Should doctors prescribe exercise?

young woman running city park

“Although the data vary by different cancer types, there is a consistent trend suggesting that moderate daily exercise has a beneficial effect on preventing certain cancers. If you are a reasonably healthy adult, your should exercise regularly.” 

Let’s look at the relationship of exercise and selected cancers. The American Society of Clinical Oncology (ASCO) has done a nice job of summarizing:

Breast Cancer

While the amount of risk reduction varies among studies (20-80%), most suggest that 30 to 60 minutes of moderate to high-intensity exercise per day lowers breast cancer risk. Women who are physically active throughout their life appear to benefit the most, but those who increase physical activity after menopause also fare better than inactive women.1

Colon Cancer

Research suggests that people who increase their physical activity can lower the chance of developing colon cancer by 30 to 40% relative to sedentary adults.1,2 A decrease in colon cancer risk can be achieved regardless of body mass index (BMI) and people who are most active benefit the most. There is insufficient evidence of a protective effect of physical activity on the risk of rectal cancer (a protective effect was seen in some case-control studies, but not in cohort studies).3

Endometrial, Lung and Ovarian Cancer

A handful of studies have suggested that women who are physically active have a 20-40% reduced risk of endometrial cancer compared to those who don’t exercise.1 Higher levels of physical activity seem to also protect against lung cancer (up to 20% reduction in risk), particularly among men.1Although less consistent, research suggests that physical activity possibly reduces the risk of ovarian and prostate cancer.

What about Other Cancers?

While observational data on the benefits of exercise for prevention of the types of cancers listed above are fairly consistent, evidence of the effects of exercise on prevention of any other type of cancer either is either insufficient or inconsistent.2,4

Prostate Cancer

Prostate cancer is one disease in which the data are not consistent, however prostate cancer is a heterogeneous disease and risk factor associations for total non-aggressive disease are different from aggressive / lethal disease. Most population based studies show similar findings, with little effect of exercise on overall incidence of prostate cancer but lower risk of aggressive prostate cancers for those with the highest levels of VIGOROUS activity (rather than any type of activity). In the Health Professionals Follow-up Study men 65 years or older who engaged in vigorous physical activity, such as running, jogging, biking, swimming or tennis at least three hours per week  had a 67% lower risk of advanced prostate cancer and 74% lower risk of fatal prostate cancer.5

Conflicting data for other malignancies

For example, one recent study found no association between physical activity and risk of developing gastric, rectal, pancreatic, bladder, testicular, kidney and hematological cancers.4 In contrast, a pooled analysis of data from prospective trials with 1.4 million participants found that physical activity was linked to lower risk of 13 cancers: esophageal, lung, kidney, gastric, endometrial, myeloid leukemia, myeloma, colon, head and neck, rectal, bladder, and breast.6Interestingly, leisure-time physical activity was associated with a higher risk of melanoma (presumably due to time spent outdoors) and prostate cancer, although it is not clear from these data whether that association was with nonaggressive or aggressive prostate cancer.

While we wait for confirmation and clarity on the role of exercise in preventing all the 200+ types of cancer – should doctors prescribe exercise? The answer is simple: yes, because evidence of the protective role of exercise is already strong for some of the most common cancers.


  1. Lee I, Oguma Y. Physical activity. In: Schottenfeld D, Fraumeni JF, editors. Cancer Epidemiology and Prevention. 3rd ed. New York: Oxford University Press, 2006.
  2. Slattery, ML. Physical activity and colorectal cancer. Sports Medicine 2004; 34(4): 239–252.
  3. Pham NM, et al. Physical activity and colorectal cancer risk: an evaluation based on a systematic review of epidemiologic evidence among the Japanese population. Jpn J Clin Oncol. 2012 Jan;42(1):2-13.
  4. Friedenreich CM, Neilson HK, Lynch BM. Eur J Cancer. State of the epidemiological evidence on physical activity and cancer prevention. 2010 Sep;46(14):2593-604.
  5. Giovannucci E, Liu Y, Leitzmann MF, et al. A prospective study of physical activity and incident and fatal prostate cancer. Arch Intern Med. 2005; 165(9):1005-1010.
  6. Moore SC, Lee IM, Weiderpass E, et al. Association of Leisure-Time Physical Activity With Risk of 26 Types of Cancer in 1.44 Million Adults. JAMA Intern Med. 2016 Jun 1;176(6):816-25.


I’m Dr. Michael Hunter. Of course, the disclaimer: Do not begin an exercise program without input from an appropriate medical professional. Many can simply start with a brisk walk for 30 minutes daily, 5 days per week. Have a wonderful day!

Physical Activity Increases Prostate Cancer Survival

What You Need to Know: Yet another study is confirming the benefits of physical activity following the diagnosis of cancer, this time of prostate cancer, on all-cause and prostate-specific survival. Higher levels of physical activity are associated with reduced rates of overall and prostate cancer–specific mortality.

Background: Few studies have investigated the association between post-diagnosis physical activity and mortality among men diagnosed with prostate cancer. The aim of this study was to investigate the effect of physical activity after a prostate cancer diagnosis on both overall and prostate cancer–specific mortality in a large cohort.

