Exercise and Cancer Outcomes

Last week, I received a call from a woman who I consider a business genius. Her exercisefriendship is a gift, and she offers a wealth of experience not only in business and finance, but also in travel, hobbies, and relationships. She is a “self-made “success who embodies the vital ammunition of hard work and the type of focus that’s necessary to complete the toughest challenges.

When she called to tell me that she had just been diagnosed with breast cancer, her usual calm and confident voice sounded panicked. The mass she felt in her breast seemed to appear overnight, and she needed advice. We talked about the type of tumor she found (ER+, meaning estrogen receptor positive) and the steps she would take in moving through her diagnosis and considering her treatment options. Then her fighter attitude returned and she declared, “I am going to exercise every day and lose 40 pounds. The fat is fueling my cancer, and I just can’t let that continue.”

I encouraged my friend to develop a plan for exercise and weight loss, but not to incorporate anything that might compromise her nutritional status while under treatment (no fad diets) and to guard against overdoing it or setting unreasonable goals. She asked me for some facts on the relationship between exercise and cancer prevention, recovery, and its role in decreasing cancer recurrence in survivors. I promised to give her the facts, but this proved to be more challenging than I expected. I could remember many articles, even blogs I wrote, encouraging women to exercise. I just needed some hard data.

There are those who believe that regular exercise can stave off illness, even some types of cancer. However, such claims are difficult to substantiate. This is due, in part, to the fact that many people who incorporate exercise into their daily lives are also more likely to pay attention to their health and check in with their doctors regularly.

While the role of exercise as a way of reducing cancer risk has been embraced by some folks in the medical community, some experts feel that the evidence just isn’t there. For example, Pam Goodwin, MD, a medical oncologist at the University of Toronto’s Mount Sinai Hospital, has conducted a great deal of research on lifestyle factors associated with breast cancer. According to Dr. Goodwin, evidence suggesting a positive effect of greater physical activity on outcomes in early breast cancer is “simply not strong enough to tell patients that their breast cancer outcomes will be improved if they become more active or lose weight.” You simply can’t scare patients with data that if they don’t exercise they will have worse outcomes in short and long term. It’s complicated, though, because it is often  hard for patients under treatment to feel like exercising.

Anne McTiernan, MD, PhD, of the Fred Hutchinson Cancer Research Center in Seattle, Washington says, “Many studies have shown that cancer survivors who are physically active have improved diagnosis.” However, she believes that these results don’t take into account other factors that can impact exercise levels (such as undetected cancer in other parts of the body that can cause fatigue and malaise). Therefore, she says that lower exercise levels might not lead to poorer prognosis as much as the specifics of the cancer itself and the treatment regimens. Surgical recovery, complications, chemotherapy regimens, and even radiation related fatigue all come into play in addition to the effects the tumor itself has on the body.

This issue was addressed in a report published this year in the Journal of Clinical Oncology by Lee Jones, PhD, from Memorial Sloan Kettering Cancer Center in New York City. In the report, Dr. Jones states, “The majority of investigations of the impact of exercise on cancer outcomes have assumed that cancer is a genetic and physiologically homogeneous disease.” However, since there are many different types of cancer, he argues that a “once size fits all, generic version of exercise” isn’t appropriate for all cancer patients, and that an exercise program should be tailored to each patient based on his/her particular medical profile.

To this end, Dr. Jones has created a framework that uses a “precision oncology approach” to help researchers investigate exercise as a possible anticancer treatment. He divides his approach into seven steps, as follows:

  • Discovery: The use of well-designed epidemiological studies that investigate the correlation between post diagnosis exercise and cancer outcomes.
  • Evaluation of Causality: Since only a few studies have been published that examine the relationship between post diagnosis exercise and cancer-specific outcomes, this step involves evaluating whether or not there is any consensus in the findings.
  • Molecular Epidemiology: Since the impact of exercise may differ as a function of cancer type, tumor size, etc., this step involves determining the effect of exercise given the particular biology of the cancer in question.
  • Preclinical testing: How exercise doses in preclinical model systems (testing on rodents, for example) can be extrapolated to equivalent doses in humans.
  • Safety and tolerability clinical trials: A prerequisite for initiating clinical exercise trials to evaluate effects on tumor biology and/or cancer outcomes is confirmation that the planned exercise dose is safe and tolerable in the target patient population.
  • Signal-seeking/biomarker-driven clinical trials: This step is designed to evaluate whether exercise treatment changes cancerous tumor pathways and explores whether there is a signal for clinical efficacy or benefit.
  • Definitive clinical trials: Large –scale, Phase III trials that are designed and able to detect clinically important differences (such as progression-free survival and overall survival) in the test setting. Conducting such trials represents a significant challenge in oncology, given the unique methodologic aspects in exercise treatment trials (eg, specialized facilities, equipment, and personnel required to deliver and implement the intervention).

The bottom line is: evidence does not clearly support the idea that exercise will aid in cancer recovery and/or decrease the chance of recurrence. Every cancer is different, and anyone facing the disease should educate themselves as best they can about how exercise could be helpful to them. That said, there is little doubt that staying active and healthy is good for the body and can boost the immune system. When it comes to battling cancer, more ammunition is a good thing.

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