Active Surveillance vs. Active Treatment for Prostate Cancer: Understanding PSA, Gleason Grade, and MRI

Research-informed explainer — last updated April 12, 2026

Most men diagnosed with low-risk prostate cancer — a Gleason score of 6 (Grade Group 1), PSA below 10, and no high-risk imaging features — can safely defer treatment in favor of active surveillance without compromising long-term survival. However, the definition of "low risk" has been refined substantially by MRI-targeted biopsy, which catches higher-grade cancers that systematic biopsy misses, and by genomic assays that quantify the biological aggressiveness of the tumor independent of grade.

The research behind how prostate cancer is staged and how surveillance candidates are identified comes from specialists at leading urology and imaging centers. Katarzyna Macura, formerly at Johns Hopkins, is a co-author of PI-RADS v2 (2,888 citations) and PI-RADS v2.1 (2,300 citations) — the standardized reporting systems radiologists use to describe prostate MRI findings. Daniel Margolis contributed to the PRECISION trial (2,924 citations), which demonstrated that MRI-targeted biopsy detects significantly more clinically significant cancers and significantly fewer indolent cancers than standard systematic biopsy. Mark Litwin, Professor and Chair of the Department of Urology at UCLA, published landmark quality-of-life outcome data across all treatment modalities (2,249 citations) and developed the EPIC instrument used to measure function across urinary, sexual, bowel, and hormonal domains (1,500 citations). Vipul Patel at Florida Cancer Specialists and Robert H. Lurie Comprehensive Cancer Center contributed robotic prostatectomy outcomes data. Michael Morris at Memorial Sloan Kettering, whose work on integrative genomics of advanced prostate cancer (3,599 citations) and PSMA-targeted therapy (2,383 citations) illuminates what happens when surveillance-appropriate cancers eventually progress.

What the tests mean: PSA, Gleason grade, and Grade Group

PSA (prostate-specific antigen) is a protein produced by prostate tissue. Elevated PSA prompts biopsy but is not cancer-specific — benign prostatic hyperplasia and prostatitis also raise PSA. PSA density (PSA divided by prostate volume) and PSA velocity (rate of rise) provide additional context.

Gleason score grades the architectural pattern of prostate cancer cells under microscopy. It is expressed as the sum of the two most prevalent patterns (primary + secondary). A Gleason 3+3=6 cancer has no pattern higher than 3 and is considered low risk. A Gleason 3+4=7 (Grade Group 2) is intermediate risk; 4+3=7 (Grade Group 3) is higher intermediate risk; Gleason 8 (Grade Group 4) and 9-10 (Grade Group 5) are high risk.

Grade Group (1–5) is a simplified system that maps directly to Gleason scores and is increasingly used in clinical communication:

The role of prostate MRI before biopsy

The PRECISION trial — to which Daniel Margolis contributed — enrolled 500 biopsy-naive men with elevated PSA and compared MRI-targeted biopsy against standard 12-core systematic transrectal ultrasound biopsy. MRI-targeted biopsy detected 38% more clinically significant cancers (Gleason Grade Group 2 or higher) and 89% fewer clinically insignificant cancers (Gleason 6). This means that MRI before biopsy reduces overdiagnosis of cancers that do not need treatment.

The PI-RADS (Prostate Imaging Reporting and Data System) score standardizes how radiologists report MRI findings:

PI-RADS 4 or 5 on MRI typically warrants targeted biopsy even if systematic biopsy was previously negative, because MRI-targeted cores have a substantially higher yield for Grade Group 2+ cancer in these lesions.

Active surveillance vs. active treatment: the comparison

Mark Litwin's 2008 NEJM study enrolled 1,201 men treated for localized prostate cancer and followed their quality of life for 2 years using the EPIC instrument. Surgery was associated with worse urinary incontinence and sexual function; radiation with worse bowel and urinary irritative symptoms; and hormone therapy with fatigue, hot flashes, and sexual dysfunction. No single treatment was superior across all domains — the right choice depends heavily on individual baseline function, priorities, and cancer risk.

Genomic risk tools beyond Gleason grade

For men with Grade Group 1 or 2 cancers who are on the margin between surveillance and treatment, genomic assays can provide additional risk stratification:

• Oncotype DX Genomic Prostate Score (GPS): Predicts likelihood of adverse pathology at surgery and is validated for men on active surveillance.
• Decipher Biopsy: Predicts likelihood of metastasis at 10 years.
• Prolaris: Measures tumor cell cycle progression gene expression as a metastasis predictor.

These tests are particularly useful for men with Grade Group 2 disease — the group where the surveillance vs. treatment decision is least clear. A high genomic risk score in a Gleason 3+4 cancer may tip the recommendation toward treatment; a low score reinforces surveillance.

When surveillance is not appropriate

Active surveillance is generally not recommended for:

• Grade Group 3–5 (Gleason 7 with primary pattern 4, or Gleason 8–10)
• Clinical stage T3 or T4 disease (tumor extending beyond the prostate)
• PSA above 20
• Very high PSA density (greater than 0.15 ng/mL/cc)
• Life expectancy less than 10 years (in which case watchful waiting — with no intent to intervene — may be appropriate instead)

Michael Morris's integrative genomics of advanced prostate cancer research contextualizes what surveillance candidates face if their cancer eventually progresses to metastatic disease — including PSMA-targeted therapy and genomic alterations (BRCA1/2, CDK12) that affect treatment eligibility. This progression trajectory, while uncommon for well-selected surveillance patients, informs why high-risk features at diagnosis warrant definitive treatment.

Questions to ask your doctor

• Has my tumor been biopsied with MRI targeting, or only with standard systematic biopsy? If standard, should I have an MRI before deciding on surveillance?
• Is my cancer truly Grade Group 1, or does my biopsy show any Grade Group 2 cores that might affect the surveillance recommendation?
• Would a genomic test like Oncotype DX GPS or Decipher help clarify my risk beyond the biopsy grade?
• What is the monitoring schedule for active surveillance, and what findings would trigger a recommendation to treat?
• If I eventually need treatment, which modality — surgery or radiation — would be best given my anatomy and functional goals?

The bottom line

Active surveillance is appropriate and safe for most men with Grade Group 1 prostate cancer and careful selection of Grade Group 2 disease. The keys to safe surveillance are accurate staging — through MRI-targeted biopsy and consideration of genomic testing — and a rigorous monitoring protocol with defined criteria for recommending treatment. Men whose Gleason grade or other risk features have been established only through standard systematic biopsy should consider whether MRI-targeted rebiopsy would change their risk classification before committing to surveillance or treatment.