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Chapter 6

Risk Stratification and Staging

This chapter is general patient education from the book Prostate Cancer, Explained. It is not medical advice for your specific situation. Always discuss your care with your own doctor.

Chapter Opening — David's Story

David, a 62-year-old engineer, sat in his urologist's office staring at his biopsy report. "Grade Group 2, Gleason 3+4, PSA 8.5, two of twelve cores positive," the doctor read aloud. David's mind raced — was this bad? Was it good? His urologist explained that these numbers, combined with his physical exam, would place him in a specific "risk group" that would guide every treatment decision going forward. "Think of it like a GPS for your cancer journey," the doctor said. "We need to know exactly where you are before we can map the best route forward."

Part 1: Why Risk Stratification Matters

If you have read the previous chapters, you now know your PSA level, your Gleason score (Grade Group), and what your biopsy and imaging showed. This chapter explains how doctors combine all of these pieces of information into a single profile — your risk group — that guides every treatment decision.

Not all prostate cancers are the same. Some grow so slowly that they may never cause harm in a man's lifetime. Others are aggressive and need prompt treatment. Risk stratification is the process of sorting cancers into categories based on how likely they are to grow, spread, and cause problems.¹ ²

Your risk group determines:

The three main ingredients that go into your risk group are:

  1. PSA level — the blood test discussed in Chapter 3
  2. Grade Group (Gleason score) — the aggressiveness score from your biopsy discussed in Chapter 4
  3. Clinical T stage — how much cancer the doctor can feel on exam or see on imaging

Additional factors such as the number of positive biopsy cores, PSA density, and genomic test results can further refine your risk profile.¹ ²

The three ingredients of risk
Your risk profile is built from three ingredients PSA Level Blood test Under 10Lower 10 to 20Intermediate Over 20Higher Over 40Very high Grade Group Biopsy under the microscope GG 1Slow growing GG 2Mostly slow GG 3Moderate GG 4Aggressive GG 5Very aggressive Clinical T Stage Exam and imaging T1Cannot be felt T2Inside prostate T3Beyond prostate T4Nearby organs YOUR NCCN RISK GROUP Very Low → Low → Intermediate → High → Very High Refined further by: positive cores, PSA density, and genomic tests when needed.
PSA, Grade Group, and clinical T stage combine into your overall risk group.

Part 2: The TNM Staging System

Doctors around the world use a standardized system called TNM staging to describe the extent of cancer. TNM stands for Tumor, Nodes, and Metastasis. The current version is the AJCC (American Joint Committee on Cancer) 8th edition, published in 2017.³ ⁴

T — Tumor (How far has the cancer grown?)

The T stage describes the size and extent of the primary tumor in the prostate:

Important note: There are two types of T staging:

N — Nodes (Has the cancer spread to nearby lymph nodes?)

M — Metastasis (Has the cancer spread to distant parts of the body?)

When more than one site of metastasis is present, the most advanced category is used. M1c is the most advanced.³

Part 3: AJCC Prognostic Stage Groups

The AJCC 8th edition combines T, N, and M with PSA level and Grade Group to create prognostic stage groups. This is different from many other cancers where staging is based on anatomy alone.⁴ ⁵

An important and unique feature of prostate cancer staging: some organ-confined cancers (T1–T2) can be Stage III based on high PSA or aggressive Grade Group. This is different from most other cancers where Stage III always means the cancer has grown beyond the organ.⁵

Part 4: NCCN Risk Groups — The System Your Doctor Likely Uses

While AJCC staging is important for communication and research, most treatment decisions in the United States are guided by the NCCN risk group system. This system divides clinically localized prostate cancer (no spread to lymph nodes or distant sites) into categories based on the likelihood of the cancer progressing.¹ ²

Very Low Risk (not a formal NCCN category on the main algorithm but referenced in guidelines)

Low Risk

Intermediate Risk — Has one or more intermediate risk factors (IRFs):

Intermediate risk is further divided into two important subgroups:¹

Favorable Intermediate Risk — Has ALL of the following:

Unfavorable Intermediate Risk — Has one or more of the following:

High Risk — Has one or more of the following (but does not meet very high risk criteria):

Very High Risk — Has at least TWO of the following:

Why the favorable vs. unfavorable intermediate distinction matters:

This is one of the most important distinctions in prostate cancer. Research has shown that men with favorable intermediate-risk cancer have outcomes similar to low-risk patients, while men with unfavorable intermediate-risk cancer have outcomes closer to high-risk patients.⁶ This distinction affects whether active surveillance is an option, whether hormone therapy is added to radiation, and the intensity of treatment recommended.

