CHICAGO — The widely used cancer drug Avastin can help keep ovarian cancer in check, but only if used for a long period of time, researchers reported here Sunday.

Another study, also presented at the annual meeting of the American Society of Clinical Oncology, showed that men with high-risk prostate cancer lived longer if they were treated with radiation in addition to hormone-blocking drugs.

And a drug derived from a marine sponge lengthened the lives of women with advanced breast cancer by about 2 ½ months.

Avastin, made by the Genentech unit of Roche, slows the development of blood vessels that nourish tumors and is perhaps the world's best-selling cancer drug. It is already approved for use in treating colorectal, breast, lung, kidney and brain cancers.

The ovarian-cancer trial involved 1,873 women with newly diagnosed Stage 3 or Stage 4 ovarian cancer who had undergone surgery to remove as much cancer as possible. The women received either standard chemotherapy and a placebo, standard chemotherapy and Avastin, or standard chemotherapy and Avastin followed by as many as 10 months of Avastin by itself.

For those who got the extended Avastin treatment, it took a median of 14.1 months for the cancer to start worsening, compared with 10.3 months for those who received only standard chemotherapy and the placebo. The short-term use of Avastin did not lead to significantly better results than the standard chemotherapy alone.

Some ovarian-cancer experts were cautious. They said it was still too early to tell whether women who got the extended Avastin lived longer and whether the quality of their lives was improved.

"I think we need survival data before we can enthusiastically endorse it," said Dr. Robert Morgan, an ovarian- cancer specialist at the City of Hope medical center in Duarte, Calif.
The prostate-cancer study involved 1,200 men whose disease upon diagnosis had spread to the area around the prostate gland or who had other high risk factors, such as a high PSA level.

In the trial, 74 percent of the men who had received the radiation therapy were alive after seven years, compared with 66 percent of those who had received only the hormone therapy. Only 10 percent of those who received radiotherapy died from prostate cancer itself, compared with 26 percent of those who received only the androgen-deprivation.

The drug derived from the marine sponge, called eribulin, was tested in a trial involving 762 women with metastatic breast cancer who had already received several different drugs. They received either eribulin or their doctor's choice of another drug.

Those who got eribulin lived a median of 13.1 months, compared with 10.7 months for those who got the doctor's choice of drug.

ANDREW POLLACK