Elsevier

The Lancet

Volume 349, Issue 9056, 29 March 1997, Pages 906-910
The Lancet

Articles
Population-based study of long-term survival in patients with clinically localised prostate cancer

https://doi.org/10.1016/S0140-6736(96)09380-4Get rights and content

Summary

Background

Choice of treatment in localised prostate cancer has been hampered by a lack of unbiased, representative data on outcome. Most existing data have come from small cohorts at specialised academic centres; precise overall and cancer-grade-specific data are not available, and the data are subject to differential staging bias. Randomised clinical trials have been undertaken, but the results will not be available for another decade. We have carried out a large population-based study to ascertain overall and prostate-cancer-specific survival in men treated by prostatectomy, radiotherapy, or conservative management.

Methods

Data for 59 876 cancer-registry patients aged 50-79 were analysed. We examined the effect of differential staging of prostate cancer by analysing the data both by intention to treat and by treatment received. Estimated survival was calculated by the Kaplan-Meier method.

Findings

By the intention-to-treat approach, 10-year prostate-cancer-specific survival for grade 1 cancer was 94% (95% CI 91-95) after prostatectomy, 90% (87-92) after radiotherapy, and 93% (91-94) after conservative management. The corresponding survival figures in grade 2 cancers were 87% (85-89), 76% (72-79), and 77% (74-80); those in grade 3 cancer were 67% (62-71), 53% (47-58), and 45% (40-51). Although the intention-to-treat and treatment-received analyses yielded similar results for radiotherapy and conservative management, the 10-year disease-specific survival after prostatectomy differed substantially (83% [81-84] by intention to treat vs 89% [87-91] by treatment received).

Interpretation

The overall and cancer-grade-specific survival found in this study differ substantially from those in previous studies. Previous studies that used a treatment-received approach have generally overestimated the benefits of radical prostatectomy. We found that grade 3 tumours are highly aggressive irrespective of stage.

Introduction

This year, about 334 500 men in the USA will be diagnosed as having prostate cancer, the most common non-skin cancer in American men.1 The optimum management of this cancer remains controversial.2, 3 In an attempt to address the controversies, large randomised trials have been initiated, but their results will not be available for another decade.4, 5

In the absence of such evidence, several organisations have developed practice guidelines for patients with prostate cancer. They have identified overall and cause-specific mortality as crucial elements in treatment decision-making.6, 7 Structured literature reviews based on meta-analysis techniques have been undertaken by the American Urological Association6 and the Prostate Disease Patient Outcomes Research Team,3 to ascertain estimates of these endpoints after different treatments. These reviews, however, were hampered by the small amount of published data on overall and disease-specific survival both in, and especially in settings other than, academic medical centres.8, 9, 10, 11 Although there are population-based estimates of these endpoints for conservative management, no such information is available for radical prostatectomy and radiotherapy.

Another obstacle to meta-analyses and their interpretation is differential staging.12 The staging of surgical patients includes lymph-node dissection, and most patients found to have positive lymph nodes intraoperatively do not proceed to complete radical prostatectomy.13 By contrast, only a small percentage of patients who receive radiotherapy or conservative management undergo lymph-node dissection.14 Such patients may therefore have positive lymph nodes and distant disease, but they are classified as having localised cancer. Almost all published studies have used a treatment-received rather than an intention-to-treat analysis. Consequently, patients given radiotherapy or conservative management are understaged relative to those who undergo prostatectomy; this factor results in an exaggeration of the benefit of prostatectomy.3

A final difficulty is the lack of data on outcomes in relation to cancer grade, the most important predictor of progression in prostate cancer15, 16, 17, 18 and a key determinant of the net treatment benefit in several decision models.19, 20 Although data from the individual studies in the meta-analyses3, 6 could be combined, statistically meaningful data could not be generated because of the small number of patients in each cohort. In an effort to address these limitations, two studies analysed pooled data assembled from many institutions to generate grade-specific data.18, 21 Although limited data are available for conservative management and prostatectomy, there are no comparable data for radiotherapy in these analyses. Furthermore, whether these data, derived from selected institutions and not uniformly complete, are representative of outcomes in the general population is not clear.

We undertook a population-based study to ascertain overall and prostate-cancer-specific survival in men treated for clinically localised prostate cancer by conservative management, prostatectomy, and radiotherapy in diverse clinical settings; to provide empirical data that can be used to examine the potential impact of differential staging on outcomes; and to provide survival estimates stratified by the key prognostic factor of cancer grade.

Section snippets

Methods

The data used for this study were compiled by the Surveillance, Epidemiology, and End Results (SEER) Program,14 which collects information on all cancer cases diagnosed in Connecticut, Hawaii, New Mexico, Iowa, Utah, San Francisco-Oakland, Detroit, Atlanta, and Seattle. Data elements recorded include cancer stage and grade at diagnosis, initial cancer treatment, and vital status.22 Because rigorous quality control procedures are applied,23 the data are nearly complete with respect to

Results

Our study population consisted of 59 876 men (table 1). The mean length of follow-up was 44·5 months; 10% of patients were followed up for 92 months or longer. Radical prostatectomy was the most common treatment modality. Patients who underwent prostatectomy were, on average, 5 years younger than those undergoing radiotherapy or conservative management (table 1). Of the 24 257 men scheduled to undergo prostatectomy, 89% underwent lymph-node dissection, 51% had pathologically localised cancer,

Discussion

For any medical treatment, informed decisions about treatment choice can be made only if unbiased, representative data on outcomes for each option are available. Ideally, such data are derived from randomised clinical trials. If such trials have not been done, however, population-based studies and meta-analyses are often used to provide suggestive estimates about outcomes. Interpretation and application of meta-analyses based on study-level data, however, can be difficult because the inclusion

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