What is "significant" prostate cancer?
Not all prostate cancer is the same. Many prostate cancers grow so slowly they would never cause harm, while others need treatment. The word "significant" is how doctors and risk calculators separate the two.
How prostate cancer is graded
When a biopsy finds cancer, a pathologist looks at how the cancer cells are arranged under the microscope. The two most common patterns are added into a Gleason score, which is now reported as a simpler Grade Group from 1 to 5.
| Grade Group | Gleason score | How it usually behaves |
|---|---|---|
| 1 | 3+3 = 6 | Low grade. Grows slowly and very rarely spreads. Usually monitored rather than treated. |
| 2 | 3+4 = 7 | Intermediate, favorable. Mostly slow-growing pattern with some more aggressive cells. Some men can be monitored; many are treated. |
| 3 | 4+3 = 7 | Intermediate, unfavorable. More of the aggressive pattern. Usually treated. |
| 4 | 4+4 = 8 | High grade. Usually treated. |
| 5 | 9 or 10 | Highest grade. Most likely to spread. Treated, often with more than one approach. |
Grade Groups were adopted by the International Society of Urological Pathology in 2014 (Epstein et al., Am J Surg Pathol 2016). You may see both numbers on a pathology report.
Where the line is drawn
"Clinically significant" usually means Grade Group 2 or higher (Gleason 7 or more). These are the cancers that can grow and spread if left alone, and the ones worth finding early. Grade Group 1 cancer is generally not counted, because finding and treating it adds side effects without helping men live longer.
That is exactly what the risk numbers on mypsalevel estimate: the chance a biopsy would find Grade Group 2 or higher cancer. A 20% estimate means about 20 in 100 men with results like yours would have significant cancer on biopsy, and 80 would not.
Grade isn't the only thing that matters. Your urologist also weighs how much cancer is in the biopsy cores, your PSA and PSA density, what the MRI shows and whether the cancer can be felt on exam. Some pathologists also report cribriform or intraductal patterns, which make a Grade Group 2 cancer behave more like a higher grade.
If you have low-grade cancer
For most men with Grade Group 1 cancer, the recommended approach is active surveillance: regular PSA tests, periodic MRI and repeat biopsies when needed, with treatment only if the cancer shows signs of changing. This is endorsed by the American Urological Association, the American Society for Radiation Oncology and the Society of Urologic Oncology.
The strongest evidence comes from the ProtecT trial in the UK, which followed more than 1,600 men with mostly low-risk cancer for 15 years. About 3 in 100 died of prostate cancer, and the rate was similar whether men were first monitored, had surgery or had radiation (Hamdy et al., NEJM 2023). Men in the monitoring group, which was less intensive than today's active surveillance, avoided or delayed treatment side effects, though their cancer was more likely to progress and many eventually had treatment.
Questions to ask your urologist
- If a biopsy finds cancer, how likely is it to be Grade Group 1 versus 2 or higher?
- Would an MRI first help decide whether I need a biopsy at all?
- If I had low-grade cancer, would you recommend active surveillance?