Newly Created Risk Stratification Database Aids in Predicting Outcomes in Prostate Cancer
The pan-Canadian Prostate Cancer Risk Stratification database was created to report on the patient, tumor, and treatment factors that were predictive of biochemical and clinical outcomes in patients who underwent radiotherapy for prostate cancer. Risk stratification in the management of those with prostate cancer plays a key role in directing appropriate therapy based on prognosis, according to the findings of a study by Rodrigues et al published in the Journal of the National Comprehensive Cancer Network.
The complexity surrounding the management of nonmetastatic prostate cancer centers on the mix of multiple considerations—risk stratification, the balance between treatment efficacy and toxicity, the competing risk of death from cancer vs other causes, and patient preferences. Although multiple pretreatment risk stratification systems exist, the establishment of a universally accepted classification is still needed. Improvements to risk stratification systems for prostate cancer, which have been addressed by the National Comprehensive Cancer Network (NCCN), include the definition of a very low–risk category, reassessment of the interface between intermediate- and high-risk categories, and creation of a new extreme-risk category.
Study Details
The Genitourinary Radiation Oncologists of Canada created the pan-Canadian Prostate Cancer Risk Stratification database to explore various risk stratification issues in prostate cancer. The investigators reported on the biochemical and clinical outcomes of this newly created database and explored the NCCN risk stratification system for predicting radiotherapy outcomes in prostate cancer.
Data were collected on 7,974 patients who underwent radiotherapy from four institutions with seven unique databases. The institutions were the British Columbia Cancer Agency, Princess Margaret Hospital, McGill, and Laval. They included a provincial database, two low–dose rate brachytherapy databases, one combined high–dose rate plus external-beam radiotherapy database, and three external-beam radiotherapy databases.
The risk stratification categories were calculated from information from the new database, including three Genitourinary Radiation Oncologists of Canada groups (low, intermediate, and high risk) and five NCCN groups (very low, low, intermediate, high, and very high risk). (See the full article for definitions of the risk groups.)
The mean age of the patients was 66.5 years. The mean prostate-specific antigen (PSA), PSA velocity, and PSA doubling time were 9.19 ng/mL, 0.27 ng/mL/yr, and 1.17 years, respectively. About 45% of patients had T1 disease, and 46% had T2 disease. As for Gleason grade distribution, 65% scored between 2 and 6 and 30% scored 7. Nearly half of all patients were risk-stratified as low or very low, and approximately 14% as high or very high. Some type of brachytherapy was used as primary treatment in about two-thirds of patients, and hormonal therapy was used in 38%.
Age, Gleason Score, and Treatment Type Are Among Predictive Factors
For both biochemical failure–free survival and overall survival (the study endpoints), multivariate modeling showed that age, PSA, T stage, Gleason score, and type of treatment were predictive of outcome. At a median follow-up for the entire database of 78.9 months, 1,442 patients (19%) had biochemical failure–free survival (as defined by the American Society for Radiation Oncology), with the majority having a biochemical failure before initiation of any salvage therapy.
For all patients in the new database, Kaplan-Meier analysis of the existing classification systems showed good separation of the biochemical failure–free survival and overall survival curves (log-rank P < .0001). In addition, of the 1,230 patients (15%) who died, 273 (22%) were confirmed as cancer-related deaths, and 821 (67%) died of other causes.
Clinical Implications
The investigators confirmed that risk stratification in the management of prostate cancer makes it possible to predict the risk associated with both positive and negative clinical outcomes. It also helps to direct appropriate therapy and to identify inclusion/exclusion criteria for clinical trial stratification.
Furthermore, their analysis suggested that implementing more than three risk categories, consistent with the approach by the NCCN, may have prognostic benefits, particularly in brachytherapy patients. For instance, there was a difference between very low–risk and low-risk groups regarding biochemical failure-free survival. The investigators noted that the Kaplan-Meier information confirmed the high curability of all forms of low-risk prostate cancer.
“In addition to the reporting of important clinical outcomes related to radiotherapy treatment, this newly formed database will allow for the systematic investigation of various aspects of nonmetastatic prostate cancer pretreatment risk stratification/categorization,” concluded the investigators.
George Rodrigues, MD, of London Health Sciences Centre, London, Ontario, is the corresponding author of the article in the Journal of the National Comprehensive Cancer Network.
This study is supported by the Canadian Association of Radiation Oncology ACURA research award and the Ontario Institute of Cancer Research High Impact Trials Program. The authors reported no potential conflicts of interest.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
