Cancer of the Prostate: Incidence in the USA

Introduction

Prostate cancer is the most common noncutaneous cancer diagnosed in the United States. In 2014 it was estimated that 233,000 men will be newly diagnosed with prostate cancer. Prostate cancer represents 14% of all new cancer diagnoses in the United States during 2014. Only skin cancer affects more men than prostate cancer in the United States.

Prostate cancer is the second leading cancer killer of men in the United States behind lung and bronchus cancer. The disease was projected to kill 29,480 men in the United States in 2014. In comparison, 232,670 and 40,000 women were expected to be diagnosed with and killed by breast cancer, respectively, in 2014.

Men living in the United States have a 15.33% (1 in 7 men) lifetime risk of developing prostate cancer. Lifetime probability of dying from prostate cancer in the United States is 2.71% (one in 37 men). Current 5-year relative survival rates for local and regional prostate cancer approach 100%. Men with distant prostate cancer at diagnosis have a 27.9% probability of 5-year survival.

Prostate cancer incidence varies throughout the continental US. The District of Columbia (194.4), Delaware (177.3), and Louisiana (169.3) have the highest incidence of prostate cancer diagnoses per 100,000 men. The District of Columbia also has the highest prostate cancer mortality per 100,000 men (38.3), with Alabama (28.9) and Georgia (27.1) having the second- and third-highest, respectively.

Modern trends in prostate cancer diagnosis in the United States

The discovery and adoption of prostate-specific antigen (PSA) testing has led to a tremendous increase in the diagnosis and treatment of prostate cancer. PSA is a protease derived from prostate tissue and acts to cleave gel-forming proteins from the seminal vesicles, thereby liquefying ejaculate and increasing sperm mobilization for improved fertilization. Though PSA is now routinely used in the detection of prostate cancer and surveillance of prostate cancer treatment, the enzyme is not a cancer-specific marker and is measurable in patients without prostate pathology as well as benign disease. Independent of the presence of cancer, serum PSA increases with age and prostate volume.

PSA was not initially valued as a prostate cancer screening marker. Even after PSA was discovered, its lack of specificity for malignant disease resulted in a slow adoption. In 1986 the Food and Drug Administration (FDA) approved PSA testing to monitor relapse after curative prostate cancer treatment. The availability of FDA-approved PSA kits, along with concurrent refinement of the sextant transrectal-ultrasound-guided prostate biopsy and improvements in local prostate cancer treatment led by Walsh’s development of the nerve-sparing retropubic radical prostatectomy, paved the way for a dramatic paradigm shift in the early detection of prostate cancer.

In 1991, in the New England Journal of Medicine , Catalona et al. reported the use of PSA test as part of first-line prostate cancer screening that detected nearly 32% of prostate cancers that would have been missed by digital rectal examination (DRE) alone. Then again in 1994, Catalona et al. published a landmark multisite, prospective trial evaluating the use of PSA as a reliable indicator for the detection of prostate cancer via sextant prostate biopsy. The study noted that for approximately every 100 men aged 50–75 years screened with PSA, approximately 15 would have a serum PSA greater than 4.0 ng/mL, and approximately four to five of these men would have clinically significant prostate cancer detected on biopsy. That same year, the FDA approved PSA as the first serum tumor marker in the early detection of cancer.

After the seminal paper published in 1987 in which Stamey et al. identified PSA as a serum marker for prostate cancer, the incidence of prostate cancer in the United States rose approximately 12% each year until it peaked in 1992 (at 237.2 per 100,000 men). Welch and Albertsen reported data from the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) program, that showed that overall incidence of prostate cancer in the United States rose 26% (from 119 to 150.5 per 100,000 men) between 1986 and 2005. PSA testing was adopted faster in the United States than in European countries, which may explain the increased incidence of prostate cancer in the United States compared to many European countries over the same time period. Figure 14.1 shows age-adjusted prostate cancer incidence in the United States from 1975 to 2011.

Between 2001 and 2010, the incidence of prostate cancer in the United States decreased by approximately 2.2% annually. During this time, prostate cancer mortality also decreased to an average of 3.4% annually. African-American men experienced a twofold higher death rate from prostate cancer compared to Caucasian men (50.9 vs. 21.2 per 100,000 men) during this time, yet African-American men only experienced a mild improvement in death rate (−3.8% annually) compared to Caucasian men (−3.1% annually) over the same time period.

The median age of men at the time of prostate cancer diagnosis was 72.2 years in 1988–1989 before PSA. The median age dropped to 67.2 years between 2004 and 2005. The increase in prostate cancer diagnoses between 1986 and 2005 was greatest in younger men: the incidence increased over sevenfold among men younger than 50 years (1.3–9.4 per 100,000 men), threefold for men aged 50–59 years (58.4–212.7 per 100,000 men), and twofold for men aged 60–69 years (349.4–666.9 per 100,000 men). For older men aged 70–79 years, there was little change (819.2–896.8 per 100,000 men) over the same time period. For men older than 80 years, prostate cancer incidence declined dramatically (1146.5–637.4 per 100,000 men).

The modern era of prostate cancer detection has led to a stage migration at time of prostate cancer diagnosis. In 1986, fewer than one-third of men diagnosed with prostate cancer had organ-confined disease. Today well over two-thirds of diagnosed men have organ-confined disease. Between 1984 and 1988, 34% of prostate cancer tumors were classified as “well differentiated” compared to only 4% of patients from 1999 to 2003. This is likely due to changes in pathological grading rather than disease characteristics. Over nearly the same time period, the incidence of stage IV prostate cancer decreased approximately 6.4% each year, from 28.1 per 100,000 men in 1988 to 12.3 per 100,000 men in 2003. Five-year survival for stage IV prostate cancer without distant metastasis improved over the time span, from 41.6% in 1988 to 62.3% in 2001.

Risk factors for the development of prostate cancer

Age, family history, race/ethnicity, BRCA1/2 mutations, and Lynch syndrome are the only well-established risk factors for the diagnosis of prostate cancer. Several other factors have been espoused in recent years, particularly in the lay press, to contribute to prostate cancer risk. As will be explored here, much of the associations between these factors and prostate cancer lack definitive scientific evidence to extract causation.