Dr. Kerry Courneya on Exercise as Cancer Therapy: Key Insights from Found my Fitness

In this episode of the "Found my Fitness" podcast, host Dr. Rhonda Patrick welcomes Dr. Kerry Courneya, a leading researcher in exercise oncology from the University of Alberta. Dr. Courneya discusses the transformative shift in understanding exercise not just as a beneficial lifestyle choice, but as a crucial therapeutic intervention in cancer care. The conversation delves into how exercise impacts cancer prevention, enhances treatment tolerance and effectiveness, improves survival outcomes, and boosts psychological well-being for cancer patients and survivors. This episode is highly relevant for anyone interested in cancer prevention, patients currently undergoing treatment, cancer survivors, healthcare professionals, and those seeking to understand the powerful biological effects of exercise on chronic disease.

Key Insights / Core Messages

• Exercise has transitioned from an optional health benefit to a core therapeutic intervention in cancer care, demonstrably recalibrating tumor biology, improving treatment tolerance, and extending survival.
• For cancer prevention, regular moderate-to-vigorous exercise (150-300 min/week moderate or 75-150 min/week vigorous) significantly lowers the risk for 8-10 cancer types, even mitigating risks associated with obesity, family history, and smoking. More exercise generally yields greater risk reduction up to the upper guideline limits.
• Muscle mass is critically important for cancer survival. Resistance training helps build and maintain muscle, countering cancer-related wasting (cachexia, a condition that causes severe weight loss and muscle wasting), improving treatment tolerance (especially chemotherapy), and is linked to better outcomes.
• Exercise during cancer treatment helps manage debilitating side effects like fatigue (counterintuitively, activity reduces fatigue more than rest), improves sleep, reduces anxiety and depression, and critically, can enhance patients' ability to complete prescribed chemotherapy and radiation regimens on schedule and at full dosage.
• Exercise directly influences tumor biology by improving blood vessel quality within tumors, thereby enhancing oxygen and drug delivery (making chemotherapy and radiation more effective), and increasing shear stress in blood vessels, which can kill circulating tumor cells and potentially reduce metastasis.
• Exercise acts as a form of immunotherapy, boosting the immune system's ability to surveil and kill cancer cells by increasing the activity and number of immune cells like Natural Killer (NK) cells and T-cells, and potentially improving their infiltration into tumors.
• Beyond physical benefits, exercise provides profound psychological advantages for cancer patients, including a sense of control, normalcy, reduced anxiety and depression, and significantly mitigating the fear of cancer recurrence or progression.

The Shifting Paradigm: Exercise as Cancer Therapy

Dr. Patrick opens by highlighting the significant evolution in the perception of exercise within oncology. For decades, it was considered merely supportive for general health, but overwhelming evidence now positions it as a vital therapeutic tool. Dr. Courneya, a pivotal figure in this field with over 600 peer-reviewed studies, explains that structured exercise interventions directly impact tumor biology, treatment efficacy, and patient survival.

Exercise for Cancer Prevention: Risks, Doses, and Mechanisms

Dr. Courneya outlines the landscape of cancer prevention. While smoking remains the top preventable risk factor, followed by obesity and excessive alcohol consumption, exercise is a powerful tool, particularly for non-smokers of healthy weight. Research indicates exercise can lower the risk of 8-10 different cancers, including common types like colon, breast, and endometrial cancer. The standard public health guideline is 150 minutes of moderate-intensity or 75 minutes of vigorous-intensity aerobic exercise per week, but Dr. Courneya emphasizes a dose-response relationship: benefits increase up to 300 minutes moderate / 150 minutes vigorous exercise per week. The evidence suggests intensity matters, with vigorous activity providing roughly double the benefit per minute compared to moderate. Importantly, exercise confers protective benefits regardless of other risk factors like obesity, smoking history, or even family history (though less evidence exists for highly penetrant genetic mutations like BRCA1/2). The mechanisms involve improved metabolic health (e.g., glucose regulation), reduced inflammation, and enhanced immune function. While structured exercise is key, breaking up sedentary time with "exercise snacks" or vigorous intermittent lifestyle physical activity (VILPA) is also beneficial, though the evidence is strongest for sustained moderate-to-vigorous activity.

The Crucial Role of Muscle Mass and Resistance Training

A significant focus is placed on the importance of muscle mass. Cancer can lead to cachexia, a devastating muscle-wasting syndrome. Emerging research strongly links low muscle mass (sarcopenia, sometimes occurring alongside obesity – sarcopenic obesity) to poorer treatment tolerance, increased risk of recurrence, and reduced survival across various cancers. While aerobic exercise has been the traditional focus, resistance training is gaining recognition for its critical role in building and preserving muscle mass. Dr. Courneya notes studies where resistance training, even just two or three times per week, helped patients *gain* muscle mass during chemotherapy, potentially improving drug metabolism and tolerance. This highlights the need to incorporate strength training both preventatively (building a reserve) and during treatment.

