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10-Year PROTECT Data Underscore Significance of Precision Medicine in Prostate Cancer

Danielle Bucco
Published: Monday, Jan 22, 2018

Malcolm Mason, MD
Malcolm Mason, MD
Prostate cancer survival was not significantly different among active monitoring, surgery, and radiotherapy for patients with prostate cancer, according to 10-year follow-up findings of the PROTECT study.

In the study, a total of 1643 men were randomized to the 3 treatment arms with no meaningful differences among the 3 groups at baseline. The primary endpoint of prostate cancer-specific mortality was approximately 1% in each group.1

“Although the prostate cancer-specific mortality was only 1%, the overall mortality was 10% at a median of 10 years,” explained Malcolm Mason, MD.

The rate of disease progression among men assigned to surgery or radiotherapy was less than half the rate among men assigned to active monitoring, but did not translate into significant differences.

In an interview with OncLive, Mason, a professor at the Institute of Cancer and Genetics, Cardiff University, discusses the significance of the 10-year follow-up of the PROTECT study for patients with prostate cancer and what it means for the field going forward.

OncLive: Please provide an overview of the PROTECT study for patients with prostate cancer.

Mason: The purpose of the PROTECT study was to directly test 3 major modalities of treatment for localized prostate cancer. The 3 modalities were external beam radiotherapy, radical prostatectomy, or deferred local treatment. Around the time this was set up 15 years ago, the terminology around deferred treatment was not settled. We now understand what active surveillance means. The term that was previously used was “active monitoring,” which was not the same since our protocols were different.

The idea of this study was to invite healthy men for prostate-specific antigen (PSA) screening. The unique thing about this study was that men were counselled about the uncertainties of treating early prostate cancer and were informed about the randomized trial before they even had a diagnosis. That’s important because that meant that men could consider the trial and the uncertainties without the overwhelming thoughts that they would receive if they had just had a diagnosis of cancer. That made all the difference.

Around 1600 men with localized prostate cancer were identified and were randomized 3 ways between surgery, radiotherapy, or active monitoring. That was a unique achievement in this field.

What were the results from the 10-year follow-up?

Astonishingly, after a median follow-up of 10 years, the primary endpoint of prostate cancer-specific mortality was only 1%. We did not expect those results when the trial was set up. That tells us about the natural history of this type of prostate cancer. Keeping in mind how it was diagnosed, we took men who were otherwise healthy and were offered a PSA test, so these were not men who had already presented to their urologist with symptoms. That says something about the natural history of localized prostate cancer when it is detected in that way. It was quite a healthy population, but if you look at clinical disease progression, which was defined in several ways, there was a difference. 

Radical and curative treatments, either surgery or radiotherapy, manifestly do reduce the likelihood of disease progression by about half. That is a big result; however, it is still only a phenomenon that affects a minority of men.

It is wrong to use PROTECT as an argument to say that we just should not be treating men with differed treatment and they should all be treated immediately. That is not the case because most men do not need treatment. However, whether deferred treatment is right for an individual man depends on the patient's perception of the risks of disease progression and how much that means to them—versus the side effects they would certainly receive if they had immediate treatment with surgery or radiotherapy. 

The study showed that if you look at patient-reported outcomes, both radiotherapy and surgery can have detrimental effects in terms of toxicity. The effects after surgery are urinary, whereas there are bowel side effects after radiotherapy. Both treatments can also cause sexual dysfunction.

If we are counselling patients, is it wrong to offer differed treatment? I believe the answer to that is, “no,” but it would be wrong to offer it without explaining to patients the increased risk of disease progression on deferred treatment. If patients are having treatment, is there a best option in terms of efficacy of whether surgery is better than radiotherapy? The answer is, “no.” They appear to be the same. There has been a perception that results of surgery are better than those with radiotherapy. This randomized trial says that is not the case and if you have patients randomized both ways, the outcomes are the same. 

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