From CNN Medical Correspondent Eileen O'Connor

WASHINGTON (CNN) -- The National Cancer Institute mailed letters Monday to thousands of doctors, encouraging them to use chemotherapy with radiation in treating cervical cancer after a series of studies showed such treatment can cut death rates in half.

Dr. Edward Trimble, head of surgery at the NCI's therapy evaluation program, said the findings are "very significant."

The results of five separate studies found that women with invasive cervical cancer have better rates of survival when they receive chemotherapy, including the drug cisplatin, along with radiation therapy.

"This is a very big deal," Trimble said. "It should change the way women with cervical cancer are treated. We want to get the word across, so we are mailing this announcement to thousands of doctors who treat cervical cancer."

This is the first such announcement since 1995, the last pertaining to the treatment of breast cancer.

Until now, surgery or radiation therapy alone had been considered the standard treatment for cancer that had spread either within the cervix or regionally, within the pelvis.

"The findings of these five trials are remarkably consistent," NCI director Richard D. Klausner said in a statement. "They are likely to change the standard of care for invasive cervical cancer."

Three of the reports were posted on the Web site of the New England Journal of Medicine, in an effort to inform the medical community more quickly about the findings. Trimble said the NCI is trying to work with the media and patient advocacy groups as well to get the information to patients.

The five studies tested various combinations of chemotherapy and radiation on several hundred patients at hospitals across the country, versus radiation alone. All the patients had cancer that had spread beyond the cervix, but was still confined to the pelvis.

Those receiving the combination therapy showed higher survival rates. NCI's clinical announcement also said "significant results were seen using cisplatin alone or cisplatin in combination" with other agents, although the best chemotherapy regime was not determined.

Dr. Ira Horowitz, an oncologist at Emory University uninvolved in the studies, said his medical center has been using both radiation and chemotherapy for years with good results. Horowitz said he believes more widespread use of these treatments will considerably decrease the death rate.

Trimble said potentially, if used, the new standard treatment could cut deaths in half. Trimble points out that 90 percent of cervical cancer could be prevented through regular gynecological exams and pap smears.

Cervical cancer, which usually affects women between 35 and 55, is expected to kill about 4,800 women in the United States this year.