Prostate Cancer Practice Patterns and Quality of Life: the Prostate Cancer Outcomes Study

Abstract

Prostate cancer is the most commonly diagnosed (non-skin) cancer among men in the United States, with 179 000 new cases and 37 000 deaths expected in 1999 ( 1 ). Although $5 billion is spent annually for the care of those diagnosed with prostate cancer ( 2 ), a systematic evaluation of practice patterns and the impact of treatments on health-related quality of life (HRQOL) on a national scale has yet to be conducted. In 1994, the National Cancer Institute (NCI) initiated the Prostate Cancer Outcomes Study (PCOS) to investigate variations in the initial treatment of prostate cancer and to describe HRQOL outcomes in a large, heterogeneous cohort of newly diagnosed prostate cancer patients treated in community medical practices. The study is the most comprehensive population-based outcomes study focusing on prostate cancer ever conducted and complements the national prostate cancer research agenda. The main purpose of this commentary is to provide the rationale and objectives for the PCOS and to describe how the study fills a critical gap in the understanding of men's experiences with prostate cancer. Better knowledge of treatment outcomes is desired by thousands of patients, families, and clinicians who deal with prostate cancer every day. The PCOS was initiated to obtain more comprehensive and generalizable information about the effects of treatments on HRQOL outcomes. Information about HRQOL is also important, from a cancer surveillance perspective, for providing a broader perspective for interpreting recent trends in prostate cancer incidence and mortality. Given the uncertainty about the efficacy of selected interventions, it is essential to document the complete burden of the disease in order to characterize the extent to which progress is being made. A second purpose of this commentary is to describe the design, methods, and limitations of the PCOS in order to enhance the understanding and interpretation of numerous ongoing and planned research projects using the data collected. The incidence rate of prostate cancer has increased dramatically during the past decade, largely as a result of the rapid dissemination of prostate-specific antigen (PSA) screening, although incidence rates have been declining in more recent years ( 3 , 4 ). The use of radical prostatectomy has also increased, particularly among men 65 years old or older ( 5 , 6 ). Mortality rates have changed little over the past two decades, although a declining trend has occurred since 1991, following an increase during the mid-1980s. The failure to observe a more substantial and rapid impact of interventions on mortality may be due to several reasons. First, the majority of men initially diagnosed with the disease die with, rather than of, prostate cancer ( 7 , 8 ). This is due in part to the advanced median age at diagnosis of prostate cancer (age 71 years) as well as to the prolonged natural history of early-stage prostate cancer ( 9 ). Therefore, it may take many years to observe an impact of some interventions on population rates. Second, screening and aggressive treatments may not reduce cause-specific mortality. To date, there are no completed randomized trials that have definitively established the efficacy of screening for prostate cancer or of aggressively treating patients with early-stage disease with either external-beam radiation therapy or radical prostatectomy ( 10 , 11 ). Observational studies of large population-based cohorts demonstrate that 15-year survival of selected patients with localized tumors who are conservatively managed is quite favorable and appears similar to that of the age-matched U.S. population ( 8 , 12 ). The prolonged natural history and late age at diagnosis, in addition to the lack of definitive evidence for the efficacy of interventions, have contributed to the uncertainty and disagreement about whether to screen asymptomatic men and how to best manage patients diagnosed with nonmetastatic prostate cancer ( 13 - 16 ). While there is a lack of convincing evidence on the effects of surgery or radiotherapy on prostate cancer mortality, there is evidence that these therapies can have detrimental effects on urinary, bowel, and sexual functions in some individuals. Given the incompleteness of information regarding mortality effects, it is difficult to quantify and reconcile the tradeoffs of specific treatment strategies. Uncertainty remains about the exact levels of impairment that patients can expect after receiving different treatments because, until recently, the impact of prostate cancer on long-term HRQOL outcomes had not been thoroughly investigated in representative cohorts. Much of the early research on outcomes of prostate cancer treatment was limited to small samples from highly selected case series treated in tertiary referral centers ( 14,17-20 ). Some of these influential reports may have underestimated the long-term effects of treatment. For example, estimates of incontinence were as low as 5%