Neoplastic Disease
Kenneth G. Schellhase
CLINICAL PEARLS
Prevention
Few interventions other than smoking cessation are known to be effective for cancer prevention.
Most cancer prevention studies are performed in younger populations. Caution should be used when generalizing these results to older populations.
While evidence of an association is strong, a causal link between obesity and cancer risk has not been established nor is there evidence that weight loss will reduce cancer risk.
Residential radon exposure is an overlooked environmental health risk.
The US Surgeon General estimates that within 10 years of quitting smoking the risk of lung cancer is reduced to half that of a current smoker.
Screening
Evidence regarding the benefit of screening interventions should be held to a high standard.
Screening in the geriatric patient requires balancing life expectancy with the anticipated benefits and risks of screening.
Randomized trials suggest that it takes at least 5 years before there is a mortality benefit from screening tests.
For most cancers, we lack clear evidence about when to stop screening.
There continue to be multiple acceptable options for colorectal cancer screening.
Despite the high mortality burden of lung and ovarian cancers, routine screening for these diseases is still not recommended.
Survivors
There are roughly 10 million cancer survivors in the United States today, triple the number from 30 years ago.
Most cancer survivors are elderly.
Primary care physicians can, and should, provide routine cancer survivor care for their patients.
Most cancer surveillance regimens are fairly straightforward.
Guidelines for common cancers can help primary care physicians provide appropriate routine follow-up testing in cancer survivors.
BURDEN OF CANCER IN THE ELDERLY
Despite advances in prevention, detection, and treatment, cancer is still an enormous health burden in the United States, and this burden is particularly heavy for the elderly. Table 38.1 shows the incidence and mortality rates, as well as ICD-9 codes, for a number of cancers common in the elderly. More than half of all new cancer diagnoses are in patients older than 65. Cancer is the most common cause of death for both men and women aged 60 to 79, and the second leading cause of death in patients aged 80 and older.1 Additionally, the word “cancer” evokes a special dread (and among some, still a certain stigma) like few other diseases. Consequently, the very discussion of cancer can have important emotional dimensions for our patients, which we should not underestimate.
TABLE 38.1 COMMON MALIGNANCIES IN THE GERIATRIC POPULATION (>65 Y) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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CANCER-RELATED CARE AS PART OF PRIMARY CARE
Primary care physicians have a critical role to play in providing cancer-related care throughout the lifespan of their geriatric patients. To provide some perspective, Figure 38.1 depicts the cancer care continuum. The continuum starts with the prevention and screening/symptom phases, comprising typical primary care services that are of an indefinite and continuous duration. These services include primary prevention of cancer, cancer screening, and evaluation of presenting symptoms. If cancer is detected by screenings or symptoms, patients move from this continuity model to the acute-care model of the diagnosis phase, where definitive diagnostic maneuvers may be performed by primary or specialty physicians, depending on the particular cancer. Patients then move to the treatment phase. The treatment phase is characterized by episodic care, with a duration usually measured only in months. In this phase, the treatment of cancer by surgery, chemotherapy, or radiation therapy is typically managed by specialists, with the exception of certain skin cancers. After treatment, patients enter the survivorship phase, another period of indefinite duration where the continuity-based follow-up care provided to cancer survivors takes the form of chronic disease care. In addition to showing the importance of primary care physicians in the cancer-related care of the geriatric patient with cancer, Figure 38.1 shows that care uniquely provided by cancer-related specialists occupies a critical, although relatively brief, period in the cancer care continuum.
