The United States has the highest rates of breast cancer in the world. The incidence varies greatly around the world: it is lowest in less-developed equatorial countries and greatest in the more developed poleward countries. For example, the incidence rates per 100,000 women varies from a low of 18 in Eastern Asia and 22 in sub-Saharan Africa, to quadruple that in other areas, such as 78 in Western Europe and 90 in North America. However, survival rates in the Western world are high. For example, more than 8 out of 10 women (84%) in England diagnosed with breast cancer survive for at least 5 years.
Do vitamin D levels affect survival? That is, do women with higher vitamin D levels live longer than women with lower levels? Dr Adriana Villasenor and colleagues, of the University of California at San Diego measured vitamin D levels in 585 breast cancer survivors and followed them for an average of 9 years in an attempt to find out.
Villaseñor A, Ballard-Barbash R, Ambs A, Bernstein L, Baumgartner K, Baumgartner R, Ulrich CM, Hollis BW, McTiernan A, 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. 2013 Jan 30.
They started their paper with some reassuring news:
“Despite limited evidence on the association of vitamin D with outcomes in breast cancer survivors, some clinicians advise breast cancer patients to use vitamin D supplements.”
I was glad to read this as it means some doctors are assuring that women do not have to face breast cancer survival vitamin D deficient.
The authors found that after the mean of nine years of follow up, 110 women had died with 48 women dying from breast cancer.
The unadjusted associations of serum vitamin D with overall survival suggested a linear dose–response pattern (p for trend = 0.21). Compared to women with levels < 20 ng/ml, women with levels > 30 ng/ml had a decreased risk of overall mortality (HR = 0.58); however that effect disappeared with statistical adjustments such as age, race, body weight, season of blood draw, smoking status, and outdoor physical activity. Perhaps the effect went away because the authors corrected for factors that not only affect survival, but also affect vitamin D levels.
The 5-year overall survival rates in women with levels >30 ng/ml compared to levels < 20 ng/ml were 98.4 and 97.6 %, respectively. The comparable 10-year survival figures were 88.0 and 84.8%, respectively. Compared to participants with <20 ng/ml, the age-adjusted association for those with 25(OH)D levels >30 ng/ml was a 48% lower overall mortality.
In relation to breast cancer survival, they found no association between vitamin D levels and risk of breast cancer specific mortality. The unadjusted association of serum vitamin D with breast cancer–specific survival did not indicate a linear dose response pattern but there was a trend (p = 0.18). The breast cancer specific five-year survival rates were approximately 98%, regardless of serum 25(OH)D status, However, the 10-year rates ranged from 91.7 % with levels < 20 ng/ml to much better survival (95.5 %) with levels >30 ng/ml.
It is instructive to read the authors paragraph on all the studies done to date on 25(OH)D and breast cancer survival.
“In 2009, Goodwin et al reported that 512 non-Hispanic white women with the lowest serum 25(OH)D (<20 ng/mL) had a statistically non-significant 71% increased risk of overall mortality, compared to those with 25(OH)D concentrations >32 ng/mL. In a nested case control study with 250 matched pairs, Jacobs et al reported a non-significant 13% increased odds of overall mortality in breast cancer survivors with 25(OH)D <20 ng/mL, compared to those with serum 25(OH)D>20 ng/mL. In a cohort of 1,295 post-menopausal women, Vrieling et al reported with those with 25(OH)D <14 ng/mL had a 55% increased risk of overall mortality compared to those with 25(OH)D >22 ng/mL. Most recently (2012), in a Norwegian population-based study among 251 breast cancer patients, Tretli et al report women with 25(OH)D >33 ng/mL had a decreased risk of overall mortality, compared to women with 25(OH)D <18.4 ng/mL.”
In other words, to date, apparently all the studies show that breast cancer survivors with high vitamin D levels live longer; someone should do a meta-analysis.
Breast cancer survivors can either do nothing but wait for more studies, risking being vitamin D deficient, or take enough vitamin D (5,000 IU/day) to obtain natural levels (around 50 ng/ml) while waiting for more studies. The choice is yours.