Devita, Hellman, and Rosenberg's Cancer

LWBK1006-04 LWW-Govindan-Review November 24, 2011 11:19

68 DeVita, Hellman, and Rosenberg’s CANCER: Principles and Practice of Oncology Review

Answer 4.29. The answer is C.

Available evidence suggests that there is a decreased risk of breast cancer

associated with consumption of soy products. This hypothesis was borne

from initial observations of lower incidences of breast cancer in women

in Asia, where soy consumption is high. Soybeans contain genistein and

daidzein, whose metabolites have several biologic effects, including inhi-

bition of the epidermal growth factor receptor tyrosine kinase activity and

competition with estrogen for the estrogen receptor. In a meta-analysis of

18 studies, a modest decrease (odds ratio, 0.86) in the risk of breast cancer

was noted with high soy intake.

Answer 4.30. The answer is D.

Large studies including the Nurses’ Health Study and the Health Profes-

sionals’ follow-up study showed no impact of high consumption of fruits

and vegetables in the prevention of cancer.

Answer 4.31. The answer is C.

There is good evidence suggesting an increased risk of colon cancer and

postmenopausal breast cancer in individuals who are obese or physically

inactive. This relation has not been established for rectal cancer. In colon

cancer, postulated mechanisms of obesity-related carcinogenesis include

insulin resistance, elevated levels of insulin and insulin-like growth fac-

tor, and inflammation. These contribute to cellular proliferation, DNA

damage, and tumor growth. Improved colonic transit time in subjects

who are physically active is another possible mechanism contributing to

decreased risk of colon cancer in this cohort. The effects of obesity and

physical inactivity have been more pronounced in men compared with

women.

Please refer to Question 4.30 for a more detailed discussion on the

relationship between these factors and postmenopausal breast cancer.

Answer 4.32. The answer is C.

An etiologic association exists between high BMI and cancers of the

esophagus (adenocarcinoma), endometrium, kidney, colon, and breast

(postmenopausal), whereas such evidence in ovarian cancer is inconclu-

sive. Obesity increases gastroesophageal reflux disease, which is a known

risk factor for esophageal adenocarcinoma. The obesity epidemic in North

America may, in part, be responsible for the dramatic increase in the inci-

dence of this cancer during the past two decades. There is a linear risk

between increasing weight and endometrial cancer, which, like breast can-

cer, is hormonally dependent. The mechanisms are believed to be similar

as well, with an increase in circulating estrogen levels in overweight or

obese women. In kidney cancer, there is a 7% increase in risk for every

unit increase in the BMI. The data in ovarian cancer at this time are

inconclusive, and a positive association, if any, is weak.