The most important distinction
Favorable vs. unfavorable intermediate risk Favorable All must be true: ✓ Only 1 intermediate risk factor ✓ Grade Group 1 or 2 ✓ Under 50% of cores positive Behaves more like low-risk cancer ✓ Active surveillance an option ✓ Surgery alone ✓ Radiation, often no hormones ~95% metastasis-free at 10 yrs Unfavorable Any one qualifies: • 2 to 3 intermediate risk factors • Grade Group 3 (Gleason 4+3) • 50% or more of cores positive Behaves more like high-risk cancer ✗ Surveillance not recommended ✓ Surgery (may need more after) ✓ Radiation + short hormones ~85 to 90% metastasis-free at 10 yrs Same “intermediate” label — very different cancers Mr. A: PSA 12, GG 2, T1c, 2/12 cores → 1 factor → FAVORABLE Mr. B: PSA 12, GG 3, T2b, 7/12 cores → several factors → UNFAVORABLE
The favorable vs. unfavorable split changes treatment recommendations dramatically.

Regional Disease (N1, M0):

Cancer found in pelvic lymph nodes but no distant spread. This is treated differently from localized disease and typically requires combination therapy.¹

Metastatic Disease (M1):

Cancer that has spread beyond the pelvis. This is further categorized by volume of disease (oligometastatic vs. polymetastatic) and hormone sensitivity (castration-sensitive vs. castration-resistant), which are discussed in detail in Chapter 12.¹

Regional and metastatic disease
When cancer spreads: N and M N — Lymph Nodes Prostate N0 No cancer in lymph nodes N1 Cancer in pelvic (regional) nodes Open circles = clear · filled = involved M — Metastasis M0 No distant spread M1a Distant lymph nodes M1b Bone (most common) M1c Other organs (less common) Bone is the most common site of spread
N describes nearby lymph nodes; M describes distant spread, most often to bone.

Part 5: Staging Workup — What Tests Do You Need?

The imaging tests you need depend on your risk group (discussed in detail in Chapter 5):¹ ⁷

If staging imaging reveals regional lymph node metastases or distant metastases, the treatment approach changes significantly, and patients are redirected to the appropriate treatment algorithms.¹

Which staging tests you need
What staging tests do you need? Your NCCNrisk group Low & Favorable Intermediate Prostate MRI (if not already done) No routine staging imaging Chance of spread is very low (~1%) Unfavorable Intermediate, High & Very High Prostate MRI CT + bone scanoption A PSMA PET/CTreplaces both Chance of spread ~5 to 40% Any risk with symptoms gets targeted imaging — bone pain → bone scan or MRI; neurological symptoms → spine MRI. If imaging finds nodes or distant spread, the treatment approach changes significantly (see Chapters 12 to 13). PSMA PET should ideally be done before starting hormone therapy.
Your risk group decides how much staging imaging you actually need.

Part 6: Calculators and Nomograms — Refining Your Risk

Beyond risk groups, several mathematical tools (called nomograms) can provide more personalized risk estimates. These tools combine multiple factors to calculate the probability of specific outcomes.⁸ ⁹

CAPRA Score (Cancer of the Prostate Risk Assessment)

Developed at the University of California, San Francisco, the CAPRA score uses five factors:⁸ ⁹

The score ranges from 0 to 10. Higher scores indicate higher risk. The CAPRA score has been validated to predict biochemical recurrence, metastasis, cancer-specific mortality, and overall mortality across multiple treatment types.⁸ ⁹

MSKCC Nomograms (Memorial Sloan Kettering Cancer Center)

These online calculators (available at mskcc.org/nomograms) provide personalized predictions for:⁸ ¹⁰

You enter your specific clinical information and the calculator generates a percentage probability for each outcome.

Partin Tables

Originally developed at Johns Hopkins, the Partin Tables predict the pathological stage at surgery (organ-confined, extraprostatic extension, seminal vesicle invasion, or lymph node involvement) based on PSA, Grade Group, and clinical stage. They were most recently updated in 2017.¹¹

Roach Formulas

Developed by Dr. Mack Roach III, these simple formulas estimate:¹² ¹³

Risk of lymph node involvement:

$$\text{LN risk (\%)} = \frac{2}{3} \times \text{PSA} + (\text{Gleason score} - 6) \times 10$$

Risk of seminal vesicle involvement:

$$\text{SV risk (\%)} = \text{PSA} + (\text{Gleason score} - 6) \times 10$$

For example, a man with PSA of 15 and Gleason 7 would have:

Important caveat: The Roach formula was developed in the early PSA screening era and may overestimate risk in contemporary patients with mainly T1c/T2 disease detected through routine screening.¹³ ¹⁴ However, when validated against extended pelvic lymph node dissection, the formula remains reasonably accurate with an AUC of approximately 80%.¹⁵ The Roach formula is also used to determine which patients may benefit from pelvic lymph node radiation — the POP-RT trial established a benefit of whole pelvis radiotherapy in patients with >35% risk of lymph node involvement by the Roach formula.¹⁶

PSA Doubling Time (PSADT)

This is not a nomogram but an important calculation, especially after treatment. It measures how quickly PSA is rising. A shorter doubling time (e.g., 12 months) suggests slower-growing cancer. PSADT is discussed further in Chapter 13.

