Monitoring low-risk prostate cancer matched surgery on survival at 15 years

Active surveillance means a prostate cancer is monitored rather than treated, with regular PSA tests and repeat biopsies, and treatment held in reserve. The single randomised trial that compared it directly against surgery and radiotherapy found that after 15 years, prostate cancer mortality was low in all three groups and statistically indistinguishable between them — while metastases and disease progression were roughly twice as common in the monitored group. Those two findings are both the case, and understanding why is the whole subject.

The trial

Between 1999 and 2009 in the United Kingdom, 82,429 men aged 50 to 69 had a PSA test as part of the ProtecT study. Localised prostate cancer was diagnosed in 2,664 of them, and 1,643 agreed to be randomised: 545 to active monitoring, 553 to prostatectomy and 545 to radiotherapy [s1]. The 15-year analysis, published in 2023, had complete follow-up for 1,610 men — 98% of those enrolled [s1].

Death from prostate cancer occurred in 45 men overall, 2.7% of the trial: 17 (3.1%) in the active-monitoring group, 12 (2.2%) in the prostatectomy group, and 16 (2.9%) in the radiotherapy group, with P = 0.53 for the overall comparison [s1]. Death from any cause occurred in 356 men (21.7%), with similar numbers in all three groups [s1]. In other words, over fifteen years these men were roughly eight times more likely to die of something other than prostate cancer.

Where the groups did diverge

The secondary outcomes separated clearly. Metastases developed in 51 men (9.4%) under active monitoring, against 26 (4.7%) after prostatectomy and 27 (5.0%) after radiotherapy [s1]. Long-term androgen-deprivation therapy was started in 69 monitored men (12.7%), against 40 (7.2%) and 42 (7.7%) [s1]. Clinical progression occurred in 141 (25.9%), against 58 (10.5%) and 60 (11.0%) [s1].

Set against that, 133 men in the active-monitoring group — 24.4% — were alive at the end of follow-up without having had any prostate cancer treatment at all [s1].

So monitoring produced more disease events without producing more deaths from the disease, across fifteen years. That is the trade a man is actually choosing between: a higher chance of the cancer advancing and needing treatment later, against a substantial chance of never being treated.

An important limit on who the trial describes

ProtecT was not a trial of low-risk cancer only. A risk-stratification analysis found that more than one third of the men had intermediate- or high-risk disease at diagnosis [s1]. The trial also reports that no differential effects on cancer-specific mortality were seen in relation to baseline PSA level, tumour stage or grade, or risk-stratification score [s1].

That cuts both ways. It means the result is not confined to the mildest cancers — but it also means a man being offered surveillance today, under criteria that generally exclude higher-risk disease, is not exactly the man in the trial.

What the guideline does with this

The American Urological Association's guideline on clinically localised prostate cancer, amended in 2026, states that for patients with low-risk prostate cancer, clinicians should recommend active surveillance as the preferred management option — a strong recommendation at evidence grade A [s2]. For favourable intermediate-risk disease, it says clinicians should discuss active surveillance, radiation therapy and radical prostatectomy [s2]. The guideline cites ProtecT directly as the relevant data for low-risk disease [s2].

Its statement of intent is worth quoting in the guideline's own terms: surveillance aims to maintain quality of life by deferring or delaying definitive treatment when the cancer is unlikely to cause death or significant harm, while keeping curative treatment available if that changes [s2].

On how surveillance should be run, the guideline is brief and specific. Patients managed with active surveillance should be monitored with serial PSA values and repeat prostate biopsy [s2]. MRI should be used to augment risk stratification, but should not replace periodic surveillance biopsy [s2]. Both statements are graded as expert opinion, which is a candid acknowledgement that the optimal surveillance protocol has not been settled by trial evidence.

The guideline is also explicit that whole-gland or focal ablation remains investigational for low- and intermediate-risk disease, without high-quality data comparing it against surgery, radiation or surveillance [s2].

Why this connects back to screening

The reason active surveillance exists is that PSA screening finds cancers that would never have caused symptoms. The AUA's early-detection guideline makes the link explicit: clinicians should inform patients undergoing a prostate biopsy that there is a risk of identifying a cancer with a sufficiently low risk of mortality that it could safely be monitored rather than treated [s3].

That sentence is doing a lot of work. It is a screening guideline telling clinicians to warn patients, before the biopsy, that the biopsy may find something best left alone. Surveillance is the mechanism by which the harms of overdiagnosis are meant to be contained — and it only contains them if the men diagnosed, and the clinicians treating them, are willing to leave a diagnosed cancer in place.

The trial evidence says that over fifteen years, for the men in ProtecT, doing so did not cost lives. It also says it cost more metastases and more hormone therapy. Both belong in the conversation.

This article describes trial findings and guideline statements. It is not medical advice, and management decisions belong with a reader and their clinical team.

Sources

• Fifteen-Year Outcomes after Monitoring, Surgery, or Radiotherapy for Prostate Cancer — New England Journal of Medicine, 2023-03-11
• Clinically Localized Prostate Cancer: AUA/ASTRO Guideline Amendment (2026) — American Urological Association, 2026
• Early Detection of Prostate Cancer: AUA/SUO Guideline (2026) — American Urological Association, 2026