Aging and Cancer

The world’s population is growing older, and this increase in older-age individuals has become a key issue. The future of older persons involves significant medical, public health, economic, social, and ethical issues.[1] The public considers the three most important issues to be aging, the environment, and cancer.

Although 65 years is regarded as the age for retirement, it is more realistic to refer to older persons as those over age 75 years. The number of people over age 85 years is increasing especially rapidly. The most rapidly expanding group in terms of the percentage increase in numbers is those over age 100 years. Prior to 1992, population projections by the US Bureau of Census were underestimated, because the estimates excluded fertility rates, immigration, and prolonged longevity. Since that time, these factors have been included in projections.

America is growing older[2]; during the past century, the US population over the age of 65 years has increased tenfold. In 1930, 1 in every 15 persons was over 65 years; in 1990, 1 in 8; and in 2030, 1 in 4 will pass that age mark. In 1990, 12.5% of the US population was over age 65 years. In 2030, this will expand to 21.1%. The oldest baby boomers will reach age 65 years in 2010, and age 85 years by 2030. Their average age in 2040 will be 85 years.

The average life span will also continue to increase. Life expectancy in the United States increased by 25 years in the past century; females born today can expect to live to the age of 85 years, and males, to the age of 77 years.[3] The maximum life span has been projected to be as long as 120 years. Survival beyond the age of 80 years has increased in many developed countries.[4]

New technology and changes in lifestyle account for some of this longevity. Improved sanitation and the use of antibiotics over the past 50 years have made it possible for people to live longer. With reduced smoking, improved diet, and exercise, the death rate from coronary heart disease and vascular diseases has plunged significantly. This has resulted in a new era of degenerative diseases, including Alzheimer’s disease and cancer.

Attitudes toward aging must undergo a major change. Aging is often perceived as an end of life. Older patients are associated with poor prognosis, cognitive impairment, decreased quality of life, limited life expectancy, and decreased social worth. These negative perceptions have impaired efforts to maintain the health of older persons. To reverse this negative trend, the elimination of terms like "senior citizens," "golden age," "elderly," "frail old," or "older-old," has been encouraged. The preferred term is "older persons," which emphasizes the physiologic status of the person.

Cancer

Cancer is primarily a disease of older persons.[3] Over 60% of all cases of cancer are diagnosed after age 65 years, with 67% of cancer deaths occurring in this older group. Compared to 1990, in 2020 the population will increase by 12%, but the incidence of cancer will increase by 60% (Table 1). Up to age 50 years, the incidence of cancer is greater in women. After age 60 years, there is a remarkable increase in cancer incidence among men, reflecting the increase in prostate and lung cancer (Figure 1).[5]

There are many reasons why cancer occurs more frequently in older persons. Older persons have less resistance and longer exposure to carcinogens, a decline in immune competence, an alteration in antitumor defenses, decreased DNA repair, defects in tumor-suppressor genes, and differences in biological behavior, including angiogenesis.

There has been progress in the fight against cancer, and high rates of cure—for example, in acute leukemia in children, testis cancer, Hodgkin’s disease, and others—have decreased mortality among persons under age 55 years. In those over age 55, however, there has been an increase in cancer mortality.

During the normal process of aging, there is a progressive age-related reduction in the function of many organs. At age 70 years, the physiologic functions of some organ systems may be performing at 50% of those measured at age 30 years. There may be a decrease in hepatic clearance, renal clearance, lung function, immune competence, and marrow cellularity. These changes have profound effects on tolerance of cancer treatments involving surgery, radiation therapy, or chemotherapy.

Nevertheless, in considering treatment for older patients with cancer, the physiologic performance of the patient is of prime importance. The existence of other comorbid diseases is also an important factor influencing the decision-making process. However, chronologic age alone should not guide treatment choices for an older cancer patient.

