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“A critical weekly review of important new research findings for health-conscious readers” 

SOY ISOFLAVONES & RECURRENT PROSTATE CANCER

The interest level in natural and complementary treatments for cancer has never been higher in the medical and scientific communities than it is now.  For decades, now, this area of research was often relegated to the fringes of the clinical research community, while most mainstream academic research centers and Big Pharma companies focused on the design and testing of new biochemical therapies with improved therapeutic and safety profiles.  With the 5-year overall survival rate among all patients with cancer approaching a record 65 percent, we have, unquestionably, made enormous improvement in our ability to cure many of the cancers that, not too long ago, were associated with a very high risk of death.  Cancer physicians also have far more effective medications available now to control the noxious side effects of many of our “front-line” cancer therapies, which have had the beneficial effect of further reducing suffering and morbidity among thousands of cancer patients as they undergo their daily treatments. 

Despite the  admirable (and ongoing) progress that has been achieved over the past four decades in cancer care, however, nearly 600,000 cancer patients will still succumb to their disease this year in the United States, alone.  Thus, more effective cancer prevention strategies are necessary to reduce the number of new cases of cancer, and more effective (and less toxic) cancer therapies must be identified.  Moreover, with the annual cost of many new cancer therapies now running into the hundreds-of-thousands of dollars per patient, per year, our already unsustainable (and still rising) health care costs demand that the cancer care community rigorously evaluate less costly approaches to cancer prevention and treatment.

Because so-called “natural products” are relatively inexpensive, widely available, and generally non-toxic, there is a growing interest in studying these agents using the same high-level prospective, randomized clinical trials that are routinely used by pharmaceutical companies and academic medical centers to evaluate promising new drug therapies.  Because of their great complexity and high cost, however, randomized clinical trials are best reserved for studying novel therapies for which there is at least some laboratory (“preclinical”) or early-phase clinical data available that suggests some potential benefit to humans.  Until recently, however, and most likely due to inherent biases against natural products by the mainstream clinical research community in the past, very little high-level clinical research has been performed to definitively evaluate natural products as disease prevention and treatment agents.  Fortunately, and despite shrinking research funding over the past decade, there has been a recent surge in the number of large randomized, prospective, controlled clinical research trials reporting their findings of the effects of natural products on disease prevention and treatment.

As the vast majority of natural products and lifestyle-related research in the past has been based upon low-powered research methods, it should come as no surprise that recent high-level prospective clinical research studies have, more often than not, found little or no benefit associated with the use of many of these supplements and products.  (Moreover, in some cases, several very popular and highly recommended vitamins and dietary supplements have actually been found to be potentially harmful.)   However, a great deal of promising high-level clinical research has yet to be done in order to fully and accurately assess the, literally, hundreds of natural products for which there is at least some preclinical data supporting potentially beneficial health effects.  (In my forthcoming book, “A Cancer Prevention Guide for the Human Race,” I will be comprehensively reviewing and analyzing the available laboratory and clinical research data on natural products and lifestyle strategies as an integral approach to a cancer prevention lifestyle.  The publication of this groundbreaking and authoritative evidence-based cancer prevention guide is tentatively scheduled for May of this year.)

In many respects, prostate cancer is the male counterpart of breast cancer in women.  Analogous to breast cancer in women, prostate cancer is the most common cancer that occurs in men (excluding minor skin cancers), and the second most common cause of cancer death.  In 2009, an estimated 192,000 new cases of prostate cancer were diagnosed in the United States alone, and approximately 27,000 American men died of this disease in the same year.  In most industrialized nations, prostate cancer accounts for approximately 25 percent of all cancer diagnoses in men (similar to the percentage of breast cancer cases among all cancer cases diagnosed in women).

A newly published prospective, early-phase, clinical pilot study from Canada evaluated the effects of a soy beverage (“soy milk”) on the progression of recurrent prostate cancer in 29 men following radiation therapy for their cancers.  This study, which has just been published in the journal Nutrition and Cancer, was not a placebo-controlled randomized study, however, this small phase II clinical study prospectively followed these patient volunteers for 6 months, during which time serial measurements of the level of prostate-specific antigen (PSA) in their blood was performed (PSA is the primary prostate tumor marker that is measured both to detect early prostate cancer and to identify recurrences of this type of cancer.)

