Prostate Cancer in the Elderly

Introduction

Prostate cancer is a disease of the elderly, with the peak incidence of diagnosed disease at 80 years of age. While many view prostate cancer as an indolent disease, it still remains the second leading cause of cancer death among men in the United States, second only to lung cancer. Men aged ≥75 at diagnosis account for over 50% of prostate cancer deaths and almost 25% of the incidence; however, this group represents fewer than 10% of all men in the United States ≥40 years of age.

In 2010, the US census estimated the number of men ≥75 years old at about 7,250,000. Of those who are aged ≥75 years old, 1,136,000 were living with prostate cancer diagnosed sometime in the past 20 years. Thus about 15% of men aged ≥75 have prostate cancer or were treated for prostate cancer in the past. As the male population ages and life expectancy increases, the prevalence of prostate cancer in the ≥75 age group will increase. By 2021 males born in the Baby Boom era (1946–1964) will begin to mature into the age group of men ≥75 years old. The actuarial predictions in Table 7.1 illustrate life expectancy for healthy elderly men.

The magnitude of prostate cancer in elderly men

The impact prostate cancer will have on elderly individuals is largely determined by the grade and stage of their disease at diagnosis in the context of their health status. The elderly often have high-risk prostate cancer at presentation. Of those with clinical stage T1c (no palpable abnormalities on digital rectal exam [DRE], with an elevated prostate-specific antigen [PSA] serum level), M0 tumors, and age ≥75, greater than 25% have high-risk disease (defined as PSA ≥20 ng/mL and/or Gleason score ≥8). In contrast, high-risk disease accounts for less than 16% of all men with stage T1c prostate cancer at diagnosis.

Not only do the elderly commonly have high-risk prostate cancer at diagnosis, the frequency of distant metastases (M1) at diagnosis among men increases with age. In a recent SEER study, metastatic disease was present in 8, 13, and 17% of men in age groups 80–84, 85–89, and >90, respectively. Indeed almost half of all men with M1 disease at diagnosis are ≥75 years old when diagnosed. Similarly, the 5-year prostate-specific mortality was 13, 20, and 30% for men diagnosed with prostate cancer at ages 80–84, 85–89, and >90, respectively.

Higher-stage disease at diagnosis leads to a higher chance of disease-specific mortality. However, this could be explained by selection bias. Bias may stem from urologists only performing biopsies on older men with rapidly rising or markedly elevated PSAs, or with large prostatic nodules/masses on DRE. Such practice would result in a higher proportion of elderly men diagnosed with prostate cancer having very aggressive disease compared with younger men; however, it could not explain how, of all men diagnosed with stage T1cNxM0 disease, PSA < 10, Gleason score ≥8, almost 40% are aged 75 and older at diagnosis. These findings along with those from autopsy studies from the United States and overseas, give compelling support to the contention that the elderly do have more aggressive prostate cancer.

Pathologic characteristics

In an autopsy study, men ≥70 years old were not only more likely to have any prostate cancer, but also more likely to have larger and higher-grade cancers than younger men. There are many hypothesized reasons for the greater incidence of prostate cancer with higher Gleason scores (on average) among the elderly. These include relatively impaired immune responses in the elderly, which reduce host resistance to malignancies developing. Additionally, epigenetic changes and cumulative exposure to carcinogens with aging result in greater DNA abnormalities, the development of more prostate as well as other causes, and less differentiated cancers.