More than two-thirds (68%) of all prostate cancers in the United States qualify for active surveillance, according to a study published in the September issue of the Journal of Urology.
And if a more stringent definition of surveillance eligibility is used, 44% of cases would be candidates for monitoring instead of immediate treatment, say senior author Ian M. Thompson III, MD, from the University of Texas Health Science Center at San Antonio, and colleagues.
These "target" figures are especially credible because they come from a population-based study funded by the National Cancer Institute, and the 3828 participants from Texas undergo regular prostate-specific antigen (PSA) testing.
The authors explain that most previous reports of the actual rates of active surveillance are biased because they come from patient series at centers where patients are treated or are derived from tumors detected at urology practices.
The Texas cohort provides "an opportunity to determine what could be a national target for rates of eligibility," write the study authors.
Of the 320 men in the cohort who developed prostate cancer from 2000 to 2012, 281 had data that were sufficient to allow scoring on very detailed surveillance scorecard.
Disease characteristics, such as a high Gleason score, rendered 131 of the 320 men ineligible for active surveillance. But 123 of the men (44%) met a conservative set of criteria and were eligible for surveillance.
These "lowest-risk" patients had a PSA density below 15%, fewer than three cores involved with cancer, a Gleason score of 6 or less, and cancer involving 50% of biopsy volume or less.
Another 64 men (24%) were eligible when a more expansive set of criteria was used. These "higher-risk" men had fewer than five cores with Gleason 3 + 3 cancer and only one core of Gleason 3 + 4 cancer with up to 15% of the core involved with the Gleason 3 + 4 disease.
When the two groups were combined, 187 patients (68%) were eligible for active surveillance.
Predictably, the number of men who actually chose active surveillance was much lower. From 2000 to 2007, 11% of the men diagnosed with prostate cancer opted for surveillance. From 2007 to 2012, 35% of the men opted for surveillance.
These numbers are to be expected, the authors explain, because the study was conducted during "a period of changing patterns in care," and patients were treated by "a broad spectrum of community urologists."
Active surveillance should be offered to "an expanded population of well-informed men who may value preserving function above a small risk of disease progression," write Marc Dall'Era, MD, from the University of California, Davis, and Peter Carroll, MD, from the University of California, San Francisco, in an accompanying editorial.
In other words, the approach is not just for the lowest-risk cases, they opine.
They explain that "the risks of adverse disease-specific outcomes will likely be higher with the inclusion of men with more intermediate-risk features." However, the "absolute risk may still be low," they write.
Two Cases of Either Metastatic Disease or Prostate Cancer Death
Dr Thompson and his colleagues also looked at treatment data on 178 of the study patients. For the 74 who underwent radical prostatectomy, final pathologic review findings were available.
This allowed the team to compare the initial findings with the more authoritative final findings.
Compared with the initial needle biopsy findings, 33% of the men who met the lowest-risk criteria for active surveillance and 25% who met the higher-risk criteria were upgraded and/or upstaged at final review.
These upgrades and upstages are "of some concern," concede the study authors. But one upstaging phenomenon, in particular, worries urologists, they report.
"It is important to note that of all cases upstaged from the cohort, five men had seminal vesicle invasion, perhaps the most meaningful metric of upstaging, but none of these men were from either group eligible for active surveillance," they write.
Perhaps even more important, the study authors observe, is that if the well-documented phenomenon of upgrading or upstaging "truly translated to subsequent consequential outcomes," then "far greater" rates of disease progression, metastases, and death would have been reported in other series of patients. And that has not happened.
Drs Dall'Era and Carroll agree. "We know from several well-described surveillance cohorts that the risk of progression to metastatic disease and dying of prostate cancer with expectant management is low, but not zero," they write.
The pair also point to the current study as proof that active surveillance is a reasonable approach, not just for "very-low-risk" disease, but for low- and intermediate-risk prostate cancer, too.
Notably, two of the 320 patients in the Texas cohort either experienced metastatic disease or died of prostate cancer.
One of these patients met the expanded criteria and was eligible for active surveillance. "While this could argue against active surveillance, it is notable that this patient underwent radical prostatectomy immediately following diagnosis," the authors explain.
The other patient, who was ineligible for surveillance under either definition, was treated definitively but experienced disease progression.
This study has limitations, including the high participation rate of Hispanic men relative to national demographics. These men represented 36% of the cohort overall and 26% of men with prostate cancer.
Coauthor Ian M. Thompson Jr, MD, from University of Texas Health Science Center at San Antonio, reports financial interest and/or other relationships with Exosome Diagnostics, Oncocell MDX, Magforce, Myriad Genetics, and NanoTX Therapeutics.
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