Prostate Cancer Screening Cuts Death Risk

Men who have annual prostate specific antigen (PSA) screenings may be dramatically reducing their risk of death from prostate cancer, researchers say.

A new study found that patients diagnosed with prostate cancer who had regularly undergone the yearly blood test had a less aggressive form of the disease at diagnosis -- translating into a threefold reduction in the likelihood of death when compared with patients who had skipped the screening.

"A simple blood test called PSA may decrease deaths from prostate cancer because it appears to discover prostate cancers at a more curable time," said study author Dr. Jason Efstathiou, of the department of radiation oncology at Brigham and Women's Hospital and Dana Farber Cancer Institute, in Boston.

Efstathiou notes that more than 50 percent of American men over the age of 50 have had at least one PSA test -- a figure that rises to nearly 75 percent for men over the age of 65.

Nevertheless, scientists have recently been exploring alternatives to the annual PSA testing protocol that could offer more accurate risk assessments, ranging from increasing the frequency of PSA testing itself to scrapping the test altogether in favor of exams that measure cancer protein antibody levels.

To date, however, the standard annual PSA exam -- which measures dangerously elevated levels of a protein produced by the prostate -- remains the most common form of prostate cancer screening, alongside digital rectal exams conducted in the physician's office.

Physicians and patient advocacy groups are conflicted about the wisdom of across-the-board screening of any kind.

Some experts point out that elderly patients, in particular, may find that a slowly progressing prostate cancer that goes undiagnosed and untreated may ultimately pose no threat to their well-being or life expectancy. Arduous and perhaps unnecessary surgical or radiation treatment could, on the other hand, drastically diminish their quality of life.

The stakes, however, are high. Prostate cancer is second only to skin cancer as the most common type of cancer to strike American men. According to American Cancer Society estimates, more than 230,000 American men will be newly diagnosed with prostate cancer by the end of 2005. Approximately 30,350 of these men will eventually die of the disease.

Efstathiou and his team analyzed the medical records of 1,492 men who had been diagnosed with localized prostate cancer between 1988 and 2002. All the men had experienced a recurrence of prostate cancer after having their prostates removed post-diagnosis -- a procedure known as radical prostatectomy.

The researchers found that the 841 men who had undergone yearly PSA testing before their diagnosis were more likely to survive the disease than the 611 men who had not been screened regularly.

The study authors, who presented their findings Wednesday at the American Society for Therapeutic Radiology and Oncology's meeting in Denver, noted that men who had a history of PSA testing were found to have had less aggressive cancer at the time of their diagnosis.

PSA-screened patients had been diagnosed with a low-risk form of prostate cancer nearly 65 percent of the time, compared with just under 24 percent for non-screened men.

Patient follow-up further revealed that over an estimated 10-year period following cancer recurrence, patients who had been PSA-tested were about three times less likely to die than those who had not been tested.

While the chance of dying was found to be slightly greater than 11 percent among the general male population, Efstathiou and his colleagues noted that men following the PSA protocol appear to have only a 3.6 percent chance of mortality due to prostate cancer.

Efstathiou cautioned that the findings need to be confirmed by larger-scale studies.

"The good news is that there are currently three randomized trials on the order of 100,000 patients or more that are currently ongoing in the U.S. and Europe, and they will give us definitive answers by 2008," he said. "Meanwhile, our study may give some clues as to what those large trials will reveal."

Dr. Durado Brooks, director of prostate and colorectal cancers with the American Cancer Society, noted the clues are not all that earth-shattering.

"It's not really surprising that men who were detected by screening had less aggressive tumors, lower-risk disease, and earlier-stage cancer," he said. "We already know that, when you screen a large population, you do find a larger proportion of earlier-stage disease."

But, he added, "I think the primary point of the study is that even when patients failed initial treatment, there was still a mortality benefit in having been diagnosed with an earlier-stage disease."

More information

For more on prostate cancer, check out the American Cancer Society.

Hormone Linked to Aggression in Mice

New research with mice offers more evidence that a specific hormone plays a major role in people's ability to take care of others and avoid conflict.

If the findings hold true for humans, scientists might get one step closer to a treatment for people with autism because they often lack an essential sense of empathy, researchers said.

The study, by a team of Japanese and American researchers, found that when mice were genetically engineered to not process the hormone oxytocin, the males became more aggressive and the females often forgot to take care of their babies.

Recent research has linked oxytocin -- no relation to the painkiller OxyContin -- to the ability of people to trust others. The new research is important because it expands on the role of oxytocin, said Paul Zak, director of the Center for Neuroeconomics Studies at Claremont Graduate University in Claremont, Calif.

"We're finding (oxytocin) is much more related to social behaviors, and social behavior deficits," said Zak, who worked on the research into oxytocin and trust.

In other words, oxytocin seems to be connected to how humans interact with each other -- and how the interactions can go wrong, he added.

Oxytocin is produced in the brain and released by the pituitary gland. Among other things, it seems to play a role in reproduction and perhaps even in the mysterious phenomenon called love.

Similar hormones appear in many animals, even including insects, said study co-author Katsuhiko Nishimori, a molecular biology researcher at Tohoku University in Sendai, Japan. In higher animals, the hormones seem to affect both reproduction and behavior.

Nishimori and colleagues bred mice that did not have "receptors" that would allow them to process oxytocin. Then they watched how the mice behaved.

The study findings appear in this week's issue of the Proceedings of the National Academy of Sciences.

The male mice were highly aggressive, quicker to attack intruders and more likely to fight them for a longer period. It wasn't clear, however, if the missing hormone might lower some other types of aggression.

The male mice were also more likely to forget the identity of females they had met.

As for the female mice, they sometimes forgot to retrieve their babies when they wandered off.

What does this all mean for people?

It's not entirely clear, Zak said, adding, "the extrapolation from mice to humans is a bit of a leap."

Still, it's possible the research could help scientists develop a treatment for people with autism. They can sometimes be aggressive or have trouble relating to other people, he said.

And, while researchers haven't proven it, some researchers suspect that problems with oxytocin may help explain autism, Zak said.

More information

To learn more about oxytocin, visit Colorado State University.