Harrison's Internal Medicine Chapter 78. Prevention and Early Detection of Cancer
Prevention and Early Detection of Cancer: Introduction Improved understanding of carcinogenesis has allowed cancer prevention and early detection (also known as cancer control) to expand beyond the identification and avoidance of carcinogens. Specific interventions to prevent cancer in those at risk, and more sensitive and specific screening for early detection of cancer are the goals.
Cancer Screening Screening is a means of detecting disease early in asymptomatic individuals, with the goal of decreasing morbidity and mortality. While screening can potentially save lives and has been shown to do so in cervical, colon, and probably breast cancer, it is also subject to a number of biases that can suggest a benefit when actually there is none. Biases can even mask net harm. Early detection does not in itself confer benefit. To be of value, screening must detect disease earlier, and treatment of earlier disease must yield a better outcome than treatment at the onset of...
Breast self-examination, clinical breast examination by a care giver, and mammography have been advocated as useful screening tools. Only screening mammography alone and screening mammography with clinical examination have been evaluated in randomized controlled trials. MRI is being assessed and is more accurate than mammography in women at high risk due to genetic predisposition or in women with very dense breast tissue.
Physical Activity Physical activity is associated with a decreased risk of colon and breast cancer. A variety of mechanisms have been proposed. However, such studies are prone to confounding factors such as recall bias, association of exercise with other health-related practices, and effects of preclinical cancers on exercise habits (reverse causality). Recommending adults to engage in at least 30 min of vigorous activity for ≥3 days a week is good health advice, though its effects on cancer incidence are unproven.
Cancer Chemoprevention Chemoprevention involves the use of specific natural or synthetic chemical agents to reverse, suppress, or prevent carcinogenesis before the development of invasive malignancy.
Cancer develops through an accumulation of genetic and epigenetic changes that are potential points of intervention to prevent cancer. The initial changes are termed initiation. The alteration can be inherited or acquired through the action of physical, infectious, or chemical carcinogens.
Chemoprevention of Breast Cancer Hormonal manipulation is being tested in the primary prevention of breast cancer. Tamoxifen is an antiestrogen with partial estrogen agonistic activity in some tissues, such as endometrium and bone. One of its actions is to upregulate transforming growth factor β, which decreases breast cell proliferation. In randomized placebo-controlled trials to assess tamoxifen as adjuvant therapy for breast cancer, tamoxifen reduced the number of new breast cancers in the opposite breast by more than a third.
Potential Biases of Screening Tests The common biases of screening are lead time, length-biased sampling, and selection. These biases can make a screening test seem beneficial when actually it is not (or even causes net harm). Whether beneficial or not, screening can create the false impression of an epidemic by increasing the number of cancers diagnosed. It can also produce a shift in proportion of patients diagnosed at an early stage that improves survival statistics without reducing mortality (i.e.
Screening for Specific Cancers Widespread screening for cervical, colon, and likely breast cancer is beneficial for certain age groups. A number of organizations have considered whether or not to endorse routine use of certain screening tests. Because these groups have not used the same criteria to judge whether a screening test should be endorsed, they have arrived at different recommendations. The U.S. Preventive Services Task Force (USPSTF), the Canadian Task Force on Preventive Health Care, and the American Cancer Society (ACS) publish screening guidelines (Table 78-3).
Improved understanding of carcinogenesis has allowed cancer prevention and early detection (also known as cancer control) to expand beyond the identification and avoidance of carcinogens. Specific interventions to prevent cancer in those at risk, and more sensitive and specific screening for early detection of cancer are the goals. Carcinogenesis is not simply an event but a process, a continuum of discrete cellular changes over time resulting in more autonomous cellular processes.
Chemoprevention of Cancers of the Upper Aerodigestive Tract Smoking causes diffuse epithelial injury in the head, neck, esophagus, and lung. Patients cured of squamous cell cancers of the lung, esophagus, head, and neck are at risk (as high as 5% per year) of developing second cancers of the upper aerodigestive tract. Cessation of cigarette smoking does not markedly decrease the cured cancer patient's risk of second malignancy, even though it does lower the cancer risk in those who have never developed a malignancy.