Exercise During Cancer Treatment: Tolerance, Side Effects, and Prehabilitation

Exercising during active cancer treatment presents unique challenges but offers substantial rewards. Dr. Courneya addresses the common fear and fatigue patients experience. Counterintuitively, studies consistently show that patients who exercise during treatments like chemotherapy report *less* fatigue than those who rest. Exercise also improves sleep quality, anxiety, and depression. Crucially, it enhances treatment tolerance – the ability to complete the full course of therapy. Patients who exercise may experience fewer dose reductions or delays in chemotherapy, which is critical for maximizing the chances of a cure. Some studies, including one by Dr. Courneya's group, found that weight training specifically was linked to better chemotherapy completion rates. The concept of "prehabilitation" – exercising *before* starting treatments like surgery or chemotherapy – is also discussed. While the evidence in cancer is still developing compared to other surgical fields, prehab aims to get patients fitter beforehand, potentially improving recovery and function post-treatment.

Mechanisms: How Exercise Fights Cancer Biologically

Dr. Courneya details several compelling biological mechanisms:

• Improved Tumor Perfusion and Oxygenation: Exercise can normalize the chaotic and leaky blood vessels within tumors, improving blood flow. This enhances the delivery of chemotherapy drugs to the tumor and increases oxygen levels, making tumors more sensitive to radiation therapy. Studies in rectal cancer patients showed exercise during chemo-radiation led to higher rates of complete tumor response.
• Killing Circulating Tumor Cells (CTCs): Exercise increases blood flow velocity and shear stress within blood vessels. This physical force can damage and destroy fragile CTCs shed from the primary tumor as they travel through the bloodstream, potentially reducing the risk of metastasis – the spread of cancer to distant organs, which is the primary cause of cancer death.
• Metabolic and Hormonal Changes: Exercise improves glucose control and can reduce levels of insulin and IGF (Insulin-like Growth Factor), which are known growth factors for many cancer cells.
• Anti-Inflammatory Effects: Chronic inflammation can fuel cancer growth, and exercise generally has systemic anti-inflammatory effects.
• Immune System Enhancement: Exercise boosts immune function, increasing the number and cytotoxic activity of NK cells and T-cells, which are crucial for recognizing and eliminating cancer cells (immunosurveillance). Preclinical studies show exercise can increase the infiltration of these immune cells into the tumor itself. Dr. Courneya refers to exercise as potentially the "original immunotherapy."

Exercise as Monotherapy and in Active Surveillance

A particularly exciting area is the use of exercise in "active surveillance." This approach is used for some low-grade, slow-growing cancers (most notably prostate cancer) where immediate treatment might cause more harm than benefit. Patients are monitored closely without active treatment. Dr. Courneya describes research, including his own study using High-Intensity Interval Training (HIIT) in men on active surveillance for prostate cancer. The study found that HIIT lowered Prostate-Specific Antigen (PSA) levels and, in lab experiments, serum from the men who exercised slowed the growth of prostate cancer cells *in vitro*. This suggests exercise might delay or even prevent the need for active treatment in these individuals. HIIT was often chosen for such studies because higher intensity exercise appears to provide a stronger stimulus for beneficial biological changes (immune, metabolic, inflammatory).

The Powerful Psychological Impact of Exercise

Beyond the physical, Dr. Courneya emphasizes the profound psychological benefits, which patients often rate as highly important. Exercise can restore a sense of control and normalcy disrupted by a cancer diagnosis. It demonstrably reduces anxiety and depression associated with cancer and its treatments. A key finding from Dr. Courneya's research is that exercise significantly reduces the "fear of cancer recurrence or progression," a pervasive and debilitating issue for many survivors who live with uncertainty about their future health. This psychological resilience is crucial for overall quality of life.

Implementation Challenges and the Path Forward

Despite the strong evidence, exercise adoption among cancer patients remains low. Diagnosis and treatment often lead to a significant *decrease* in activity levels. Overcoming this requires intervention and support. The role of the oncologist is critical; when doctors recommend exercise, patients take it seriously. Encouragingly, major oncology organizations like the American Society of Clinical Oncology (ASCO) now have guidelines recommending aerobic and resistance exercise for patients undergoing curative-intent therapy. Resources like Livestrong at the YMCA and programs within major cancer centers are growing, but access and insurance coverage remain challenges. However, Dr. Courneya points out the potential cost-effectiveness: preventing even a small number of cancer recurrences (which can cost healthcare systems hundreds of thousands or millions of dollars per patient) through relatively inexpensive exercise programs offers substantial value.

Important Considerations and Caveats

While overwhelmingly beneficial, Dr. Courneya advises nuance. Exercise isn't a universal cure-all. Rare preclinical studies have shown exercise potentially accelerating growth in specific tumor models, though the pattern isn't clear. In humans, exercise can sometimes exacerbate certain treatment side effects like radiation-induced skin irritation, diarrhea, or hand-foot syndrome if not managed properly. Patients with bone metastases require careful exercise prescription to avoid fractures. Additionally, outdoor exercise increases sun exposure, raising skin cancer risk if precautions (sunscreen, protective clothing) aren't taken. However, Dr. Courneya stresses that for the vast majority of patients, the benefits of appropriately prescribed exercise far outweigh these potential risks.

Conclusion

Dr. Kerry Courneya provides a compelling, evidence-based case for integrating exercise across the entire cancer care continuum – from prevention through treatment and into long-term survivorship. Exercise offers a unique dual benefit: improving quality of life by managing symptoms and psychological distress, while simultaneously impacting disease biology to potentially enhance treatment effectiveness and survival. His core message, "Don't take cancer lying down," encapsulates the empowering role activity can play. With growing support from oncologists and expanding resources, exercise is increasingly recognized not just as advisable, but as an essential component of optimal cancer care.