Chapter 19: Cancer and the Older Person

INTRODUCTION

In the United States, as the life expectancy increases there would be an increase in older individuals in terms of both absolute numbers and proportions of the total population.^1,2,3,4 By 2050 it is expected that there would be approximately 70 million individuals over 65 years of age.¹ This older population has a high risk for cancer and also a higher cancer mortality rate.³ This increase in incidence and mortality would mean better understanding of the disease and the consequences of the disease in the older population so as to provide optimal care. An older person's ability to tolerate treatment to prolong life or cure cancer or have quality of life depends on a complex assessment of interaction of individual person's physiological aging process, comorbidities, psychosocial, environmental factors, cancer, and cancer treatment itself.⁵ In this chapter the author plans to review the challenges confronting older patients who are coping with cancer and to discuss various strategies to manage these challenges effectively.

AGING AND CANCER

Older population has a high risk for cancer and also a higher cancer mortality rate. An age-adjusted cancer mortality rate is 1068/100,000 for those over 65 years of age as compared with 67/100,000 for those under 65.³ Various reasons have been proposed to explain the increased individual risk, including genetic factors and environmental factors^6,7,8 such as DNA damage by reactive oxygen species, toxic agents, and UV rays, epigenetic alteration, differential gene expression, telomere shortening, stem cell loss of function, and death. The following factors may also increase susceptibility of aging tissues to carcinogens: (1) cumulative exposure to environmental toxins and free radicals (carcinogens) and (2) immunological (diminished tumor surveillance).^6,7,8

Key physiological changes due to aging that impact cancer and treatment include the following:

1. There is a decrease in total body water and lean body mass. This is coupled by increase in body fat (eg, benzodiazepines, gabapentin).⁹ There may be also a decreased protein binding (phenytoin) and a decreased rate of oxidation/reduction (phase I) reactions (eg, benzodiazepines, tricyclics, SSRIs). Overall hepatic metabolism of many drugs through the cytochrome P-450 enzyme system decreases with aging.^{9,10,11,12,13}

2. There is a decrease in GFR due to decreased renal mass and renal blood flow.⁹

3. Vision problems increase with age, including the risk for glaucoma, cataract, and age-related macular degeneration.

4. Hearing issues increase, including otosclerosis, presbycusis, and tinnitus.

5. Cardiovascular system: aberrant heart rhythms and extra heart beats become more common. The baroreceptors that monitor blood pressure become less sensitive. Quick changes in position may cause dizziness from orthostatic hypotension.¹⁰

6. Respiratory: the total lung capacity remains constant but vital capacity decreases and residual volume increases.

7. Gastrointestinal: the liver is less efficient in metabolizing drugs and repairing damaged liver cells. Reduced peristalsis of ...