Qualy #53 - Screening for prostate cancer
This Qualys episode, featuring insights from Ted Schaeffer, M.D., Ph.D., delves into the controversies surrounding prostate cancer screening. It explains PSA, its interpretation with age, free PSA, and density, and highlights advanced tests like the 4K score for better risk assessment.
Deep Dive Analysis
10 Topic Outline
Introduction to Prostate Cancer and PSA Controversy
Understanding Prostate Specific Antigen (PSA) and its Function
How PSA Leaks into the Bloodstream and its Relation to Prostate Size
Factors That Can Cause PSA Levels to Rise
Normal and Abnormal Age-Adjusted PSA Values
The Role of Percent Free PSA in Cancer Detection
PSA Density as a Predictive Marker for Prostate Cancer
The 4K Score and Prostate Health Index (PHI) Tests
How 4K Score Discriminates Aggressive Prostate Cancer
Interpreting 4K Score Probabilities for Metastatic Cancer Risk
5 Key Concepts
Prostate Specific Antigen (PSA)
PSA is a protein produced by the prostate gland whose normal function is to liquefy semen. It is prostate-specific, not cancer-specific, and its levels in the blood are a good biomarker for prostate size, though they can also be affected by infection or cancer.
Percent Free PSA
This is a diagnostic metric used to help differentiate between PSA produced by benign prostate overgrowth and that from cancerous cells. A lower percentage of free PSA in the blood is correlated with a higher likelihood of prostate cancer.
PSA Density
PSA density is a calculation of the amount of PSA per gram of prostate tissue. It serves as a strong predictor of prostate conditions, with higher densities indicating a greater concern for potential cancer.
4K Score (4 Kallikrein Test)
A sophisticated blood test that measures four specific prostate proteins (PSA, percent free PSA, intact PSA, and hk2) and uses an algorithm to calculate an individual's percentile chance of having high-grade, aggressive, lethal prostate cancer.
Prostate Health Index (PHI)
A diagnostic test similar to the 4K score, which also leverages the distinct ways prostate cancer cells produce PSA. It uses specific PSA-based proteins, such as minus two pro PSA, to assess prostate cancer risk.
7 Questions Answered
PSA is a protein made by the prostate to liquefy semen, but its use in screening is controversial because its levels can rise due to various factors (age, size, infection, cancer), making it prostate-specific but not cancer-specific.
PSA levels can increase due to getting older, having a larger prostate (benign prostatic hyperplasia), prostate infection (prostatitis), and even physical manipulation like a rectal exam.
Normal PSA values are age-adjusted; for example, the median PSA for a 40-year-old is around 0.5-0.6 ng/ml, and for a 50-year-old, it's about 1 ng/ml, generally increasing with each decade.
Percent free PSA helps to distinguish whether an elevated total PSA is more likely from benign prostate growth or cancer; a lower percentage of free PSA is associated with a higher probability of prostate cancer.
PSA density is the ratio of PSA level to prostate volume, providing insight into how much PSA is produced per gram of tissue. A PSA density above 0.1 or 0.15 is considered a red flag for potential prostate cancer.
The 4K Score and Prostate Health Index (PHI) analyze multiple PSA-related proteins to more accurately discriminate between benign conditions and aggressive, high-grade prostate cancer, offering a more precise risk assessment and potentially reducing unnecessary biopsies.
A 4K score provides a percentile chance of dying from metastatic prostate cancer within 20 years; for instance, a score less than 7.5% indicates a 1.6% chance, while a score greater than 7.5% suggests a 16-17% chance.
6 Actionable Insights
1. Utilize 4K Score for Prostate Cancer Risk
Consider using the 4K score or Prostate Health Index (PHI) test, which discriminates between cancerous and benign prostate cells and provides a percentile chance of having high-grade, aggressive prostate cancer. A 4K score less than 7.5% indicates a low risk (1.6% chance of dying from metastatic prostate cancer in 20 years), while a score greater than 7.5% indicates a higher risk (16-17% chance in 20 years).
2. Monitor PSA Density Thresholds
Be aware that a PSA density greater than 0.1 raises a red flag, and a density greater than 0.15 indicates a higher concern for prostate issues, prompting further investigation.
3. Interpret Free PSA Levels
Understand that a high percent free PSA is associated with a larger prostate and a lower chance of prostate cancer, while a low percent free PSA suggests a higher likelihood that the PSA is produced from a gland with prostate cancer.
4. Seek Workup for Elevated PSA
If you are a younger person and your PSA is more than 2.5, it is generally considered abnormal and warrants further workup, though not necessarily an immediate biopsy.
5. Understand Age-Adjusted PSA Norms
Be aware that normal PSA levels are age-adjusted; for example, a 40-year-old’s normal PSA is around 0.5-0.6 ng/ml, while a 50-year-old’s is around 1 ng/ml, with levels generally increasing by decade.
6. Avoid PSA Test Post-Rectal Exam
Do not check a PSA on a man immediately after a rectal exam, as the exam could artificially raise PSA levels by creating more insult and increasing the flow of PSA into the bloodstream.
3 Key Quotes
it is not cancer specific it's prostate specific and it's actually a very good biomarker for prostate size
Ted Schaeffer, M.D., Ph.D.
pretty much every guy is going to die with prostate cancer but fortunately most men will not die from prostate cancer but our job is to figure out when a guy has prostate cancer as you alluded to earlier is this the bad one
Peter Attia, M.D.
psa is a protein it's made by the prostate and its normal function is to liquefy semen
Ted Schaeffer, M.D., Ph.D.