TUESDAY, Oct. 30 (HealthDay News) -- Among prostate cancer patients undergoing a high-tech form of radiation therapy, exposure to a higher amount of radiation over a shorter time span poses no added risk for impaired sexual function, new research reveals.

"For men getting a high dose of radiation in a shorter amount of time than is typical -- meaning getting higher doses per day for fewer days -- a loss of sexual function is the chronic side effect that concerns most," noted study co-author Dr. Eric Horwitz, a clinical director in the department of radiation oncology at Fox Chase Medical Center in Philadelphia.

"But we found that sexual function wasn't any worse than when patients got radiation in the conventional high-dose way," he said.

Horwitz and lead author Mark Buyyounouski, also at Fox Chase, were expected to present their team's findings at the annual meeting of the American Society for Therapeutic Radiology and Oncology, in Los Angeles.

The finding comes on the heels of work conducted at Fox Chase last year. That study indicated that high-dose radiation should be considered the first line of attack in combating prostate cancer, given that it appears to be the most effective way to limit the disease's spread.

The team focused on a form of radiation therapy called intensity-modulated radiation therapy (IMRT). According to the American Cancer Society, IMRT is a cutting-edge, 3-D form of high-dose radiation therapy. The treatment is delivered by a computer-controlled machine that moves around the patient to target diseased tissue while avoiding healthy tissue, thereby allowing for the safer use of higher doses of radiation.

In the current study, Horwitz and his colleagues tracked the IMRT radiation treatment outcomes of 155 men diagnosed with intermediate to high-risk prostate cancer.

Half the men were assigned to receive 2 Gray (Gy -- a measurement of radiation) in 38 sessions spread over seven and a half weeks.

The other half were exposed to 2.7 Gy in 26 sessions spread over just five weeks.

All the patients then completed questionnaires regarding treatment side effects six months, 12 months, and 24 months following radiation.

Older age, as well as poor sexual function prior to radiation, did increase the risk for sexual impairment after radiation treatment, the researchers said. However, they report no appreciable difference in sexual function between the men receiving the shorter course/higher dose regimen or the more conventional regimen.

"The key to curing more prostate cancer is to give higher does of radiation," observed Horwitz. "And over the last few years, more and more men have been getting higher dose radiation, because the radiation oncology community knows that dose matters and that low dose radiation is just not effective compared to high dose. And this study shows that we have the ability to give these high doses in different ways, and in all these ways, men do very well."

Horwitz said he and his colleagues plan to take the current research to the next level.

"We will build on this experience and go with even higher doses," he said, "to see how that impacts not only sexual function but urinary and bowel function as well."

Dr. Peter T. Scardino is chairman of the department of urology and head of the Prostate Cancer Program at the Memorial Sloan-Kettering Cancer Center in New York City. He described the finding as a small but important step toward developing shorter course/higher dose radiation therapies.

"This is the trend nowadays," said Scardino. "This is where this is going: toward a time when perhaps we will be giving radiation therapies all in a single day."

"Animal studies have already indicated that you may be able to achieve as much or more with a single dose of radiation than with a protracted course," Scardino noted. "So, the big question is, are you going to find more complications as a result of this kind of a shift in dosage? Now, cutting back from seven and a half weeks to five weeks is a slight move in this direction, but they found no difference in sexual side effects, and that's valuable. And I certainly think we'll be seeing a lot more research in this area."

More information

There's more on radiation therapy for prostate cancer at the American Cancer Society  .

THURSDAY, Sept. 13 (HealthDay News) -- The HIV epidemic among gay men can't be explained by their number of sexual partners, U.S. researchers report.

More than half the new HIV infections diagnosed in the United States in 2005 were among gay men, a team at the University of Washington, Seattle, noted. In addition, as many as one in five gay men living in cities may be HIV-positive.

But the sexual behaviors of gay and heterosexual men in the United States may not be as different as most people think, the researchers said.

In fact, two surveys found that most gay men have a similar rate of sex with unprotected partners compared to straight men or women.

"Just because gay men continue to have much higher levels of HIV, we can't jump to the conclusion that that means that they are promiscuous or that prevention messages aren't working," said lead researcher Steven Goodreau, an assistant professor of anthropology.

In the study, Goodreau and a colleague, Dr. Matthew R. Golden, analyzed data from two large population-based surveys. Using those figures, they estimated how many sex partners gay men and straight men and women have, and what number of gay men have either insertive or receptive anal sex, or both.

The report is published in the Sept. 12 online edition of Sexually Transmitted Infections.

"We found that even if gay men behave the same way heterosexuals do -- in terms of sexual partner numbers -- gay men would still have a huge HIV epidemic," Goodreau said.

Conversely, "even if heterosexual men behaved the way gay men do, they would not have a huge HIV epidemic," he added.

In fact, for straight men and women to experience an epidemic of HIV infection as widespread as that of gay men, they would have to have an average of almost five unprotected sexual partners every year -- almost three times the rate of the average gay male, Goodreau and Golden found.

So, why the higher HIV risk for gay men? "A couple of different things could give gay men an overall higher risk for HIV than heterosexuals," Goodreau said.

One reason HIV remains epidemic among gay men is that anal sex is much more conducive to the transmission of HIV transmission than is vaginal sex, the researcher said.

"That puts gay men at much higher risk overall," he said.

