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. 2018 Feb 28;16(1):31.
doi: 10.1186/s12916-018-1019-5.

The Cambridge Prognostic Groups for improved prediction of disease mortality at diagnosis in primary non-metastatic prostate cancer: a validation study

V J Gnanapragasam  1   2 , O Bratt  3 , K Muir  4 , L S Lee  5 , H H Huang  5 , P Stattin  6   7 , A Lophatananon  4
Affiliations

The Cambridge Prognostic Groups for improved prediction of disease mortality at diagnosis in primary non-metastatic prostate cancer: a validation study

V J Gnanapragasam et al. BMC Med. .

Abstract

Background: The purpose of this study is to validate a new five-tiered prognostic classification system to better discriminate cancer-specific mortality in men diagnosed with primary non-metastatic prostate cancer.

Methods: We applied a recently described five-strata model, the Cambridge Prognostic Groups (CPGs 1-5), in two international cohorts and tested prognostic performance against the current standard three-strata classification of low-, intermediate- or high-risk disease. Diagnostic clinico-pathological data for men obtained from the Prostate Cancer data Base Sweden (PCBaSe) and the Singapore Health Study were used. The main outcome measure was prostate cancer mortality (PCM) stratified by age group and treatment modality.

Results: The PCBaSe cohort included 72,337 men, of whom 7162 died of prostate cancer. The CPG model successfully classified men with different risks of PCM with competing risk regression confirming significant intergroup distinction (p < 0.0001). The CPGs were significantly better at stratified prediction of PCM compared to the current three-tiered system (concordance index (C-index) 0.81 vs. 0.77, p < 0.0001). This superiority was maintained for every age group division (p < 0.0001). Also in the ethnically different Singapore cohort of 2550 men with 142 prostate cancer deaths, the CPG model outperformed the three strata categories (C-index 0.79 vs. 0.76, p < 0.0001). The model also retained superior prognostic discrimination in the treatment sub-groups: radical prostatectomy (n = 20,586), C-index 0.77 vs. 074; radiotherapy (n = 11,872), C-index 0.73 vs. 0.69; and conservative management (n = 14,950), C-index 0.74 vs. 0.73. The CPG groups that sub-divided the old intermediate-risk (CPG2 vs. CPG3) and high-risk categories (CPG4 vs. CPG5) significantly discriminated PCM outcomes after radical therapy or conservative management (p < 0.0001).

Conclusions: This validation study of nearly 75,000 men confirms that the CPG five-tiered prognostic model has superior discrimination compared to the three-tiered model in predicting prostate cancer death across different age and treatment groups. Crucially, it identifies distinct sub-groups of men within the old intermediate-risk and high-risk criteria who have very different prognostic outcomes. We therefore propose adoption of the CPG model as a simple-to-use but more accurate prognostic stratification tool to help guide management for men with newly diagnosed prostate cancer.

Keywords: All-cause mortality; Cambridge Prognostic Groups; Cancer-specific mortality; Competing risks; Improved treatment section; Non-metastatic disease; Prognostic prediction; Prostate cancer; Stratification; Treatment selection.

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Conflict of interest statement

Ethics approval and consent to participate

Ethical permission for data collection for PCBaSe is covered by ref. 2013–153-31 provided by the Research Ethics Board at Umeå University. Ethics for data collection in the Singapore cohort is covered by CIRB ref. 2009/1053/D approved by the Singhealth Centralised Institutional Review Board.

Consent for publication

Not applicable. No patient identifiable data was used or is presented.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1
Fig. 1
Cumulative incidence curves for prostate cancer-specific survival in the PCBaSe cohort (n = 72,337) stratified by the a Cambridge Prognostic Groups and b current three-strata risk groups as a comparator model
Fig. 2
Fig. 2
Ten-year prostate cancer and other-cause mortality rates stratified by each Cambridge Prognostic Group (CPG) category in the PCBaSe cohort (n = 72,337). Red prostate cancer mortality, blue other-cause mortality
See this image and copyright information in PMC

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