SUNDAY, June 6 (HealthDay News) -- New research points toward novel ways to treat ovarian and prostate cancer, while producing a disappointment for those with a certain form of colon cancer.

Both the ovarian and prostate cancer trials could change clinical practice, with more women taking the drug bevacizumab (Avastin) to combat the disease in its advanced stages and more men getting radiation therapy for locally advanced prostate cancer, according to researchers who presented the findings Sunday at the American Society of Clinical Oncology (ASCO) annual meeting in Chicago.

A third trial, looking at the effectiveness of cetuximab (Erbitux) in treating certain colon cancer patients, found the drug made little difference to their survival.

The first study found that adding Avastin to standard chemotherapy (carboplatin and paclitaxel) and continuing with "maintenance" Avastin after chemo actually slowed the time-to-disease recurrence in women with advanced ovarian cancer.

Avastin is an anti-angiogenic drug, meaning it interferes with a tumor's blood supply.

"This is the first molecular-targeted and first anti-angiogenesis therapy to demonstrate benefit in this population and, combined with chemotherapy followed by [Avastin] maintenance, should be considered as one standard option for women with this disease," said lead researcher Dr. Robert A. Burger, director of the Women's Cancer Center at Fox Chase Cancer Center in Philadelphia.

"This is a new potential treatment paradigm for stage 3 and 4 ovarian cancer," added Dr. Jennifer Obel, an attending physician at Northshore University Health System and moderator of a Sunday news conference at which these results were presented.

The phase 3 study involved almost 1,900 women with stage 3 and stage 4 ovarian cancer.

Those who received standard chemotherapy plus Avastin, and then maintenance Avastin, for up to 10 months lived just over 14 months without their disease progressing compared with about 10 months for those receiving standard chemotherapy alone.

Those who received chemo plus Avastin but no maintenance drug lived without a recurrence for 11.2 months, a difference not considered statistically significant.

"I'm cautiously optimistic about this data. It clearly shows that those who had maintenance [Avastin] had improved profession-free survival," said Dr. Robert Morgan, co-director of the gynecologic oncology program at City of Hope Cancer Center in Duarte, Calif. "I think we have to wait for longer term outcomes before we make definite conclusions. It's too early for overall survival benefit data."

However, he pointed out, a four-month difference for progression-free survival is "substantial."

Doctors are already using Avastin off-label widely to treat ovarian cancer, he said, although it is not yet approved for this use. It has been shown to be more active in this cancer than in many cancers for which it is approved, Morgan noted.

"Clinicians will need to make decisions based upon the specific subsets of patients with advanced ovarian cancer, including the stage of the cancer," added Dr. Ursula Matulonis, director of medical gynecologic oncology at Dana-Farber Cancer Institute and an associate professor of medicine at Harvard Medical School in Boston.

"Also, Avastin has a lot of side effects," she pointed out. "The physician has to balance the benefit vs. the risk."

A second phase 3 study presented Sunday found that adding radiation to hormone therapy, also known as androgen-deprivation therapy (ADT) in patients with locally advanced or high-risk prostate cancer reduced the seven-year risk of dying by 43 percent compared to treating with hormone therapy alone.

"We know that radiation is better if added to ADT, but we didn't know if we could treat patients with ADT alone," said Obel. "The message here is that radiation is an indispensable element in the treatment of high-risk prostate cancer patients."

In the Canadian study, more than 1,200 men were randomized to receive either hormone therapy alone or hormone therapy with radiation.

Over the next seven years, those in the combination group had a 43 percent lower risk of dying from prostate cancer, the team found.

"After seven years, 74 percent of patients with the combined treatment were alive as compared to 66 percent in the ADT group alone," noted study author Dr. Padraig Warde, deputy head of the radiation medicine program at the University of Toronto's Princess Margaret Hospital. "At seven years, only 10 percent of patients who received radiation and ADT had died of prostate cancer vs. 21 percent in the ADT-alone group."

"Patients treated with the combined treatment -- radiation and hormones -- live longer and are less likely to die of prostate cancer," he said. "Radiation treatments should be part of the treatment package for this group of patients."

Also, radiation doses are higher today and may be even more potent, he added.

Finally, yet another phase 3 study -- albeit one with less encouraging results -- found that the monoclonal antibody drug cetuximab (Erbitux) did not aid people with (potentially curable) early-stage colon cancer if they carried the normal form of the KRAS gene.

The finding was a blow, given that Erbitux has helped patients with more advanced cancers.

Patients in this study had the normal form of the KRAS gene, for which the drug works in more advanced cancer.

The more than 1,600 patients in the study were followed for almost 16 months and were also treated with conventional chemotherapy.

"Much to our surprise, the trial showed that patients receiving standard therapy compared to those receiving cetuximab with standard therapy had no difference in outcomes," said study author Dr. Steven Alberts, a professor of oncology at the Mayo Clinic College of Medicine in Rochester, Minn. "It also indicates that disease in earlier stages may be different than diseases in later stages."

The trial, which was supported by the U.S. National Institutes of Health, Bristol-Myers Squibb, ImClone, Sanofi-Aventis and Pfizer, was halted after researchers realized there was no added benefit.

More information

Visit the U.S. National Cancer Institute for these and other types of cancers.