Lung Cancer Chest x-ray and sputum cytology have been evaluated in randomized lung cancer screening trials. No reduction in lung cancer mortality has been seen, although all the controlled trials have had low statistical power. Even screening of high-risk subjects (smokers) has not proven beneficial. Spiral CT can diagnose lung cancers at early stages; however, false-positive rates are high. Spiral CT screening increases the number of lesions detected and increases the number of diagnostic and therapeutic procedures. However, its capacity to save lives is unproven.
Recent reductions in cancer mortality are
due in part to risk reduction behaviors like
smoking cessation and more strongly to early
detection of cancer coupled with appropriate
therapy. Yet, there are no validated molecular
biomarker tests for the early detection of any
cancer (see Table I). Among the list of Food
and Drug Administration (FDA)-approved
biomarkers, none have been approved for
cancer early detection and screening.
The Seventh Directive complements these harmonization efforts
with requirements on when and how firms must prepare consolidated financial accounts.
Both directives effectively prescribe a common set of accounting rules for both
consolidated and unconsolidated (or parent-only) financial statements. The directives had
to be transformed into national laws by the member states during the late 1980s and early
1990s. As a result, accounting standards across EU member states are fairly similar,
though not necessarily equal in every respect.
An important part of evaluating the auditor’s objectivity and professional skepticism is for the audit committee to gauge
the frankness and informative nature of responses to open-ended questions put to the lead audit engagement partner (and
members of the audit engagement team as appropriate).
When the husband strays, it is the other woman (Sushmita Sen) who is blamed for the same and is demonized all
through the film. The husband is absolved of adultery and he returns to his legitimate partner i.e. the wife at the
end of the story. The significance of the title i.e. Biwi no.1 is because the wife is successful in bringing the
husband back to the domestic arena – seen as the victory of the „traditional‟ (wife) over the „modern‟
(mistress/vamp). Such a portrayal has strong moral connotations associated with it. ...
The M-F model is scanty in that it only describes a single country and contains no representation
of how the rest of the world responds to, and interacts with, what it does. And the logical
framework of M-F is impoverished in that (like the IS-LM model itself), while “the money
supply” plays a key role, money has no accounting relationship to any other variable. The model
also contains no explicit analysis of what happens when either goods and services or financial
assets are traded between countries.
Various needles were used to collect tissue for cytological or histological diagnosis. Franzen
et al. developed a fine needle and guide for prostatic aspiration by the transrectal route
(figure 8). The Franzen needle and guide were designed to allow accurate needle placement
into the abnormal area palpated by the fingertip. It was secured by the metal ring fixed to
the fingertip and a plate in the palm of the hand. A rubber fingerstall was pulled over it and
a 23- or 25-gauge needle was used. Up to six passes could be made in one session (Berner
and Orell, 2010).
Consistent success in selling requires certain innate talents; training and desire alone are not enough.
Putting bankers through a sales training class has never been proven to yield a permanent increase
in sales productivity unless their immediate supervisor is strongly supportive of selling. Lukewarm
compliance and simply going through the motions just won’t cut it; we need managers who are
passionate advocates committed to this program.
Velocity encoded phase-contrast magnetic resonance imaging (VE-PC MRI) is another
imaging technique used to noninvasively measure Achilles tendon strain and changes in its
force-displacement relationship concomitant with chronic unloading and subsequent
recuperation. This technique will be reviewed in terms of its ability to quantify the Achilles
tendon Young’s modulus (MPa) from a stress-strain curve.
The question of population - of population pressure, of population and human rights - and the
links between these related issues and poverty, environment, and development proved to be
one of the more difficult concerns with which we had to struggle. The differences of
perspective seemed at the outset to be unbridgeable, and they required a lot of thought and
willingness to communicate across the divides of cultures, religions, and regions.
Another such concern was the whole area of international economic relations.