CHAPTER GOALS AND STRUCTURE
The goal of this chapter is to guide primary care physicians in caring for patients in the three main parts of the cancer
care continuum in Figure 38.1: (i) Cancer prevention services, (ii) cancer screening services, and (iii) routine care of the cancer survivor. Therefore, the section “Primary Prevention of Cancer” focuses on effective interventions that may reduce the risk of getting cancer. The section “Secondary Prevention: Screening for Cancer” presents evidence-based recommendations for prevention and screening services for common cancers, with consideration given to the appropriate use of screening in elderly populations with limited life expectancy. The section “Routine Care of the Cancer Survivor” is an acknowledgment of the relatively recent phenomenon of tremendous growth in the number of cancer survivors, most of whom are elderly. This section examines the role of the primary care physician in the care of the cancer survivor in the context of a chronic disease model and presents recommendations for routine follow-up care of survivors of common cancers.1,2
care continuum in Figure 38.1: (i) Cancer prevention services, (ii) cancer screening services, and (iii) routine care of the cancer survivor. Therefore, the section “Primary Prevention of Cancer” focuses on effective interventions that may reduce the risk of getting cancer. The section “Secondary Prevention: Screening for Cancer” presents evidence-based recommendations for prevention and screening services for common cancers, with consideration given to the appropriate use of screening in elderly populations with limited life expectancy. The section “Routine Care of the Cancer Survivor” is an acknowledgment of the relatively recent phenomenon of tremendous growth in the number of cancer survivors, most of whom are elderly. This section examines the role of the primary care physician in the care of the cancer survivor in the context of a chronic disease model and presents recommendations for routine follow-up care of survivors of common cancers.1,2
 Figure 38.1 Cancer continuum. |
Clinical issues surrounding the workup, diagnosis, or treatment of cancer will not be addressed in this chapter. Although many primary care physicians will work up and definitively diagnose cancer, these broad areas are beyond the scope of this text. Additionally, while many generalist physicians may feel comfortable with the initial management of potential cancer recurrence as well as late effects and complications of treatment, these areas are also beyond the scope of this chapter.
PRIMARY PREVENTION OF CANCER
Most studies of the primary prevention of cancer, whether by lifestyle interventions, chemoprevention or other means, focus on nongeriatric populations. The rationale for this is simple: Younger populations are thought to be more likely to benefit because these preventive interventions will take years to have an impact on cancer risk. Carcinogenesis is thought to start slowly, many years before clinically evident cancer is noted. In other words, if an 80-year-old smoker does not have some smoking-related cancer, getting him to stop smoking is not likely to have a large impact on his risk of dying from cancer. Therefore, the evidence of any benefit for the primary prevention of cancer will be limited for the elderly. However, our patients still come to us wanting to know what they can do to decrease their risk of cancer. The following discussion reviews the potential benefit of common cancer prevention interventions.
Lung Cancer and Smoking Cessation
Cigarette smoking is the greatest preventable cause of disease in the United States, most notably leading to increased risk of death from lung and many other cancers and to increased risk of heart disease (Evidence Level A). Lung cancer is by far the leading cause of cancer death in both men (32% of all cancer deaths in 2004) and women (25% of all cancer deaths in 2004), with a dismal 15% overall 5-year survival rate.1 In addition, there is evidence that exposure to secondhand cigarette smoking also increases cancer risk. Although nicotine is highly addictive, there are effective methods to aid patients with smoking cessation, including nicotine replacement, antidepressant medications, and behavioral interventions.3 Recently, Medicare adopted a policy to reimburse physicians for smoking cessation counseling for Medicare enrollees who currently smoke and have a smoking-related illness. The sooner patients accomplish and sustain smoking cessation, the sooner they will accrue the health benefits of having stopped smoking. The US
Surgeon General estimates that the risk of lung cancer is reduced to half that of a current smoker within 10 years of quitting.4 The time lag until health benefits accrue to recipients of secondhand smoke is unknown.
Surgeon General estimates that the risk of lung cancer is reduced to half that of a current smoker within 10 years of quitting.4 The time lag until health benefits accrue to recipients of secondhand smoke is unknown.
Skin Cancer and Limiting Sun Exposure
Skin cancer is the most common form of neoplasm in the United States, with over 1 million cases annually.5 In 2004, melanoma was expected to account for 55,000 skin cancers and nearly 8,000 deaths.1 Mortality from other forms of skin cancer is rare, although given the generally high incidence of skin cancer, the overall burden of suffering from these other forms is substantial. There is limited evidence suggesting that significant sun exposure early in life is associated with increased risk of skin cancer in adulthood and that counseling to limit sun exposure may be effective at reducing ultraviolet light exposure. However, there is no direct evidence linking interventions to limit ultraviolet light exposure (e.g., protective clothing or sunscreen) with decreased skin cancer incidence or death. Patients may nonetheless be motivated to limit sun exposure given the possibility of benefit, lack of harm, and concerns about premature aging of the skin from extensive exposure (Evidence Level C).
