Influence of Exercise on Immune System Function in Men Undergoing Prostate Cancer Treatment

Research that has an impact in clinical populations and settings is one of the many strengths of EXSS.  This week we report on the work of Dr. Erik Hanson who examines how exercise may influence immune system function in men who are undergoing prostate cancer treatment.  Many thanks to Erik for developing this week’s EXSS Impact content.

Why did you do this study?Hanson1

There are ~14 million cancer survivors in the US with another 1.7 million cases expected this year. Cancer survivor number is projected to continue rising over the next decade and comes with a price tag of 75 billion dollars in treatment costs. There is good news in that the cancer incidence rates are still high, cancer-related mortality is declining. Better treatment, earlier detection, and the inclusion of complementary therapies (i.e. exercise) have contributed to higher 5-year survival rates across many different cancers.

With the decline in cancer mortality comes a new problem. Cancer survivors have improved duration of life, but a focus on quality of life needs to take centre-stage. Unfortunately, while cancer treatments are effective at slowing tumour growth, each has many different side effects. Among the most common are fatigue, changes in body composition (loss of muscle and bone, increased fat), aerobic capacity, strength, and physical function, all of which directly impact quality of life. Recent research has begun exploring the effects of exercise in cancer survivors. Current results suggests that exercise is typically well tolerated and often reduces some of the side effects. Improvements in strength, body composition, and fitness levels are the most common, each of which then can alter fatigue, physical function, and quality of life.

At UNC, our work focuses on the immune system. The immune systems plays a critical role in preventing tumour development, progression and recurrence and is affected by cancer treatment. The immune system is also highly responsive exercise and increases the number of cells in the blood that are available to fight off pathogens and tumour cells. In healthy individuals, the normal response is an increase in cell number immediately after exercise that then drops below resting levels during recovery before returning to normal after a good night of sleep. This is known as a biphasic response. Recently, this response was characterised in breast cancer survivors, but it has not been examined in any other cancer types or treatments. Exercise has been recommended by several national governing bodies to help reduce treatment-related side effects, but the impact on the immune system remains unknown. The purpose of this study was to comprehensively examine the immune response in men undergoing prostate cancer treatment to a single bout of aerobic exercise to gain insight into the safety and efficacy of the current guidelines for cancer survivors.

Natural killer cell number in response to a bout of intermittent cycling exercise in men with prostate cancer (PCa & ADT) and healthy, matched controls (CON). Times with / different letters are significantly different from each other (P < 0.01)

Natural killer cell number in response to a bout of intermittent cycling exercise in men with prostate cancer (PCa & ADT) and healthy, matched controls (CON).
Times with / different letters are significantly different from each other (P < 0.01)

What did you do and what did you find in this study?

The men in this study were prostate cancer survivors who had completed their primary treatment (PCa) or were still on a secondary treatment (ADT). These men performed a moderate bout of cycling intervals lasting ~45 mins. Immune function was assessed at rest and then after 0, 2, and 24h of recovery.

The primary outcome in this study was the natural killer cell populations, as these particular immune cells are critical to tumour suppression and respond particularly well to exercise. Following one bout of moderate exercise, the number of natural killer cells increased immediately after exercise and decreased at 2h of recovery, following the same biphasic response that was shown in healthy individuals (CON). There were no differences between the different groups at any point. Similar findings for other immune cell populations in these men indicate the response to exercise was consistent.

Hanson3How do these findings impact the public?

These results are the continued steps in ensuring that exercise is safe for cancer survivors, but this time with a specific focus on immune function. This study only used one exercise session, whereas in the future there is a need to examine the response to several bouts of training. Our research group plans to continue exploring this area and hopes to expand to include resistance training and different types of cancer patients, both during and after treatment.