Until recently, PSA was commonly recommended as a screening mechanism for detecting prostate cancer.
statistics
Description
1.
Build
the model (Prostate-specific antigen study)
A university medical center urology group (Stamey, et al., 1989)
was interested in the association between a prostate-specific antigen (PSA) and
a number of prognostic clinical measurements in men with advanced prostate
cancer. Data were collected on 97 men who were about to undergo radical
prostectomies. (download the data, “PSA.txt” from CANVAS).
|
column |
Variable name |
Description |
|
1 |
Identification number |
1-97 |
|
2* |
PSA level |
Serum prostate-specific antigen level (mg/ml) |
|
3* |
Cancer volume |
Estimate of prostate cancer volume (cc) |
|
4* |
Weight |
Prostate weight (gm) |
|
5* |
Age |
Age of patient (years) |
|
6 |
Benign prostatic |
Amount of benign prostatic hyperplasia (cm2) hyperplasia |
|
7 |
Seminal vesicle invasion |
Presence or absence of seminal vesicle invasion: 1 if yes;
0 if no |
|
8 |
Capsular penetration |
Degree of capsular penetration (cm) |
|
9 |
Gleason score |
Pathologically determined grade of disease (6,7,8), higher
indicates worse prognosis |
Background: Until recently, PSA was commonly recommended as a
screening mechanism for detecting prostate cancer. To be an efficient screening
tool it is important that we understand how PSA levels relate to factors that
may determine prognosis and outcome. The PSA test measures the blood level of
prostate-specific antigen, an enzyme produced by the prostate. PSA levels under
4 ng/mL (nanograms per milliliter) are generally considered normal, while
levels over 4 ng/mL are considered abnormal (although in men over 65 levels up
to 6.5 ng/mL may be acceptable, depending upon each laboratorys reference
ranges). PSA levels between 4 and 10 ng/mL indicate a risk of prostate cancer
higher than normal, but the risk does not seem to rise within this six-point
range. When the PSA level is above 10 ng/mL, the association with cancer
becomes stronger. However, PSA is not a perfect test. Some men with prostate
cancer do not have an elevated PSA, and most men with an elevated PSA do not
have prostate cancer. PSA levels can change for many reasons other than cancer.
Two common causes of high PSA levels are enlargement of the prostate (benign
prostatic hypertrophy (BPH)) and infection in the prostate (prostatitis).
Use the data to
build a multiple regression model to predict PSA level from the cancer volume,
Prostate weight, and Age. A reasonable strategy would be to:
1) Examine
the relationship between the response and the potential predictors.
2) Decide
whether any of the variables should be transformed.
3) Perform
a model selection using the desired response and predictors.
4) Given
the selected model, examine the residuals and check for influential cases.
5) Repeat
the process, if necessary.
6) Interpret
the model and discuss any model limitations.
