LWBK1006-04 LWW-Govindan-Review November 24, 2011 11:19
66 DeVita, Hellman, and Rosenberg’s CANCER: Principles and Practice of Oncology Reviewsecond cancers. Common second cancers after radiation include those of
the breast, thyroid, esophagus, and lung, as well as leukemia.Answer 4.18. The answer is D.
Induction of DNA double-strand breaks, telomere instability, and dys-
function are all effects of radiation exposure. It was initially believed that
the mutagenic and cytogenetic effects of ionizing radiation occurred in
the first few cell divisions after exposure, but it is now thought that this
kind of damage can occur in several generations in progeny of radiation-
exposed cells.Answer 4.19. The answer is D.
Individuals who lack skin pigment have a history of sunburn, have a
family history of skin cancer, and live closer to the equator have a higher
risk of developing skin cancer. The development of malignant melanoma
is less dependent on the total exposure of sunlight; rather, acute exposures
causing sunburn is of greater concern. A history of five or more sunburns
in adolescence doubles the risk of developing melanoma. In addition, the
site of development does not seem to be related to the site of chronic
exposure in melanoma.Answer 4.20. The answer is D.
In the familial form of malignant melanoma, deletions and mutations
of CDKN2A are most often seen. CDKN2A encodes p16INK4A and
p14ARF, both tumor suppressors. Oncogene activation involving the RAS
pathway is also seen in melanoma. Clinically, its development seems to
be related to acute, repeated sunburn rather than chronic exposure.Answer 4.21. The answer is C.
Asbestos is responsible for approximately 5% to 7% of all lung cancers
and acts in synergy with tobacco in smokers. Mutations in p53 are fairly
rare in mesotheliomas.Answer 4.22. The answer is D.
Quetelet’s Index (or BMI) is calculated as the weight (in kilograms) divided
by the square of the height (in meters). Being overweight is defined as
a BMI of 25.0 to 29.9 kg/m^2 , whereas a BMI greater than 30 kg/m^2
constitutes being obese. Approximately one-third of the US population
in 2000 met this definition of obesity with physical inactivity being the
likely cause.Answer 4.23. The answer is B.
Recall bias is commonly encountered in case-control studies examining
the effect of dietary factors in causing cancer. Another type of bias seen is
control selection bias. Individuals under study (cases) may overemphasize
their consumption of foods traditionally considered unhealthy, which may
skew the results observed.