Part 7: Life Expectancy Estimation — A Critical Factor

Life expectancy is one of the most important factors in prostate cancer treatment decisions. Because prostate cancer often grows slowly, a man's overall health and expected lifespan significantly influence whether treatment will provide benefit.¹⁷ ¹⁸

General guidelines:¹⁷ ¹⁸ ¹⁹

Tools for estimating life expectancy include:¹⁷

When using life tables, the NCCN recommends adjusting based on overall health:¹⁷

For example, if the life table says a 70-year-old man has a life expectancy of 14 years:

This is not an exact science, and these are estimates for groups of patients, not predictions for individuals. However, they help frame the conversation about whether the potential benefits of treatment outweigh the risks.¹⁷

Part 8: Biomarkers — Beyond Standard Risk Groups

As discussed in Chapter 3, biomarkers are tests that provide additional information about your cancer. In the context of risk stratification, biomarkers fall into three categories:²¹ ²²

Diagnostic biomarkers — Help determine if you have cancer (discussed in Chapter 3):

Prognostic biomarkers — Help predict how the cancer will behave regardless of treatment:²¹ ²² ²³

Predictive biomarkers — Help predict whether a specific treatment will benefit you:²¹ ²²

Important caveats about genomic tests:²¹ ²² ²⁴

The NCCN states that the primary method for personalizing treatment remains standard risk stratification (PSA, Grade Group, T stage), not genomic tests. Advanced tools are recommended only when they have the potential to change management and should not be ordered reflexively.²¹ ²²

The AUA/ASTRO guidelines similarly recommend that clinicians should not routinely use tissue-based genomic biomarkers for risk stratification but may use them selectively when added risk stratification may alter clinical decision-making.²⁴

Examples of when genomic tests may be helpful:²⁴

Toxicity biomarkers — An emerging area:

The three types of biomarkers
Understanding biomarkers Diagnostic “Do I have cancer?” Before or instead of biopsy • PCA3, ExoDx, SelectMDx (urine) • 4Kscore, PHI (blood) • ConfirmMDx (tissue) Helps decide if biopsy is needed Prognostic “How will it behave?” After biopsy or surgery • Decipher (22-gene) • Prolaris, Oncotype DX GPS • ArteraAI, ProMark Helps decide treatment intensity Predictive “Will this help me?” Before choosing treatment • ArteraAI (hormone benefit) • BRCA/HRR (PARP inhibitors) • MSI-H/dMMR (immunotherapy) Helps choose the right treatment Not every patient needs genomic testing. These tests help most when the result would change your decision.
Biomarkers answer three different questions: do I have it, how will it behave, and what will help.

Part 9: Putting It All Together — Your Cancer Profile

When your doctor discusses your cancer with you, they are combining all of these elements into a comprehensive profile. Here is an example of what a complete risk assessment might look like:

"Mr. Smith, your cancer profile shows:

This profile tells the treatment team that Mr. Smith has a cancer that is unlikely to spread quickly, that he has many years of life ahead, and that he has several good treatment options including active surveillance, surgery, or radiation — all with excellent long-term outcomes.

Questions to Ask Your Doctor

  1. What is my NCCN risk group, and what does it mean for my treatment options?
  2. What is my clinical T stage, and how was it determined?
  3. What is my AJCC prognostic stage?
  4. Do I need staging imaging (CT, bone scan, or PSMA PET), and why or why not?
  5. Would a genomic test like Decipher or Prolaris help in my situation?
  6. What is my estimated life expectancy, and how does that affect treatment recommendations?
  7. Can you show me my risk on a nomogram like CAPRA or the MSKCC calculator?
  8. Based on my risk profile, what are the chances that my cancer will spread if treated? If not treated?

Myth vs. Fact

Myth: "Stage IV prostate cancer means there is no hope."

Fact: Stage IVA (lymph node positive, no distant spread) is often curable with combination therapy. Even Stage IVB (metastatic) prostate cancer can be controlled for many years with modern treatments. The word "stage" can be misleading — always ask your doctor what your specific situation means for your prognosis.

Myth: "A high Gleason score means the cancer has already spread."

Fact: Gleason score describes how the cancer cells look under the microscope (aggressiveness), not where the cancer has spread. A man can have a high Gleason score with cancer still confined to the prostate, and a low Gleason score with cancer that has spread (though this is less common).

Myth: "If my PSA is low, my cancer must be low risk."

Fact: While PSA is an important factor, some aggressive cancers produce relatively little PSA. Risk is determined by the combination of PSA, Grade Group, and stage — not any single factor alone.

Myth: "Genomic tests can tell me exactly what will happen."

Fact: Genomic tests provide probability estimates, not certainties. They are one piece of the puzzle that, combined with standard clinical information, helps guide decisions. No test can predict the future with 100% accuracy.

Key Takeaways

Support Resources

From diagnosis to risk group
Your journey to a risk group PSA Blood testPSA numberCh. 3 DRE ExamClinical T stageCh. 3 MRI Prostate MRIPI-RADS, locationCh. 5 Biopsy PathologyGrade Group, coresCh. 4 Riskgroup This chapterNCCN + AJCCCh. 6 Refined by nomograms (CAPRA, MSKCC, Partin, Roach), genomic tests, and life expectancy. TREATMENT DECISION → Ch. 7 to 13
Each test contributes a piece; together they define your risk group and guide treatment.

References

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