(See also our related story Prostate Cancer - Who Needs Treatment?
Due to aggressive prostate cancer screening, more men than ever before are being diagnosed with small, low-grade tumors that may pose little immediate threat.
Oncologists are offering some of these men close monitoring - called active surveillance - without any immediate treatment. Why not treat? Some prostate tumors may never progress significantly, and both surgery and radiation pose the risk of impotence, incontinence and other side effects.
But many men are uncomfortable about only being monitored while hoping that their low-risk tumors never grow. So clinical researchers are exploring noninvasive interventions that might further lower the odds that untreated tumors will turn nasty.
Can Diet and Lifestyle Affect Prostate Cancer Outcome?
June Chan, PhD, epidemiologist for the UCSF Comprehensive Cancer Center's Prostate Cancer Program, is addressing a session on nontoxic interventions at a symposium on active surveillance of prostate cancer on January 12 and 13 at UCSF's Mission Bay campus.
Chan and Peter Carroll, MD, chair of urology, associate dean and director of clinical services for the UCSF Comprehensive Cancer Center, lead a National Cancer Institute-funded UCSF clinical trial called MENS - Molecular Effects of Nutritional Supplements.
The goal of MENS is to determine whether antioxidant-containing extracts from tomatoes or fish oil might lessen recurrence of cancer, or cause genetic changes in the prostates of men undergoing active surveillance.
Dietary surveys and serum analysis from very large observational studies - such as the Physicians' Health Study - have led some researchers to conclude that certain antioxidants in foods may play a role in helping to prevent some cancers. In addition, studies suggest that individual variations in genes that metabolize these antioxidants may also interact with nutrient levels to modify cancer risk.
Participants in MENS are undergoing biopsy before and after taking supplements or placebo pills. After taking the pills for three months, patients will remain in the study for 21 more months of clinical follow-up. Participants will be "blinded," and even the researchers will not know who was randomly assigned to receive supplements or placebo until the participants are "unblinded" at the completion of follow-up and data collection.
Good for Hearts and Maybe for Prostates Too
Carroll continues to lead studies on the effects of diet and lifestyle modification with lifestyle-change advocate and UCSF Clinical Professor Dean Ornish, MD.
Ninety-three men undergoing active surveillance took part in their first study. About half ate a vegan diet with supplements. The men participated in moderate aerobic exercise, yoga, meditation and a weekly support group session. Initial follow-up showed no cancer progression among the group that changed diet and lifestyle - while disease worsened in six men in the control group.
Carroll and Ornish have begun new clinical research aimed at identifying biologic mechanisms that might account for any beneficial effects of nutritional supplementation or comprehensive lifestyle change in men on active surveillance. Questions include whether these changes switch on protective genes or turn off harmful genes.
Carroll notes that even among men with prostate cancer, heart disease rivals the cancer as a leading killer. "I think whether diet plays a major role in reducing prostate cancer risk is still unknown," Carroll says. "But regardless of the diagnosis, I still recommend that men eat well, modify their weight and get exercise."
In keeping with the theme of heart disease prevention possibly doubling as a prostate cancer foil, Chan and UCSF colleagues also are exploring clinical trial designs on statins, drugs already widely used to lower cholesterol in heart disease patients. The Health Professionals Follow-up Study and other observational studies suggest a possible association between statin use and a lowered incidence of prostate cancer, Chan says.
"As far as I know, there has not yet been a randomized clinical trial with a statin intervention for men diagnosed with prostate cancer," Chan says. "We are interested in designing a trial analogous to MENS, in which we use statins as the treatment to better understand the possible biological effects of the drug on the prostate microenvironment."
Role of Hormone Manipulation Uncertain
Other symposium speakers will discuss a possible role for treating men undergoing active surveillance with pharmaceuticals that affect sex hormones.
Drugs that block the hormonal action of testosterone are a mainstay of the treatment of advanced prostate cancer. In addition, the drug finasteride - already marketed as a treatment to improve urine flow in men with enlarged prostates and as a drug for hair loss - has been studied as a potential prostate cancer preventive in a controlled clinical trial in 18,000 men age 55 and over.
The Prostate Cancer Prevention Trial indicated that men taking five milligrams of finasteride daily developed fewer prostate cancers. Unfortunately, the benefit does not appear to be absolute. Although men developed fewer prostate tumors overall, there was a higher incidence of apparently more-advanced-grade cancers in the treated group.
Whether finasteride or related drugs might play a role in treating men already diagnosed with prostate cancer remains an open question. In addition, researchers are interested in manipulating not only testosterone, but estrogen, as well, which some researchers suspect may also play a role in determining prostate cancer risk.
- Prostate Cancer — Who Needs Treatment?
- UCSF Today, January 10, 2007
- Genitourinary Cancer Epidemiology and Population Science (G-CEPS)
- UCSF Department of Urology
- Prostate Cancer Conference Presents Worldwide Experts
- UCSF News Release, January 4, 2007