The time interval during which the level of PSA in the blood doubles is an important indicator of the rate of progression of recurrent prostate cancer.  In this small prospective clinical pilot study, the consumption of approximately 500 ml of soy beverage per day, for 6 months, was associated with an actual decline in PSA levels in 4 (14 percent) of these patient volunteers, while another 8 (28 percent) of these recurrent prostate cancer patients experienced a greater than 100 percent increase in their PSA doubling times.  However, another 5 patients (17 percent) experienced a 50 percent or greater decrease in their PSA doubling times during the 6 month duration of this study, which was an unfavorable development.  Thus, during the brief duration of this intriguing small pilot study, 42 percent of men with early recurrence of their prostate cancer experienced either a decrease in the biochemical extent of their recurrent cancers or a significant biochemical slowing of the progression of their recurrent disease.

Whether or not longer durations of soy intake will be able to sustain the impressive results of this study is not clear at this time.  More importantly, whether or not these observed favorable effects of daily soy intake on PSA levels and PSA doubling times will actually translate into prolonged survival (or not) is also unknown at this time.  It will require several larger and longer-term randomized, placebo-controlled, blinded, prospective clinical trials of soy foods and soy isoflavone supplements to answer these critical questions (several of which are already underway).  Meanwhile, the overall safety profile for moderate amounts of soy intake in men appears to be quite favorable, and so many prostate cancer experts are cautiously recommending soy-derived foods for men with prostate cancer, and for men who are at an increased risk of developing prostate cancer, pending the completion of these larger prostate cancer research studies.

For a much more detailed and comprehensive evaluation of the role of soy foods, and other dietary supplements and lifestyle modifications, in the prevention of prostate cancer (and other cancers), look for the publication of “A Cancer Prevention Guide for the Human Race” in the spring of this year.

I and the staff of Weekly Health Update would like to take this opportunity to thank the more than 100,000 new and returning readers who have visited our premier global health information website this month, alone.  As always, we enjoy receiving your feedback and questions, and I continue to try to personally answer as many of your inquiries as I possibly can.

In view of the extreme devastation and human misery brought about in Haiti and Chile by the recent earthquakes, Weekly Health Update asks our tens of thousands of caring readers to give generously to established charities that are currently working in that country to assist the injured, the ill, and the homeless there.  There are many such legitimate charities, including the following two:

http://www.redcross.org/

http://www.imcworldwide.org/haiti

For a somewhat lighter perspective on Dr. Wascher, please click on the following YouTube link: 

http://www.youtube.com/watch?v=7-Tdv7XW0qg

Welcome to Weekly Health Update

“A critical weekly review of important new research findings for health-conscious readers”

SOY ISOFLAVONES REDUCE BREAST CANCER

RECURRENCE RISK

Regular readers of this column are already aware of the controversy surrounding soy isoflavone intake and breast cancer risk.  As happens frequently in clinical research (unfortunately), contradictory research findings have made it difficult to understand the true relationship between dietary soy intake and breast cancer risk (if one exists).  There is, for example, both laboratory and clinical data suggesting that a diet rich in soybean-derived products may be associated with a lower risk of developing breast cancer.  At the same time, because genistein and other dietary isoflavones are known to weakly mimic the effects of estrogen, there has been some concern that a diet rich in isoflavone “phytoestrogens” may increase both the risk of developing a new breast cancer and the risk of developing a recurrence of a previous breast cancer.  (In fact, there is data from laboratory research studies showing that genistein can indeed fuel the growth of human breast cancer cells growing in culture dishes, when exposed to high concentrations of this soy-derived isoflavone.)

A growing body of public health research, primarily from Asian countries where tofu and other soy-based foods are frequently consumed, appears to link increased soy consumption with a decreased lifetime breast cancer risk, particularly when soy-based foods are consumed during adolescence, during the time when development of the female breast is most active (Soy & Breast Cancer Risk).  (Interestingly, there is also recent research suggesting that soy products might also reduce the risk of prostate cancer, which is another hormonally driven cancer:   Genistein & Prostate Cancer Cells, Dietary Soy & Prostate Cancer Risk.)