Methods: Data from 4,623 men diagnosed with localized prostate cancer 1997–2002 and followed-up until 2012 were analyzed. Researchers in Sweden examined the association between post-diagnosis recreational MET-h/d, time spent walking/bicycling, performing household work or exercising, and time to overall and prostate cancer–specific death. All models were adjusted for potential confounders.


  • Men who walked or cycled for 20 minutes a day or more had a 30% lower risk for all-cause mortality and a 39% decreased risk for prostate cancer–specific mortality compared with men who walked or cycled less than 20 minutes a day, investigators report.
  • For those exercising 1 or more hours a week, all-cause mortality was reduced by 26% and prostate cancer–specific mortality by 32% compared with men who reported exercising less than 1 hour a week.
  • After considering all time spent walking, cycling, exercising, and doing household work, researchers found that all-cause mortality was 37% lower while prostate cancer–specific mortality was 22% lower for men who had a total MET of 5 or more hours a day compared with those who had a total MET of less than 5 hours a day.


Activity After Prostate Cancer Diagnosis Overall Mortality Prostate Cancer–Specific Mortality
  Walking/cycling <20 min/day vs ≥20 min/day 0.70 0.61
  Household work <1 h/day vs ≥1 h/day 0.71 0.86
  Exercise < 1 h/wk vs ≥1 h/wk 0.74 0.68

Conclusions: Higher levels of physical activity were associated with reduced rates of overall and prostate cancer–specific mortality.

Impact: This study further strengthens previous results indicating beneficial effects of physical activity on survival among men with prostate cancer.

Reference: Cancer Epidemiol Biomarkers Prev; 1–8. ©2014 AACR.

Colonoscopy Could Prevent 40% of Colorectal Cancers

A large, long-term study from Harvard School of Public Health suggests that 40% of all colorectal cancers might be prevented if we all underwent regular colonoscopy screenings.

Background: In the USA, nearly 137,000 people were found to have colon cancer in 2009, and nearly 52,000 died that year from the diserase. Colorectal cancer is the second-leading cause of cancer-related death in the USA.

The Study: Researchers analyzed data from 88,902 participants in two long-term studies (the Nurses’ Health Study and the Health Professionals Follow-up Study). Based on questionnaires that participants filled out every two years between 1988 and 2008, the researchers obtained information on colonoscopy and sigmoidoscopy procedures. They documented 1,815 cases of colorectal cancer, and 474 deaths from the disease.

Findings: Both colonoscopy and sigmoidoscopy (the latter screens for cancer in the distal, lower part of the colorectal) lowered the risk of either getting colorectal cancer or dying from it. Only colonoscopy decreased the risk for cancers in the upper (proximal) colon, but not to the degree that it did for lower colorectal cancers.

  1. If all participants had undergone colonoscopy, 40% of colorectal cancers (including 61% distal, and 22% proximal) would have been prevented.
  2. Sigmoidoscopy alone is likely insufficient for reducing the risk of upper colon cancer.
  3. People who get an all-clear report from their colonoscopy have a significantly lower chance of colorectal cancer for up to 15 years after the procedure (although the data support repeat screening at shorter intervals among individuals with a personal history of an adenoma (a benign tumor of the colon, but one that can become cancer over time; also, more frequent if you have higher risk features such as a family history of the disease).
  4. Colorectal cancers found within 5 years of colonoscopy had different molecular characteristics, compared with cancers found more than 5 years after a colonoscopy, and may be more difficult to detect or completely remove.

My Take: This new research supports our current guidelines that call for a colonoscopy every 10 years for those at average risk for colon or rectal cancer. The reduction in risk of getting (or dying from) colon cancer is large. I’m Dr. Michael Hunter, and yes I am due this year for my own colonoscopy. Are you?

The small print: The material presented herein is informational only, and is not designed to provide specific guidance for an individual. Please check with a valued health care provider with any questions or concerns. As for me, I am a Harvard- , Yale- and UPenn-educated radiation oncologist, and I practice in the Seattle, WA (USA) area. I feel genuinely privileged to be able to share with you. If you enjoyed today’s offering, please consider clicking the follow button at the bottom of this page.

Available now: Understand Colon Cancer in 60 Minutes; Understand Brain Glioma in 60 Minutes. Both can be found at the Apple Ibooks store. Coming Soon for iPad:  Understand Breast Cancer in 60 Minutes; Understand Colon Cancer in 60 Minute; Understand Colon Cancer in 60 Minutes; Understand Brain Glioma in 60 Minutes. Thank you.

Reference: Reiko Nishihara, Kana Wu, Paul Lochhead, Teppei Morikawa, Xiaoyun Liao, Zhi Rong Qian, Kentaro Inamura, Sun A. Kim, Aya Kuchiba, Mai Yamauchi, Yu Imamura, Walter C. Willett, Bernard A. Rosner, Charles S. Fuchs, Edward Giovannucci, Shuji Ogino, Andrew T. Chan. Long-Term Colorectal-Cancer Incidence and Mortality after Lower Endoscopy. New England Journal of Medicine, 2013; 369 (12): 1095 DOI:10.1056/NEJMoa1301969