We are getting into the “season” when there is a plethora of cancer news, primarily due to forthcoming annual meeting of the American Society of Clinical Oncology meeting, which is scheduled to begin in two weeks in Chicago.
Unlike years past, when the abstracts were embargoed until the scientific studies had been presented at the meeting, this year ASCO released almost all of the abstracts last evening. Only a handful of the most significant abstracts have been withheld from the public release.
One of the abstracts highlighted by ASCO had to do with vitamin D levels of women diagnosed with breast cancer. The results of that study are certainly thought provoking, and will undoubtedly add to the discussion on the role of vitamin D in health and its influence on cancer incidence and prognosis.
We need to bear in mind that all we have so far is an abstract of the research, which essentially represents the most preliminary form of reporting scientific results. The actual public presentation of the data won’t happen until the ASCO meeting. That’s when other researchers have a chance to listen to the information, get clarification of the data, and ask questions of the researchers.
Based on what I do have available to review at this time, this study certainly appears to be well done and will likely raise as many or more questions than it answers.
According to the abstract, the researchers at 3 University of Toronto (Canada) hospitals took blood samples from 512 women who were diagnosed with breast cancer. The women studied were all diagnosed between 1989 and 1995, and the course of their disease was followed until 2006.
What the researchers found was very interesting.
37.5 % of the women had low vitamin D levels which were considered deficient. 38.5 % had intermediate levels, or what the researchers called “insufficient.” The remaining women—24% of those studied—had adequate levels of vitamin D at the time of their diagnoses.
The researchers found that there was a seasonal variation associated with vitamin D levels, as would be anticipated, with higher levels when the blood was drawn in the summer, and lower levels when the diagnoses and blood drawing occurred in the winter.
There were some other factors that were associated with vitamin D levels, including lower vitamin D levels in women who drank less alcohol, or consumed lower amounts of vitamin E, grains and retinol in their diets.
Premenopausal women and those with higher body mass indexes—a measure of overweight and obesity—also had lower vitamin D levels.
But here is the part of the research that is so interesting:
The time to recurrence of breast cancer was significantly lower in women with insufficient vitamin D levels, compared to women with adequate vitamin D levels in their blood samples. Overall survival was also significantly better in women with adequate vitamin D as compared to those who were deficient.
For women with estrogen receptor negative breast cancer—which is known to be a more aggressive form of breast cancer—their survival was not related to their vitamin D status.
As noted in a press release that accompanied the abstract, “after 10 years of follow-up, 83 percent of women with adequate levels remained free of metastases and 85 percent were still alive, compared with only 69 percent and 74 percent, respectively, of women with vitamin D deficiency. Most of these deaths were attributed to breast cancer.”
The conclusion of the researchers was simple and straightforward in the abstract: “Vitamin D deficiency is common at breast cancer diagnosis and is associated with poor prognosis.”
In the same press release, the researchers clearly pointed out that these results need to be confirmed by a second trial, which is already underway. If that research supports these findings, then, as noted by the lead researcher on the team, they “recommend(s) a new randomized clinical trial examining the effects of raising blood levels of vitamin D on outcomes in women with breast cancer.”
As I mentioned, this is certainly a provocative study.
There are certain things we look for in studies of this type, including the fact that the women were not selected at random, but represented all the women who presented for treatment of their breast cancer who met certain criteria. The blood levels were obtained at the same equivalent time, namely when the cancer was diagnosed.
There has been a lot of research published on vitamin D and its relationship to cancer, some of which has supported a possible role of vitamin D in reducing the incidence of various cancers, other research suggesting that higher vitamin D levels at the time of diagnosis of certain cancers may be associated with an improved prognosis, and other research claiming the role of vitamin D in cancer incidence is limited.
We struggle with what to tell people to do when it comes to vitamin D and their health.
Clearly, the evidence indicates that vitamin D benefits bone and muscle health. It may also influence cancer and other diseases such as autoimmune diseases and multiple sclerosis.
Yet when it comes to understanding vitamin D levels of people in the United States and elsewhere, we have much to learn. We know many people—especially those with darker complexions and the elderly—have vitamin D deficiency.
We don’t routinely measure vitamin D levels as part of a routine physical, yet maybe it’s time for us to consider doing that.
Many experts believe that the current dietary guidelines for daily vitamin D intake are too low. Some advocate daily sun exposure to maintain vitamin D levels, while the American Cancer Society and others say that you should not “seek the sun” for vitamin D replacement. That’s because there are risks to daily sun exposure, and there are safer alternatives in over-the-counter vitamin D3 supplements which avoid skin wrinkling and increased risk of skin cancer over time.
With all of these questions and all of these controversies, it is time to move forward and get the answers.
I applaud the caution of the Canadian researchers in tempering the expectations that will inevitably follow the release of their report.
They emphasize that we need to confirm their results, and if that confirmation does occur, then we need to do a clinical trial to determine whether vitamin D supplementation can influence the incidence of breast cancer.
We also need to focus our resources in bringing together knowledgeable experts to guide us on the appropriate daily vitamin D dietary recommendations. We need to do the studies that will answer the question whether or not vitamin D does reduce cancer risk, and for which cancers.
As I have said before and will continue to say, there is enough research that has been published which suggests there is a relationship between vitamin D intake, vitamin D blood levels and cancer risk and incidence.
But the type of studies that have to be done to provide us with the best evidence have not yet been done. Those studies will require a significant commitment of researchers, money and willing participants. They will take years to complete.
The problem I have is that in the past we have had suggestions that various vitamins reduced the risk of cancer. When properly studied however, those claims didn’t hold up. Not only did they not hold up, in some cases they were actually associated with an increased risk of harm.
The conclusion: just because it’s a vitamin doesn’t mean it doesn’t have risks.
I am looking forward to hearing this presentation in Chicago in two weeks.
I suspect I will come out of that meeting with the same thoughts I have going in, namely that we need to find out whether vitamin D is really the miracle vitamin that some claim, or is just another example of a failed hope that didn’t survive the careful scrutiny afforded by a well-designed clinical trial.
Millions of people are awaiting the answer.
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I will post links on this story at a later time.
