Q&A with Dr. Janet Stanford about coffee reducing the risk of prostate cancer recurrence
Dr. Janet Stanford and colleagues Drs. Marian Neuhouser, Jonathan Wright and Marni Stott-Miller at Fred Hutchinson Cancer Research Center and graduate student Milan Geybels at Maastricht University in the Netherlands recently published results of a study in Cancer Causes & Control that found coffee consumption is associated with a reduced risk of prostate cancer recurrence and progression. Read the Fred Hutch news release here. Stanford goes into more detail about the findings below.
Q: When you looked at coffee drinking and the risk of prostate cancer, what did you find?
A: Well, I think it’s important to point out that this particular study didn’t look at the risk of developing prostate cancer. This study was focused on taking a large cohort of men who were previously diagnosed with prostate cancer and following them to see whether their pattern of coffee or tea consumption – or both – related to their risk of having their prostate cancer relapse or progress after their initial diagnosis.
We found that about 60 percent of men in the study consumed at least one cup of coffee per day, and 14 percent consumed four or more cups per day. In the overall analysis, which was based on more than six years of follow-up after prostate cancer diagnosis, the men who consumed at least one cup of coffee per day had a 56 percent reduced risk of prostate cancer recurrence or progression compared to men who consumed one or fewer cups per week. The effect was a bit stronger among men who drank four or more cups a day, who had 59 percent lower risk of cancer recurrence.
Q: So is your study a reason for prostate cancer survivors to be heavy coffee drinkers?
A: Not necessarily. In fact, we observed a significant decline in risk of recurrence in men who drank just one cup a day, and so based on our data, a man would not need to drink a large number of cups of coffee per day to benefit from its potential chemopreventive effects.
Q: When you looked at tea consumption and the risk of prostate cancer recurrence, what did you find?
A: For tea consumption we found no association with prostate cancer recurrence. Tea has a much lower level of caffeine than coffee, for one thing, and it also has different chemical components that do not overlap with those found in coffee.
Q: When you looked at coffee drinking and risk of death from prostate cancer what did you find?
A: We tried to look at death from prostate cancer but in our cohort there were only 38 men who died of their prostate cancer, and that number was too small to have any statistical power to evaluate an association between coffee drinking and prostate cancer mortality. Future studies with much larger numbers will have to be conducted before we’ll know whether there is any effect on disease-specific mortality.
Q: What do you think accounts for the preventive effect of coffee on prostate cancer recurrence?
A: Caffeine and other chemical components of coffee have been shown in laboratory studies to reduce cancer-cell proliferation and metastasis as well as enhance cancer-cell death. In addition, some of the substances in coffee have been shown to have both anti-inflammatory and antioxidant effects, which would in theory be beneficial in terms of chemoprevention activity. There are also some compounds in coffee that may alter DNA methylation, a biochemical change in the DNA that may influence the activation or deactivation of cancer-associated genes. Thus, there are several potential biological mechanisms by which coffee might have health benefits for secondary prevention of prostate cancer.
Q: In your study could you differentiate between drinkers of caffeinated versus decaf coffee?
A: Unfortunately the survey we used to collect beverage consumption information from this cohort of patients did not specifically sort out caffeinated or decaffeinated coffee, so we don’t know if it’s the caffeine per se that makes a difference in preventing prostate cancer from coming back.
Q: Did you look at the difference between different methods of coffee preparation, such as drip versus espresso?
A: Good question. Again, the survey we used to collect information from this group of patients did not query the preparation method for the coffee that was consumed. Future studies specifically designed to assess coffee intake in association with prostate cancer relapse or progression would want to make sure to capture nuances such as method of preparation and caffeinated versus decaffeinated coffee. In addition, our study collected information on usual coffee and tea consumption prior to prostate cancer diagnosis. Future studies would also need to inquire about whether consumption patterns may have changed substantially after diagnosis.
Q: Did you find any potential negative health effects among men who drank for our more cups of coffee per day, such as high blood pressure?
A: We couldn’t determine those types of associations in this study. One would need to carefully measure blood pressure, for example, before and after coffee consumption. We did not do that in this study. However, to raise an important point, coffee consumption for some men may not be recommended based on their medical history. Men with high cholesterol, high blood pressure or cardiac arrhythmias may be advised by their physician not to consume excessive amounts of coffee, particularly caffeinated coffee.
Q: How common is recurrence of prostate cancer after initial diagnosis and treatment?
A: Of men who are diagnosed with clinically localized cancer and are treated with curative intent, up to a third over time will experience a recurrence of their prostate cancer. But there’s typically an extended time period between diagnosis and recurrence, so if we could delay relapse and extend that disease-free interval by five or 10 years – so that those who do recur have their cancer come back at age 75 instead of 65, for example – that would be an important benefit for prostate cancer patients.
Q: Have other studies shown a link between coffee and reduced risk of cancer recurrence?
A: Some studies of brain and ovarian cancer, for example, have found an association between coffee and reduced risk of developing cancer, but few studies have evaluated coffee in relation to the cancer coming back or progressing, so in that respect our study is one of the first to examine patient outcomes related to coffee consumption. A recent large study from Harvard – using data from the Health Professionals Follow-up Study – found a very similar result: a 60 percent reduction in risk of developing metastatic or lethal prostate cancer associated with coffee consumption. So, the evidence is accumulating that there may be benefit from coffee drinking when it comes to preventing prostate cancer recurrence and progression.
Q: What about coffee as a primary preventive agent for prostate cancer? Is there any evidence that it might prevent the disease in the first place?
A: I don’t believe that in humans there have been any clinical trials of coffee as a primary preventive agent for prostate cancer. That would be something of interest, because the literature on coffee consumption related to risk of developing prostate cancer is mixed. Some studies have shown a positive effect and some, including one from our research group, have shown no association between coffee consumption and risk of developing the disease. But more and more what we’re finding is that factors involved in the development of cancer are not necessarily the same ones that are involved in encouraging or preventing the cancer from recurring or progressing after diagnosis and treatment. That’s true for both environmental and lifestyle-related exposures as well as underlying genetic factors.
Q: So, in a nutshell, based on your study, what would you tell men about coffee and prostate cancer?
A: Well, I think if a man has been diagnosed with prostate cancer and he’s a coffee drinker then he should continue with his usual pattern of coffee consumption. A daily cup of coffee may offer some health benefits in terms of preventing or delaying prostate cancer recurrence or progression. More studies are clearly needed, but at this point I’d suggest that a small amount of coffee for most men is not going to be harmful and may provide some health benefit.
Q: Is there anything you’d like to add?
A: We continue to search for positive things men can do on their own to help improve their chances of remaining cancer free, and we think this is a step in the right direction. . It would appear based on our study and other recent evidence that coffee consumption at even a modest dose of a cup a day may offer some benefit to prostate cancer survivors.
Dr. Janet Stanford is a member of the Public Health Sciences Division and co-director of the Prostate Cancer Research Program at Fred Hutchinson Cancer Research Center.