Sports Medicine: Just the Facts

BENEFITS OF EXERCISE IN THE
CANCER PATIENT

• There are many proven benefits of exercise in the
  cancer patient. Aerobic exercise can improve quality
  of life and psychologic health in cancer patients
  undergoing treatment (Mock et al, 2001; Dimeo et al,
  1999) and in cancer survivors (Burnham and Wilcox,
  2002; Courneya et al, 2003).
  •Exercise has been shown to reduce fatigue in cancer
  patients and can be prescribed as primary therapy.
  (Dimeo, Rumberger, and Keul, 1998; Dimeo et al,
  1999; Mock et al, 2001; Scwartz et al, 2001)
  •Exercise has been well-studied in the patient with
  prostate cancer.
  
  
  • In addition to prostatectomy and radiation therapy,
    many men are placed on antiandrogen therapy,
    which can reduce bone density, reduce lean muscle
    mass, and cause fatigue. Resistance exercise in men
    undergoing androgen deprivation can reduce
    fatigue, and improve quality of life and overall mus-
    cular fitness (Segal et al, 2003).
  
  
  • There is debate about the effect of exercise on
    prostate-specific antigen(PSA) levels (Kratz et al,
    2003; Leventhal et al, 1993; Oremek and Seiffert,
    1996). A set of guidelines from the U.K.
    Department of Health recommends that PSA testing
    not be performed for 48 h after vigorous exercise to
    avoid confusion or misinterpretation (Weston and
    Parr, 2003).
  
  
  
  

EXERCISE FOR PREVENTION
OF CANCER

• While treatment of the athlete with cancer may prove
  to be more challenging, the prevention of cancer
  should be where physicians are focusing their atten-
  tion. There are nearly 170 observational epidemio-
  logic studies of physical activity and cancer risk
  (Friedenreich and Orenstein, 2002). Exercise is fre-
  quently used as a modifier of coronary artery disease
  risk, and the same advice should be applied for the
  prevention of certain cancer.
  •Exercise can be safely advised for most patients
  given its large benefit and relatively low risk. While
  exercise can be safely prescribed, not every form of
  cancer has had a proven preventive benefit from exer-
  cise (Byers et al, 2002). There is insufficient data to
  support exercise as a preventative mechanism in lung,
  testicular, ovarian, kidney, pancreatic, thyroid, and
  melanoma. Studies are difficult to interpret because

of confounding variables such as smoking status and

lifestyle.

• The American Cancer Society 2001 guidelines (Byers
  et al, 2002) compiled evidence in support of various
  risk factors and potential modifiable lifestyle issues in
  prevention of cancer.


• Colon cancer
  
  
  • There was convincing evidence that regular, moder-
    ate to vigorous physical activity helped prevent colon
    cancer. There have been 51 studies conducted with 43
    reporting a positive result. The risk reduction aver-
    aged 40–50% and up 70% reductions were found
    with the highest activity levels. The effect did not
    appear to be compounded by other risk factors for
    cancer such as dietary intake or body mass index
    (Friedenreich and Orenstein, 2002; McTeirnan et al,
    1998).
    •Exercise may decrease colon cancer rates because of
    decreased gastrointestinal transit times that decrease
    mucosal exposure to carcinogens. Exercise may also
    increase the level of prostaglandin F, which inhibits
    colonic cell proliferation. It is also hypothesized that
    bile acids secretion may be lower in physically active
    persons and confer a protective effect.
    •Breast cancer
  
  
  • There is also convincing evidence that breast cancer
    risk can be reduced with regular exercise. Thirty-two
    of 44 studies have shown positive effects of exercise
    on cancer prevention. The inconsistent outcomes in
    breast cancer may be related to differences in the eti-
    ology of breast cancer among different subgroups
    (Friedenreich and Orenstein, 2002; McTeirnan et al,
    1998).
    •Physical activity may lower levels of biologically
    available sex hormones. A decreased lifetime expo-
    sure to estrogen may mitigate breast cancer risk.
    Physical activity affects ovarian estrogen produc-
    tion, increases sex hormone-binding globulin, and
    may decrease body fat secondarily decreasing fat-
    produced estrogen.
    •A recent investigation (Dorn et al, 2003) studied
    physical activity and breast cancer risk in pre- and
    postmenopausal women. Their results indicate a pro-
    tective effect on both pre- and postmenopausal
    women who performed strenuous physical activity.
    This effect was seen in women who exercised 3.5 h or
    more per week on average. An even stronger protec-
    tive effect was noted in those women who reported
    that level of activity 20 years prior to the investiga-
    tion. Risk of cancer was reduced by almost 50%.
  
  
  
  


• Endometrial cancer
  
  
  • Nine of 13 studies found a decrease in the risk of
    endometrial cancer with physical activity. Some
  
  
  
  

600 SECTION 7 • SPECIAL POPULATIONS