Prostate-specific antigen velocity has been associated with increasing prostate cancer-specific mortality.
Prostate-specific antigen (PSA) velocity (PSAV) has been associated with increasing prostate cancer-specific mortality (PCSM) following radical prostatectomy. A study recently published in Cancer suggests that serial PSA screening may lead to a decrease in PCSM.
“We are in an era where physicians are using the PSA a lot for screening but don’t yet have the fundamental knowledge about whether this approach will allow our patients to live longer,” says lead author Neil E. Martin, MD, from the Department of Radiation Oncology at Brigham and Women’s Hospital in Boston. “While the studies to answer those questions are continuing, we are left in the meantime with the situation where there is much interest in screening, but little ability to tell men what they want to know. We are forced to use circumstantial evidence to try to better inform our patients and ourselves.”
The records of 1,095 men from a prospective cancer screening study who underwent a radical prostatectomy between 1989 and 2002 were assessed. Clinical and pathologic features were compared between three time frames: before 1995, from 1995 to 1998, and after 1998. The data was evaluated for an association between the year of diagnosis and PSAV > 2 ng/mL per year.
“Over that time period more men were enrolled in the trial and the included men had increasing time that they were screened with the PSA test,” Martin says. “We tried to look at how things had changed over time by breaking the results into three time periods representing the early, middle, and more recent PSA era.”
They found a statistically significant reduction in the number of men presenting with a PSAV > 2ng/mL per year over the period. In the earliest timeframe, 35% of the men presented with this PSAV value compared to 22% and 12% later on. In addition, over the course of the study, men also had increasing numbers of PSA tests performed prior to their diagnosis, indicating a greater duration of screening.
“From the results of this study we can’t tell our patients that having an annual PSA test is going to lengthen their life,” says Martin. “There is growing evidence that men screened with the test are less likely to have the more aggressive forms of prostate cancer at diagnosis. This study further reinforces that evidence.”
Dr. Martin pointed out that this study looked backwards at data already collected in another trial. In addition, it only included men who had surgery, which limits the ability to extrapolate findings to other treatment methods.
“This is one more piece of evidence to support screening, but it certainly won’t change anyone’s mind about the use of PSA,” Martin says. “We really need to wait on the results of the two big screening trials currently underway. When those come out all the recommendations will need to be reviewed.”
Christopher Saigal, MD, MPH, is from the Jonsson Comprehensive Cancer Center at University of California at Los Angeles and was not involved in the study. He says that the results are what earlier research would lead one to expect.
“We know that screening has reduced the proportion of men presenting with metastatic cancers, with bigger or higher grade tumors,” Saigal says. “There has been a stage-shift over the years as we find more cancers at an earlier stage. It makes sense that when high pre-treatment PSAV, which is associated with increased recurrence risk and death, is examined in newly diagnosed men that they should have a more favorable risk profile as screening becomes more widespread.”
Saigal also found it interesting that this cohort included men over 70 years of age. Many studies exclude men in that age group.
“It looks like from this study that even men over 70 had a decrease in the proportion of cancers with a high PSAV value,” Saigal says. “Even in this older cohort there seemed to be an effect of screening, although I would expect the proportion of very old men in this group would be small. However, we still do not know the seriousness of the cancers and whether these men would have died from other causes long before the cancer got them.”
Martin NE, et al. The influence of serial prostate-specific antigen (PSA) screening on the PSA velocity at diagnosis. Cancer. 2008;113:717-22.
Kurt Ullman is a veteran freelance health and medical writer based out of Indianapolis.