Prostate Cancer Risk Assessment and the UCSF-CAPRA Score
Prostate cancer is the most common cancer diagnosed among American men, and causes more deaths annually among men than any other tumor except lung cancer. However, only a small proportion of prostate cancers diagnosed are ultimately lethal. A large majority of men found to have prostate cancer ultimately die of other causes, most commonly cardiovascular disease. All available treatments for prostate cancer (surgery, radiation therapy, hormonal therapy, and others) carry a risk of complications, side effects, and other impacts to the patient's long-term quality of life. Before making a decision regarding treatment for prostate cancer it is important to estimate the likelihood that a given tumor will recur after treatment, progress, and pose a threat to life.
Risk Assessment Methods
Risk Assessment systems are not intended to replace individualized clinician-patient decision making, but rather to provide a straightforward instrument for facilitating disease risk classification in clinical decision making and in future research.
There are many approaches to risk assessment including the D'Amico classification, a variety of nomograms and the UCSF-CAPRA Score.
Risk classification (D'Amico): The classification developed by D’Amico and colleagues is one of the most widely used and is a good starting point for risk assessment. This system uses PSA level (blood test), Gleason grade (microscopic appearance of the cancer cells), and T stage (size of the tumor on rectal exam and/or ultrasound) to group men as low, intermediate, or high-risk. Low-risk: PSA less than or equal to 10, Gleason score less than or equal to 6, and clinical stage T1-2a Intermediate risk: PSA between 10 and 20, Gleason score 7, or clinical stage T2b High-risk: PSA more than 20, Gleason score equal or larger than 8, or clinical stage T2c-3a
Limitations: Does not account for multiple risk factors
Patient one: Gleason 3+4, PSA 3.2, stage T1c cancer in one biopsy core
Patient two: Gleason 4+3, PSA 19.2, stage T2b cancer involving eight cores
• Both patients are classified as intermediate risk, althought patient two would have much higher disease risk.
Nomograms: Pioneered in prostate cancer by Kattan and colleagues is an approach that incorporates multiple risk variables to produce mathematical models that predict the likelihood of disease recurrence or progression. The models are often presented as nomograms, graphical calculating devices that allow determination of the score based on values presented on a paper table. Many such instruments have been developed for prostate cancer. Memorial Sloan-Kettering Cancer Center provides an on-line calculator which allows some of the models to be calculated. A few of these nomograms are well known and have been validated in multiple settings.
Limitations: care must be taken in interpreting the predictions from the calculators.
• A model developed using data from patients treated by a high-volume surgeon in a large city, may not be valid for those treated by a lower-volume surgeon in rural area. In general, nomograms developed using data from academic series tend to be somewhat overly optimistic when applied in the community practice setting.
• Each nomogram is developed using a different set of patients in a different setting, and usually using different definitions of cancer recurrence or progression. Because the definitions of recurrence and progression are not consistent across nomograms, scores from the different treatment nomograms (e.g. pre-prostatectomy and pre-brachytherapy) cannot be used to compare the likelihood of a good result from one type of treatment versus another type of treatment for an individual man. Each nomogram is deisgned to give a prediction of treatment success only after a treatment decision has already been made.
The UCSF-CAPRA score
In a effort to address the limitations of these approaches to risk assessment UCSF developed the Cancer of the Prostate Risk Assessment (UCSF-CAPRA) score. CAPRA is a straightforward 0 to 10 score. It is nearly as easy to calculate as the D’Amico classification, yet with accuracy comparable to the best nomograms. A CAPRA score is valid across multiple treatment approaches and it predicts an individual's likelihood of metastasis, cancer-specific mortality, and overall mortality.
The score is calculated using points assigned to: age at diagnosis, PSA at diagnosis, Gleason score of the biopsy, clinical stage and percent of biopsy cores involved with cancer. These variables are outlined below.