View findings of study on prostate cancer in perspective

As doctors caring for prostate cancer patients, we are deeply concerned that the report on Sept 16 may lead to erroneous conclusions by men about their prostate cancer care ("99% of early prostate cancer patients survive 10 years").

The report, which was taken from the Washington Post, suggests a recent clinical trial concluded that active surveillance and radical treatment have the same good outcome in all early-stage prostate cancers.

This is not true. As with all clinical trials, the details matter.

Active surveillance is a strategy to monitor men with low-risk, early-stage prostate cancer and defer treatment when necessary.

This requires repeat blood tests and prostate biopsies to delay radical treatment until tests show cancer progression. It is not the same as no treatment.

There are three issues to highlight to put this study in the right perspective:

• The trial focused mainly on low-risk, early-stage cancer.

Early-stage prostate cancers are heterogeneous, with different risks for metastasis (spreading to other parts of the body).

The study recruited mainly very low-risk, early-stage prostate cancer patients in the early 2000s. Most urologists manage such cases conservatively (that is, observation, mostly in the form of active surveillance) today.

Men with aggressive early-stage prostate cancer should not be managed by active surveillance, as they develop lethal metastatic spread without radical treatment.

• More active-surveillance patients developed metastatic cancer spread.

Men who received active surveillance were twice as likely to have cancer spread than those who had radical treatment. It is reasonable to believe that the higher rates of metastasis will lead to lower survival and higher mortality rates when the study matures with longer follow-up.

• Statistical bias in the surveillance group may affect interpretation of the results.

More than half of the men who were monitored subsequently received surgery or radiation, but their survival results were included under the surveillance arm rather than the treatment arm because of study design.

This affects the results because the surveillance group is contaminated with men who received treatment, so the comparison may not show a significant difference in survival at this point.

All things considered, it would be reasonable to conclude that active surveillance should be an option for men with low-risk, early-stage prostate cancer.

However, these men need to have regular follow-up assessments, as the study suggests that they have an increased risk of cancer spread, compared with men who receive immediate treatment.

Sim Hong Gee (Dr)

Chairman

Chapter of Urologists

College of Surgeons Singapore

Edmund Chiong (Dr)

President

Singapore Urological Association

A version of this article appeared in the print edition of The Straits Times on September 28, 2016, with the headline 'View findings of study on prostate cancer in perspective'. Print Edition | Subscribe