Cancer Incidence and Mortality

The American Cancer Society (ACS) estimates the total number of new cancer cases and deaths from cancer each year. Table 2 lists ACS estimates for 2000.[6] Cancers of the breast, lung, prostate, and colorectum are the leaders in incidence, reflecting the impact of age on their occurrence. Although these cancers also lead as the cause of death, survival among women with breast cancer might appear to be improving due to earlier detection. The management of the more common cancers in older persons will be considered in separate reports in future issues of Oncology.

Treatment

A number of studies have reported on age bias in the management of cancer in older persons.[7] Attitudes toward aging have affected decisions by physicians, patients, and patients’ families. In short, older patients have been discriminated against based on chronologic age.

Older age has been associated with less screening for cancer, less staging when a diagnosis has been made, less aggressive therapy, and no treatment at all. Older women tend to have fewer mammograms for breast cancer and fewer smears for cervical cancer. Physicians have favored conservative treatments rather than curative major surgical procedures in this population, despite reports that even healthy persons over 100 years of age can tolerate major surgery. If radiotherapy or chemotherapy is used at all, less aggressive regimens may be planned for older patients. Logistic considerations, such as transportation or social support, also contribute to their undertreatment.

Older patients have been underrepresented in clinical trials of cancer therapy.[7] Several explanations have been suggested beyond that of age bias, including (1) exclusion of older persons based on criteria for eligibility in a trial, (2) presence of comorbidity, (3) use of aggressive therapy that produces toxicity unacceptable to older persons, (4) lack of trials designed for older persons, (5) limited therapeutic expectations by physicians, relatives, and patients, (6) failure to refer patients to centers where trials are available, and (7) lack of financial, social, and logistic support required for participation in trials.[8] The first reason aside, it is unfortunate that eligible older patients are excluded from clinical research trials. Providers should be encouraged to enroll eligible candidates in clinical trials, regardless of age.

The expansion of useful technologies in the treatment of cancer and other diseases of the older population and the rapid growth of the older population are major determinants of increasing health-care costs. Currently, four working Americans support one retiree, but soon there will be only two per retiree. Plans need to be developed that encourage people to save for their own retirement and concomitant health-care needs. The demand on long-term care facilities will be phenomenal.

Geriatric Oncology

In the initial evolution of the subspecialty of medical oncology, gerontology was one of nine relevant subjects.[9] In the subsequent 25 years, the number of certified medical oncologists has grown at an enormous rate—now exceeding 8,163—and there is no apparent surplus of these subspecialists. The magnitude of therapeutic advances in the field was well demonstrated at the 2000 annual meeting of the American Society of Clinical Oncology, where there were 24,000 attendees, approximately one-half from foreign countries. Perhaps an inkling of the awareness of the need for geriatric oncologists was also apparent. As one measure of this need, comprehensive texts on geriatric oncology are now available.[10]

To meet the anticipated demand on medical oncologists in the care of older patients in the 21st century, geriatricians and medical oncologists have begun to take constructive measures. Educational programs are evolving that emphasize the role of geriatric oncologists. Education of trainees in oncology, as well as oncologists in practice, will include orientation in the many syndromes in geriatric medicine, including an emphasis on dementia, depression, incontinence, delirium, osteoporosis, and failure to thrive. The new area of geriatric oncology will need to emphasize geriatric training, cancer screening and detection, research on aging and cancer, clinical trials for older persons, and funding for cancer care.

Primary care physicians, geriatricians, and oncologists need to prepare themselves for the impending care demands of older persons with cancer. Complete management of older persons with malignant disease will involve an interdisciplinary effort that includes surgeons, gynecologists, radiotherapists, medical oncologists, and geriatricians who coordinate the patient’s therapeutic needs and convey them to the primary care physician.

On a final note, it can be instructive to consider that pets, like their human companions, are living longer and healthier lives because of antibiotics, vaccines, and better diet and care. However, when cats and dogs pass the age of 10 years, more than one-half die as a result of cancer. Clearly, aging and cancer are not limited to the human race.