Exercise, wellness, and response to prostate cancer treatment
Posted Sep 17 2008 2:02pm
In the USA, as of 2008, there are about 1.8 million prostate cancer survivors alive today. That’s 20 percent of all the cancer survivors in America. They may have had definitive therapy (surgery, radiation, cryotherapy, etc.) and give every sign of complete elimination of their cancer. They may be on “watchful waiting” and never have received any form of active treatment for their disease. They may be less fortunate and have progressive disease.
The one thing they all have in common is that they may live for many years after their initial diagnosis, and they have to be able to deal with the chronic and late effects of their initial treatment as well as the constant fear of recurrence. As a consequence, these patients and their families are often concerned and interested in such issues as diet and exercise, and how they may influence disease outcomes.
Historically, there has been limited evidence that any modifiable lifestyle factors can affect cancer-related outcomes in prostate cancer survivors. However, this has changed in recent years, and there are increasingly clear signs of a relationship between obesity and risk for more aggressive forms of prostate cancer.
First, the incidence of prostate cancer has been increasing in historically low-incidence countries (e.g., China and Japan) at the same time that these countries have started to adopt more Western lifestyles, with their higher rates of obesity. These observations suggest that obesity may be a risk factor for prostate cancer, but such a correlation has yet to be proven. Indeed, data from the Health Professionals Follow-Up Study suggest that obesity was protective for men who had a family history of prostate cancer or were under 60 years of age.
Second, although there is no definitive association between obesity and risk for prostate cancer, there are conclusive data to show that obesity is associated with prostate cancer mortality. In 2003, Calle et al. published data showing that men with a body mass index (BMI) of ≥ 30 kg/m 2 had a risk for prostate cancer death that was 20 to 34 percent higher than that of men with a BMI of 18.5 to 24.9 kg/m 2. Other studies have shown that a higher BMI was associated with higher-grade tumors and non-organ-confined disease in men who underwent radical prostatectomy for localized prostate cancer. These data suggest that even if obesity is not related to risk for prostate cancer, it may make it more likely that one develops a higher-grade, more lethal prostate cancer.
We do not intend to conduct an extensive review of the literature to confirm that there is an association between obesity and the apparent aggressiveness of prostate cancer. Suffice it to say that such an association is now well known, and there are clear implications for prostate cancer patients. These can be summarized as follows:
Obesity is a known risk factor for aggressive disease in men with a diagnosis of prostate cancer.
Loss of weight and emphasis on a healthier lifestyle may reduce an obese patient’s risk for progressive prostate cancer after an initial diagnosis.
To date we have no definitive evidence to support the idea that adopting a healthier lifestyle can improve the survival of obese patients after a diagnosis of prostate cancer. In fact what we have is a series of potential research questions to which we need answers:
Does weight reduction have an impact on the course of prostate cancer in obese men?
Can weight reduction in obese men after treatment for localized prostate cancer lead to improved recurrence-free survival?
Can weight reduction in men with relapsed disease help to slow clinical progression?
Is there any correlation between race and obesity as risk factors for progressive prostate cancer?
As the number of men who are survivors of prostate cancer steadily increases, we need to clearly identify lifestyle — as well as medical — interventions that may be effective in preventing recurrence and progression, while also promoting good overall health.
We believe it is appropriate to conclude this article by quoting from an article by Kristal and Gong:
We now have good evidence that obesity increases the risk of aggressive prostate cancer, but reduces the risk of low-grade, nonaggressive cancer. In addition, several studies have found that obesity increases the risk of biochemical recurrence following prostatectomy; … While accepting the current limitations in our knowledge base, it is our opinion that it is appropriate for physicians to counsel their patients to lose weight following prostate cancer diagnosis and motivate this change in behavior by emphasising the likely benefit of improving long-term outcome.