Although epidemiological research is, increasingly, suggesting that a diet rich in soybean-derived foods might lower a woman’s lifetime risk of developing breast cancer, many breast cancer experts have remained apprehensive regarding dietary isoflavone intake in women with a prior history of breast cancer, in view of the estrogen-like effects of these “phytoestrogens.”  As I have already noted, there is considerable research data available to suggest that soy-derived isoflavones can, at least under certain laboratory conditions, stimulate estrogen-sensitive breast cancer cells to grow and divide.  These research findings have left many oncologists feeling uncomfortable in recommending soy-based foods to their breast cancer patients.  Now, a newly publish public health study in the Journal of the American Medical Association suggests that soy-based foods may actually reduce the risk of breast cancer recurrence, and death due to any cause, in women who have previously been diagnosed with this very common form of cancer.

In this study, which was performed in Shanghai, China, 5,042 female breast cancer survivors (ages 20 to 75 years) were followed for an average of almost 4 years.  All of these patient volunteers underwent detailed surveys regarding their lifestyle habits, including their diets.  These patients, who were originally diagnosed with breast cancer between 2002 and 2006, were surveyed at 6, 18, 36 and 60 months following their original diagnosis with breast cancer.  

The results of this study indicate that the breast cancer survivors who consumed the greatest amount of soy-based foods in their daily diets were 32 percent less likely to experience a recurrence of their breast cancer when compared to the women who consumed the least amount of soy-based isoflavones.  Moreover, the women who consumed the greatest amount of soy were also 29 percent less likely to die, from any cause, when compared to the women who consumed the least amount of soy-derived foods.

A particularly interesting and unexpected finding of this study was that both women with estrogen sensitive breast cancers and women with tumors that were not sensitive to estrogen appeared to experience a significantly decreased risk of breast cancer recurrence if they frequently consumed soy products.  Another important finding of this study was that women who were taking the estrogen-blocking cancer treatment drug tamoxifen also appeared to enjoy a reduced risk of breast cancer recurrence with higher levels of dietary soy intake.  Additionally, the researchers noted that high levels of soy intake appeared to be about as effective in reducing the risk of breast cancer recurrence as the breast cancer prevention drug tamoxifen, alone.

The results of this very important study mirror the findings of the only other prospective clinical study that has looked at the impact of soy-based foods on breast cancer recurrence (the “Life After Cancer Epidemiology,” or “LACE,” study).  The LACE study, which was performed in the United States, followed nearly 2,000 breast cancer survivors for, on average, more than 6 years.  In the LACE study, women who were taking tamoxifen, and who also consumed the highest amount of soy-based dietary isoflavones, were 50 percent less likely to develop a recurrence of their breast cancer when compared to women who reported the lowest consumption of soy-derived foods.

As I have pointed out previously, epidemiological research studies based upon dietary surveys are susceptible to several types of bias which, in turn, can cause researchers to draw the wrong conclusions.  In this case, however, there are now two large prospective cohort studies that have reached essentially the same conclusions (albeit with a rather limited duration of patient follow-up).  Both studies strongly suggest that high levels of soy-based isoflavones in the diet may be able to significantly reduce the risk of breast cancer recurrence.  Based upon the findings of this large Chinese study, the apparent cancer risk reduction effect associated with high levels of soy intake also appears to benefit premenopausal and postmenopausal women, as well as women who are taking the estrogen-blocking drug tamoxifen, women with estrogen-sensitive tumors, and women with (counter-intuitively) estrogen-resistant tumors.

In view of the limited duration of patient follow-up in both of these clinical breast cancer studies, as well as the limitations of survey-based epidemiological research in general, I would like to see updated data from both of these studies after at least 10 years of patient observation before I would be willing to tell my breast cancer patients that they should significantly increase their dietary soy intake.  On the other hand, the rather compelling data presented by both of these clinical research studies will also make me less anxious when any of my breast cancer patients decide, of their own accord, to increase their intake of soy-derived isoflavones.

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Disclaimer: As always, my advice to readers is to seek the advice of your physician before making any significant changes in medications, diet, or level of physical activity