Pumping heavy doses of chemotherapy drugs right into the abdomen boosted survival of women with advanced ovarian cancer by 16 months in what experts call the first big advance in more than a decade against one of the most lethal cancers in women.

There's a high price, though: The treatment is so tough that nearly 6 in 10 women in a study could not endure it and switched to standard intravenous chemotherapy. Side effects included abdominal pain from bloating and problems with the catheter used to infuse the drugs.

Still, the National Cancer Institute is urging doctors to begin using the procedure, its first endorsement of any cancer treatment since 1999. Six medical groups focused on ovarian cancer joined in the recommendation.

The study was reported in Thursday's New England Journal of Medicine.

Dr. Steven A. Cannistra of Harvard Medical School wrote in an editorial that the 16-month jump in survival "is one of the largest benefits ever observed" from a new therapy for gynecologic cancer.

About 80 percent of women are diagnosed after ovarian cancer has spread because early symptoms are so mild. It is the top killer among gynecologic cancers in this country. Last year, about 22,200 American women were diagnosed and about 16,200 died from it, according to the cancer institute. Fewer than half its victims survive five years after diagnosis.

To improve on that, doctors at dozens of U.S. hospitals, led by Dr. Deborah Armstrong at Johns Hopkins Kimmel Cancer Center, compared chemo regimens in 415 women. Each had surgery to remove ovarian tumors, but some hard-to-reach cancer cells remain in the abdominal cavity. It's tough for IV chemo drugs to reach those cells, and there's a limit to how high a dose can be given through the bloodstream.

Half the women in the study got standard intravenous chemotherapy with Taxol and cisplatin. The others got IV Taxol, then abdominal infusions of cisplatin and more Taxol at high doses.

The drugs were given through an implanted seal with a catheter, or tiny tube, hanging down into the abdominal cavity. The women rolled back and forth to bathe all the cancer cells in the mixture.

Median survival was about four years and two months for women who received only IV chemotherapy, but was just over 5 1/2 years for women who also got at least some of the abdominal chemotherapy.

But only 42 percent could tolerate all six cycles of abdominal chemotherapy.

"It's not perfect, but it is certainly a major improvement in outcome," the biggest in ovarian cancer since Taxol was introduced nearly 15 years ago, said Dr. Richard Barakat, chief of gynecologic oncology at Memorial Sloan-Kettering Cancer Center.

Barakat was not involved in the study, but based on its results is now offering the treatment as standard care. He said 70 percent of patients now last through the treatment, "but it's not a walk in the park," with some women faring poorly and others unsuited for it.

Armstrong, associate professor of oncology, gynecology and obstetrics at Johns Hopkins, said she believes her results can be improved, and new studies are trying different chemo drugs, dose schedules and catheter types.

Dr. Carolyn Runowicz, president of the American Cancer Society and a gynecologic cancer specialist who gives the treatment, said blockages and other catheter problems can be resolved and that this study — the third major one with similar results — will lead to more advances.

While more women on the abdominal treatment survived, their quality of life was significantly worse until weeks after treatment ended.

Mary McFadden, a 68-year-old retired secretary from Ocean Pines, Md., near the end of the abdominal treatment, said Tuesday she has been too exhausted to do any household chores, has weak legs and is occasionally nauseous. She also has to urinate every hour during treatments.

"My husband's been doing everything" at home, she said.

Ann Henriques, 49, of Nyack, N.Y., who also is nearly done with her treatment, said she has to recline for days after the abdominal infusions because of abdominal pressure and has suffered acid reflux and aches in her joints, but it has never been "intolerable."

"It's going to save lives. I think it saved mine," she said.