Major Finding: One study found that men on active surveillance after a prostate cancer diagnosis are almost 19 times as likely to die from other causes as from prostate cancer over 10 years. Another study found that over 5 years, not a single man diagnosed with prostate cancer died of the disease while under active surveillance, and only 3% died of other causes.
Data Source: Two prospective cohort studies of men with low-grade prostate cancer, one with 452 men followed for 10 years, and the other with 532 men followed for 5 years.
Disclosures: Both investigators said that they had no conflicts of interest. Dr. Whitson's study was supported by the University of California, San Francisco; Dr. Klotz's study was supported by the Prostate Cancer Research Foundation of Canada.
SAN FRANCISCO — Men who were diagnosed with low-grade prostate cancer have little to fear from a strategy of “watchful waiting,” also called “active surveillance,” according to two longitudinal studies
In one study, Dr. Laurence Klotz, chief of urology at the University of Toronto, followed a prospective cohort of 452 men for 10 years. During that time there were only five deaths from prostate cancer. The men in the study were 18.6 times more likely to die from other causes than from prostate cancer.
Among the original cohort, 315 men (70%) had stable disease. “In this group none have metastasized, none have been upgraded, and none have been treated,” Dr. Klotz said during a press briefing.
“So we took these 315 patients and [asked], 'If we apply various PSA [prostate-specific antigen] triggers to this stable cohort, how does it perform?'” Dr. Klotz said. “And the remarkable thing is that these patients very frequently have a trigger for intervention.”
This suggests that none of these triggers for intervention based on PSA values is very reliable. For example, 84% of the men with stable disease had two or more successive PSA tests during the study indicating a PSA velocity greater than 2 ng/mL per year.
Other commonly used measures of PSA kinetics also yielded false-positive signals in these men with stable disease. Among those unreliable measures were PSA linear regression, differences between first and last PSA, and PSA threshold greater than 10 ng/mL.
“The bottom line is, these commonly used PSA triggers give what we consider to be a false signal for intervention very, very frequently,” Dr. Klotz said. “You have to interpret these values with caution.”
In the other study, Dr. Jared Whitson of the University of California, San Francisco, followed 532 men with low-grade prostate cancer for a mean of 55 months. The overall survival was 97%, and not a single man died from prostate cancer.
The men received prostate biopsies every 12-18 months, and 69% were still in active surveillance at the end of the study.
Of the 83 men who opted for radical prostatectomy, only 26 (31%) reached stage pT3, and only 22 (27%) had an extracapsular extension.
“Even among men who had not been upgraded, about 20% over 5 years will decide to be treated despite no change,” Dr. Whitson said at the press briefing.
“What we are doing now is using the PSA not as a trigger for intervention, but as a trigger for further diagnostic tests,” Dr. Klotz said.
'What we are doing now is using the PSA not as a trigger for intervention,' but as a trigger for diagnostic tests.
Source DR. KLOTZ
My Take
Active Surveillance Not Yet Standard
The studies by Dr. Klotz and Dr. Whitson both suggest that active surveillance is a reasonable strategy in men with low-grade prostate cancer. But I think it's still too soon to say that this strategy is the standard of care. In all fairness, I think we need to be a bit careful in saying that this is something we ought to be offering everyone. We just don't know enough about it yet.
What we really need from studies of active surveillance is longer-term follow-up. We need to know how many of these men we might have saved by active treatment vs. how many went on to never have to worry about prostate cancer. There are many adjuvant therapies that we can offer if they fail: radiation therapy, hormonal therapy, chemotherapy, and now immunotherapy. So I think the critical question is, what do we give up with active surveillance? We don't know that yet.
Most of these active surveillance protocols have a significant amount of fallout, some of it due to the treating physicians and some of it driven by the patients. One of the problems is that most of our patients concentrate on the PSA level. But a PSA level obtained today and one obtained tomorrow may be very different. Often patients get very anxious about active surveillance. PSA could stand for “patient-stimulated anxiety.”