Watchful waiting may be appropriate for most prostate cancer cases

by Crystal Phend

Deferring curative treatment for low-risk prostate cancer may be a good option for many men ages 70 and younger, a population-based observational study affirmed.

In the national Swedish prostate cancer registry, the cumulative 10-year prostate cancer-specific mortality rate was only 2.4% for men at low risk who opted for watchful waiting or active surveillance, according to Pär Stattin, MD, PhD, of Umeå University Hospital in Umeå, Sweden, and colleagues.

This rate was not significantly different than the 0.7% rate among men who opted for radical prostatectomy or radiation instead, they reported online ahead of print in the July 7 Journal of the National Cancer Institute.

“This strategy [of initial surveillance] appears to be suitable for many of these men,” they wrote.

Their data are similar to those from a recent U.S. study and add to a growing list of population-based studies suggesting that things are much different in the era of prostate specific antigen (PSA) screening, according to an accompanying editorial.

Before widespread PSA use, 10-year prostate cancer mortality ranged from 15% to 23%, wrote Siu-Long Yao, MD, of Merck Research Laboratories in Kenilworth, N.J., and Grace L. Lu-Yao, PhD, of the University of Medicine and Dentistry of New Jersey in New Brunswick.

Most remarkable is that “survival in most (Gleason ≤7 disease), but not all (Gleason 8 to 10), patients with localized disease managed conservatively is now similar to that of age-matched control subjects,” they wrote.

However, the price of earlier stage diagnosis with PSA screening has been a roughly 40% increase in diagnosed cases since 1985 and growing concern about overtreatment of these predominantly localized cancers.

Given the growing popularity of surveillance in the face of these issues, Stattin’s group assessed mortality from prostate cancer and competing causes in patients in the National Prostate Cancer Register of Sweden Follow-up Study.

The study included 6,849 patients diagnosed with local clinical stage T1 or T2 prostate cancer from 1997 through 2002 who had a Gleason score of 7 or less and a serum PSA under 20 ng/mL.

Routine clinical practice resulted in active surveillance or watchful waiting for 2,021 men, radical prostatectomy for 3,399, and radiation therapy for 1,429.

Overall, the calculated 10-year cumulative prostate cancer–specific mortality was similar among groups at 3.6% with surveillance (95% CI 2.7% to 4.8%), 2.4% with immediate prostatectomy (95% CI 1.8% to 3.3%), and 3.3% with immediate radiation therapy (95% CI 2.5% to 5.7%).

More than a third of the men (2,686) had low-risk prostate cancer with clinical stage T1, Gleason score 2 to 6, and serum PSA level under 10 ng/mL. These patients were more likely to have been put on surveillance (40.4% versus 22.5% with intermediate-risk tumors).

Not surprisingly, patients with more comorbidity were also more likely to have gone on surveillance instead of immediate definitive therapy with a rate of 28.4% among those with a Charlson index of 0 to 1 compared with 43.8% with a Charlson index of 2 or higher.

The researchers noted that this “strong selection bias” was a result of the observational design but reflected clinical practice.

After a median of 8.2 years of follow-up, all-cause mortality in the surveillance group was “similar to that of the background population, whereas all-cause mortality was lower than expected in the radiation therapy group and especially in the prostatectomy group,” Stattin’s group wrote.

The 10-year cumulative risk of dying of competing causes was higher in the watchful waiting and active surveillance group at 19.2% (95% CI 17.2% to 21.3%) compared with 8.5% (95% CI 7.3% to 9.8%) with immediate prostatectomy and 14.2% (95% CI 11.7% to 16.9%) with immediate radiation therapy.

After adjustment for age, risk category, socioeconomic status, and Charlson index, initial definitive treatment appeared to lower risk of prostate cancer–specific mortality in the low- and intermediate-risk cases combined, with a relative risk of 0.49 for prostatectomy versus surveillance (95% CI 0.34 to 0.71) and 0.70 for radiation versus surveillance (95% CI 0.45 to 1.09).

However, the difference in absolute risk even in this comparison with the biggest relative difference between treatment groups was “still very modest,” the researchers cautioned in the paper, at just 1.2% after 10 years for prostatectomy versus watchful waiting.

Contemporary active surveillance protocols are likely to result in even better prostate-cancer specific mortality figures, they suggested.

Stattin’s group cautioned, though, that longer follow-up is needed given that most patients currently diagnosed with localized prostate cancer are in their 60s and have a life expectancy of more than 15 years.

They also warned that they had no data on tumor extent in core biopsy specimens, serum PSA levels after the date of diagnosis, or progression to metastatic disease.

Crystal Phend is a MedPage Today Senior Staff Writer.

Originally published in MedPage Today. Visit MedPageToday.com for more prostate cancer news.

email

Comments are moderated before they are published. Please read the comment policy.