Diet, Obesity, and Cancer Risk
The evidence supporting a link between high fruit and vegetable consumption and decreased risk of cancer has been conflicting, with early reports suggesting benefit, but more recent research indicating less-certain effects on risk. Despite uncertain benefits, some professional organizations endorse fruit and vegetable consumption as a way to lower cancer risk5 (Evidence Level C). However, these diets may be recommended in elderly patients on other clinical grounds (e.g., part of a balanced diet, prevention of constipation, beneficial effects on lipids from fiber), and in moderation, there is little risk of harm for the typical patient.
Emerging literature now links obesity to increased risk of several types of cancer6 (Evidence Level B). To date, this evidence comes only from observational studies, so thus far obesity has not been shown to be causally related to cancer risk. It has also not been shown that interventions in obese individuals that decrease body weight result in reduced cancer risk. Therefore, we clearly lack the evidence at this time to recommend weight loss to patients as a means to reduce cancer risk. However, there are numerous other clinical grounds on which to recommend maintaining healthy body weight.
Environmental Hazards
There are ubiquitous environmental hazards—other than secondhand smoke—that may contribute to cancer risk, although most environmental health issues have historically been addressed at the level of the public health system. Patients at particular risk for environmental exposures, such as asbestos, can usually be identified through obtaining careful social and occupational histories. However, one environmental health issue that is often overlooked, yet appropriately addressed at the level of the individual patient, is ionizing radiation from residential radon gas exposure. Radon is the second leading cause of lung cancer, after cigarette smoking, and is estimated to cause 5% to 10% of lung cancers in the United States (Evidence Level B). Radon results from the natural radioactive decay of uranium in the soil, and its exposure occurs most commonly in the basement level of private homes through small foundation cracks. High soil radon levels are more common in the upper Midwest of the United States but can occur anywhere. Residential radon exposure has been shown in multiple meta-analyses to be correlated with increased lung cancer risk.7 The Environmental Protection Agency (www.epa.gov) offers detailed advice to homeowners on how to test for and correct problems with radon gas. Currently, there is no evidence that radon abatement programs will reduce lung cancer risk.
Chemoprevention of Cancer
The possibility of chemoprevention of cancer through the use of vitamin supplements or a number of pharmaceuticals (e.g., aspirin) has received significant attention in recent years. Despite a number of large observational studies of various chemopreventive agents showing an association between the intake of these substances and reduced cancer risk, no consistent evidence has emerged from randomized trials that would support recommending chemoprevention for the primary prevention of cancer in average-risk patients (Evidence Level B). Indeed, the U.S. Preventive Services Task Force (USPSTF) has recently recommended against the use of β-carotene for cancer prevention owing to the evidence of increased lung cancer risk in heavy smokers using this supplement.3
There has been some preliminary evidence from observational studies suggesting a role for both cyclo-oxygenase-2 (COX-2) inhibitors and 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) in cancer prevention8,9 (Evidence Level B). Randomized cancer prevention trials of these agents may take place in the near future, although in the case of COX-2 inhibitors, this may depend on further clarification of cardiovascular risks. Nevertheless, it is critical for physicians to bear in mind the higher standards of evidence demanded by the ethical foundations of screening and prevention (discussed in the section “Secondary Prevention: Screening for Cancer”) before prescribing or endorsing such preventive interventions.
While the USPSTF has recommended against using tamoxifen for chemoprevention in women at average risk for breast cancer, there may be a role for this drug as primary prevention in women at high risk for breast cancer, as indicated by family history or genetic testing
(Evidence Level B). However, given the higher risk of thromboembolic events and other harms or adverse effects in geriatric patients, the risks of tamoxifen use for primary prevention are likely to outweigh the expected benefits in this age-group.10 Consequently, any decision to use tamoxifen as primary breast cancer prevention in geriatric patients should not be pursued without prior consultation with an oncologist and thorough consideration of the particular patient.
(Evidence Level B). However, given the higher risk of thromboembolic events and other harms or adverse effects in geriatric patients, the risks of tamoxifen use for primary prevention are likely to outweigh the expected benefits in this age-group.10 Consequently, any decision to use tamoxifen as primary breast cancer prevention in geriatric patients should not be pursued without prior consultation with an oncologist and thorough consideration of the particular patient.