In addition, HIV transmission is more easily transmitted through the penis than via the vagina or the anus, Goodreau said. Heterosexuals tend to maintain the same role (insertive vs. receptive), while gay men can switch roles -- making the transmission of HIV more likely, he noted.

So, for gay men and straight men who have the same number of partners and have unprotected sex, gay men are more likely to transmit and receive HIV, Goodreau said. "That's why you can get huge epidemics among gay men and virtually none among heterosexual men," he said.

To end the HIV epidemic, gay men would need to have significantly lower rates of unprotected sex than those seen among the straight men, Goodreau believes.

One expert believes the study does have its flaws, however.

"The information here is mostly based on people's reports of their own behavior," said Philip Alcabes, an associate professor at the School of Health Sciences of Hunter College/City University of New York. "When trying to make use of information on self-reported sexual behavior, we have to remember that it isn't clear that anybody tells the truth," he said.

More information

For more on HIV, visit the U.S. Department of Health and Human Services.

FRIDAY, May 18 (HealthDay News) -- Amid the controversy around mandated vaccination of young girls against the human papillomavirus (HPV), some experts are beginning to wonder whether the shot should also be given to boys.

While males cannot get HPV-linked cervical cancer, they make up half of the equation when it comes to spreading the sexually transmitted virus. And a new study released last week shows that the virus is also a leading cause of throat cancer, which affects both sexes.

"This is a viral infectious process, and the majority of the time it is passed through heterosexual contact. And I think it's important to consider boys as equal players in that process," said Dr. Michael Bookman, director of medical gynecologic oncology at Fox Chase Cancer Center in Philadelphia.

"Boys are not as prone to [HPV-linked] cancer as girls, but they are obviously involved in the transmission, and there is some risk of cancer in boys, as well," he added.

No one is debating the effectiveness of the vaccine, called Gardasil. The shot is targeted against the four strains (out of 15) of HPV that are thought to trigger 70 percent of cervical cancers.

Since its approval for use in girls and women between the ages of 9 and 26 by the U.S. Food and Drug Administration last June, several states have moved to mandate Gardasil's inclusion into routine school vaccination programs. That's because vaccinating before the onset of sexual activity is most effective in preventing HPV infection.

Those efforts have met with strong opposition, however. Some conservative groups worry the vaccine will encourage sex among young people, while other critics view the mandates as an intrusion on parental rights. Most state measures do give parents the right to opt out of the program, however.

So far, those debates have centered on young girls. But, in more rare instances, boys and men can fall prey to HPV as well. Reporting last week in the New England Journal of Medicine, a team of researchers at Johns Hopkins University confirmed that infection with HPV via oral sex is by far the leading cause of throat cancer, which strikes 11,000 American men and women each year. HPV is also a major cause of anal cancer and genital warts, both of which affect either sex.

The threat of throat cancer is especially troubling, Bookman said, because doctors traditionally only look for these malignancies in long-time smokers and drinkers. "Head and neck exams are more associated with smoking and alcohol and less associated with HPV, although that's changing," he said.

And while girls and women typically see a gynecologist for their Pap smear to look for cervical cancer, "how many boys and men are going to go to a doctor and ask them to look at their throat? It's just not that common," Bookman said.

Debbie Saslow is director of breast and gynecological cancers at the American Cancer Society. She agreed that HPV also poses a threat to males, but she's not yet convinced that Gardasil would help protect them.

"We have been considering vaccination for boys since day one, but the problem is that there is just no data yet -- everything is holding until we get data that the vaccine actually works in boys," she said.

Gardasil's maker, Merck & Co., is largely responsible for pulling that data together. However, according to Bookman, "they took a more conservative stance when they approached the FDA for licensure, registration and vaccine recommendations -- their safety data base was stronger for girls than boys."

Saslow also is doubtful whether Gardasil -- which costs $360 per three-shot regimen -- would prove to be cost-effective if provided to boys as well, at least in terms of preventing the biggest threat, cervical cancer.

"It may be cost-effective to vaccinate boys if not that many girls get vaccinated," she said. "But if most of the female population ends up getting vaccinated, then vaccinating boys won't add very much."

But what about the vaccine's cost-effectiveness in preventing anal and throat cancers, plus genital warts, among boys? Saslow said that since Gardasil has not yet been proven to be effective in boys, or to be effective against cancers outside the cervix, those points remain up in the air. "We still have all these questions that we need to look at," she said.

Another expert, Dr. Robert Frenck, a professor of pediatrics at Cincinnati Children's Hospital, was equally noncommittal. Frenck, who sits on the American Academy of Pediatrics' committee on infectious diseases, said his group is "in the process of developing the recommendations for HPV vaccine use." He said the AAP recommendations would focus only on the vaccine's "currently [FDA] licensed usage," which is exclusively for females.

Still, Bookman believes that, should Gardasil prove effective in boys, widening its use to both sexes "is the correct way to try and do things."

"What about everything that we know about controlling any other type of infectious process? Where we wouldn't discriminate on the basis of sex, we would vaccinate universally," he said. "Yes, in women cervical cancer is a more serious risk statistically than other cancers in men. But I think that the best way of controlling it with a vaccine is to use it broadly."

More information

Learn more about HPV and cervical cancer at the U.S. Centers for Disease Control and Prevention.