and the fifth study found a beneficial effect in the age-adjusted analysis but not in the more complicated multivariate analysis (Villasenor).
When the data was pooled the hazard ratio for estimated risk of dying in the highest vs. lowest quintile was .56 (95% CI=0.4-0.7, p<0.0001) . That is women with the higher Vitamin D levels were about half (46%) as likely to die as those in the lower levels. There was also a strong linear inverse dose-response relationship between serum vitamin D and breast cancer fatality rates, that is, the higher the level of vitamin D the lower the chance of dying.
It should be noted that the vitamin D levels were not particularly high in any of these studies; the lowest quintile, depending on the study, was between 14 and 20 ng/ml and the upper quintile was defined as above between 22 to 32 ng/ml. This isn’t much as we often suggest women with breast caner to try and maintain serum vitamin D levels in the high 60s or even higher.
These data while compelling are far from absolute proof as they could be the result of reverse causation. That is it could be that the disease lowers vitamin D levels and that the worse the disease, the lower the vitamin D levels become. Few scientists seem to be buying that theory though and given the low risk of harm from supplementing to elevate vitamin D, it seems reasonable to not wait until they settle their debating. Thus we will continue to encourage women diagnosed with breast cancer to have their vitamin D levels tested and to supplement as necessary to achieve decent levels. Whether there is added benefit in long term survival for those with much higher levels is not clear from this paper.
Anticancer Res. 2014 Mar;34(3):1163-6.
Meta-analysis of Vitamin D Sufficiency for Improving Survival of Patients with Breast Cancer.
Mohr SB, Gorham ED, Kim J, Hofflich H, Garland CF.
Background/Aim: To determine whether higher serum 25-hydroxyvitamin D [25(OH)D] at diagnosis is associated with longer survival of patients with breast cancer.
MATERIALS AND METHODS:
A meta-analysis was performed of five studies of the relationship between 25(OH)D and mortality from breast cancer. A pooled hazard ratio was calculated using a random-effects model. The Der Simonian-Laird test was used to assess homogeneity.
Higher serum concentrations of 25(OH)D were associated with lower case-fatality rates after diagnosis of breast cancer. Specifically, patients in the highest quintile of 25(OH)D had approximately half the death rate from breast cancer as those in the lowest.
High serum 25(OH)D was associated with lower mortality from breast cancer. Serum 25(OH)D in all patients with breast cancer should be restored to the normal range (30-80 ng/ml), with appropriate monitoring. Clinical or field studies should be initiated to confirm that this association was not due to reverse causation.
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Baumgartner K, Baumgartner R, Ulrich CM, Hollis BW,
McTiernan A and Neuhouser ML: Associations of serum 25-
hydroxyvitamin D with overall and breast cancer-specific
mortality in a multiethnic cohort of breast cancer survivors.
Cancer Causes Control 24: 759-67, 2012.
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Vandorpe T, Brouckaert O, Peuteman G, Laenen A, Verlinden L,
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MR, Bouillon R and Wildiers H: Vitamin D status at breast cancer
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Chang-Claude J: Serum 25-hydroxyvitamin D and
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cohort study: Breast cancer research 13: 74, 2012.
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