SECONDARY PREVENTION: SCREENING FOR CANCER
Criteria for Appropriate Screening
Screening for cancer—the attempt to find preclinical disease in asymptomatic patients—has long been central to providing primary care services to geriatric patients. Because virtually any test could be used as a screening test, general criteria have been developed by clinical epidemiologists to guide the appropriate use of screening tests; these criteria can be applied to potential cancer screening tests as well as for other disease screening. As summarized in Table 38.2, when employing screening tests, we must consider disease factors such as prevalence and burden of illness, patient factors such as the willingness to undergo testing, test factors such as accuracy of results, and social factors such as cost-effectiveness.
All these domains must be considered in determining whether to recommend screening (or preventive interventions) on a population basis. Often, the most difficult criterion for which direct evidence needs to be established is the requirement that treatment of patients with screen-detected disease must lead to better outcomes than treatment of patients with clinically detected disease. Apart from this, there is no justification to expose patients to the risks that are inherent in any screening program. This is critical to remember because the ethical foundation for screening and preventive interventions differs from the ethical foundation of “traditional” medical care composed of diagnosis and treatment, and this difference demands a higher standard of evidence demonstrating the benefit of screening tests.11 Reasons for this include the following: (a) Most screened patients will not benefit from screening, (b) most patients suffering harm from screening will never benefit from it, and (c) historically, screening has occurred because it has been advocated by physicians and not sought by patients.
TABLE 38.2 CRITERIA FOR APPROPRIATE SCREENING | |
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Inappropriate Screening
Many physicians have had at least one patient who has elected to undergo helical (low-dose) computed tomography (CT) scanning for lung cancer screening or possibly even the “whole body” CT scan or magnetic resonance imaging that is typically performed at free-standing for-profit imaging centers in major metropolitan areas. While lung cancer screening through helical CT scan does hold legitimate promise as an appropriate screening test, the evidence of its beneficial effect on lung cancer mortality is still very preliminary, and the magnitude of potential harms ensuing from false-positive workups should not be underestimated. Large National Institute of Health-sponsored clinical trials currently under way may provide the needed evidence. In the absence of this evidence, patients should be encouraged to enroll in clinical screening trials but to otherwise refrain from self-referral for these services. Indeed, the use of full-body CT screening is a clear-cut example of inappropriate screening. There is no current evidence of its benefit to patients and there are no large clinical screening trials under way; yet there is evidence of harm to patients from this screening modality.12
Cancer Screening in Geriatric Patients: Special Considerations
Most of the large, well-designed studies of screening efficacy that provide support to current cancer screening recommendations (e.g., breast cancer, colorectal cancer) were performed in populations with middle-aged to “young” elderly patients up to around age 70. Yet these patients continue to seek and receive cancer screening well beyond the age for which we have good supporting data. In general terms, one would expect the benefits of screening to decline with advancing age for at least three reasons:13
Tumors tend to be less aggressive in older patients, so these patients are more likely to die from other comorbid conditions (e.g., cardiovascular disease) rather than from cancer.
Increasing comorbidity and frailness from advancing age may make the diagnostic workup for a positive screen fraught with risk, or the rigors and side effects of definitive treatment may become unacceptable.
The potential harms of screening weigh more heavily, in view of points 1 and 2.
 Figure 38.2 Individualized cancer screening in the elderly. (Based on: Walter LC, Covinsky KE. Cancer screening in elderly patients: A framework for individualized decision making. JAMA. 2001;285(21):2750-2756.). |
However, because overall cancer incidence rises with increasing age, the predictive value of a positive screen is greater—that is, a positive screen is more likely to represent real disease. Further, we see increasing numbers of surprisingly healthy patients in their eighties and beyond, which complicates generic recommendations about the correct age at which cancer screening must be stopped. Given these competing considerations, Walter and Covinsky have proposed a conceptual framework to help individualize decisions about screening in elderly patients.14 Summarized in Figure 38.2, this framework includes quantitative assessments based on life expectancy and estimates of risk reduction from screening that must be blended with qualitative judgments about potential harms of screening and patient preferences, in order to arrive at a more informed, individualized decision about whether to proceed with screening.
TABLE 38.3 RISK (PERCENTAGE) OF DYING FROM CANCER IN REMAINING LIFETIME FOR MEN AND WOMEN AT SELECTED AGES AND LIFE EXPECTANCY QUARTILESa | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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